sailboat energy transformation

• Water Power Technologies Office
• IRA Tax Credit Opportunities
• Water Power Careers
• WPTO Contacts & Organization
• Water Power Educational Resources
• Water Power Projects Map
• Water Power Strategy & Accomplishments
• How Hydropower Works
• Hydropower Benefits
• History of Hydropower
• Hydropower Glossary
• Pumped Storage Hydropower
• Environmental & Hydrologic Systems Science
• Grid Reliability, Resilience, & Integration (HydroWIRES)
• Hydropower Data Access & Analytics
• Low-Impact Hydropower Growth
• Modernization, Maintenance, & Cybersecurity
• Advantages of Marine Energy
• Marine Energy Glossary
• Foundational R&D
• Marine Energy Data Access & Analytics
• Powering the Blue Economy
• Reducing Barriers to Testing
• System Design & Validation
• Water Power Prizes & Competitions
• WPTO SBIR/STTR Programs
• WPTO Seedling & Sapling Program
• Water Power Publications
• WPTO R&D Deep Dive Webinars
• WPTO Stakeholder Webinars

The world’s most ancient shark—a sleepy, near-blind creature called the Greenland shark—eluded scientists until 2018 when they finally caught the large fish on camera . Did you know these oceanic blind spots are more common than not? About 80% of the ocean is still a mystery, according to the National Oceanic and Atmospheric Administration . This vast, unmapped territory is home to an unknown number of species—about 91% of which are unclassified.

Now, a bright yellow device called the SeaRAY autonomous offshore power system (or SeaRAY AOPS) could help scientists study the unmapped ocean and, at the same time, protect its mysterious species from more pollutants. The small, portable device makes clean energy from the motion of the ocean’s waves and collects and sends data, like an oceanic cell tower. Although many previous marine energy systems only produced small amounts of power, the SeaRAY AOPS can generate between 100 watts and 20 kilowatts—enough energy to power anything from a seafloor data-gathering system to a medium-sized subsea vehicle or surface vessel.

To conserve our oceans and power the blue ocean economy, the U.S. Department of Energy’s Water Power Technologies Office invests in carbon-free marine energy devices, like C-Power’s SeaRAY AOPS. C-Power designed the SeaRAY’s wave energy converter, which uses two undulating side floats to transform the ocean’s motion into energy. To make the SeaRAY “smart,” researchers at the National Renewable Energy Laboratory gave it brains: a novel field data collection, storage, and transmission system, called Modular Ocean Data Acquisition (MODAQ), that researchers can also use to control the SeaRAY from anywhere in the world.

Soon, after the SeaRAY’s first six-month sea trial in Hawaii, the device could power offshore fish farms, shipping, desalination devices for remote communities and disaster-recovery situations, or even deep sea robotic fish that can help researchers study marine wildlife, like the elusive Greenland shark.

“Water, water, everywhere,” said C-Power’s CEO Reenst Lesemann in a nod to The Rime of the Ancient Mariner , a poem about a ship’s crew dying of thirst while surrounded by endless salt water. For the modern mariner, the SeaRAY ensures that offshore operations won’t suffer thirst—for power, at least.

To conserve our oceans and power the blue ocean economy , the U.S. Department of Energy Water Power Technologies Office invests in carbon-free marine energy devices, like C-Power’s SeaRAY AOPS. C-Power designed the SeaRAY’s wave energy converter, which uses two undulating side floats to transform the ocean’s motion into energy. To make the SeaRAY “smart,” researchers at the National Renewable Energy Laboratory (NREL) gave it brains: a novel field data collection, storage, and transmission system, called Modular Ocean Data Acquisition (MODAQ), that researchers can also use to control the SeaRAY from anywhere in the world.

C-Power’s banana-yellow SeaRAY could power the booming ocean economy with clean energy produced by ocean waves. (From left) Rebecca Fao, Mark Murphy, Casey Nichols, Ismael Mendoza, and Andrew Simms, members of the NREL team, met with C-Power CEO Reenst Lesemann (far right) at NREL Flatirons Campus, before the SeaRAY’s first sea trial off Hawaii. Photo courtesy of Vern Slocum, NREL

The first SeaRAY device was just a mooring line and an anchor. Now, outfitted with GPS, 4G, Wi-Fi, and cloud data storage, the latest SeaRAY is smarter than most smartphones.

When the SeaRAY surfs the waves at the U.S. Navy Wave Energy Test Site in Hawaii, it won’t be alone. Project partners, like BioSonics, will bring their sea-faring technologies to see just how much the SeaRAY can power. BioSonics’ subsea environmental monitoring system will search for two underwater dangers: human intruders (for defense) and noise pollution that can disrupt or even injure marine mammals . Through the Triton Initiative with the Pacific Northwest National Laboratory , BioSonics’ monitoring system will also collect data on how marine energy devices (like the SeaRAY) impact electromagnetic fields, marine animal interactions, and marine habitats. That way, the SeaRAY can protect the global environmental with its clean, ocean-resourced energy and guard local environments, too.

Saab, a world leader in electric underwater robotics, will pair the SeaRAY with its Sabertooth autonomous underwater vehicle , which is essentially a sea drone. In the first attempt to power the surfboard-sized Sabertooth with 100% renewable energy, the vehicle will zoom around the ocean before docking at the SeaRAY to charge and deposit data.

“With Saab,” said Lesemann, “we can prove that you don't need that expensive, complex, carbon-intensive vessel to babysit up top. For ocean-going vessels, on an annual basis, that ship can produce about 7,000 cars’ worth of carbon dioxide.”

The Sabertooth might not need a babysitter, but an environmental sensor from another partner—the National Atmospheric and Oceanic Administration—will need a ride. The sensor will hitch one from the Sabertooth, so it can zoom around the deep and collect data on zooplankton, which are a cornerstone of the marine food chain and good indicators of ocean pollution levels.

C-Power made sure the SeaRAY causes minimal pollution either on the water or getting there. The company designed its device to be easily transportable in a standard shipping container. Once in Hawaii, a small boat will tow it to the testing spot. “ You can deploy it,” said Lesemann, “with a lightly crewed vessel, with minimal expense and low carbon emissions.”

Before the SeaRAY shipped out, NREL’s team of mechanical engineers put the device through rigorous tests to make sure it could handle volatile ocean conditions. “The ocean is a very harsh environment for a machine to operate reliably in,” said Scott Lambert, a mechanical engineer at NREL who designed the SeaRAY’s test rig—a type of dynamometer—from scratch. Unlike other dynamometers, which are typically used to stress-test wind turbine generators, Lambert’s new hydraulic dynamometer switches direction faster, simulating the ocean’s erratic tides and waves, to test the SeaRAY’s surfing skills.

The NREL engineers also ensured that the SeaRAY’s brains (MODAQ) and seafloor energy storage systems worked as intended.

“We’re essentially building a satellite,” said Andrew Simms, a research technician at NREL. “Our challenges in Hawaii are vast. The ocean is corrosive. It’s scary. It’s harsh. And we wanted to make sure everything was set before we took it offshore.”

Data from the Hawaii sea trial will not only confirm how well the SeaRAY AOPS can power offshore industries, but also how the team can make the SeaRAY even smaller, lighter, more efficient, and more adaptable for a wider range of applications.

Besides providing clean power for a booming ocean economy , the SeaRAY could one day power scientific expeditions, helping to unveil the 80% of ocean life that remains a mystery. Those missions need clean power—and fast. Warming oceans will disrupt ecosystems and cause extinctions of creatures that might be critical to ocean health or host vital medicinal chemicals. The elusive and ancient Greenland shark might lose its Arctic habitat before scientists can catch another glimpse of the strange giants.

Without clean energy solutions like the SeaRAY AOPS, far more marine wildlife oddities could be lost to time .

Save 40% off! Join our newsletter and get 40% off right away!

Sailboat Life

Sailboat Cruising and Lifestyle Magazine.

Sailboat Solar Systems and How-To

Solar on a sailboat goes together like hands and gloves, but sailboat solar systems can be installed in a variety of ways. The solar components themselves create an infinite combination of possibilities for off-grid sailing. Victron Energy chargers, Renogy Panels, Sunpower Yachts, BlueSea Systems, and many more brands have entered the marketplace, and that’s not including the lithium battery companies.

To simplify things, we’ve compiled three sailboat solar systems videos to give you an overview of what’s possible. And to help you decide on your own simple solar panel setup for sailing.

How-To Install Solar Panels on Your Sailboat

This system from Zingaro shows flexible panels summing 300w of power on a 38′ catamaran.

300W Solar System:

• Three 100w solar flexible panels
• 1 MPPT Solar charger controller

View on Amazon >>

100W HQST Flexible Solar Panels $100-$200

20amp Solar Charge Controller by Victron Energy $150-$200

Simple Sunpower Solar System

This simple solar system from The Fosters shows a quick and easy setup with limited space on top of a bimini.

Sunpower Solar Panels are considered by most in the industry as the gold standard. They use the highest-efficiency solar cells and have top-notch build quality. In this simple installation, three 50w panels are just enough to get you started. Plus, it’s the most affordable installation!

150w Starter Solar System

• Three 50w Flexible Solar Panels
• A Single 15amp solar charge controller

50W Sunpower Solar Panels $150-$200

75v/15amp Solar Charge Controller by Victron Energy $100-$124

Off-Grid on a DIY Solar Powered Sailboat

Here’s a special installation that turned a derelict sailboat into an off-grid sailing machine!

Simon has transformed this derelict sailboat into an epic off-grid solar-powered and fossil-fuel-free cruising catamaran. He’s been living aboard and renovating the boat for the past 3.5 years We’re excited to show you the transformation as well as how he plans to propel the boat without the use of diesel or fossil fuels!

5280w Solar System for Electric Powered Catamaran

• 16 Rigid solar panels (330w each)
• 20kwh of Lithium Batteries

240W Rigid Solar Panels $250-$300

200AH Lithium 4d Battery $1200-$1200

Share this post!

Throw in your two cents, start a discussion cancel reply, related articles.

The Voyage of the Sea Star – 35ft Sloop to Bermuda

Living Aboard a 30-36ft Sailboat: A Guide for the Curious and Adventurous

Summer Sailboat Video, Bikinis, Sails, and Fun

Saved Up For This Dream

How a Sail Works: Basic Aerodynamics

The more you learn about how a sail works, the more you start to really appreciate the fundamental structure and design used for all sailboats.

It can be truly fascinating that many years ago, adventurers sailed the oceans and seas with what we consider now to be basic aerodynamic and hydrodynamic theory.

When I first heard the words “aerodynamic and hydrodynamic theory” when being introduced to how a sail works in its most fundamental form, I was a bit intimidated.

“Do I need to take a physics 101 course?” However, it turns out it can be explained in very intuitive ways that anyone with a touch of curiosity can learn.

Wherever possible, I’ll include not only intuitive descriptions of the basic aerodynamics of how a sail works, but I’ll also include images to illustrate these points.

There are a lot of fascinating facts to learn, so let’s get to it!

Basic Aerodynamic Theory and Sailing

Combining the world of aerodynamics and sailing is a natural move thanks to the combination of wind and sail.

We all know that sailboats get their forward motion from wind energy, so it’s no wonder a little bit of understanding of aerodynamics is in order. Aerodynamics is a field of study focused on the motion of air when it interacts with a solid object.

The most common image that comes to mind is wind on an airplane or a car in a wind tunnel. As a matter of fact, the sail on a sailboat acts a bit like a wing under specific points of sail as does the keel underneath a sailboat.

People have been using the fundamentals of aerodynamics to sail around the globe for thousands of years.

The ancient Greeks are known to have had at least an intuitive understanding of it an extremely long time ago. However, it wasn’t truly laid out as science until Sir Isaac Newton came along in 1726 with his theory of air resistance.

Fundamental Forces

One of the most important facets to understand when learning about how a sail works under the magnifying glass of aerodynamics is understanding the forces at play.

There are four fundamental forces involved in the combination of aerodynamics and a sailboat and those include the lift, drag, thrust, and weight.

From the image above, you can see these forces at play on an airfoil, which is just like a wing on an airplane or similar to the many types of sails on a sailboat. They all have an important role to play in how a sail works when out on the water with a bit of wind about, but the two main aerodynamic forces are lift and drag.

Before we jump into how lift and drag work, let’s take a quick look at thrust and weight since understanding these will give us a better view of the aerodynamics of a sailboat.

As you can imagine, weight is a pretty straight forward force since it’s simply how heavy an object is.

The weight of a sailboat makes a huge difference in how it’s able to accelerate when a more powerful wind kicks in as well as when changing directions while tacking or jibing.

It’s also the opposing force to lift, which is where the keel comes in mighty handy. More on that later.

The thrust force is a reactionary force as it’s the main result of the combination of all the other forces. This is the force that helps propel a sailboat forward while in the water, which is essentially the acceleration of a sailboat cutting through the water.

Combine this forward acceleration with the weight of sailboat and you get Newton’s famous second law of motion F=ma.

Drag and Lift

Now for the more interesting aerodynamic forces at play when looking at how a sail works. As I mentioned before, lift and drag are the two main aerodynamic forces involved in this scientific dance between wind and sail.

Just like the image shows, they are perpendicular forces that play crucial roles in getting a sailboat moving along.

If you were to combine the lift and drag force together, you would end up with a force that’s directly trying to tip your sailboat.

What the sail is essentially doing is breaking up the force of the wind into two components that serve different purposes. This decomposition of forces is what makes a sailboat a sailboat.

The drag force is the force parallel to the sail, which is essentially the force that’s altering the direction of the wind and pushing the sailboat sideways.

The reason drag is occurring in the first place is based on the positioning of the sail to the wind. Since we want our sail to catch the wind, it’s only natural this force will be produced.

The lift force is the force perpendicular to the sail and provides the energy that’s pointed fore the sailboat. Since the lift force is pointing forward, we want to ensure our sailboat is able to use as much of that force to produce forward propulsion.

This is exactly the energy our sailboat needs to get moving, so figuring out how to eliminate any other force that impedes it is essential.

Combining the lift and drag forces produces a very strong force that’s exactly perpendicular to the hull of a sailboat.

As you might have already experienced while out on a sailing adventure, the sailboat heels (tips) when the wind starts moving, which is exactly this strong perpendicular force produced by the lift and drag.

Now, you may be wondering “Why doesn’t the sailboat get pushed in this new direction due to this new force?” Well, if we only had the hull and sail to work with while out on the water, we’d definitely be out of luck.

There’s no question we’d just be pushed to the side and never move forward. However, sailboats have a special trick up their sleeves that help transform that energy to a force pointing forward.

Hydrodynamics: The Role of the Keel

An essential part of any monohull sailboat is a keel, which is the long, heavy object that protrudes from the hull and down to the seabed. Keels can come in many types , but they all serve the same purpose regardless of their shape and size.

Hydrodynamics, or fluid dynamics, is similar to aerodynamics in the sense that it describes the flow of fluids and is often used as a way to model how liquids in motion interact with solid objects.

As a matter of fact, one of the most famous math problems that have yet to be solved is exactly addressing this interaction, which is called the Navier-Stokes equations. If you can solve this math problem, the Clay Mathematics Institute will award you with $1 million!

There are a couple of reasons why a sailboat has a keel . A keel converts sideways force on the sailboat by the wind into forward motion and it provides ballast (i.e., keeps the sailboat from tipping).

By canceling out the perpendicular force on the sailboat originally caused by the wind hitting the sail, the only significant leftover force produces forward motion.

We talked about how the sideways force makes the sailboat tip to the side. Well, the keep is made out to be a wing-like object that can not only effectively cut through the water below, but also provide enough surface area to resist being moved.

For example, if you stick your hand in water and keep it stiff while moving it back and forth in the direction of your palm, your hand is producing a lot of resistance to the water.

This resisting force by the keel contributes to eliminating that perpendicular force that’s trying to tip the sailboat as hard as it can.

The wind hitting the sail and thus producing that sideways force is being pushed back by this big, heavy object in the water. Since that big, heavy object isn’t easy to push around, a lot of that energy gets canceled out.

When the energy perpendicular to the sailboat is effectively canceled out, the only remaining force is the remnants of the lift force. And since the lift force was pointing parallel to the sailboat as well as the hull, there’s only one way to go: forward!

Once the forward motion starts to occur, the keel starts to act like a wing and helps to stabilize the sailboat as the speed increases.

This is when the keel is able to resist the perpendicular force even more, resulting in the sailboat evening out.

This is exactly why once you pick up a bit of speed after experiencing a gust, your sailboat will tend to flatten instead of stay tipped over so heavily.

Heeling Over

When you’re on a sailboat and you experience the feeling of the sailboat tipping to either the port or starboard side, that’s called heeling .

As your sailboat catches the wind in its sail and works with the keel to produce forward motion, that heeling over will be reduced due to the wing-like nature of the keel.

The combination of the perpendicular force of the wind on the sail and the opposing force by the keel results in these forces canceling out.

However, the keel isn’t able to overpower the force by the wind absolutely which results in the sailboat traveling forward with a little tilt, or heel, to it.

Ideally, you want your sailboat to heel as little as possible because this allows your sailboat to cut through the water easier and to transfer more energy forward.

This is why you see sailboat racing crews leaning on the side of their sailboat that’s heeled over the most. They’re trying to help the keel by adding even more force against the perpendicular wind force.

By leveling out the sailboat, you’ll be able to move through the water far more efficiently. This means that any work in correcting the heeling of your sailboat beyond the work of the keel needs to be done by you and your crew.

Apart from the racing crews that lean intensely on one side of the sailboat, there are other ways to do this as well.

One way to prevent your sailboat from heeling over is to simply move your crew from one side of the sailboat to the other. Just like racing sailors, you’re helping out the keel resist the perpendicular force without having to do any intense harness gymnastics.

A great way to properly keep your sailboat from heeling over is to adjust the sails on your sailboat. Sure, it’s fun to sail around with a little heel because it adds a bit of action to the day, but if you need to contain that action a bit all you need to do is ease out the sails.

By easing out the sails, you’re reducing the surface area of the sail acting on the wind and thus reducing the perpendicular wind force. Be sure to ease it out carefully though so as to avoid luffing.

Another great way to reduce heeling on your sailboat is to reef your sails. By reefing your sails, you’re again reducing the surface area of the sails acting on the wind.

However, in this case the reduction of surface area doesn’t require altering your current point of sail and instead simply remove surface area altogether.

When the winds are high and mighty, and they don’t appear to be letting up, reefing your sails is always a smart move.

How an Airplane Wing Works

We talked a lot about how a sail is a wing-like object, but I always find it important to be able to understand one concept in a number of different ways.

Probably the most common example’s of how aerodynamics works is with wings on an airplane. If you can understand how a sail works as well as a wing on an airplane, you’ll be in a small minority of people who truly understand the basic aerodynamic theory.

As I mentioned before, sails on a sailboat are similar to wings on an airplane. When wind streams across a wing, some air travels above the wing and some below.

The air that travels above the wing travels a longer distance, which means it has to travel at a higher velocity than the air below resulting in a lower pressure environment.

On the other hand, the air that passes below the wing doesn’t have to travel as far as the air on top of the wing, so the air can travel at a lower velocity than the air above resulting in a higher pressure environment.

Now, it’s a fact that high-pressure systems always move toward low-pressure systems since this is a transfer of energy from a higher potential to a lower potential.

Think of what happens when you open the bathroom door after taking a hot shower. All that hot air escapes into a cooler environment as fast as possible.

Due to the shape of a wing on an airplane, a pressure differential is created and results in the high pressure wanting to move to the lower pressure.

This resulting pressure dynamic forces the wing to move upward causing whatever else is attached to it to rise up as well. This is how airplanes are able to produce lift and raise themselves off the ground.

Now if you look at this in the eyes of a sailboat, the sail is acting in a similar way. Wind is streaming across the sail head on resulting in some air going on the port side and the starboard side of the sail.

Whichever side of the sail is puffed out will require the air to travel a bit farther than the interior part of the sail.

This is actually where there’s a slight difference between a wing and a sail since both sides of the sail are equal in length.

However, all of the air on the interior doesn’t have to travel the same distance as all of the air on the exterior, which results in the pressure differential we see with wings.

Final Thoughts

We got pretty technical here today, but I hope it was helpful in deepening your understanding of how a sail works as well as how a keel works when it comes to basic aerodynamic and hydrodynamic theory.

Having this knowledge is helpful when adjusting your sails and being conscious of the power of the wind on your sailboat.

With a better fundamental background in how a sailboat operates and how their interconnected parts work together in terms of basic aerodynamics and hydrodynamics, you’re definitely better fit for cruising out on the water.

Get the very best sailing stuff straight to your inbox

Nomadic sailing.

At Nomadic Sailing, we're all about helping the community learn all there is to know about sailing. From learning how to sail to popular and lesser-known destinations to essential sailing gear and more.

Quick Links

Business address.

1200 Fourth Street #1141 Key West, FL 33040 United States

Copyright © 2024 Nomadic Sailing. All rights reserved. Nomadic Sailing is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means to earn fees by linking to Amazon.com and affiliated sites.

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• My Account Login
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 17 February 2020

Convergent Evolution of Boats with Sails

• A. Bejan 1 ,
• L. Ferber 2 &
• S. Lorente 3  

Scientific Reports volume  10 , Article number:  2703 ( 2020 ) Cite this article

5827 Accesses

5 Citations

3 Altmetric

Metrics details

• Anthropology
• Energy science and technology
• Engineering
• Evolutionary theory
• Mechanical engineering
• Renewable energy

This article unveils the geometric characteristics of boats with sails of many sizes, covering the range 10 2 –10 5  kg. Data from one hundred boat models are collected and tabulated. The data show distinct trends of convergent evolution across the entire range of sizes, namely: (i) the proportionality between beam and draft, (ii) the proportionality between overall boat length and beam, and (iii) the proportionality between mast height and overall boat length. The review shows that the geometric aspect ratios (i)–(iii) are predictable from the physics of evolution toward architectures that offer greater flow access through the medium.

Similar content being viewed by others

A hydrodynamics assessment of the hammerhead shark cephalofoil

Matthew K. Gaylord, Eric L. Blades & Glenn R. Parsons

Terminal ballistic analysis of impact fractures reveals the use of spearthrower 31 ky ago at Maisières-Canal, Belgium

Justin Coppe, Noora Taipale & Veerle Rots

The relevance of rock shape over mass—implications for rockfall hazard assessments

Andrin Caviezel, Adrian Ringenbach, … Perry Bartelt

Introduction

Nature impresses us with images, changes and tendencies that repeat themselves innumerable times even though “similar observations” are not identical to each other. In science, we recognize each ubiquitous tendency as a distinct phenomenon . Over the centuries, our predecessors have summarized each distinct phenomenon with its own law of physics, which then serves as a ‘first principle’ in the edifice of science. A principle is a ‘first principle’ when it cannot be deduced from other first principles.

This aspect of organization in science is illustrated by the evolution of thermodynamics to its current state 1 , 2 . For example, 150 years ago the transformation of potential energy into kinetic energy and the conservation of “caloric” were fused into one statement—the first law of thermodynamics—which now serves as a first-principle in physics. It was the same with another distinct tendency in nature: everything flows (by itself) from high to low. This, the phenomenon of one-way flow, or irreversibility, was summarized in another statement at the same time—the second law of thermodynamics—which serves as another first-principle in physics.

Why do the most common occurrences need such a long time to be recognized as natural tendencies (phenomena), and even longer to be recorded in physics with a short statement, a first principle? Because the evolution of the human mind is an integral part of the evolution of the human, to adapt and survive while struck by unexpected dangers, environmental, animal, and human. The first thing that we question is the unusual (the “surprise”, which means being grabbed from above, as if in the claws of a predator). Questioned the least are the most common observations, the familiar, the not threatening. This is why new questions in science are rare.

Nowhere is the human approach to science more evident than in the face of the natural phenomenon of evolutionary organization 1 , 3 . Images, morphing images, impress us constantly, yet the most common images go unnoticed. For example, the oneness of natural tree-shaped architectures of the inanimate realm (e.g., river basins) and the animate realm (e.g., human lungs, city traffic) is evident and intriguing. Recent articles are drawing attention to phenomena of evolution that are general and belong in physics 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 . This literature shows that such phenomena are predictable. Examples are the architectures of lungs 24 and corals 25 , the life span and life travel of animals, vehicles, rivers and the winds 26 , the round cross sections of all jets and plumes 27 , the dendritic architecture and S-shaped history of dendritic solidification such as snowflakes 28 , the arrow of time of evolutionary organization 29 , and the fact that humans prefer unwittingly certain shapes and proportions, from the shapes of the Egyptian pyramids 30 and the shapes of fires (piles of fuel) 31 , to the golden-ratio shape of drawings, images and text.

Because of its physics basis, the phenomenon of evolution can be imagined the way it happened, in retrospect. Further ahead along this line, evolution can be not only predicted but also witnessed in our life time, for example, by observing technological evolution. The geometric similarity of modern commercial aircraft 32 , like the similarity of helicopters 33 and automobiles 34 , shows that human movement on the world map is facilitated by the generation and persistence of certain shapes and structures.

In this paper we strengthen this message by questioning an evolutionary phenomenon of technology that is evident (Fig.  1 ) but goes unquestioned. Why do boats with sails look the same? They have sails that are roughly as tall as the length of the hull. They have hulls that are longer than they are wide. Furthermore, they are submerged to a depth that is greater when the hull is wider. The boat has been this way since antiquity. Even more intriguing is that the large boat looks just like the small boat. Why?

The geometric similarity of boats with sails, clockwise: ancient Egyptian galley, the essential length scales of the moving body, and modern sailboats (photo: Adrian Bejan).

The reason for all these observations is the human tendency to move more easily on earth 1 , 3 . The vehicle architecture that emerges is a reflection of the urge of all its builders and users to move more easily, to have greater access to the surroundings. In recorded times, this tendency gave birth to artifacts (vehicles) in which people encapsulate themselves to acquire greater access. From this idea, the convergent evolution of all boats with sails is deducible.

The boat moves horizontally with the speed V w on the surface of the water. The wind with the speed V a engages the sail with the force,

where C D ~ 1 is the drag coefficient, ρ a is the air density, and (HL/2) is the sail area: H is the height of the mast, and L is the hull length. The driving force F a is matched by the drag force experienced by the hull against the water,

where D x is the hull width, D y is the depth of the submerged portion of the hull, ρ w is the water density, and C f is the skin friction coefficient for turbulent flow, the order of magnitude of which is C f ~ 10 −2   35 . Note the two terms in the square brackets: the first accounts for the drag experienced by the hull frontally, as a blunt body, and the second is due to the fluid friction along the hull. As we show later in the discussion of Fig.  2 , the forces that propel the boat can vary depending on the angle of attack.

Two cases showing the relationship between wind speed (W), apparent wind speed (A), boat speed (S) and apparent wind angle (β). The sails are trimmed to account for apparent wind angle.

From the balance between F w and F a emerges the ratio V w /V a , which is larger when the quantity in square brackets in Eq. ( 2 ) is smaller. This quantity varies in accord with the two aspect ratios of the configuration, D x /D y and D x /L, subject to the displaced volume of water (D x D y L), which is fixed because it is dictated by the total weight of the boat. It is easy to show analytically that the quantity in the square brackets in Eq. ( 2 ) is minimum when

This settles the question of the shape of the hull and that of most fish: they should be slender in profile, and relatively round when viewed in cross section.

What about the shape of the sail? When the aspect ratios of Eqs. ( 3 , 4 ) apply, the drag force in the water [Eq. ( 2 )] becomes

From the balance between Eqs. ( 1 ) and ( 5 ) we deduce that

which in view of C D ~ 1, C f ~ 10 −2 , and ρ w /ρ a ~ 10 3 , becomes

In the evolutionary pursuit of higher boat speeds V w , the height of the sail approaches the length of the hull. Expressed in terms of scale analysis, the conclusion is that H and L must have the same scale because V w and V a represent the same scale (no wind, no travel; fast wind, fast travel).

With the three aspect ratios now predicted (D x /D y , L/D x , H/L) the evolutionary direction of the boat model selected in Fig.  1 is complete, and can be drawn in three dimensions. The shape viewed from above is L/D x , while from the front and from the side it is respectively D x /D y and H/L. There are only three shapes because the configuration of the simplest model (Fig.  1 ) has only three degrees of freedom. Each of these shapes refers to the external look of the model.

Boat designs are more complicated because in addition to external shape they also have internal structure. The internal structure has additional geometric details, which have increased in number during boat evolution. Three frames from this evolutionary sequence are aligned chronologically in Fig.  3 , from two thousand years ago (Egyptian galley) to Columbus crossing the Atlantic (1492) and Napoleon’s navy (1800). In antiquity the internal structure was the simplest: one mast supporting one sail. Over time, the sails and the masts became more numerous as the speed and carrying capacity of the boats increased for the benefit of the people who constructed, owned and operated them. Modern monohulled sailboats align more with the Egyptian galley in that there is typically a single mast. The fastest monohulls in the world have a single mast and achieve maximum speeds with 2–3 sails.

The evolution of boats with sails over the past two thousand years: Egyptian galley, Columbus and Napoleon.

In Fig.  3 the three boats are presented in frames of the same size in order to stress two additional points. In time, the complexity of the architecture increases as the internal structure morphs. Yet, in every frame the external shapes are the same as those that we predicted for the simplest model without internal structure (Fig.  1 ).

Features of internal structure can be predicted by continuing the analysis started in Eqs. ( 1 – 7 ). Assume that the lone sail in Fig.  1 is supported by one mast, which is modeled as an elastic rod of height H and diameter d. The mast bends under the horizontal force received from the sail, which is F a , Eq. ( 1 ). The mast is a beam in pure bending, because it is slender enough so that its slenderness H/d exceeds 50.

The highest stresses occur at the base of the mast, where the bending moment is maximum and of order F a H. This moment is balanced by the moment due to the nonuniform distribution of stresses in the mast cross section. The stresses are tensile on the forward (convex) side of the mast in bending, and compressive on the aft (concave) side. If the material is such that σ is the order of magnitude of the highest allowable (tensile and compressive) stresses at the base, then the bending couple in the cross section is of order σd 2  × d, where the σd 2 are the forces of the couple (tensile and compressive, both aligned with the mast) and d is the arm of the couple, which is transversal to the mast. From the requirement of rotational equilibrium, F a H ~ σd 3 , we obtain

which, in view of Eq. ( 7 ), becomes

To summarize, the predicted evolutionary design has the three external shapes discussed previously, plus one internal shape, d/H, the mast slenderness. One formula, Eq. ( 9 ), governs the evolution of this technology, past and future. A stronger material (larger σ) makes a more slender (thinner, lighter) mast, which in turn decreases the dead weight of the vessel (and the submerged portion of the hull), reduces hull friction and increases the boat speed.

Comparison with Current Designs

In the modern era, physics principles have played a guiding role in the improvements that have been made in the design of boats with sails. The icon of the central role of physics in boat design is Euler’s entry 36 in the 1727 contest for the King’s prize for the solution to the nautical problem to determine the best way to place the masts on vessels, and the relation between their positions and the number and height of the masts. Since then, fluid dynamics and naval engineering grew as scientific domains, as did naval vessel technology before and after the advent of steam power 37 , 38 , 39 , 40 , 41 , 42 . In this section we compare the current state of sail boat architecture with the design features predicted theoretically.

Table  1 consists of 96 single hulled sailboats with a variety of models, years, dimensions, weights, and designs 43 . The variables D x, D y, L, and H correlate to Beam, Hull Depth, Overall Length, and Height, respectively, which are defined in Fig.  4 . The displacement [kg] is the mass of the boat, which is equal to the mass of the water that is displaced by the boat.

The main dimensions used in yacht construction.

PHRF is the performance indicator, which stands for Performance Handicap Racing Fleet. PHRF is a handicapping standardization that equates the performance of different boats. It is designed to rate the boat design characteristics only, and is impartial to the talent of the skipper and crew. With this in mind, the skipper and crew who sail the best overall race from boat handling and tactical perspective should be awarded as the victors.

Boats are given PHRF ratings based on empirical data including dimensional characteristics, materials, past race finishes, similar boats scaling, and comparisons to other handicap systems. The PHRF system also accounts for three ranges of wind conditions (light, moderate, heavy breeze) by utilizing distinct constants for the ratings formula. Like all handicapping systems, PHRF is imperfect due to the opportunity to inject subjectivisms but is the most-widely accepted handicapping systems in the U.S.

For the scope of this article, it should be known that the lower or negative ratings correlate to faster boats. For instance, the fastest boat in Table  1 is the DK 46 with a PHRF rating of 30, and the slowest is the Bullseye with a rating of 360. In moderate conditions, the DK 46 should be 1.75 times faster boat-for-boat than the Bullseye when utilizing the correction factor formula. The correction factor is then applied to the overall time, generating a “corrected time” that generates a one-to-one comparison between the different boats. The boat with the lowest corrected time is the winner of the race.

Plotted in Figs.  5 – 7 are the actual measurements extracted from Table  1 . The three figures show the aspect ratios D x /D y , L/D x and H/L versus the boat displacement. Noteworthy is that the three aspect ratios do not depend on the displacement. This means that the main aspects of the configuration did not change over time, as the displacement increased in history (cf. Fig.  3 ).

The ratio D x /D y (beam/draft) according to the data presented in Table  1 .

The ratio L/D x (overall length/beam) according to the data presented in Table  1 .

The ratio H/L (height/overall length) according to the data presented in Table  1 .

The results provided by Eqs. ( 3 ), ( 4 ) and ( 7 ) predict the convergent evolution observed in Figs.  5 – 7 . The geometrical ratios that define the shape of the boats with sails are permanent characteristics over the ages and cultures.

Due to the number of unique designs, calculating the exact performance of a yacht is dependent on a significant number of intrinsic properties as well as external factors. Different boats achieve peak performances at specified degrees from the wind direction in specific conditions. ‘Degrees’ refers to the boat pointing angle relative to the true wind direction. Ultimately, as the boat moves faster and increases the apparent wind velocity (wind speed plus boat speed), the apparent wind angle becomes small relative to the true wind angle.

The fastest boats in the world are almost always sailing ‘upwind’ (with sails pulled in closer to the hull mid-line) because they can generate significant boat speed relative to the wind speed. This phenomenon is depicted in Fig.  2 . Note the two distinct instances, where the boat speed (S 1  < S 2 ) and the angle of attack (β 1  > β 2 ) change, while the true wind speed W is constant. The apparent wind vector A increases with the boat speed when the boat direction and the true wind vector do not change. The sail’s (or airfoil’s) leading edge will point in the direction of the apparent wind to generate lift. As the boat speed continues to increase, the apparent wind angle moves forward until the sail is pulled to centerline (cf., Fig.  2 ), at which point the boat has reached is maximum speed for its relative boat angle from the true wind direction.

There are various calculations to generate boat speed using a characteristic dimension. One example is the critical velocity or \({{\rm{V}}}_{{\rm{c}}}\cong 1.25\,{({\rm{LWL}})}^{1/2}\) . This formula follows from the fact that the bow of a sailboat moving through the water produces a transverse wave, and at critical velocity the wave extends the length of the waterline, which essential traps the boat in the trough, not allowing it to escape the transverse wave, and so capping its velocity. There are various circumstances that can allow a boat to go faster than V c, such as “surfing” external waves or utilizing hydro-foils to lift the hull out of the water.

Bejan, A. Freedom and Evolution: Hierarchy in Nature, Society and Science (Springer Nature, Switzerland AG, 2020).

Book   Google Scholar  

Kakac, S. Evolution of the science of thermodynamics: the history. J. Thermal Science and Technology 36 (2), 1–6 (2016).

Google Scholar  

Bejan, A. & Lorente, S. The constructal law and the evolution of design in nature. Phys. Life Rev. 8 , 209–240 (2011).

Article   ADS   Google Scholar  

Basak, T. The law of life: The bridge between Physics and Biology. Phys. Life Rev. 8 , 249–252 (2011).

Delgado, J. M. P. Q. The constructal law: from man-made flow systems to pedestrian flows. Phys. Life Rev. 10 , 197–198 (2013).

Article   ADS   CAS   Google Scholar  

Reis, A. H. Constructal theory: From engineering to physics, and how flow systems develop shape and structure. Appl. Mech. Rev. 59 , 269–282 (2006).

Chen, L. Progress in the study on constructal theory and its applications. Sci. China, Ser. E: Technol. Sci. 55 (3), 802–820 (2012).

Article   Google Scholar  

Reis, A. R. Design in nature, and the laws of physics. Phys. Life Rev. 8 , 255–256 (2011).

Kasimova, R. Optimal shape of anthill dome: Bejan’s constructal law revisited. Ecological Modelling 250 , 384–390 (2013).

Wang, L. Universality of design and its evolution. Phys. Life Rev. 8 , 257–258 (2011).

Ventikos, Y. The importance of the constructal framework in understanding and eventually replicating structure in tissue. Phys. Life Rev. 8 , 241–242 (2011).

Lucia, U., Ponzetto, A. & Deisbroeck, T. S. A thermo-physical analysis of the proton pump vacuolar-ATPase: the constructal approach. Nature Scientific Reports 4 , 6763 (2014).

Miguel, A. The emergence of design in pedestrian dynamics: locomotion, self-organization, walking paths and constructal law. Phys. Life Rev. 10 , 168–190 (2013).

Kasimova, R. G., Tishin, D. & Kacimov, A. R. Streets and pedestrian trajectories in an urban district: Bejan’s constructal principle revisited. Physica A 410 , 601–608 (2014).

Article   ADS   MathSciNet   Google Scholar  

Mavromatidis, L. E., Mavromatidi, A. & Lequay, H. The unbearable lightness of expertness or space creation in the “climate change” era: a theoretical extension of the “constructal law” for building and urban design. City Cult. Soc. 5 , 21–29 (2014).

Miguel, A. F. Natural flow systems: acquiring their constructal morphology. Int. J. Design Nature & Ecodynamics 5 , 230–241, https://doi.org/10.2495/DNE-V5-N3-230-241 (2010).

Kacimov, A. R., Klammler, H., Il’yinskii, H. & Hatfield, K. Constructal design of permeable reactive barriers: groundwater – hydraulics criteria. J. Eng. Math. 71 , 319–338 (2011).

Article   MathSciNet   Google Scholar  

Reis, A. H. & Gama, C. Sand size versus beachface slope—an explanation based on the constructal law. Geomorphology 114 (3), 276–283 (2010).

Miguel, A. F. The physics principle of the generation of flow configuration. Physics of Life Reviews 8 , 243–244, https://doi.org/10.1016/j.plrev.2011.05.010 (2011).

Article   ADS   PubMed   Google Scholar  

Miguel, A. F. & Rocha, L. A. O. Tree-shaped Fluid Flow and Heat Transfer. Cham, Switzerland: Springer; 2018.

Lorenzini, G., Moretti, S. & Conti, A. Fin Shape Optimization Using Bejan’s Constructal Theory (Morgan & Claypool Publishers, 2011).

Rocha, L. Convection in Channels and Porous Media: Analysis, Optimization, and Constructal Design (VDM Verlag, Saarbrücken, 2009).

Lorenzini, G. & Biserni, C. The Constructal law: From design in nature to social dynamics and wealth as physics. Phys. Life Rev. 8 , 259–260 (2011).

Reis, A. H., Miguel, A. F. & Aidin, M. Constructal theory of flow architecture of the lungs. Med. Phys. 31 , 1135–1140 (2004).

Article   CAS   Google Scholar  

Miguel, A. F. Constructal pattern formation in stony corals, bacterial colonies and plant roots under different hydrodynamics conditions. J. Theor. Biol. 242 , 954–961 (2006).

Bejan, A. Why the bigger live longer and travel farther: animals, vehicles, rivers and the winds. Nature Scientific Reports 2 , 594, https://doi.org/10.1038/srep00594 (2012).

Bejan, A., Ziaei, S. & Lorente, S. Evolution: Why all plumes and jets evolve to round cross sections. Nature Scientific Reports 4 , 4730, https://doi.org/10.1038/srep04730 (2014).

Bejan, A., Lorente, S., Yilbas, B. S. & Sahin, A. Z. Why solidification has an S-shaped history. Nature Scientific Reports 3 , 1711, https://doi.org/10.1038/srep01711 (2013).

Bejan, A. Maxwell’s demons everywhere: evolving design as the arrow of time. Nature Scientific Reports 4 , 4017, https://doi.org/10.1038/srep04017 (2014).

Article   ADS   CAS   PubMed   Google Scholar  

Bejan, A. & Périn, S. Constructal theory of Egyptian Pyramids and flow fossils in general, section 13.6 in A. Bejan, Advanced Engineering Thermodynamics , 3 rd ., Wiley, Hoboken, 2013.

Bejan, A. Why humans build fires shaped the same way. Nature Scientific Reports 5 , 11270, https://doi.org/10.1038/srep11270 (2015).

Bejan, A., Charles, J. D. & Lorente, S. The evolution of airplanes. J. Appl. Phys. 116 , 044901 (2014).

Chen, R., Wen, C. Y., Lorente, S. & Bejan, A., The evolution of helicopters. J. Appl. Physics , 120 , article 014901 (2016).

Bejan, A. The Physics of Life: The Evolution of Everything (St. Martin’s Press, New York, 2016).

Fossati, F. Aero-Hydrodynamics and the Performance of Sailing Yachts , International Marine/McGraw-Hill First Edition, Camden, Me (2009).

Leonhard Euler’s 1728 Essay to the French Royal Academy: E004, translated & annotated by Ian Bruce from Meditationes super problemate nautico de implantatione malorum, quæ proxime accessere. Ad premium anno 1727 à Regia Scientiarum Academia promulgatum , Paris, 1728.

Daniel Bernoulli, Hydrodynamics, translated by T. Carmody and H. Kobus (Dover, New York, 1968).

Johann Bernoulli, Hydraulics , translated by T. Carmody and H. Kobus (Dover, New York, 1968).

Lazare Carnot, Essai sur les Machines en Général (Dijon, 1783).

Gillispie, C. C. Lazare Carnot, Savant (Princeton University Press, Princeton, NJ, 1971).

Prandtl, L. Essentials of Fluid Dynamics (Blackie & Son, London, 1952).

Cardwell, D. S. L. From Watt to Clausius (Cornell University Press, Ithaca, NY, 1971).

Sailboat Data Compare Boats, https://sailboatdata.com/sailboat , Accessed: July 2016.

Download references

Author information

Authors and affiliations.

Duke University, Department of Mechanical Engineering and Materials Science, Box 90300, Durham, NC, 27708-0300, USA

Lockheed Martin Space, 12257 South Wadsworth Boulevard, Littleton, CO, 80125, USA

Villanova University, Department of Mechanical Engineering, Villanova, PA, 19085, USA

You can also search for this author in PubMed   Google Scholar

Contributions

A.B. and S.L. developed the theory, wrote the manuscript, and made Figures 1 and 3; L.F. collected the boats data (Table 1), contributed to the manuscript, and drew Figures 2 and 4–7.

Corresponding author

Correspondence to A. Bejan .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

Bejan, A., Ferber, L. & Lorente, S. Convergent Evolution of Boats with Sails. Sci Rep 10 , 2703 (2020). https://doi.org/10.1038/s41598-020-58940-5

Download citation

Received : 02 October 2019

Accepted : 17 January 2020

Published : 17 February 2020

DOI : https://doi.org/10.1038/s41598-020-58940-5

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

This article is cited by

Locomotion rhythm makes power and speed.

• H. Almahmoud

Scientific Reports (2023)

By submitting a comment you agree to abide by our Terms and Community Guidelines . If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Service Locator

• Angler Endorsement
• Boat Towing Coverage
• Mechanical Breakdown
• Insurance Requirements in Mexico
• Agreed Hull Value
• Actual Cash Value
• Liability Only
• Insurance Payment Options
• Claims Information
• Towing Service Agreement
• Membership Plans
• Boat Show Tickets
• BoatUS Boats For Sale
• Membership Payment Options
• Consumer Affairs
• Boat Documentation Requirements
• Installation Instructions
• Shipping & Handling Information
• Contact Boat Lettering
• End User Agreement
• Frequently Asked Questions
• Vessel Documentation
• BoatUS Foundation
• Government Affairs
• Powercruisers
• Buying & Selling Advice
• Maintenance
• Tow Vehicles
• Make & Create
• Makeovers & Refitting
• Accessories
• Electronics
• Skills, Tips, Tools
• Spring Preparation
• Winterization
• Boaters’ Rights
• Environment & Clean Water
• Boat Safety
• Navigational Hazards
• Personal Safety
• Batteries & Onboard Power
• Motors, Engines, Propulsion
• Best Day on the Water
• Books & Movies
• Communication & Etiquette
• Contests & Sweepstakes
• Colleges & Tech Schools
• Food, Drink, Entertainment
• New To Boating
• Travel & Destinations
• Watersports
• Anchors & Anchoring
• Boat Handling
• ← Technology

Create Power While Under Sail

Advertisement

Want to keep your sailboat's batteries charged without a generator or running the engine? A hydrogenerator might be the solution.

Modern hydrogenerators are lightweight and generate an impressive amount of battery charging power.

Sailors tend to use their engines far less than the average powerboater, and this creates an immediate problem of how to satisfy a boat's electrical needs. Lighting, electronics, refrigeration, and entertainment systems all require electricity to operate — all demands placed on the boat's battery bank. Solar panels, wind generators, and diesel generators have their place, but all have drawbacks.

I faced such a challenge many years ago on my first Atlantic crossing. We wondered how we were going to keep the batteries charged. By today's standards our electrical demands were modest, but we had no diesel generator. We calculated that we would need to run our main engine for two to three hours per day, a very inefficient and noisy way to charge the battery bank. Solar panels were rejected solely on cost, and there was no convenient place on the old ketch for a wind generator. Ultimately we settled for a "towed generator" — a small propeller at the end of a stiff line was trailed behind the boat, which turned a generator mounted on the back deck of the boat.

Watt and Sea's hydrogenerators are usually fastened on the transom. The lifting up and down is similar to a rudder blade's handling.

Modern iterations of the hydrogenerator are far more compact and easier to deploy. There are several manufacturers, but all use the same basic principle: they transform water flow energy into electricity using an alternator. Looking like a cross between a small outboard motor and a retractable rudder, modern systems are capable of putting out impressive amounts of power with minimum drag. In fact, all the boats in the last Vendée Globe race used hydrogenerators for producing all of their electrical energy needs. This made crucial weight savings by not requiring a heavy generator and the associated fuel tank.

Watt and Sea Hydrogenerator

In this video, you can watch one of the popular Watt and Sea units being towed behind a fairly modest sailboat. At 8 knots of boat speed in 14 knots of wind, the unit is putting out an impressive 16 amps of power. Price depends on which unit you choose, but expect to pay around $3,000 for a complete system.

• Watt and Sea
• Sail-Gen – Dedicated Water Generator
• Hydrogenerator Save Marine H240

Related Articles

The truth about ceramic coatings for boats.

Our editor investigates the marketing claims of consumer-grade ceramic coatings.

Fine-Tune Your Side Scan Fishfinder

Take your side-scanning fishfinder off auto mode, and you’ll be spotting your prey from afar in no time

DIY Boat Foam Decking

Closed-cell foam flooring helps make boating more comfortable. Here’s how to install it on your vessel

Click to explore related articles

Contributing Editor, BoatUS Magazine

A marine surveyor and holder of RYA Yachtmaster Ocean certification, BoatUS Magazine contributing editor Mark Corke is one of our DIY gurus, creating easy-to-follow how-to articles and videos. Mark has built five boats himself (both power and sail), has been an experienced editor at several top boating magazines (including former associate editor of BoatUS Magazine), worked for the BBC, written four DIY books, skippered two round-the-world yachts, and holds the Guinness World Record for the fastest there-and-back crossing of the English Channel — in a kayak! He and his wife have a Grand Banks 32.

BoatUS Magazine Is A Benefit Of BoatUS Membership

Membership Benefits Include:

Subscription to the print version of BoatUS Magazine

4% back on purchases from West Marine stores or online at WestMarine.com

Discounts on fuel, transient slips, repairs and more at over 1,200 businesses

Deals on cruises, charters, car rentals, hotel stays and more…

All for only $25/year!

We use cookies to enhance your visit to our website and to improve your experience. By continuing to use our website, you’re agreeing to our cookie policy.

To revisit this article, visit My Profile, then View saved stories .

• Backchannel
• Newsletters
• WIRED Insider
• WIRED Consulting

Jack Stewart

The Funky Boat Circling the Planet on Renewable Energy and Hydrogen Gas

Victorien Erussard, an experienced ocean racer from the city of Saint-Malo in the north of France, was halfway through a dash across the Atlantic when he lost all power. Sails kept the boat moving, but Erussard relied on an engine and generator to keep the electronics running. He temporarily lost his autopilot and his navigation systems, jeopardizing his chances of winning the 2013 Transat Jaques Vabre race.

Never again, he thought. “I came up with the idea to create a ship that uses different sources of energy,” he says. The plan was bolstered by the pollution-happy cargo ships he saw while crossing the oceans. "These are a threat to humanity because they use heavy fuel oil."

Five years on, that idea has taken physical form in the Energy Observer , a catamaran that runs on renewables. In a mission reminiscent of the Solar Impulse 2, the solar-powered plane that Bertrand Picard and André Borschberg flew around the world a few years back , Erussard and teammate Jérôme Delafosse are planning to sail around the planet, without using any fossil fuel. Instead, they'll make the fuel they need from sea water, the wind, and the sun.

The Energy Observer started life as a racing boat but now would make a decent space battle cruiser prop in a movie. Almost every horizontal surface on the white catamaran is covered with solar panels (1,400 square feet of them in all), which curve gently to fit the aerodynamic contours. Some, on a suspended deck that extends to the sides of the vessel, are bi-facial panels, generating power from direct sunlight as well as light reflected off the water below. The rear is flanked by two vertical, egg whisk-style wind turbines, which add to the power production.

Propulsion comes from two electric motors, driven by all that generated electrical energy, but it’s the way that’s stored that’s clever. The Energy Observer uses just 106-kWh (about equivalent to a top-end Tesla) of batteries, for immediate, buffer, storage and energy demands. It stores the bulk of the excess electricity generated when the sun is shining or the wind is blowing as hydrogen gas. An electrolyzer uses the current to spilt the water into hydrogen and oxygen. The latter is released into the atmosphere, and the H2 is stored in eight tanks, made from aluminum and carbon fiber, which can hold up to 137 pounds of compressed hydrogen. When that energy is needed, the H2 is run through a fuel cell and recombined with oxygen from the air to create electricity, with water as a byproduct. That’s the same way fuel cell cars, like the Honda Clarity and Toyota Mirai work.

By storing energy this way instead of with banks of batteries, Erussard made the Energy Observer three times lighter than the similarly sized MS Tûranor PlanetSolar, which became the first boat to circumnavigate the globe using only solar power in 2012.

And the new vessel is kind to the ears as well as the planet. “There’s zero sound pollution, it’s a true pleasure to navigate on this vessel,” Erussard said on stage at the recent Movin’On future mobility conference in Montreal, Canada.

Inside there’s a gleaming white helm, with two captains chairs, and living quarters that wouldn’t look out of place in 2001: A Space Odyssey , with an almost harshly minimalist white design. The team designed the furnishings to be as light as possible too, because a lighter boat uses less energy, and so is more efficient.

The team isn’t rushing things. The mission started in June 2017, and will last six years, reach 50 countries, and make 101 stops. The vessel has already travelled 7,000 nautical miles, to port cities around the French coast, and is now in the Mediterranean. It’s due to arrive in Venice on July 6, and spend 10 days in port, where the crew will meet the public, and set up an interactive exhibit to showcase environmentally friendly technologies.

“The idea with this ship is to prove a potential energy system of the future,” Erussard says. He’s determined that the same types of energy generation and storage that he’s using onboard could be used on land too, to reduce dependence on fossil fuels, and maybe one day to clean up those container ships he'll pass en route.

• PHOTO ESSAY: These flowers are actually fireworks
• How Tesla is building cars in its parking lot
• The new arms race threatening to explode in space
• How technology helped me cheat dyslexia
• The next generation of Wi-Fi security will save you from yourself
• Hungry for even more deep-dives on your next favorite topic? Sign up for the Backchannel newsletter

Matt Reynolds

Jeremy White

Reece Rogers

Aarian Marshall

Sabrina Weiss

Scott Gilbertson

Mark Andrews

Brenda Stolyar

Rhett Allain

Parker Hall

Advertisement

Sustainable energy propulsion system for sea transport to achieve United Nations sustainable development goals: a review

• Open access
• Published: 06 April 2023
• Volume 4 , article number  20 , ( 2023 )

Cite this article

You have full access to this open access article

• Zhi Yung Tay 1 &
• Dimitrios Konovessis 2  

5188 Accesses

8 Citations

2 Altmetric

Explore all metrics

The cost of renewable energy technologies such as wind and solar is falling significantly over the decade and this can have a large influence on the efforts to reach sustainability. With the shipping industry contributing to a whopping 3.3% in global CO 2 emissions, the International Maritime Organization has adopted short-term measures to reduce the carbon intensity of all ships by 50% by 2050. One of the means to achieve this ambitious target is the utilisation of propulsion systems powered by sustainable energy. This review paper summarises the current state of the adoption of renewable energy and alternative fuels used for ship propulsion. Special focus is given to the means of these alternative energies in achieving the United Nations Sustainable Development Goals, in particular Goal 7 (Affordable and Clean Energy), Goal 9 (Industry, Innovation and Infrastructure) and Goal 13 (Climate Action). A state-of-the-art for various ships powered by renewable energy and alternative fuels is investigated and their technologies for mitigating carbon emissions are described. The cost for each technology found in the literature is summarised and the pros and cons of each technology are studied.

Similar content being viewed by others

Putting the Pieces Together for Sustainable Shipping

Energy Transition in Maritime Transport: Solutions and Costs

Energy Efficiency and Management Onboard Ships

Avoid common mistakes on your manuscript.

1 CO 2 emission trends

1.12 billion metric tons of carbon dioxide (CO 2 ) were released by ocean-going vessels in 2007 [ 1 ]. This value was equivalent to the annual greenhouse gas (GHG) emissions from over 205 million cars [ 1 ]. In addition, international shipping contributed to around 3.3% of global annual CO 2 emissions calculated in the third greenhouse study by the International Maritime Organisation (IMO) [ 2 ]. Since global trade is constantly growing, IMO also predicted that the emissions from international shipping could grow between 50 and 250% by 2050 [ 3 ].

Based on the data found on IEA’s website that track the CO 2 emissions from international shipping [ 4 ], the emission reduction was not on track with the IMO’s goal. The emission rate from the shipping fleet alone was about 800 million metric tonnes of CO 2 in 2019, 794 million metric tonnes in 2020 and increased to 833 million metric tonnes in 2021 [ 5 ]. This trend was not consistent with the goals set by the IMO and thus alternative energy sources have to be sought to support and work towards the goal of cutting CO 2 emissions by 50% by 2050 [ 2 ].

The maritime industry contributes to over 90% of shipping all around the world [ 6 ]. With an estimated emission of around 1,056 million tonnes of CO 2 in 2018, the maritime industry itself was responsible for 2.89% of global GHG emissions [ 7 ]. However, with the onset of new renewable technologies and alternative fuels, the emissions from the maritime industry are expected to be cut down significantly. The industrial revolution for ship propulsion led to innovative technologies such as steamships and the introduction of coal, followed by new generation ships powered by oil. The 4 th industrial revolution for ship propulsion will see the use of clean energy in the evolution and growth of the shipping industry. Currently, thanks to the mission set by IMO, ships using heavy fuel oil (HFO) that produce GHG such as Sulphur Oxides (SO x ) and Nitrogen Oxides (NO x ) were required to reduce their sulphur content to 0.5% or less in 2020 [ 8 ]. Furthermore, stricter measures were put in place in Emission Control Areas (ECA) such as the North Sea and the coast of the United States, designated under the MARPOL Annex V1 [ 9 ]. Technology has also evolved, and shipping companies are considering various methods to achieve the intended zero emissions in their ships, such as using electric propulsion ships loaded with batteries, and next-generation marine fuels such as hydrogen, ammonia and biofuel. Furthermore, the use of wind and solar power is also being considered as a hybrid propulsion system integrated with conventional diesel-powered vessels to reduce fuel consumption and carbon emissions.

According to a report by International Energy Agency [ 10 ], the current policy framework estimates that low- and zero-carbon fuels are projected to make up roughly 2% of total energy consumption in international shipping in 2030 and 5% in 2050 [ 10 ]. This falls severely short of the 15% in 2030 and 83% in 2050 set in the Net Zero Scenario [ 10 ]. To reduce emissions, other renewable energy technologies need to be implemented such as the technology of using ammonia as the fuel source for international shipping, which is the main low-carbon fuel that is projected to reduce emissions in the Net Zero Emissions Scenario [ 10 ]. The various initiatives to decarbonise the shipping industry in alignment with the UN SDGs are provided in the next section.

2 Sea transportation and United Nations Sustainable Development Goals

The shipping industry and research community have been actively seeking means to reduce GHG emissions since the initial strategy for the reduction of GHG emissions from ships was adopted by IMO in 2018. Various methodologies and technologies were proposed such as via the installation of exhaust gas cleaning systems [ 11 , 12 ] (EGCS, also known as scrubbers), slow steaming [ 13 , 14 ], achieving fuel efficiency using big data and machine learning systems [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ], optimization of ship engineering design [ 23 , 24 , 25 ], innovative ship design to reduce ship resistance [ 26 , 27 ] and many more. Numerous state-of-the-art reviews on the utilisation of alternative fuel (AF) and renewable energy (RE) in the maritime industry in achieving the climate target have been covered, e.g., in [ 28 , 29 , 30 ]. Law et al . [ 31 ] made a comparison of AF for shipping in terms of lifecycle energy and cost and reviewed 22 potential pathways toward decarbonisation of the shipping sector. Wang et al . [ 32 ] summarised the low and zero-carbon fuel technologies of marine engines and proposed the future development of low and zero-carbon ships. A techno-economic assessment of alternative marine fuels for inland shipping was presented by Percic et al. [ 33 ], Korberg et al. [ 34 ] and Fam et al. [ 34 ] where the Percic et al . [ 33 ] article highlighted that methanol as the most economical AF. The usage of AF and technologies for short-sea shipping were also covered in [ 35 , 36 ]. The current state of ship propulsion and alternative options from the aspects of costs, infrastructure, regulations etc. in achieving decarbonisation by 2050 were highlighted in [ 37 ]. A comprehensive review of the means to decarbonise the shipping industry via assessment of fuels, efficiency measures and policies was highlighted in [ 38 , 39 ]. The articles suggested that LNG must be combined with various efficiency measures to meet the 50% climate target whereas wind assistance presents a strong potential to reduce fuel consumption.

While numerous review articles touched on the utilization of RE and AF in the maritime industry from the techno-economical, fuel efficiencies, policies etc. points of view, this review article is motivated by the role the maritime industry could play in achieving the United Nations (UN) Sustainable Development Goals (SDGs) to eradicate poverty and achieve sustainable development by 2030 via the use of RE and AF. Set up in 2015 and adopted by the UN Member State, the UN SGDs are a collection of 17 interlinked global goals designed to be a “shared blueprint for peace and prosperity for people and the planet, now and into the future” [ 40 ]. The IMO as part of the UN family is actively working towards the 2030 Agenda for Sustainable Development and the associated SDGs. The IMO has committed to reducing GHG from international shipping by at least 50% by 2050 compared to the 2008 level, with a vision to phase GHG out entirely in this century. Recognizing the fact that around 90% of traded goods are carried by sea transportation [ 41 ], there is no doubt that the 2030 Agenda for Sustainable Development could only be achieved with sustainable sea transportation.

The IMO has taken steps towards raising awareness of the UN SDGs in the maritime industry looking to further cooperation and partnership building to help implement the 2030 Agenda [ 42 ]. While the IMO has summarized the role of sea transportation in meeting the 17 SDGs, this review paper shall focus in particular on the adaptation of RE and AF to achieve SDG 7: Ensure access to affordable, reliable, sustainable and modern energy for all , SDG 9: Build resilient infrastructure, promote sustainable industrialisation and foster innovation and SDG 13: Take urgent action to combat climate change and its impact . These three SDGs are selected due to the urgent need to fight climate change and there has been a significant technology advancement utilising renewable and sustainable energy as ship propulsion systems. In this review paper, a comprehensive study will focus on the use of RE and AF to achieve SDG7, SDG9 and SDG13.

The paper will be organised into the following chapters: The paper will first summarise the state-of-the-art of the current RE- and AF-powered shipping vessels, their advantages and disadvantages. While the authors acknowledge that numerous comprehensive review articles have been attributed to this subject, this section that focuses on the RE and AF technologies, carbon and GHG reduction, and their pros and cons are necessary to be included to provide essential background for further discussion in Chapter 4. The utilization of RE and AF as the power sources for sea transportation as a means to tackle climate change (SDG13) is then outlined in Chapter 4. This is followed by a review of how these alternative sources of energy could be used to achieve SDG7, SDG9 and SGD13. Last but not least, a summary of the use of sustainable energy ship propulsion systems to achieve the UN SDGs is provided.

3 Technology review: renewable energy-and alternative fuel-powered propulsion systems for ships

According to the statistics of CO 2 emitted from various transportation means from 2000 to 2020 [ 43 ], shipping contributes to an average of 10.86% of total CO 2 emission from the transportation sector (see Fig.  1 ). Although this number is relatively small compared to other sectors, such as land transport (i.e., road freight vehicle, passenger vehicle and rail in Fig.  1 )—76.67%, and comparable to aviation—11.14% (note that these values are not plotted in Fig.  1 but calculated directly from the data obtained from [ 43 ]), the continuing growth of sea-borne goods transportation could result in a surge of global GHG emissions by 50% by 2050 if no initiatives are taken to mitigate the GHG emissions [ 44 ]. The shipping industry has been looking into RE and AF-powered propulsion systems as a means to achieve this goal. Renewable energies such as wind and solar produce power without releasing harmful GHGs like CO 2 into the atmosphere. As part of a global energy future, clean energy is important for the environment to reduce the risk of environmental disasters, such as fuel spills and natural gas leaks arising from the traditional use of hydrocarbon fuel. On the other hand, AF—any fuels that are not petroleum based—such as liquified natural gas (LNG), hydrogen, ammonia, biofuels and methanol could play a significant role in mitigating carbon and other GHG emissions. Note that although it is possible to produce 100% clean ammonia and hydrogen from renewables, also known as green ammonia and green hydrogen respectively, these two fuels are classified as AF in this paper as they can also be produced from non-renewables and thus produces CO 2 and GHG emission in the production process.

Carbon emissions from various means of transportation [ 43 ]

In this section, the state-of-the-art technology review of the currently available RE and AF-powered shipping vessels will focus on the various types of technologies, their carbon and GHG emission, pros and cons as well as some examples of existing and conceptual designs to provide a background for facilitating the discussion in Sect.  3.7 . This section is not meant to provide comprehensive coverage of RE and AF for ship and interested readers may refer to the aforementioned review articles [ 28 , 29 , 30 , 31 , 32 , 33 , 37 , 45 ] and those listed in the following subsections for different RE and AF.

3.1 Renewable energy

The commonly used RE propulsion system found in ships are the wind, solar and nuclear propulsion system. These renewables are clean and produce zero-carbon emissions. Over the years, the efficiency of these renewable technologies has improved, and the costs have been reduced significantly making them potential clean sources of energy as alternatives to fossil fuels.

3.1.1 Wind propulsion

Wind energy has been harnessed since 3500 BC by the Egyptians [ 46 ] and allowed the realization of Magellan’s expedition 500 years ago which led to the first expedition to circumnavigate the globe. With the rising concern of global warming and climate change, naval architects and marine engineers have revisited this old concept of ship propulsion which has huge potential to address the modern-day’s challenge of GHG emissions.

The yearly-averaged wind speed around the major maritime route is reported to be around 2 to 6 m/s in the tropical region with increasing wind speed as it goes beyond the subtropical climate as shown in Fig.  2 [ 47 ]. This abundance of wind resources could be captured by wind energy-extracting technologies installed onboard the ship. An economic and operational review of wind-assisted ship propulsion technology is given in [ 48 ]. Depending on the type of wind energy technology installed onboard the ship, a fuel reduction of up to 90% and CO 2 emissions reduction of up to 80% could be achieved. Some of the wind-assisted propulsion system (WAPS) class notations adopted by DNV-GL [ 49 ] are presented in Fig.  3 . In this section, the focus is emphasized on three common technologies for the wind-powered/wind-assisted ship, i.e., (i) wing sail technology, (ii) Flettner rotor technology and (iii) kite technology.

Global yearly averaged wind speed in m/s at 100 m above sea level [ 47 ]

Common WAPS class notation and Standard ST-0511 by DNV [ 49 ]

(i) Wing sail technology

Wing sail technology is an adaptation to the earliest wind-assisted technology by propelling the ship using the soft sail, which is flexible and can be stowed when needed. The modern wing sail technology, also known as the hard sail, was inspired by the design of the wings of an aeroplane where the aerofoil shape has a better lift-to-drag ratio as compared to the traditional soft sail [ 50 ]. The installation of wing sails on a ship improves the aerodynamic performance by decreasing the drag, thus increasing the vessel’s speed [ 51 ]. Several commercial vessel proposals adopt various wing sail technologies to harness wind by different means, i.e., (a) hard sail (rigid wing sail) (b) soft sail and (c) airfoil hull.

(a) Hard sail (rigid wing sail)

An example of the hard sail wind propulsion system is the Oceanbird wind-driven cargo ship which relies 90% on wind energy to sail [ 52 ]. The remaining 10% of the auxiliary power requirement could be powered by clean energy such as liquid biogas. The installation of hard-wing sails is expected to save 90% of the fuel equivalent to a reduction of 90% in GHG emissions [ 53 ]. More wing sails could be installed on the ship to improve the performance in terms of speed of the vessel, e.g., a total of five wing sails were proposed to be installed on Oceanbird as shown in Fig.  4 a to achieve a speed of 17 knots, comparable to the speed of a fuel-powered ship [ 54 ]. The number of wing sails could be increased depending on the power requirement. E.g., the next-generation hybrid sailing cargo vessel—UT Challenger (Fig.  4 b) proposed by the University of Tokyo is equipped with nine 360-degree rotating hard-wing sails [ 55 , 56 ]. The power requirement and encountering wind speed from which the required Thrust \(T\) could be calculated as [ 51 ]

where \(\rho\) is the mass density of air, \(v\) the apparent wind speed, \(A\) the area of wing sail and \({C}_{T}\) the thrust coefficient.

Ships equipped with wind sail technology. a Ocean Bird ( www.theoceanbird.com ). b UT challenger ( www.wind-ship.org/en/utwindchallenger ). c B9 Sail ( www.b9energy.co.uk ). d Vindskip ( www.ladeas.no )

To tap on the maximum amount of wind energy, the height of the wing sail could also be elevated [ 52 , 55 ].

(b) Soft sail

Some naval architects have reconsidered the traditional soft sail in their future ship design due to the flexibility in retracting the sails when travelling in a location of low air draught or when wind resources are limited. The former allows the ship to pass through low bridges while the latter allows the reduction of ship resistance that might arise from the wing sails. Although the soft sail has a relatively lower performance compared to the rigid sail in terms of speed, the growing popularity of slow steaming makes this technology attractive as means for ship decarbonization. An example of a soft sail-powered vessel is the 100% fossil fuel-free cargo ship—B9 ship (Fig.  4 c). B9 ship is equipped with a hybrid system that uses wind energy and a biogas-powered engine where 60% of the power is harnessed by wind [ 57 ] whereas the remaining 40% is by liquid biomethane derived from municipal waste [ 57 , 58 ].

(ii) Flettner rotor technology

The Flettner rotor is an electric-powered rotating cylindrical structure built vertically on the deck of the ship [ 59 ]. As wind past through the rotating cylinder, this creates the Magnus effect where a lateral force perpendicular to the direction of the airstream is created and thus generates a forward thrust as shown inFig.  5 [ 60 ]. The first ship to be powered by vertical rotors was built by German engineer Anton Flettner, which later gave the name to the rotor. The Flettner rotors are one of the most common wind-assisted propulsion devices and have been adopted in diesel-powered commercial ships to reduce fuel costs and carbon emissions [ 61 ].

Working mechanism of Flettner rotor [ 60 ]

The Flettner rotor has shown promising results in reducing the fuel consumption and carbon emissions of ships. For instance, the fuel consumption of the Ro-ro cargo ship—E-Ship 1 (Fig.  6 a), was reported to reduce by 22.9% with the help of four 25-m high and 4-m diameter vertical Flettner rotors on a voyage between Emden and Portugal [ 59 ]. The use of two Flettner rotors on Norsepower’s Ro-ro carrier MV Estraden (Fig.  6 b) also managed to reduce fuel consumption by 5% [ 59 ] and carbon emissions by 1% [ 62 ].

Commercial ships equipped with Flettner rotors. a E-Ship 1 ( www.enercon.de ). b MV Estraden ( www.bore.eu ). c SC Connector ( www.nosrsepower.com ). d Berge Neblina and Berge Mulhacen ( www.anemoimarine.com ). e MV Copenhagen ( www.corvusenergy.com ). f Viking Grace ( https://www.airseas.com/ )

Similar to the rigid wing sails, ships installed with Flettner rotors might not be able to pass under bridges easily due to their air draught limitation. To overcome this problem, a tiltable Flettner rotor was thus invented such as the world’s first tiltable Flettner rotors fitted on the Ro-ro vessel—SC Connector [ 63 ] shown inFig.  6 c and the four ‘folding’ rotor sails on two bulk carriers, i.e., Berge Neblina and Berge Mulhacen [ 64 ] presented inFig.  6 d. The annual CO 2 emissions and fuel consumption are estimated to be reduced by almost 25% [ 63 ] for the SC Connector and by 1,200 to 1,500 tonnes for the two Berge vessels [ 64 ].

Flettner rotor wind sailing technology has also been adopted by passenger vessels, such as the MV Copenhagen (Fig.  6 e) and Viking Grace (Fig.  6 f) where both vessels are equipped with one Flettner rotor. The rotor sail in MV Copenhagen is estimated to cut down carbon emissions by 4 to 5% [ 65 , 66 ] which amounts to an estimated annual savings of 878,000 L of diesel [ 67 ]. The CO 2 emission reductions also add up to a total of 2,344 tons per year [ 67 ]. On the other hand, Viking Grace (Fig.  6 f) is the first passenger vessel to use 100% sulphur-free LNG [ 68 ]. This vessel also uses the energy recycling system which converts the excess heat from engines to clean and carbon emission-free electricity that adds up to 700,000 kWh per year [ 68 ].

(iii) Kite technology

Kite technology is one of the methodologies explored by Airseas in propelling the Ro-ro vessel [ 69 ]. A parafoil sail also known as an automated kite seawing has been built on the Ville de Bordeaux Ro-ro vessel (Fig.  7 ). The seawing system that has a surface area of 500m 2 and flies at an altitude of 300 m uses prevailing winds to propel the ship [ 69 ]. An automated flight control system and kite technology have been implemented together to develop the seawing [ 70 ]. This seawing system is expected to reduce fuel consumption and carbon emissions by 20% and it can be installed easily on any vessels [ 66 , 70 ]. To maximize fuel savings, digital twin technology is employed, and route optimization algorithms are developed to aid in weather routing [ 70 ] and to optimize the energy harness at its wind direction and speed.

An automated kite Seawing built on Ville de Bordeaux ( www.bureauveritas.com )

Advantages and disadvantages of wind-powered/wind-assisted vessels

Out of the many potential RE, wind technology is a relatively matured technology and has been implemented in commercial vessels to reduce CO 2 and other GHG emissions. It is reported by DNV that the Flettner rotor could achieve an average fuel savings of 10%—30% and the wing sails can reduce environmental footprint by up to 45% [ 71 ]. Wind-assisted shipping technology causes the overall demand for fossil fuels to significantly reduce and thus lowers the overall operational costs of shipping to the consumer. The addition of the wind system in a vessel might be beneficial in ways such as it reduces engine and machinery wear and tear, as well as reducing machinery and structural vibration [ 48 ]. To maximize the benefits of the wind, weather routing using big data analytics and machine learning is being developed [ 72 ]. This will also reduce the disruptions by adverse weather conditions [ 73 ].

While wind power works well for smaller vessels, it is unpredictable for larger vessels. Although wind is a clean source of energy, abundance and completely free, it is unpredictable as the wind does not always blow in the direction and speed favourable to the ship's voyage. The amount of energy produced by the propeller depends on the speed of the wind [ 74 ]. Tall, wide-wing sails also have travel constraints when the ship is sailing under bridges and when the ship docks in tight ports [ 48 ]. Moreover, it is not yet ready for the ship propulsion system to be fully powered by the currently available wind technology. As the vessels required high wind speed to achieve higher energy efficiency, this may also cause ship stability and manoeuvring problems under rough sea conditions.

3.1.2 Solar propulsion

Solar energy is the cleanest and most abundance RE resource available. The total amount of solar radiation that reaches the earth's surface is given in Fig.  8 and is estimated to be in the range of 150 W/m 2 to 250 W/m 2 for the tropical to subtropical climate. When the sunlight reaches the earth's surface, this energy could be harnessed by the installation of solar technology such as solar photovoltaic (PV) panel that converts solar energy into electricity (see Fig.  9 ). Most commercial solar PV panels could achieve an efficiency between 15 to 20% while the cost of solar PV panels is also attractive between $2.60 to $3.20 per watt [ 75 ], thus making solar energy an attractive option in decarbonization. Solar panels have been added to the deck of shipping vessels in the quest to reduce CO 2 and other GHG emissions. According to the review article by Qiu et al. [ 76 ] on solar-powered vessels, ships equipped with solar PV panels are becoming one of the most promising and fastest-developing green ships. The following section shall review some of the solar technologies available in the market and examples of vessels equipped with solar PV panels. The advantages and disadvantages of the solar-powered vessel will be compared.

Surface downward solar radiation in W/m. 2 [ 47 ]

Power conversion mechanism for solar PV panel ( www.MrSolar.com )

There are two ways of powering vessels with solar PV technology. The first utilizes solar PV technology to supply electricity for handling all electrical loads whereas the second uses the hybridization of solar power with diesel engines, usually in huge vessels where high electrical loads are required [ 77 ]. Also, a hybrid system is needed as there may be insufficient space on the vessel’s deck for the installation of solar PV panels to meet the vessel’s power demands [ 77 ]. However, installing solar PV technology in vessels as part of the hybrid system is still advantageous because it is a relatively faster and simpler way to reduce fuel consumption and carbon emissions of ships.

It is possible to power passenger vessels solely with solar PV technology, e.g., the Solar Shuttle (Fig.  10 a) by SolarLab was the first vessel to depend on PV technology entirely [ 78 ]. This 42-passenger vessel does not emit carbon and eliminates the production of 2.5 tons of carbon emission annually compared to a similar-sized diesel boat [ 79 ]. India also has her first 75-passenger solar-powered ferryboat—Aditya (Fig.  10 b), capable of making 22 trips per day covering a total of 66 km [ 80 ]. This solar-supported vessel with energy storage batteries saves a total of 58,000 L of diesel.

Examples of solar-powered vessel. a SolarShuttle ( www.solarshuttle.co.uk ). b Aditya ( www.swtd.kerala.gov.in ). c Sun21 (ww.transatlantic21.org). d MS Turanor ( www.planetsolar.swiss ). e Solar Sailor ( www.change-climate.com ). f Blue Star Delos (bluestarferries.com)

Solar power has been shown to be a reliable renewable power source to provide a continuous power supply for vessels. E.g., A solar powered 6-passenger catamaran vessel—Sun21 (Fig.  10 c), equipped with PV panels on a flat rooftop became the first solar-powered vessel to cross the Atlantic in 2006 successfully whereas MS Turanor (Fig.  10 d), also a fully solar-powered catamaran, successfully circumnavigated the globe for 584 days from 2012 to 2014 [ 81 ]. Another interesting solar power-assisted ferry is the 100-passenger Solar Sailor (Fig.  10 e) which utilizes two types of RE, i.e., wind and solar to operate. The ferry has rigid sails which are covered with photovoltaic modules [ 78 ]. The sun and the wind are captured efficiently because of the rotatable sails. The propulsion system of the Solar Sailor is a hybrid system that uses electric and diesel to operate [ 78 ].

Marine solar power trials were also done on a larger passenger ferry – the 2,400-passenger Blue Star Delos (Fig.  10 f) to evaluate the use of solar power on commercial ships. By using a thin panel PV technology that was designed to withstand exposure to saltwater, the trial concluded that direct current (DC) load did receive a continuous stable supply of power from the energy storage of the low-voltage marine solar power system [ 82 ]. The build-up of dirt and salt was found to have minimal impact on the performance of the solar panels.

Advantages and disadvantages of solar power-assisted vessels

Although solar power could not completely power large commercial ships, it has been proven that it is possible to power harbour crafts such as ferries, tugboats and patrol vessels. Ferryboats used in tourism areas and other small vessels can be operated entirely by solar PV technology and this could lead to zero-carbon emissions in the tourism sector. The operational costs of a solar-powered vessel are cheaper compared to a conventional diesel-powered vessel, at the same time, the fuel consumption, carbon emissions and operational costs are significantly reduced. The best possible way to maximize the efficiency of the solar PV modules is by installing the solar PV panel on a flat roof top so that sunlight could be received without any obstructions. Additionally, the highest solar irradiation can also be captured by the panels.

Similar to wind energy, the weather conditions at the sea are unpredictable and research has yet to overcome the problem of stabilizing the output power of the ship’s propulsion system powered by solar. The efficiency of solar panels may be affected by the ambient temperature and the sun’s irradiation due to their high level of sensitivity [ 77 ]. Space for the installation of PV panels is a challenge as most ships have limited space. The photovoltaic modules also need to be placed at parts of the vessel which are greatly exposed to sunlight. The batteries, the total weight of the solar panels and other equipment may add to the overall weight of the vessel, and this may lead to ship stability issues [ 77 ].

3.1.3 Nuclear propulsion

Nuclear propulsion consists of a nuclear reactor where steam is produced from the heat exchanger to drive a turbine that then propels the vessel (see Fig.  11 ). Uranium is the most common and widely used fuel for a nuclear reactor and can be found easily in seawater and rocks, also known as Uranium ores [ 83 ]. Nuclear fuel made with Uranium extracted from seawater makes nuclear power completely renewable as Uranium extracted from seawater is replenished continuously, thereby making it an endless source of fuel supply like wind and solar. New technology breakthrough from DOE’s Pacific Northwest (PNNL) and Oak Ridge (ORNL) National Laboratories has made removing Uranium from seawater within economic reach [ 84 ].

Nuclear propulsion system ( www.man.fas.org )

The nuclear propulsion system has been used for other sea transports, especially in submarines and naval vessels. The nuclear propulsion system allows the vessels to be out in the ocean for a longer period without refuelling and this is important for submarines, naval vessels, or even ice-breakers that operate in extreme weather conditions. The world’s first nuclear-powered icebreaker – Lenin, was launched in 1959 and equipped with two OK-900 nuclear reactors [ 83 ]. The capacity of the reactors was 171 MWt each and the power delivered to the propellers is 34 MW [ 83 ]. Compared to the more recent nuclear-powered icebreaker built in 2017 – Sibir, the two 175 MWt reactors installed on the vessel can deliver 60 MW to the propellers [ 85 ], almost twice the performance as compared to its counterpart built in 1957. Considerations to utilize nuclear propulsion systems are made for merchant vessels due to their zero-carbon emissions and as a clean source of energy.

Gil et al . [ 86 ] have researched the technical and economic feasibility of nuclear propulsion systems installed in a passenger cruise ship. The vessel can utilize either the turbo-electric machinery system or the direct-drive steam turbine system to satisfy the overall power load of 81.4 MW [ 86 ]. For a conventional shaft-driven propulsion system, the direct-drive steam turbine system would be ideal whereas the turbo-electric machinery system would be more suitable if increased manoeuvrability and podded propulsion are required [ 86 ]. Interested readers on the advances in nuclear power system design may refer to [ 87 ] on the means to enhance the safety condition of nuclear-powered ships.

Advantages and disadvantages of a nuclear-powered vessel

Nuclear-powered vessels are mostly used for icebreaking as they are generally more powerful than conventional diesel-fuelled vessels [ 88 ]. According to Zerkalov [ 88 ], the amount of diesel fuel needed to perform icebreaking is about 90 metric tons of fuel daily compared to only 1 pound of Uranium required by a nuclear-powered vessel. Refuelling of a nuclear reactor only occurs once every five to seven years thereby this helps to save up heavily on fuel costs. More importantly, no GHG is produced when a vessel is sailing using the nuclear propulsion system.

However, health and safety factors remain the main reasons why vessels are slow to adopt nuclear-powered propulsion systems [ 83 ]. The risks of cancer and leukaemia are high due to the large doses of ionizing radiation and radioactive waste. The installation and maintenance costs of nuclear-powered vessels are also expensive [ 83 ].

3.2 Alternative fuels

Alternative fuels are potential fuel sources that could be used as alternatives to fossil fuels in decarbonizing the maritime industry. These fuels emit less CO 2 and GHG gas as compared to the conventional HFO or marine diesel fuel used in ship propulsion and have higher efficiency compared to the RE fuel source. Five commonly used AF, i.e., LNG, hydrogen, ammonia, biofuel and methanol are reviewed.

3.2.1 LNG fuel

LNG is one of the most environmentally friendly fossil fuels thereby making the use of LNG fuel attractive compared to the traditional HFO or marine diesel for ships [ 89 ]. LNG consists of 85 to 95% methane, along with 5–15% of ethane, propane, butane, and nitrogen. Although LNG is not that beneficial when compared to RE as it still emits carbon and traces of nitrogen oxide, it is better when compared to marine diesel as it produces less carbon and nitrogen oxide [ 90 ].

The technology of powering ships with LNG is not new and has been around for four decades [ 91 ]. According to the statistics provided by DNV, as of 2021, 251 vessels in operation use LNG as fuel and 403 in construction or confirmed [ 73 ]. The marine LNG engine uses the boil-off gas (BOF) evaporated from the liquid state when heat is introduced into the tank thereby causing the pressure in the tank to increase. The BOF may have to be released into the atmosphere by safety valves if the tank pressure gets too high due to liquid sloshing in the high sea. However, this BOF could also be routed to the ship's propulsion system and used as fuel for the power plant (see Fig.  12 ), which could reduce the fuel cost [ 92 ].

LNG fuel system with pump ( www.marine-service-noord.com )

LNG-powered vessels are gaining popularity and major ports in the world are in the process of upgrading with LNG bunkering facilities. While LNG bunker facilities are more readily available in Northern Europe, the LNG bunkering infrastructure that is required for the shipping industry is improving quickly in the Mediterranean, the Gulf of Mexico, the Middle East, China, South Korea, Japan and Singapore [ 93 ].

LNG marine propulsion systems are already in use in various vessels such as the passenger ferry—MF Glutra [ 94 , 95 ], offshore supply vessel—Viking Lady [ 95 ], and tanker—MR Tanker [ 95 ]. United Arab Shipping Corporation (UASC) has also built a massive container ship running on LNG fuel entirely [ 95 ]. The dual-fuel engines are used so that the vessel can run on LNG fuel and low-sulphur fuel oil to further reduce the CO 2 and GHG emissions. Calculations were also done for the GHG emissions, and it was reported that using a 100% LNG-powered propulsion system could reduce the CO 2 and NOx emissions by 25%, SOx by 97% and the amount of diesel particles in the atmosphere by 95% [ 95 ]. An overview of the characteristics of LNG is provided in [ 96 ].

Advantages and disadvantages of LNG fuel technology

Compared to conventional diesel oil engines, the LNG fuel system is cleaner and has a higher level of efficiency. The estimated cost for an LNG-powered vessel is 20 to 25% higher than a diesel-powered vessel [ 91 ], and the feedstock price of LNG is currently comparable with marine gasoil [ 97 ]. Moreover, the machinery of the LNG system has a longer lifespan and lower maintenance cost than an oil engine. More importantly, the carbon content in LNG is lower than diesel, therefore making LNG engines emit less CO 2 than traditional diesel engines. The technology and infrastructure needed for LNG to be utilized as fuel for vessels are readily available since the technology has been around for decades.

On the other hand, the LNG fuel system also has its cons as highlighted in [ 98 ]. For instance, LNG fuel tanks consume a large amount of space as the volume occupied by the tanks is 1.8 times larger than diesel oil. Additional space and necessary equipment are needed to store LNG as it requires a low temperature [ 99 ] to remain at cryogenic state. The LNG storage tanks must also be insulated and need specialized gas handling systems [ 99 ] thereby contributing to additional CAPEX. Also, LNG is highly flammable as it has a low flashpoint (− 188 °C), and can be dangerous if it is mixed with air [ 91 ].

3.2.2 Hydrogen fuel cell

The hydrogen fuel cell is a potential AF for decarbonising the shipping industry [ 100 , 101 , 102 ]. Hydrogen could be a form of clean RE depending on its production process. Hydrogen could be classified into three types, i.e., (i) green hydrogen derived from renewables (ii) blue hydrogen from natural gas and supported by carbon storage and sequestration and (iii) grey hydrogen from natural gas and fossil fuels. The world’s first offshore platform to produce green hydrogen from wind energy was launched in France in 2022. Green hydrogen could also be produced from ocean thermal energy [ 103 ] or wave via the installation of wave energy converters on offshore platforms [ 104 , 105 , 106 ]. This energy could be utilized in the form of fuel cells, also known as polymer electrolyte membrane (PEM) fuel cells. The PEM fuel cell comprises two electrodes, i.e., the anode and cathode where electricity is generated by chemical reactions that take place in these two electrodes. The oxygen that enters from the cathode will combine with the electron and hydrogen ions, then generates electricity and produces water as a by-product (see Fig.  13 ). As the product of hydrogen fuel cells is water and no oxides of nitrogen, sulphur, carbon, and other air pollutants are produced, it presents one of the most promising future energy resources in mitigating CO 2 and GHG emissions [ 107 , 108 , 109 ]. Furthermore, as the chemical energy of the fuel is converted directly into electricity in the hydrogen fuel cells [ 110 ], the efficiency of the energy conversion process can reach up to 40 to 80% [ 107 , 111 ]. However, since hydrogen fuel cell technology is still in the development stage, hydrogen fuel cell-powered vessels are currently in the experimental research stage and are only feasible for use on passenger vessels such as cruise ships and ferryboats [ 111 ]. The world’s first hydrogen-powered vessel—Energy Observer (see Fig.  14 a), launch a six-year expedition from 2017 to 2022 to optimize its technologies. The Energy Observer is also the first vessel in the world capable of producing decarbonized hydrogen on board from sea water and using an energy mix relying on renewable energies.

Working mechanism of hydrogen fuel cell ( www.eia.gov )

Hydrogen-powered vessel. a Energy Observer ( www.marine-insight.com ). b Nemo H2 ( www.vlootschouw.nl ). c SF BREEZE ( www.maritime-executive.com )

A feasibility study of RE was done on a 150-passenger high-speed passenger ferry – SF-BREEZE (see Fig.  14 b) [ 112 ]. The SF-BREEZE carries a total of forty-one 120-kW fuel cells which is enough for four hours of non-stop operation [ 112 ]. Even though hydrogen is the lightest fuel, a comparison between SF BREEZE and a conventional diesel ferry—Vallejo—showed that the fuel cell-powered vessel requires 10.1% more hydrogen fuel than the diesel ferry because PEM fuel cell-powered vessel is heavier due to the additional requirement for fuel cell power racks, liquid hydrogen tank, evaporator and other balance of plant items [ 112 ].

The hybridization of PEM fuel cells with batteries is a common combination in the utilization of hydrogen fuel cell technology in the ship. An example is the 88-passenger cruise boat—Nemo H2 (see Fig.  14 c), operating in Amsterdam since 2009 and the FCS Alsterwasser [ 109 ]. The hybrid propulsion system for the former is made up of a 60-kW to 70-kW PEM fuel cell which operates the electric motor with a 30-kW to 50-kW battery [ 109 , 113 , 114 ] whereas the latter comprises two fuel cell systems with a power output of 48 kW each and a 560 V lead gel battery pack [ 115 ].

Advantages and disadvantages of fuel cell powered vessels

Fuel cell-powered vessel contributes to significant carbon emission reduction and has quiet operation and better efficiency as compared to conventional diesel-powered vessel. One of the main advantages of fuel cells is that the level of efficiency increases when operating at a high temperature because it is feasible to recover heat from the exhaust gas when the operating temperature is high [ 109 ].

Several challenges hinder the adoption of fuel cells in decarbonizing ships [ 116 ], among them—poor reliability, limited lifetime, limited hydrogen supply, and last but not least, high production costs [ 109 ]. Also, as hydrogen gas does not exist on earth naturally and must be produced via processes like electrolysis or reformation of hydrocarbon fuels [ 109 ], these processes increase the operational costs of the PEM fuel cell system. Moreover, additional facilities are needed to support the fuel cell system, thus will contribute to the overall weight, and affecting the stability of the vessel [ 109 ]. For fuel cell systems to be safe, factor such as the toxicity of the fuel, the flammability limits, the temperature of auto ignition and finally the density of the fuel has to be considered [ 109 ]. As hydrogen is highly inflammable, more cost must be invested in the infrastructure for frequent monitoring of the gas storage area and a rapid venting system must be installed in case there are any leakages [ 109 ]. Although the high-temperature fuel cell system sounds appealing, there are some challenges associated with it, namely, low overall power-to-volume density, limited cycling time, poor performance and long start-up duration [ 109 ].

Despite the high investment cost involves, it is expected that the costs of hydrogen production to fall remarkedly alongside the advancement of renewable power generation technologies as manufacturing capacity for more efficient and cost-effective electrolyzers grows.

3.2.3 Ammonia fuel cell

Another source of potential AF for ship is ammonia [ 117 , 118 , 119 , 120 ]. Ammonia is produced commercially via the catalytic reaction of nitrogen and hydrogen at high temperatures and pressure known as the Baber-Bosch process, therefore does not emit any CO 2 when burned. However, ammonia does release high levels of nitrogen oxide as it has a high nitrogen content [ 121 ]. Similar to PEM fuel cells that use pure hydrogen, solid oxide fuel cells (SOFC) which use ammonia are possible sources of clean energy [ 122 ]. As the PEM fuel cell system cannot use ammonia directly [ 122 , 123 , 124 ], it can be combined with ammonia to make it feasible in generating energy [ 122 , 123 ]. Like hydrogen, ammonia can be classified into the same green, blue and grey colour scheme depending on the carbon intensity of the methods for making ammonia [ 125 ]. An example of ammonia powered vessel is the Kriti Future, which is the world’s first ammonia-powered vessel delivered in 2022 (seeFig.  15 ) [ 126 ].

World first ammonia-powered vessel, Kriti Future ( www.worldenergynews.gr )

Advantages and disadvantages of ammonia fuel

The most common method to combust ammonia is the utilization of fuel cell systems in internal combustion engines [ 123 ]. The main benefit of this method is that it produces lesser noise, reduces carbon emission, has a high level of thermal efficiency [ 97 ], is environmentally friendly, and enables fuel flexibility [ 122 ].

While carbon emissions-free ammonia, known as green ammonia, could be produced from renewables, the process of making blue and grey ammonia involves steam methane reforming (SMR) and the Haber–Bosch process consumes a lot of energy – emit 90% of CO 2 and produce around 1.8% of global CO 2 emissions, and increase production cost. Ammonia also releases a large amount of nitrogen oxides due to its high level of nitrogen content [ 121 ].

The infrastructure cost of producing ammonia is high as infrastructures that could endure high temperatures are needed to achieve a high level of fuel utilization [ 122 , 123 ]. Also, due to its toxicity, corrosion-resistant infrastructure like stainless steel is needed as ammonia is corrosive especially when there are water vapour and air in the atmosphere [ 123 ]. The aspect of the safe use of ammonia fuel cells in the maritime industry is summarised by Cheliotis et al. [ 127 ]. Insulated pressurized tanks are needed to store ammonia and this means that a larger space onboard the vessel is required for storage [ 121 ]. The space needed to use ammonia is more than the space needed to use marine gas oils, biofuels, LNG and even methanol. The costs of implementing ammonia are therefore higher than using marine gas oils or LNG and are similar to the costs of implementing hydrogen and biofuels.

3.2.4 Biofuels

Carbon–neutral biofuels such as bioethanol and biodiesel (a.k.a. fatty acid methyl ester) could be used as drop-in fuels in the shipping industry without the need for new fuel infrastructure thereby making biofuels one of the most technologically ready and high potential AF [ 128 , 129 , 130 ]. There are three generations of biofuels, i.e., (i) First-generation biofuels—biodiesel, bioethanol and biogas, produced directly from crops such as corn, soy and sugar cane [ 89 ], (ii) Second-generation biofuels produced from non-food biomass, such as lignocelluloses, wood biomass, agricultural residues, waste vegetable oil, and public waste [ 89 , 131 ] and (iii) Third-generation biofuels derived from microalgae cultivation. 99% of the current biofuels are of the first generation.

Biofuels are potential alternatives to power ships, but the unattractive costs and the limited availability of biofuels are factors that hinder the use of biofuels in the shipping industry [ 89 ]. However, the price for biofuels is predicted to be more attractive in the near future, as claimed in a report by DNV [ 97 ]. On the other hand, biofuels are also flexible because they can be mixed with existing fossil fuels and act as a replacement to power conventional diesel engines. Combusting a kilogram of biodiesel produces 2.67 kg of CO 2 [ 132 , 133 ]. This is significantly lower when compared to burning a kilogram of marine diesel i.e., 3.206 kg of CO 2 [ 134 ], and a kilogram of heavy fuel oil i.e., 3.114 kg of CO 2 [ 135 ].

As a step to head towards maritime decarbonization, NYK has conducted a trial on a bulk carrier—Frontier Sky—powered by biofuel to transport cargo from Singapore to the port of Dhamra [ 136 ]. The trial was conducted successfully to prove the feasibility of using biofuels as an alternative to fossil fuels. Similarly, a biodiesel blend that consists of 7% biofuel and 93% regular fuel was tested successfully in a trial on Frontier Jacaranda from Singapore to South Africa. The biodiesel was blended from waste cooking oil and claimed to reduce CO 2 emissions by around 5%, compliant with the International Standard Organisation’s requirement for marine fuels and requires no substantial engine modification.

Advantages and disadvantages of biofuels

Biofuels constantly receive attention worldwide due to many significant reasons. The first and main reason is because of its renewable and sustainable nature. Secondly, the production process of biodegradable biofuels generates less toxic waste [ 137 ]. Lastly, biofuels are cost-effective. When biofuel is used by a vessel, it is proven to improve the performance and efficiency of the engine [ 137 ]. The combustion process of biofuels does not release any NO x or SO x [ 138 ]. As biofuels could be produced from waste food, this is also aligned with the UN’s circular economy and sustainable development framework [ 139 ].

The first-generation biofuels which constitute 99% of the biofuels consumption today are mainly derived from feedstock such as corn and sugar beet [ 137 , 138 ]. This risks food prices as the prices may shoot up due to the high demand for feedstock [ 137 ]. Furthermore, a food crisis will occur because of the potential competition between farmers and biofuel producers for the supply of corn [ 137 ]. To create biofuels, high levels of energy are required [ 140 ] and lots of space are needed to develop biomass for first-generation biofuels [ 137 ]. This factor is highly undesirable as there must be an assurance of sufficient space to produce AF and avoid a potential food crises [ 140 ].

3.2.5 Methanol fuel

Methanol is an attractive AF as it can be produced efficiently from alternative energy sources and involves low production costs [ 141 , 142 ]. Methanol is produced from natural gas by reforming the gas with steam. Pure methanol is then created from this synthesized gas mixture via the process of conversion and distillation [ 143 ]. Methanol became a possible fuel candidate when the oil crises occurred during the 1970s and 1980s resulting in the rise in gasoline prices and causing fear of oil shortage [ 141 ]. As a result, methanol became the fuel candidate for fuel cells. Although methanol is usually not desired to be used as a transportation fuel because of its corrosiveness and high toxicity, several vessels have been running successfully by using methanol as an AF. E.g., the Ro-pax ferry—MS Stena Germanica—was retrofitted to use methanol as a fuel and equipped with methanol storage tanks [ 144 ]. The operation of methanol is expected to reduce SO x emissions by 99%, NO x by 80%, CO 2 by 15% and particulate matter by 99% [ 143 ].

Advantages and disadvantages of methanol

There is an unlimited amount of methanol readily available in the world [ 145 ] and 70 million tons of methanol are produced annually. Methanol could be completely renewable, i.e., green methanol, as it can be produced by RE. Also, as methanol is biodegradable, fuel spill of methanol is relatively less detrimental to the environment compared to an oil spill of conventional diesel oil [ 145 ].

However, methanol has a low energy content [ 141 ] as compared to other AF (20.09 MJ/kg methanol vs 45.30 MJ/kg Butane, 47.79 MJ/kg Ethane, 37.53 MJ/kg biodiesel, 42.79 MJ/kg marine diesel), and this means that a larger volume tank and massive fuel injection systems are required. Due to the high corrosiveness and toxicity in methanol, this may cause high maintenance costs to the vessels, and thus higher operating costs over the years [ 145 ]. To use methanol fuel, different infrastructures are required to withstand the high corrosivity and toxicity, and therefore existing vessels have to be retrofitted with fuel storage tanks and double-walled pipes [ 145 ].

3.3 Comparisons

The types of sustainable energy suitable for marine transport are summarised in Fig.  16 and their advantages and disadvantages are summarised in Table 1 . The energy generation from RE and AF differs significantly as RE does not require combustion whereas AF required a combustion system in the form of an internal combustion engine (ICE) or dual fuel engine. A comparison between the fuels in RE and AF categories is separated in this section. The performance of the RE-powered vessels, i.e., wind propulsion, solar propulsion and nuclear propulsion is made. Their effectiveness in achieving energy efficiency and CO 2 emissions is presented. This is then followed by a comparison between different AF, i.e., LNG, hydrogen, ammonia, biofuels and methanol.

Types of sustainable energy for ship

3.3.1 Performance of renewable energy

Renewable energy-powered vessels are known for their superiority in mitigating CO 2 and GHG emissions and achieving fuel reduction. Some of these REs have achieved a high maturity level, with some being adopted in the existing vessel and new-built vessels. E.g., the Flettner rotor and solar PV panels are two of the most used RE retrofitted into existing diesel-powered vessels. The Flettner rotor can reduce CO 2 emissions and achieve fuel reduction by up to 30% [ 48 ] whereas the fuel consumption of UT Challenger using the hard wing sail technology could be reduced by 50% [ 56 ]. The kite technology also shows promising results in reducing fuel consumption by up to 20% in a trial conducted by Airseas [ 146 ]. A summary of the fuel savings that could be achieved from various wind energy technologies is presented inTable 2 . Similarly, a significant amount of fuel, CO 2 and GHG emissions reduction could also be achieved on vessels equipped with solar PV panels.Table 3 summarizes the available information on these reductions extracted from Pan et al . [ 147 ]. The main disadvantage of wind and solar power is that it could not yet be used to fully power large commercial vessels due to the unpredictable wind and solar resources, therefore has to be integrated with the traditional diesel-power propulsion systems.

Nuclear fuel on the other hand is a relatively mature technology and has long been used in navy vessels and icebreakers. This allows vessels to stay offshore/in the sea for a longer period without refuelling and is essential for vessels operating in remote locations such as icebreakers and submarines. Nuclear has a high energy content, i.e., one Uranium fuel pellet creates as much energy as 1,000 kg of coal [ 148 ] and is completely clean but it produces radioactive waste that is harmful to human health and the environment.

3.3.2 Performance of alternative fuels

DNV-GL has reported in its Alternative Fuel Insight Platform that of the total number of vessels in the world, 0.50% are currently running on AF while the rest of the vessels are still running on conventional fuels such as diesel and HFO [ 97 ]. However, there is an increasing trend to switch to AF, where 11.84% of AF-powered vessels are currently in order.Fig.  17 shows the number of ships operating in different fuels currently in operation and on order. Among the AF, there is a high uptake of LNG.

Uptake of alternative fuels in the world fleet, July 2019. Figures reproduced from data obtained in [ 152 ]

The next best-performing AF after LNG is methanol which shows moderate to good performance in all categories. GHG emissions for methanol are similar to LNG as the former is derived from nitrogen and the latter is a petroleum-based fuel. Biodiesel performs very well in a few high-priority categories, i.e., energy density, technological maturity and capital cost, and therefore has received substantial attention from the shipping community as a potential AF. Properties of the various AF compiled from different resources are summarised in Table 4 [ 153 ]. It is to note that the qualitative comparison for different AF in Fig.  18 is for a generic study; the specifics for the case being evaluated, such as ship specifications, local conditions, access to energy carriers and so on, have to be taken into consideration for more accurate and detail analysis.

Technology maturity level for various alternative fuels [ 152 ]

4 Renewable energy and alternative fuel in ships to achieve UN SDG goals

The international shipping community has been working actively to achieve the UN SDG Goals since it was first launched in 2005. Here, the focus will be given on how sustainable propulsion systems via RE and AF could achieve SDG 7: Ensure access to affordable, reliable, sustainable and modern energy for all , SDG 9: Build resilient infrastructure, promote sustainable industrialisation an d foster innovation and SDG 13: Take urgent action to combat climate change and its impact.

4.1 SDG 7: ensure access to affordable, reliable, sustainable and modern energy for all

In the quest to seek carbon–neutral or zero-carbon alternative energies for ship propulsion systems with the aim to reduce carbon emissions, it is important to ensure that the cost per energy for these sustainable propulsion systems remains affordable as this may have a significant impact on the cost of consumerism goods. It is estimated that AF in container shipping will be almost as economical as using HFO [ 154 ].

Figure  19 shows the projected annual price for operating a container ship and a bunkering location in the Middle East in 2030, by fuel type [ 154 ]. The operational cost for the LNG power propulsion system is comparable to the conventional heavy fuel oil counterpart, at 26 million dollars per year. Other AFs that are 50% higher in annual operating cost compared to HFO are ammonia and biodiesel. E.g., the cost for the fuel cell energy consumption for the SF BREEZE was estimated to start from $5.43 per kilogram for non-renewable liquid hydrogen and $8.68 per kilogram for green hydrogen [ 114 ]. This makes the cost for the hydrogen fuel cell system twice to eight times more than a conventional diesel ferry as the current cost of PEM fuel cells is high [ 114 ].

Annual price for operating a container ship and a bunkering location in the Middle East in 2030, data obtained from Statista [ 154 ]

As the cost of hydrogen fuel cell-powered vessels is high, a hybrid system that integrates AF with diesel- or/and RE fuels is proposed. A case study was done by a team of researchers in Sweden where they considered a hybrid solar power—PEM fuel cell and diesel generator propulsion system for a cruise ship [ 155 ]. The study compared the cost of a cruise ship relying 100% on diesel generators and the hybrid RE system. Overall, it was found that it is a little more expensive to adopt a hybrid clean energy system, i.e., $260/MWh vs $223/MWh [ 155 ]. However, considering the fact that the PEM fuel cell system for the cruise ship is expected to reduce carbon emissions by 4.39% yearly which approximates 902,364 kWh [ 155 ], this presents an attractive alternative. While the cost for other AFs, i.e., biodiesel, methanol, hydrogen, and ammonia fuel cells are relatively higher as compared to their fossil fuel counterparts, the prices are expected to decrease with the increase in the maturity level of the AF technology. A.P. Moeller—Maersk for instance has reported that their recent order of six container ships that could be powered by methanol has an additional CAPEX of only 8 to 12%, which is an improvement compared to their previous order in 2021 [ 156 ].

Ship propulsion systems powered by RE such as solar, wind and nuclear power are also potential candidates that could provide affordable energy for green logistics. The cost of solar PV panels is currently at an attractive price between $2.60 to $3.20 per watt [ 75 ]. A report by Thandasherry [ 80 ] that compared the CAPEX and OPEX between the solar-powered vessel and diesel-power vessel showed that in the long run over a life cycle of 20 years, the solar power alternative can save at least three times the total cost compared to the traditional diesel-powered option.

The CAPEX for RE and AF-powered vessel is usually higher than the vessel running on fossil fuels, due to the cost of the propulsion system and special equipment needed to accommodate these RE and AF such as specialized tanks. However, the OPEX is expected to reduce in the long run. E.g., while the CAPEX for a nuclear-powered vessel could be 16.5 times higher than a conventional diesel vessel, the OPEX of the former is half of that of the latter [ 83 , 86 ]. The overall cost analysis shows the total cost of a nuclear-powered vessel will be lower than the diesel vessel after the 8 th year. This makes the nuclear-powered propulsion systems a promising candidate for decarbonizing ships considering the shipping industry has to phase out fossil fuel eventually to achieve the CO 2 emission set by IMO, i.e., 50% CO 2 reduction by 2050 and eventually phase out by 2100 [ 157 ].

4.2 SDG 9: build resilient infrastructure, promote sustainable industrialisation and foster innovation

Government spending on energy research and development is on an increasing trend as shown in Fig.  20 where the spending grew by 3% with robust expansion in Europe and the United States [ 158 ]. The marine industry has moved forward with technological advancement in seeking for AF to play a role in tackling climate change. To achieve IMO targets of reducing CO 2 emission by 50% by 2050, many innovative ideas have been proposed and adopted such as scrubbers, carbon sequestration, data analytics and machine learning and last but not least, the use of RE and AF. New infrastructure to support maritime green transition is established and this has revolutionised the supply chain to ensure sufficient, sustainable and affordable AF for the maritime industry.

Government’s spending in energy research by countries, data obtained from IEA [ 158 ]

Various countries have invested heavily in infrastructures such as the production, conversion, storage and bunkering facilities for ammonia, hydrogen and LNG needed to support the utilization of AF. Figure  21 shows the global LNG bunkering facility for various types of ships in 2021–2022 [ 159 ] where 32 LNG bunkering facilities are readily available and 42 are on order. The LNG receiving terminals are being developed rapidly as transferring LNG by pipeline is costly and therefore used less now. Driven by the short-term increase in natural gas demand due to the Russo-Ukrainian War and coupled with the rise of fuel oil, governments in Europe and Asia are transitioned away from fossil fuels and invested heavily in low-carbon energy infrastructure. It was reported that the investment in new LNG infrastructure will increase to $32 billion and $42 billion in 2023 and 2024, respectively [ 160 ]. These readily available LNG infrastructures will drive the demand for LNG-powered vessels where the total LNG supply is expected to double in coming years, approaching 636Mtpa in 2030 from 380Mtpa (million tonnes per annum) in 2021.

Global LNG infrastructure [ 159 ]

The relatively affordable ammonia fuel as an AF for the ship has driven companies such as Azane Fuel Solutions to be created to fill an existing gap in the ammonia fuel chain by developing ammonia ship bunkering infrastructure technology, products and services [ 161 ]. The bunkering terminal could be in the form of a shore-based or floating option, where the first option allows direct ship bunkering alongside the quay, whereas the second option allows for flexibility and transportation of the facility to the location where the ammonia vessel is operating. Maersk has also unveiled plans for the establishment of Europe’s largest production facility of green ammonia—a sustainable green fuel, produced from wind energy.

Fig.  22 shows the technical maturity level for various types of fuels [ 152 ]. Comparing the technical maturity level with the cost per energy in Fig.  19 , it can be deduced that in general, the cost per energy of the AF reduces with a more matured technology, i.e., a lower Technical Maturity Level (TML).

Technology maturity level for various alternative fuels, data derived from [ 152 ]. FC Fuel Cell; ICE Internal Combustion Engine; DFHP Dual Fuel High Pressure; DFLP Dual Fuel Low Pressure; HVO Hydrotreated Vegetable Oil. Technology Maturity Level (TMR) is interpreted as:. TML1—Measures that are off the shelf and commonly used on new ships. TML2—Measures that are commercially available, but not fully mature. TML3—Measures that are under piloting, and/or with only a few commercial applications. TML4—Measures that have not been tested at full scale and no piloting or full-scale testing underway

4.3 SDG 13: take urgent action to combat climate change and its impact

The annual global GHG is at a record high of around 50Gt [ 162 ], a rise of 57% since 1990 [ 163 ] as shown in Fig.  23 . The earth's temperature is projected to rise by 2.5 to 2.9 \(^\circ\) C based on the current policies and will continue to increase to 4.1 to 4.8 \(^\circ\) C if no further climate policies are enforced. The sea water level is projected to rise by 2 m under the worst-case scenario causing inundation to coastal cities and island nations [ 164 ]. Under the Nationally Determined Contributions (NDC)—a climate action plan submitted by countries under the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC) to cut emissions and adapt to climate impact by 2030 [ 165 ], the global warming projection will still be above the Paris Agreement limit set at below 2 °C compared to the pre-industrialized level [ 166 ]. In view of this, all parties, including the maritime industry must play a part in mitigating the CO 2 and GHG emissions.

Global GHG emission and warming scenarios under various policies [ 163 ]

Fig.  24 shows that a total of 614 million tons of CO 2 was emitted from ships, contributing 368 million tons of CO 2 to the atmosphere. Out of the various vessels considered in Fig.  25 , containers account for 29.9% of the CO 2 emissions [ 167 , 168 ], followed by dry bulk (27.5%) and tankers (21.1%), thereby contributing to a whopping 60% of the CO 2 emissions. As shipping still presents the most economical mode of transportation for the delivery of goods, the growth of ocean freight market will continue to grow. Therefore, the CO 2 and GHG emissions are expected to increase compared to the emissions in 2019 shown in Fig.  24 .

CO 2 emission from world fleet [ 168 ]

Yearly energy consumption of ships in relation to diesel and gasoil consumptions in 2016, data derived from DNV-GL [ 169 ]

Given this, bulk carrier companies such as Maersk have invested heavily in LNG infrastructure in the quest to decarbonize their vessels [ 161 ]. Besides that, A.P. Moller-Maersk has recently ordered six large container vessels that can be powered by green methanol, contributing to a total order of 19 vessels running on duel fuel engines that can operate on green methanol [ 156 ]. These large bulk carriers have also been equipped with RE technologies such as Flettner rotor, kite technology and solar PV panel, where significant improvements in fuel consumption and carbon emissions are reported as presented in Tables 2 , 3 .

Fig.  25 presents the yearly consumption of AF used in the shipping industry compared to diesel and gasoline in 2016 [ 169 ]. Crude oil remains the most commonly used fuel for the shipping industry which is 305% higher than gasoil and diesel. However, the use of natural gas is catching up at 243% with LNG contributing 24% and gas contributing 219%. The use of LNG and biodiesel could reduce CO 2 emissions by around 21—27% as compared to fuel oil as shown in Fig.  26 . The CO 2 emissions for other AFs such as green hydrogen, biogas and green methanol are significantly lower than fuel oil, however, the uptake of these AF is still relatively small as presented in Fig.  25 . It is to note that the CO 2 emissions for AF such as hydrogen could be significantly low when used onboard the ship (i.e., Tank to Propeller—TTP) but depending on its production process, the CO 2 emission could be even higher than oil fuel during production, e.g., hydrogen derived from methane (CH 4 ) (see Fig.  26 ).

CO 2 emission of alternative fuels during production and on-board ship, data derived from DNV-GL [ 169 ]

The initiatives taken by the shipping industry in reducing CO 2 and GHG emissions via Energy Efficiency Operational Indicator (EEOI) and Ship Energy Efficiency Management Plan (SEEMP) have managed to serve an impact on the overall reduction of CO 2 emissions (see Fig.  27 [ 170 ]). In 2050, it is projected that the CO 2 emissions will reduce by 40%, bringing the new CO 2 emissions to 1,900 million tonnes, if Scenario A1-B4 stipulated in IMO MARPOL Annex V1 measures is adopted whereas the emissions will decrease by 35% to 1,300 million tonnes if Scenario B2-1 is adopted.

Projected annual CO 2 emissions from shipping sector, data derived from [ 170 ]

The CO 2 emissions from shipping activities are projected to increase exponentially in the next few decades as shown in Fig.  27 . However, the new CO 2 emissions based on the B2-1 ‘s least stringent SEEMP criteria with a high waiver uptake have a more gradual increase rate as compared to the A1-B4’s low SEEMP criteria and low waiver uptake. An interesting point to note is that the emission reduction by EEOI will be higher in the long run as compared to the counterpart by SEEMP, due to the improved efficiency of the ship propulsion systems and the increase of uptake and maturity level of various AF in the future.

5 Conclusions

Innovative means of ship propulsion systems by the use of RE and AF were presented. The state-of-the-art of RE, i.e., solar-, wind- and nuclear-powered propulsion technology was first reviewed followed by the AF, i.e., LNG, hydrogen, ammonia, biofuels and methanol fuel-powered vessels. The pros and cons of these RE technologies and AF were also compared. While wind and solar energy could not yet be used to power large commercial vessels fully, wind-assisted vessels could reduce fuel consumption and CO 2 emissions significantly (20% for Flettner rotor, 50% for hard wing sail and 20% for kite technology). Nuclear energy is currently used mostly in navy vessels and icebreakers but has a huge advantage to being used in commercial vessels as it does not require frequent refuelling and is commercially attractive in the OPEX in the long term. The comparisons for AFs showed that the LNG performs better in most aspects except in terms of GHG emissions, where ammonia and hydrogen are the best options. The cost of ammonia and hydrogen is however too high compared to their AF counterparts.

The impacts of adopting sustainable propulsion systems in ships in achieving the UN Sustainable Development Goals were presented. Three UN SDGs were targeted, i.e., SDG 7: Ensure access to affordable, reliable, sustainable and modern energy for all , SDG 9: Build resilient infrastructure, promote sustainable industrialisation an d foster innovation and SDG 13: Take urgent action to combat climate change and its impact. For SDG 7, it was demonstrated that the cost for LNG and hybrid propulsion systems between RE/AF with diesel engines could be attractive to make such technologies feasible for adoption. Sustainable energy propulsion, in particular, LNG fuel has pushed for new infrastructure to the maritime green transition, and this has revolutionised the supply chain to ensure sufficient, sustainable and affordable AF for the maritime industry in line with SDG9. Last but not least, the RE and AF have a direct impact towards achieving SDG 13 in reducing carbon and GHG emissions, thereby playing an important role in mitigating the impact of climate change.

The IMO has created an SDGs Strategy, which calls for the strengthening of partnerships in the implementation of the SDGs. This has seen a surge in collaboration between various stakeholders such as academia, industries, government agencies and classification societies in research and technology on RE and AF. Government agencies have taken steps to support member states in implementing the SDGs in the maritime industry, with a trend of increasing government spending on energy research since 2016. E.g., the Maritime SDG Accelerator under the Danish Maritime Business Association and UN Development Program (UNDP) was introduced to enable the acceleration of sustainable innovation and business development delivering on the SDG targets. The Maritime Singapore Decarbonisation Blueprint has set a goal for all domestic harbour craft in the Singapore Sea to operate on low-carbon energy solutions by 2030 and to be fully powered by electric propulsion and net zero fuels by 2050, aligning with Singapore's commitments under the UN SDGs. The decarbonisation of the maritime industry is an ongoing effort and the current initiatives undertaken by various stakeholders in adopting RE and AF in achieving the UN SDGS are encouraging and promising. The continuous concerted effort from the stakeholders with the aim to achieve UN SGDs will ensure a more sustainable future free of poverty and all people enjoy peace and prosperity.

Abbreviations

Alternative fuel

Boil-off gas

Capital expenses

Carbon dioxide

Direct current

Emission control areas

Energy efficiency operational indicator

Exhaust gas cleaning systems

Greenhouse gas

Heavy fuel oil

Internal combustion engine

International Maritime Organisation

Liquified natural gas

Nationally determined contributions

Nitrogen oxides

Operational expenses

Photovoltaic

Polymer electrolyte membrane

• Renewable energy

Ship energy efficiency management plan

Solid oxide fuel cells

Steam methane reforming

Sulphur oxides

Sustainable Development Goals

Tank to propeller

International Convention for the Prevention of Pollution from Ships

United Nations

United Nations Framework Convention on Climate Change

Wind-assisted propulsion system

Hopkin M. Ships’ greenhouse emissions revealed. Nature. 2008. https://doi.org/10.1038/NEWS.2008.574 .

Article   Google Scholar  

ICCT. Reducing Greenhouse Gas Emissions from Ships, The International Council on Clean Transportation (ICCT), Washington DC, 2011. www.theicct.org .

UNFFC. World Nations Agree to At Least Halve Shipping Emissions by 2050, United Nations. 2018. https://unfccc.int/news/world-nations-agree-to-at-least-halve-shipping-emissions-by-2050 . Accessed 7 Oct 2022.

Connelly E, Idini B. International Shipping—Analysis—IEA, International Energy Agency. 2022. https://www.iea.org/reports/international-shipping . Accessed 7 Oct 2022.

Hellenic Shipping News. Shipping Emissions Rose Nearly 5% in 2021, Hellenic Shipping News Worldwide. 2022. https://www.hellenicshippingnews.com/report-shipping-emissions-rose-nearly-5-in-2021/ . Accessed 7 Oct 2022.

ICS. Shipping and World Trade: Global Supply and Demand for Seafarers, International Chamber of Shipping (ICS). 2022. https://www.ics-shipping.org/shipping-fact/shipping-and-world-trade-global-supply-and-demand-for-seafarers/ . Accessed 7 Oct 2022.

IMO. Fourth Greenhouse Gas Study 2020, 2020. https://www.imo.org/en/OurWork/Environment/Pages/Fourth-IMO-Greenhouse-Gas-Study-2020.aspx . Accessed 7 Oct 2022.

IRClass. Limiting the Maximum Sulphur Content of the Fuel Oils., Indian Register of Shipping (IRS). 2018. https://www.irclass.org/technical-circulars/limiting-the-maximum-sulphur-content-of-the-fuel-oils/ . Accessed 7 Oct 2022.

IMO. Emission Control Areas (ECAs) designated under MARPOL Annex VI, International Maritime Organisation (IMO). 2020. https://www.imo.org/en/OurWork/Environment/Pages/Emission-Control-Areas-(ECAs)-designated-under-regulation-13-of-MARPOL-Annex-VI-(NOx-emission-control).aspx . Accessed 7 Oct 2022.

IEA. IEA Tracking Clean Energy Progress, International Energy Agency (IEA). 2021. https://www.ieabioenergy.com/blog/publications/iea-tracking-clean-energy-progress-biofuels-bioenergy/ . Accessed 7 Oct 2022.

Kim AR, Seo YJ. The reduction of SOx emissions in the shipping industry: the case of Korean companies. Mar Policy. 2019;100:98–106. https://doi.org/10.1016/J.MARPOL.2018.11.024 .

Zhao J, Wei Q, Wang S, et al. Progress of ship exhaust gas control technology. Sci Total Environ. 2021;799:149437. https://doi.org/10.1016/J.SCITOTENV.2021.149437 .

Article   CAS   Google Scholar  

Raza Z, Woxenius J, Finnsgård C. Slow steaming as part of SECA compliance strategies among roro and ropax shipping companies. Sustainability. 2019;11:1435. https://doi.org/10.3390/SU11051435 .

Degiuli N, Martić I, Farkas A, et al. The impact of slow steaming on reducing CO2 emissions in the Mediterranean Sea. Energy Rep. 2021;7:8131–41. https://doi.org/10.1016/J.EGYR.2021.02.046 .

Hadi J, Tay ZY, Konovessis D. Ship navigation and fuel profiling based on noon report using neural network generative modeling. J Phys Conf Ser. 2022;2311:12005. https://doi.org/10.1088/1742-6596/2311/1/012005 .

Fam ML, Tay ZY, Konovessis D. An artificial neural network for fuel efficiency analysis for cargo vessel operation. Ocean Eng. 2022;264:112437. https://doi.org/10.1016/J.OCEANENG.2022.112437 .

Hadi J, Konovessis D, Tay ZY. Achieving fuel efficiency of harbour craft vessel via combined time-series and classification machine learning model with operational data. Maritime Trans Res. 2022;3:100073. https://doi.org/10.1016/J.MARTRA.2022.100073 .

Tay ZY, Hadi J, Chow F, et al. Big data analytics and machine learning of harbour craft vessels to achieve fuel efficiency: a review. J Marine Sci Eng. 2021;9:1351. https://doi.org/10.3390/JMSE9121351 .

Tay ZY,Hadi J,Konovessis D,et al. Efficient Harbor Craft Monitoring System: Time-series data analytics and machine learning tools to achieve fuel efficiency by operational scoring system, proceedings of the international conference on offshore mechanics and arctic engineering - OMAE. 2021; https://doi.org/10.1115/OMAE2021-62658 .

Hadi J, Konovessis D, Tay ZY. Self-labelling of tugboat operation using unsupervised machine learning and intensity indicator. Maritime Trans Res. 2023;4:100082. https://doi.org/10.1016/J.MARTRA.2023.100082 .

Hadi J, Konovessis D, Tay ZY. Filtering harbor craft vessels’ fuel data using statistical, decomposition, and predictive methodologies. Maritime Trans Res. 2022;3:100063. https://doi.org/10.1016/J.MARTRA.2022.100063 .

Fam M,Tay Z,Konovessis D. An artificial neural network based decision support system for cargo vessel operations, in: Proceedings of the 31st European Safety and Reliability Conference, Angers, France, 2021.

Wang H, Hou Y, Xiong Y, et al. Research on multi-interval coupling optimization of ship main dimensions for minimum EEDI. Ocean Eng. 2021;237:109588. https://doi.org/10.1016/J.OCEANENG.2021.109588 .

Ren H, Ding Y, Sui C. Influence of EEDI (energy efficiency design index) on ship–engine–propeller matching. J Marine Sci Eng. 2019;7:425. https://doi.org/10.3390/JMSE7120425 .

Roslan SB, Konovessis D, Tay ZY. Sustainable hybrid marine power systems for power management optimisation: a review. Energies. 2022;15:9622. https://doi.org/10.3390/EN15249622 .

Farkas A, Degiuli N, Martić I, et al. Greenhouse gas emissions reduction potential by using antifouling coatings in a maritime transport industry. J Clean Prod. 2021;295:126428. https://doi.org/10.1016/J.JCLEPRO.2021.126428 .

Islam H, Soares G. Effect of trim on container ship resistance at different ship speeds and drafts. Ocean Eng. 2019;183:106–15. https://doi.org/10.1016/J.OCEANENG.2019.03.058 .

Bouman EA, Lindstad E, Rialland AI, et al. State-of-the-art technologies, measures, and potential for reducing GHG emissions from shipping—a review. Transp Res D Transp Environ. 2017;52:408–21. https://doi.org/10.1016/J.TRD.2017.03.022 .

Jimenez VJ, Kim H, Munim ZH. A review of ship energy efficiency research and directions towards emission reduction in the maritime industry. J Clean Prod. 2022;366:132888. https://doi.org/10.1016/J.JCLEPRO.2022.132888 .

Inal OB, Charpentier JF, Deniz C. Hybrid power and propulsion systems for ships: current status and future challenges. Renew Sustain Energy Rev. 2022;156:111965. https://doi.org/10.1016/J.RSER.2021.111965 .

Law LC, Foscoli B, Mastorakos E, et al. A comparison of alternative fuels for shipping in terms of lifecycle energy and cost. Energies. 2021;14:8502. https://doi.org/10.3390/EN14248502 .

Wang Y, Cao Q, Liu L, et al. A review of low and zero carbon fuel technologies: achieving ship carbon reduction targets. Sustain Energy Technol and Assess. 2022;54:102762. https://doi.org/10.1016/J.SETA.2022.102762 .

Perčić M, Vladimir N, Fan A. Techno-economic assessment of alternative marine fuels for inland shipping in Croatia. Renew Sustain Energy Rev. 2021;148:111363. https://doi.org/10.1016/J.RSER.2021.111363 .

Fam M, Tay Z, Konovessis D. Techno-economic analysis for decarbonising of container vessels. In: Maria CL, Edoardo P, Luca P, Simon W, editors. Techno-economic analysis for decarbonising of container vessels. Singapore: Research Publishing; 2022.

Google Scholar  

Perčić M, Vladimir N, Fan A. Life-cycle cost assessment of alternative marine fuels to reduce the carbon footprint in short-sea shipping: a case study of Croatia. Appl Energy. 2020;279:115848. https://doi.org/10.1016/J.APENERGY.2020.115848 .

Xing H, Stuart C, Spence S, et al. Alternative fuel options for low carbon maritime transportation: pathways to 2050. J Clean Prod. 2021;297:126651. https://doi.org/10.1016/J.JCLEPRO.2021.126651 .

Sopta D,Bukša T,Bukša J,et al. 2020. Alternative Fuels and Technologies for Short Sea Shipping, Pomorski Zbornik. 18048/2020.59.04

Balcombe P, Brierley J, Lewis C, et al. How to decarbonise international shipping: Options for fuels, technologies and policies. Energy Convers Manag. 2019;182:72–88. https://doi.org/10.1016/J.ENCONMAN.2018.12.080 .

Spoof-Tuomi K, Niemi S. Environmental and economic evaluation of fuel choices for short sea shipping. Clean Technol. 2020;2:34. https://doi.org/10.3390/CLEANTECHNOL2010004 .

Messerli P. Global Sustainable Development Report (GSDR) 2019, United Nations. 2018. https://sdgs.un.org/goals . Accessed 4 Oct 2022.

OECD. Ocean shipping and shipbuilding - OECD, Organisation for Economic Co-Operation and Development (OECD). 2022. https://www.oecd.org/ocean/topics/ocean-shipping/ . Accessed 4 Oct 2022.

UN SDG. International Maritime Organisation (IMO), United Nations Department of Economic and Social Affairs. (2019). https://sdgs.un.org/un-system-sdg-implementation/international-maritime-organization-imo-34611 . Accessed 7 Feb 2023.

IEA. Transport Sector CO2 Emissions by Mode in the Sustainable Development Scenario, 2000–2030 – Charts – Data & Statistics - IEA, (n.d.). https://www.iea.org/data-and-statistics/charts/transport-sector-co2-emissions-by-mode-in-the-sustainable-development-scenario-2000-2030 Accessed 14 Dec 2022.

Comer B,Rutherford D. New IMO study highlights sharp rise in short-lived climate pollution—International Council on Clean Transportation, The International Council on Clean Transportation. 2020. https://theicct.org/new-imo-study-highlights-sharp-rise-in-short-lived-climate-pollution/ Accessed 11 Oct 2022.

Korberg AD, Brynolf S, Grahn M, et al. Techno-economic assessment of advanced fuels and propulsion systems in future fossil-free ships. Renew Sustai Energy Rev. 2021;142:110861. https://doi.org/10.1016/J.RSER.2021.110861 .

Kumar Y, Ringenberg J, Depuru SS, et al. Wind energy: trends and enabling technologies. Renew Sustain Energy Rev. 2016;53:209–24. https://doi.org/10.1016/J.RSER.2015.07.200 .

Jacobson MZ, Delucchi MA. Evaluating the Feasibility of a Large-Scale Wind, Water, and Sun Energy Infrastructure, 2009. https://www.researchgate.net/publication/242537047_Evaluating_the_Feasibility_of_a_Large-Scale_Wind_Water_and_Sun_Energy_Infrastructure . Accessed 28 Sept 2022.

Chou T, Kosmas V, Acciaro M, et al. A comeback of wind power in shipping: an economic and operational review on the wind-assisted ship propulsion technology. Sustainability. 2021;13:1880. https://doi.org/10.3390/SU13041880 .

DNV-GL. Wind-assisted Propulsion Can Cut Fuel Costs and Emissions , DNV-GL. 2020. https://www.dnv.com/expert-story/maritime-impact/Wind-assisted-propulsion-can-cut-fuel-costs-and-emissions.html . Accessed 7 Oct 2022.

Zeldovich L. New sails for old ships. Mech Eng. 2020;142:44–9. https://doi.org/10.1115/1.2020-FEB3 .

Ariffin NIB, Hannan MA. Wingsail technology as a sustainable alternative to fossil fuel. IOP Conf Ser Mater Sci Eng. 2022. https://doi.org/10.1088/1757-899X/788/1/012062 .

Oceanbird. The Oceanbird Concept, Oceanbird. 2022. https://www.theoceanbird.com/the-oceanbird-concept/ . Accessed 7 Oct 2022.

Doyle A. The Oceanbird: Swedish firm develops largest wind-driven cargo shop, World Economic Forum. 2020. https://www.weforum.org/agenda/2020/12/swedish-firm-wind-powered-cargo-ships . Accessed 7 Oct 2022.

Chadwick J. Oceanbird’s 260-ft High Sails Reduce Cargo Shipping Emissions by 90%, Daily Mail Online. 2020. https://www.dailymail.co.uk/sciencetech/article-8742949/Oceanbirds-260-ft-high-sails-reduce-cargo-shipping-emissions-90.html . Accessed 7 Oct 2022.

Pierce F. Wind Powered Ships could Reduce Fuel Use by 30%, Supply Chain. 2020. https://supplychaindigital.com/logistics/wind-powered-ships-could-reduce-fuel-use-30 . Accessed 28 Sept 2022.

Ouchi K,Uzawa K,Kanai A. Huge hard wing sails for the propulsor of next generation sailing vessel, in: The Second International Symposium on Marine Propulsors, Hamburg, Germany., 2011.

Quick D. B9 Shipping Developing 100 Percent Fossil Fuel-Free Cargo Sailing Ships, New Atlas. 2012. https://newatlas.com/b9-shipping-cargo-sailing-ships/23059/ . Accessed 7 Oct 2022.

Ship Technology. B9 Shipping Carbon Neutral Coastal Vessel - Ship Technology, Ship Technology. 2010. https://www.ship-technology.com/projects/b9-carbon-neutral/ . Accessed 7 Oct 2022.

Lu R, Ringsberg JW. Ship energy performance study of three wind-assisted ship propulsion technologies including a parametric study of the Flettner rotor technology. Ships and Offshore Structures. 2020;15:249–58. https://doi.org/10.1080/17445302.2019.1612544 .

Patowary K. Flettner Rotor: Sailing Ships Without Sails, Amusing Planet. 2021. https://www.amusingplanet.com/2021/02/flettner-rotor-sailing-ships-without.html . Accessed 9 Oct 2022.

Baltateanu D. The Return of Rotor Sail Ships: E-Ship 1 - Harnessing the Power of Wind, DriveMag Boats. 2017. https://boats.drivemag.com/features/the-return-of-rotor-sail-ships-e-ship-1-harnessing-the-power-of-wind . Accessed 7 Oct 2022.

Kuuskoski J. Norsepower rotor sail solution, MARENER 2017. 2017. https://commons.wmu.se/marener_conference/marener_2017/allpresentations/3 . Accessed 8 Jul 2022.

Ship Technology. Norsepower Fits First Tiltable Rotor Sails on SC Connector, Ship Technology. 2021. https://www.ship-technology.com/news/norsepower-rotor-sails-sc-connector/ . Accessed 7 Oct 2022.

Bartlett P. Berge BulBulkers, Seatrade Maritime. 2022. https://www.seatrade-maritime.com/sustainability-green-technology/berge-bulk-chooses-anemoi-sails-large-bulkers . Accessed 7 Oct 2022.

Manifold Times. Scandlines to Install Rotor Sail on “M/V Copenhagen” Hybrid Ferry, Manifold Times. 2019. https://www.manifoldtimes.com/news/scandlines-to-install-rotor-sail-on-mv-copenhagen-hybrid-ferry/ . Accessed 7 Oct 2022.

Gallucci, M. Sailing into 2022 with Wind-Powered Cargo Ships, Canary Media. 2022. https://www.canarymedia.com/articles/sea-transport/sailing-into-2022-with-wind-powered-cargo-ships . Accessed 7 Oct 2022.

Corvus Energy. MV Copenhagen, Corvus Energy. 2022. https://corvusenergy.com/projects/copenhagen/ . Accessed 7 Oct 2022.

Viking Line. Viking Grace, Viking Line. 2022. https://www.vikingline.com/environment/viking-grace/ . Accessed 7 Oct 2022.

BV. Airseas’ Seawing Sets Sail with First Installation on Louis Dreyfus Armateurs’ Ville de Bordeaux, chartered by Airbus, Bureau Veritas (BV). 2021. https://marine-offshore.bureauveritas.com/newsroom/airseas-seawing-sets-sail-first-installation-louis-dreyfus-armateurs-ville-de-bordeaux . Accessed 7 Oct 2022.

Airseas. Seawing - Wind Assisted Shipping, Airseas. 2022. https://www.airseas.com/ . Accessed 7 Oct 2022.

Hoffmeister H,Hollenbach U. More Commercial Ships Utilize Wind Technologies to Cut Emissions, DNV: Maritime Impact Our Expertise in Stories. 2022. https://www.dnv.com/expert-story/maritime-impact/more-commercial-ships-utilize-wind-technologies-to-cut-emissions.html . Accessed 7 Oct 2022.

IWA. Wind Propulsion (WP) & Wind Assist Shipping Projects (WASP), International Windship Association (IWA). 2022. https://www.wind-ship.org/en/wind-propulsion-wp-wind-assist-shipping-projects-wasp/ . Accessed 7 Oct 2022..

Safety4Sea. 2021 Was a Record Year for LNG Fueled Ships, says DNV, Safety4Sea. 2022. https://safety4sea.com/2021-was-a-record-year-for-lng-fueled-ships-says-dnv/ . Accessed 7 Oct 2022.

Rinkesh. Various Pros and Cons of Wind Energy (Wind Power), Converse Energy Future. 2022. https://www.conserve-energy-future.com/pros-and-cons-of-wind-energy.php . Accessed 7 Oct 2022.

Sendy, A. How much do solar panels cost in 2022?, Solar Reviews. 2022. https://www.solarreviews.com/solar-panel-cost Accessed 7 Oct 2022.

Qiu Y,Yuan C,Sun Y. Review on the application and research progress of photovoltaics-ship power system, ICTIS 2015 - 3rd International Conference on Transportation Information and Safety. Proceedings. 2015; https://doi.org/10.1109/ICTIS.2015.7232167

Kurniawan A. A review of solar-powered boat development. IPTEK J Technol Sci. 2016. https://doi.org/10.12962/J20882033.V27I1.761 .

Gursu, H. Solar and wind powered concept boats, 2014; https://doi.org/10.4305/METU.JFA.2014.2.6 .

Hanlon M. The Solar Shuttle—Solar-Powered 42-Passenger Boat, New Atlas. 2007. https://newatlas.com/the-solar-shuttle-solar-powered-42-passenger-boat/6997/ Accessed 7 Oct 2022.

Thandasherry, S. Economics of ADITYA-India’s First Solar Ferry, IEEE India. 2018. https://www.swtd.kerala.gov.in/ .

Bleicher A. Solar sailor [Dream jobs 2013-renewables]. IEEE Spectr. 2013;50:45–6. https://doi.org/10.1109/MSPEC.2013.6420144 .

Atkinson GM. Analysis of marine solar power trials on Blue Star Delos. J Marine Eng Technol. 2016;15:115–23. https://doi.org/10.1080/20464177.2016.1246907 .

Carlton JS, Smart R, Jenkins V. The nuclear propulsion of merchant ships: aspects of engineering, science and technology. J Marine Eng Technol. 2014;10:47–59. https://doi.org/10.1080/20464177.2011.11020247 .

Conca, J. Uranium seawater extraction makes nuclear power completely renewable, Forbes. 2016. https://www.forbes.com/sites/jamesconca/2016/07/01/uranium-seawater-extraction-makes-nuclear-power-completely-renewable/?sh=5c9a0aca159a . Accessed 7 Oct 2022.

Peresypkin VI. Introduction to Northern Sea route history and INSROP’s background, the 21st century—turning point for the northern sea route? 2000; https://doi.org/10.1007/978-94-017-3228-4_8 .

Gil Y,Yoo SJ, Oh J,et al. Feasibility Study on Nuclear Propulsion Ship according to Economic Evaluation, in: Transactions of the Korean Nuclear Society Spring Meeting , Transactions of the Korean Nuclear Society Spring Meeting, Gwangju, Korea, 2013: pp. 30–31. http://www.rs -.

Adumene S, Islam R, Amin MT, et al. Advances in nuclear power system design and fault-based condition monitoring towards safety of nuclear-powered ships. Ocean Eng. 2022;251:111156. https://doi.org/10.1016/J.OCEANENG.2022.111156 .

Zerkalov, G. The Nuclear Powered Icebreakers, Coursework for PH241, Stanford University, Winter 2016. (2016). http://large.stanford.edu/courses/2016/ph241/zerkalov2/ . Accessed 5 Aug 2022.

Kołwzan K, Narewski M. Alternative fuels for marine applications, Latvian. J Chem. 2012;4:398–406. https://doi.org/10.2478/v10161-012-0024-9 .

Fevre CN. le. A review of demand prospects for LNG as a marine transport fuel, 2018. https://doi.org/10.26889/9781784671143 .

Wang S,Notteboom T. LNG as a ship fuel: perspectives and challenges, 2013. https://www.porttechnology.org/technical-papers/lng_as_a_ship_fuel_perspectives_and_challenges/ . Accessed 7 Oct 2022.

Tusiani MD, Shearer G. LNG: fuel for a changing world: a nontechnical guide. LLC.: PennWell Books; 2016.

Calderón M, Illing D, Veiga J. Facilities for bunkering of liquefied natural gas in ports. Transport Res Proced. 2016;14:2431–40. https://doi.org/10.1016/J.TRPRO.2016.05.288 .

Wartsilla. Natural Gas-Fuelled Ferry GLUTRA, Wartsilla. 2022. https://www.wartsila.com/encyclopedia/term/natural-gas-fuelled-ferry-glutra Accessed 7 Oct 2022.

DNV-GL. LNG as Ship Fuel: The Future, Det Norske Veritas, Norway, 2014. https://www.dnv.com/Images/LNG_report_2015-01_web_tcm8-13833.pdf .

Kumar S, Kwon HT, Choi KH, et al. LNG: An eco-friendly cryogenic fuel for sustainable development. Appl Energy. 2011;88:4264–73. https://doi.org/10.1016/J.APENERGY.2011.06.035 .

DNV-GL. Assessment of Selected Alternative Fuels and Technologies in Shipping, DNV-GL. 2019 1–56. https://www.dnv.com/maritime/publications/alternative-fuel-assessment-download.html . Accessed 7 Oct 2022.

Aymelek M, Boulougouris EK, Turan O, et al. Challenges and opportunities for LNG as a ship fuel source and an application to bunkering network optimization. In: Carlos GS, Santos TA, editors., et al., Maritime technology and engineering. Amsterdam: CRC Press; 2014. p. 781–90.

DNV-GL. Decarbonize Shipping - DNV, DNV. 2022. https://www.dnv.com/maritime/hub/decarbonize-shipping/fuels/bridging-fuels.html . Accessed 7 Oct 2022.

Atilhan S, Park S, El-Halwagi MM, et al. Green hydrogen as an alternative fuel for the shipping industry. Curr Opin Chem Eng. 2021;31:100668. https://doi.org/10.1016/J.COCHE.2020.100668 .

De-Troya JJ, Álvarez C, Fernández-Garrido C, et al. Analysing the possibilities of using fuel cells in ships. Int J Hydrogen Energy. 2016;41:2853–66. https://doi.org/10.1016/J.IJHYDENE.2015.11.145 .

Han J, Charpentier JF, Tang T. State of the art of fuel cells for ship applications. IEEE Int Symp Indus Electron. 2012. https://doi.org/10.1109/ISIE.2012.6237306 .

Wang CM, Yee AA, Krock H, et al. Research and developments on ocean thermal energy conversion. Ceased. 2011;4:41–52. https://doi.org/10.1080/19373260.2011.543606 .

Nguyen HP, Wang CM, Tay ZY, et al. Wave energy converter and large floating platform integration: a review. Ocean Eng. 2020. https://doi.org/10.1016/j.oceaneng.2020.107768 .

Tay ZY. Energy extraction from an articulated plate anti-motion device of a very large floating structure under irregular waves. Renew Energy. 2019;130:206–22. https://doi.org/10.1016/J.RENENE.2018.06.044 .

Tay Z. Energy generation from anti-motion device of very large floating structure, in: European Wave and Tidal Energy Conference 2017 (EWTEC2017), Cork, Ireland, 2017. https://www.researchgate.net/publication/319642402_Energy_Generation_from_Anti-Motion_Device_of_Very_Large_Floating_Structure . Accessed 7 Feb 2023.

van Biert L, Godjevac M, Visser K, et al. A review of fuel cell systems for maritime applications. J Power Sources. 2016;327:345–64. https://doi.org/10.1016/J.JPOWSOUR.2016.07.007 .

Zhu J, Zhao P, Pan Y. Analysis of energy development of ship power. IOP Conf Ser Earth Environ Sci. 2020;446:52084. https://doi.org/10.1088/1755-1315/446/5/052084 .

Xing H, Stuart C, Spence S, et al. Fuel cell power systems for maritime applications: progress and perspectives. Sustainability. 2021;13:12. https://doi.org/10.3390/SU13031213 .

Wu P,Bucknall RWG. On the design of plug-in hybrid fuel cell and lithium battery propulsion systems for coastal ships, in: Marine Design XIII, CRC Press, 2018: pp. 941–951.

Zhu J, Zhao P, Pan Y. Analysis of energy development of ship power. IOP Conf Ser Earth Environ Sci. 2020;446:052084. https://doi.org/10.1088/1755-1315/446/5/052084 .

Pratt Joseph W,Klebanoff Leonard E. Feasibility of the SF-BREEZE: a Zero-Emission, Hydrogen Fuel Cell, High-Speed Passenger Ferry, Energy Innovation (8366); Hydrogen and Combustion Technology (8367) . 2016. https://rosap.ntl.bts.gov/view/dot/51783 . Accessed 13 July 2022).

Inal OB,Deniz C,İnal ÖB. Fuel Cell Availability for Merchant Ships Dynamic Modelling, Simulation Based Analysis and Optimization of Hybrid Ship Propulsion System View project Fuel Cell Availability for Merchant Ships, 2018. https://www.researchgate.net/publication/324910580 . Accessed 13 July 2022.

Pratt JW,Klebanoff LE. Feasibility of the SF-BREEZE: a Zero-Emission, Hydrogen Fuel Cell, High-Speed Passenger Ferry, Energy Innovation (8366); Hydrogen and Combustion Technology (8367). 2016. https://rosap.ntl.bts.gov/view/dot/51783 .

Zemships. One Hundred Passengers and Zero Emissions the First Ever Passenger Vessel to Sail Propelled by Fuel Cells, Zemships. 2013. https://sectormaritimo.es/wp-content/uploads/2018/01/MS_Alsterwasser.pdf . Accessed 7 Oct 2022.

van Hoecke L, Laffineur L, Campe R, et al. Challenges in the use of hydrogen for maritime applications. Energy Environ Sci. 2021;14:815–43. https://doi.org/10.1039/D0EE01545H .

Machaj K, Kupecki J, Malecha Z, et al. Ammonia as a potential marine fuel: a review. Energy Strategy Rev. 2022;44:100926. https://doi.org/10.1016/J.ESR.2022.100926 .

Zincir B,Zincir B. A Short Review of Ammonia as an Alternative Marine Fuel for Decarbonised Maritime Transportation, (n.d.). https://www.researchgate.net/publication/346037882 . Accessed 13 Dec 2022.

Al-Aboosi FY, El-Halwagi MM, Moore M, et al. Renewable ammonia as an alternative fuel for the shipping industry. Curr Opin Chem Eng. 2021;31:100670. https://doi.org/10.1016/J.COCHE.2021.100670 .

Teodorczyk A, di Blasio G, Mallouppas G, et al. A review of the latest trends in the use of green ammonia as an energy carrier in maritime industry. Energies. 2022;15:1453. https://doi.org/10.3390/EN15041453 .

Gallucci M. The ammonia solution: ammonia engines and fuel cells in cargo ships could slash their carbon emissions. IEEE Spectr. 2021;58:44–50. https://doi.org/10.1109/MSPEC.2021.9370109 .

Afif A, Radenahmad N, Cheok Q, et al. Ammonia-fed fuel cells: a comprehensive review. Renew Sustain Energy Rev. 2016;60:822–35. https://doi.org/10.1016/J.RSER.2016.01.120 .

Jeerh G, Zhang M, Tao S. Recent progress in ammonia fuel cells and their potential applications. J Mater Chem A Mater. 2021;9:727–52. https://doi.org/10.1039/D0TA08810B .

Hansson J,Fridell E,Brynolf S. On the Potential of Ammonia as Fuel for Shipping: a Synthesis of Knowledge, 2020. https://trid.trb.org/view/1706562 .

Royal Society. Ammonia: Zero-Carbon Fertiliser, Fuel and Energy Store, Royal Society. 2022. https://royalsociety.org/topics-policy/projects/low-carbon-energy-programme/green-ammonia/ . Accessed 29 Sept 2022.

Prevljak NH. World’s First Ammonia-ready Vessel Delivered, Offshore Energy. 2022. https://www.offshore-energy.biz/worlds-first-ammonia-ready-vessel-delivered/ . Accessed 7 Oct 2022.

Cheliotis M, Boulougouris E, Trivyza NL, et al. Review on the safe use of ammonia fuel cells in the maritime industry. Energies. 2021;14:3023. https://doi.org/10.3390/EN14113023 .

MAN Energy Solutions. Biofuel, MAN Energy Solutions. (2022). https://www.man-es.com/marine/strategic-expertise/future-fuels/biofuel . Accessed 29 Sept 2022.

Florentinus A,Hamelinck C,van den Bos A,et al. Potential of Biofuels for Shipping—Final Report, Lisbon (Portugal), 2012.

Mukherjee A, Bruijnincx P, Junginger M. A perspective on biofuels use and CCS for GHG mitigation in the marine sector. IScience. 2020;23:101758. https://doi.org/10.1016/J.ISCI.2020.101758 .

McGill Fuels R,Consulting William Remley E,Winther K. Alternative Fuels for Marine Applications Annex 41, IEA Advanced Motor Fuels Implementing Agreement. 2013.

Smoot G. What Is the Carbon Footprint of Biodiesel? A Life-Cycle Assessment, Impactful Ninja. 2022. https://impactful.ninja/the-carbon-footprint-of-biodiesel/ Accessed 29 Sept 2022.

Coronado CR, de Carvalho JA, Silveira JL. Biodiesel CO2 emissions: a comparison with the main fuels in the Brazilian market. Fuel Process Technol. 2009;90:204–11. https://doi.org/10.1016/j.fuproc.2008.09.006 .

EIA. Frequently Asked Questions: How Much Carbon Dioxide is Produced by Burning Gasoline and Diesel fuel?, US Energy Information Administration (EIA). 2014. https://www.patagoniaalliance.org/wp-content/uploads/2014/08/How-much-carbon-dioxide-is-produced-by-burning-gasoline-and-diesel-fuel-FAQ-U.S.-Energy-Information-Administration-EIA.pdf . Accessed 7 Oct 2022.

Krantz, G. CO2 Emissions Related to the Fuel Switch in the Shipping Industry in Northern Europe, 2016.

NYK. NYK Conducts Successful Biofuel Trial on Vessel Transporting Tata Steel Cargo, NYK Line. 2021. https://www.nyk.com/english/news/2021/20211122_01.html . Accessed 7 Oct 2022.

Datta A, Hossain A, Roy S. An overview on biofuels and their advantages and disadvantages. Asian J Chem. 2019;8:1851–8. https://doi.org/10.14233/AJCHEM.2019.22098 .

Rodionova MV, Poudyal RS, Tiwari I, et al. Biofuel production: challenges and opportunities. Int J Hydrogen Energy. 2017;42:8450–61. https://doi.org/10.1016/J.IJHYDENE.2016.11.125 .

Manifold Times. Singapore: “Frontier Jacaranda” Completes Bunker Biofuel Trial in Voyage, Manifold Times. 2021. https://www.manifoldtimes.com/news/singapore-frontier-jacaranda-completes-bunker-biofuel-trial-in-voyage/ . Accessed 7 Oct 2022.

Pulyaeva VN,Kharitonova NA,Kharitonova EN. Advantages and disadvantages of the production and using of liquid biofuels, in: IOP Conf Ser Mater Sci Eng, 2020: p. 012031. https://doi.org/10.1088/1757-899X/976/1/012031 .

Landälv I. Methanol as A Renewable Fuel–A Knowledge Synthesis, The Swedish Knowledge Centre for Renewable Transportation Fuels, Sweden, 2017; www.f3centre.se .

Svanberg M, Ellis J, Lundgren J, et al. Renewable methanol as a fuel for the shipping industry. Renew Sustain Energy Rev. 2018;94:1217–28. https://doi.org/10.1016/J.RSER.2018.06.058 .

Methanex. Sustainability Report 2020 Building a Better Future Together, Methanex Corporation. 2020. https://www.methanex.com/sites/default/files/2020-Sustainability-Report.pdf . Accessed 7 Oct 2022.

Stena Line. Stena Germanica Refuels with Recycled Methanol from Residual Steel Gases, Stena Line. 2021. https://www.stenaline.com/about-us/our-ships/stena-germanica/ Accessed 7 Oct 2022.

Andersson K, Salazar CM. Methanol as a marine fuel report. Washington DC: Methanol Institute; 2015.

Magloff, L. A Sea Kite that Helps Ships Save Fuel Undergoes Trials, Springwise. 2022. https://www.springwise.com/innovation/mobility-transport/fuel-saving-auto-kite/ . Accessed 10 Oct 2022.

Pan P, Sun Y, Yuan C, et al. Research progress on ship power systems integrated with new energy sources: a review. Renew Sustain Energy Rev. 2021;144:111048. https://doi.org/10.1016/J.RSER.2021.111048 .

NEI. Nuclear Fuel, Nuclear Energy Institute. 2022. https://www.nei.org/fundamentals/nuclear-fuel . Accessed 11 Oct 2022.

IWSA Member. Vindskip TM – Lade AS – IWSA Member, International Windship Association (IWSA). 2022. https://www.wind-ship.org/en/vindskip/ . Accessed 7 Oct 2022.

Energy Observer. Energy Observer Integrates Wind Propulsion Wings on Board!, (n.d.). https://www.energy-observer.org/resources/oceanwings-new-technology-on-board-wind-propulsion-wings .

Comer, B.,Chen, C.,Stolz, D.,et al. Rotors and Bubbles: Route-based Assessment of Innovative Technologies to Reduce Ship Fuel Consumption and Emissions, The International Council on Clean Transportation. 2019. https://theicct.org/sites/default/files/publications/Rotors_and_bubbles_2019_05_12.pdf Accessed 17 Dec 2022.

Anders J. Comparison of Alternative Marine Fuels, Det Norske Veritas, Norway, 2019. www.dnvgl.com .

The Engineering Toolbox. Combustion of Fuels - Carbon Dioxide Emission, The Engineering Toolbox. 2022. https://www.engineeringtoolbox.com/co2-emission-fuels-d_1085.html Accessed 29 Sept 2022.

Statista. Competitiveness of Alternative Fuels in Container Shipping 2030, by Fuel Type, Statista. 2022. https://www.statista.com/statistics/1267782/costs-of-using-different-types-of-alternative-fuels-for-container-ship/ . Accessed 9 Oct 2022.

Ghenai C, Bettayeb M, Brdjanin B, et al. Hybrid solar PV/PEM fuel cell/diesel generator power system for cruise ship: a case study in Stockholm Sweden. Case Studies Thermal Eng. 2019;14:100497. https://doi.org/10.1016/J.CSITE.2019.100497 .

Rasmussen PD. A.P. Moller—Maersk Continues Green Transformation with Six Additional Large Container Vessels, Maersk. (2022). https://www.maersk.com/news/articles/2022/10/05/maersk-continues-green-transformation . Accessed 6 Oct 2022.

IMO. IMO Action to Reduce Greenhouse Gas Emissions from International Shipping, International Maritime Organisation (IMO). 2022. https://sustainabledevelopment.un.org/content/documents/26620IMO_ACTION_TO_REDUCE_GHG_EMISSIONS_FROM_INTERNATIONAL_SHIPPING.pdf .

IEA. R&D and Technology Innovation, International Energy Agency (IEA). 2020. https://www.iea.org/reports/world-energy-investment-2020/rd-and-technology-innovation . Accessed 5 Oct 2022.

SEA-LNG. LNG – A Fuel in Transition, SEA-LNG. 2022. https://sea-lng.org/2022/01/sea-lng-2021-22-a-view-from-the-bridge/ . Accessed 9 Oct 2022.

Ellis D. New LNG Infrastructure Investment to Reach $42bn Annually from 2024, Gasworld. 2022. https://www.gasworld.com/new-lng-infrastructure-investment-to-reach-42bn-annually-from-2024/2023675.article . Accessed 5 Oct 2022.

Prevljak NH. Norwegian Duo to Build 1st Ammonia Bunkering Terminals, Offshore Energy. 2021. https://www.offshore-energy.biz/norwegian-duo-to-build-1st-ammonia-bunkering-terminals/ . Accessed 5 Oct 2022.

Mitchell JFB, Johns TC, Ingram WJ, et al. The effect of stabilising atmospheric carbon dioxide concentrations on global and regional climate change. Geophys Res Lett. 2000;27:2977–80. https://doi.org/10.1029/1999GL011213 .

CSS. Greenhouse Gases Factsheet, University of Michigan Centre for Sustainable Systems (CSS). 2021. https://css.umich.edu/publications/factsheets/climate-change/greenhouse-gases-factsheet . Accessed 6 Oct 2022.

Bamber JL, Oppenheimer M, Kopp RE, et al. Ice sheet contributions to future sea-level rise from structured expert judgment. Proc Natl Acad Sci USA. 2019;166:11195–200. https://doi.org/10.1073/pnas.1817205116 .

UNFCCC. The Paris Agreement, United Nations Framework Convention on Climate Change (UNFCCC). 2015. https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement . Accessed 6 Oct 2022.

Nunuz, C. Sea Level Rise, Facts and Information, Natl Geogr Mag. 2022. https://www.nationalgeographic.com/environment/article/sea-level-rise-1 . Accessed 6 Oct 2022.

Steel Ships Limited. Alternate Marine Fuels and Emissions, Steel Ships Limited. 2020. https://steel-ships.com/marine_services/alternate_fuels_and_emission_issues . Accessed 6 Oct 2022.

Hauhia E. Bulk Shipping in Numbers and Emissions, Seaber. 2021. https://seaber.io/blog/bulk-shipping-numbers-emissions . Accessed 11 Oct 2022.

DNV-GL. Alternative Fuels: The options, DNV. 2018. https://www.dnv.com/expert-story/maritime-impact/alternative-fuels.html . Accessed 6 Oct2022.

Bazari Z, Longva T. Assessment of IMO mandated energy efficiency measures for international shipping. London: International maritime organisation; 2011.

Download references

Acknowledgement

The authors would like to thank Miss Kesha Martiny D/O Yagasundaram for compilation of data.

This research was funded by MOE, Grant Number R-MOE-E103-F010.

Author information

Authors and affiliations.

Singapore Institute of Technology, 10 Dover Drive, Singapore, 138683, Singapore

Zhi Yung Tay

Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, 100 Montrose St, Glasgow, G4 0LZ, UK

Dimitrios Konovessis

You can also search for this author in PubMed   Google Scholar

Contributions

Zhi Yung Tay: Conceptualization, writing—original draft preparation, writing—review and editing, visualisation, supervision Dimitrios Konovessis: Review and editing, Funding aquisition. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Zhi Yung Tay .

Ethics declarations

Competing interests.

The authors declare that they have no competing interests.

Additional information

Publisher's note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Tay, Z.Y., Konovessis, D. Sustainable energy propulsion system for sea transport to achieve United Nations sustainable development goals: a review. Discov Sustain 4 , 20 (2023). https://doi.org/10.1007/s43621-023-00132-y

Download citation

Received : 01 November 2022

Accepted : 06 March 2023

Published : 06 April 2023

DOI : https://doi.org/10.1007/s43621-023-00132-y

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Alternative fuels
• Green shipping
• Climate change
• UN Sustainable Development Goals
• Find a journal
• Publish with us
• Track your research

Energy Transfers and Transformations

Energy cannot be created or destroyed, but it can be transferred and transformed. There are a number of different ways energy can be changed, such as when potential energy becomes kinetic energy or when one object moves another object.

Earth Science, Physics

Water Boiling Pot

There are three types of thermal energy transfer: conduction, radiation, and convection. Convection is a cyclical process that only occurs in fluids.

Photograph by Liu Kuanxi

Energy cannot be created or destroyed, meaning that the total amount of energy in the universe has always been and will always be constant. However, this does not mean that energy is immutable; it can change form and even transfer between objects. A common example of energy transfer that we see in everyday life is the transfer of kinetic energy —the energy associated with motion—from one moving object to a stationary object via work. In physics, work is a measure of energy transfer and refers to the force applied by an object over a distance. When a golf club is swung and hits a stationary golf ball, some of the club’s kinetic energy transfers to the ball as the club does “work” on the ball. In an energy transfer such as this one, energy moves from one object to another, but stays in the same form. A kinetic energy transfer is easy to observe and understand, but other important transfers are not as easy to visualize. Thermal energy has to do with the internal energy of a system due to its temperature. When a substance is heated, its temperature rises because the molecules it is composed of move faster and gain thermal energy through heat transfer. Temperature is used as a measurement of the degree of “hotness” or “coldness” of an object, and the term heat is used to refer to thermal energy being transferred from a hotter system to a cooler one. Thermal energy transfers occur in three ways: through conduction , convection , and radiation . When thermal energy is transferred between neighboring molecules that are in contact with one another, this is called conduction . If a metal spoon is placed in a pot of boiling water, even the end not touching the water gets very hot. This happens because metal is an efficient conductor , meaning that heat travels through the material with ease. The vibrations of molecules at the end of the spoon touching the water spread throughout the spoon, until all the molecules are vibrating faster (i.e., the whole spoon gets hot). Some materials, such as wood and plastic, are not good conductors —heat does not easily travel through these materials—and are instead known as insulators . Convection only occurs in fluids, such as liquids and gases. When water is boiled on a stove, the water molecules at the bottom of the pot are closest to the heat source and gain thermal energy first. They begin to move faster and spread out, creating a lower density of molecules at the bottom of the pot. These molecules then rise to the top of the pot and are replaced at the bottom by cooler, denser water. The process repeats, creating a current of molecules sinking, heating up, rising, cooling down, and sinking again. The third type of heat transfer— radiation —is critical to life on Earth and is important for heating bodies of water. With radiation , a heat source does not have to touch the object being heated; radiation can transfer heat even through the vacuum of space. Nearly all thermal energy on Earth originates from the sun and radiates to the surface of our planet, traveling in the form of electromagnetic waves, such as visible light. Materials on Earth then absorb these waves to be used for energy or reflect them back into space. In an energy transformation , energy changes form. A ball sitting at the top of a hill has gravitational potential energy , which is an object’s potential to do work due to its position in a gravitational field. Generally speaking, the higher on the hill this ball is, the more gravitational potential energy it has. When a force pushes it down the hill, that potential energy transforms into kinetic energy . The ball continues losing potential energy and gaining kinetic energy until it reaches the bottom of the hill. In a frictionless universe, the ball would continue rolling forever upon reaching the bottom, since it would have only kinetic energy . On Earth, however, the ball stops at the bottom of the hill due to the kinetic energy being transformed into heat by the opposing force of friction. Just as with energy transfers , energy is conserved in transformations. In nature, energy transfers and transformations happen constantly, such as in a coastal dune environment. When thermal energy radiates from the sun, it heats both the land and ocean, but water has a specific high heat capacity, so it heats up slower than land. This temperature difference creates a convection current, which then manifests as wind. This wind possesses kinetic energy , which it can transfer to grains of sand on the beach by carrying them a short distance. If the moving sand hits an obstacle, it stops due to the friction created by the contact and its kinetic energy is then transformed into thermal energy , or heat. Once enough sand builds up over time, these collisions can create sand dunes, and possibly even an entire dune field. These newly formed sand dunes provide a unique environment for plants and animals. A plant may grow in these dunes by using light energy radiated from the sun to transform water and carbon dioxide into chemical energy , which is stored in sugar. When an animal eats the plant, it uses the energy stored in that sugar to heat its body and move around, transforming the chemical energy into kinetic and thermal energy . Though it may not always be obvious, energy transfers and transformations constantly happen all around us and are what enable life as we know it to exist.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Production Managers

Program specialists, last updated.

October 19, 2023

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Front Robot AI

Sustainable Solutions for Sea Monitoring With Robotic Sailboats: N-Boat and F-Boat Twins

Alvaro p. f. negreiros.

1 Electrical and Computer Engineering Graduate Program, Universidade Federal Do Rio Grande do Norte, Natal, Brazil

Wanderson S. Correa

2 Computing Institute, Universidade Federal Fluminense, Niteroi, Brazil

André P. D. de Araujo

Davi h. santos, joão m. vilas-boas.

3 Academic Directorate of Information Technology, Instituto Federal de Educação Tecnológica Do Rio Grande do Norte, Natal, Brazil

Daniel H. N. Dias

4 Electrical Engineering Department, Universidade Federal Fluminense, Niteroi, Brazil

Esteban W. G. Clua

Luiz m. g. gonçalves.

Paulo Fernando Ferreira Rosa , Instituto Militar de Engenharia, Brazil

Associated Data

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

Strategic management and production of internal energy in autonomous robots is becoming a research topic with growing importance, especially for platforms that target long-endurance missions, with long-range and duration. It is fundamental for autonomous vehicles to have energy self-generation capability to improve energy autonomy, especially in situations where refueling is not viable, such as an autonomous sailboat in ocean traversing. Hence, the development of energy estimation and management solutions is an important research topic to better optimize the use of available energy supply and generation potential. In this work, we revisit the challenges behind the project design and construction for two fully autonomous sailboats and propose a methodology based on the Restricted Boltzmann Machine (RBM) in order to find the best way to manage the supplementary energy generated by solar panels. To verify the approach, we introduce a case study with our two developed sailboats that have planned payload with electric and electronics, and one of them is equipped with an electrical engine that may eventually help with the sailboat propulsion. Our current results show that it is possible to augment the system confidence level for the potential energy that can be harvested from the environment and the remaining energy stored, optimizing the energy usage of autonomous vehicles and improving their energy robustness.

1 Introduction

Autonomous robots are machines that have embedded systems with some specific purpose, which depends on the application. Nonetheless, in general, they have computational and physical resource restrictions ( Almeida, 2016 ), being the energy performance one of the main issues to be accounted for when developing such machines ( Aldegheri et al., 2018 ). Surface aquatic robotic (ASV or USV) and submersible (AUV) vehicles allow human beings to explore the ocean in innovative ways, with less cost, greater efficiency, and reducing risks inherent to marine operations, quickly following its natural course towards its ultimate goal: full automation for working in the ocean. In this direction, an emerging generation of devices and their systems is being designed and developed to operate independently, making decisions during operation, without direct control of a human operator.

Nevertheless, there are several cases where energy autonomy is still a big issue, contrasting with its reliability in the face of day-to-day missions ( Alaieri and Vellino, 2016 ). Energy autonomy refers to the robotic agent’s ability to maintain itself in a viable state for long periods, or as necessary. Its behavior must be always stable in such a way that it does not lack any vital resources. For example, in some situations, it must not exceed some limit of energy consumption. Until recently, autonomy has been always approached from a computing perspective. For example, consider the case of a battery-operated robot that is released to perform its task without outside intervention. When the task is completed or when the battery charge decreases, the robot returns to a base for recharging and/or further instructions. Thus, in this case, only certain aspects of robot behavior can be considered autonomous, for example, computational and control decisions. On the other hand, without a human in the loop , this kind of robot would not be able to replenish its energy to perform the task. In the case of this work, the robot should be long-running, for weeks or even months without intervention, as it will be explained further. So, the human in the loop is not possible and all energy management should be done by the robot system itself.

Hence, in this paper, we aim to introduce a novel energy estimation and management process, based on the Restricted Boltzmann Machine (RBM). An RBM is a stochastic network that can be used for representing undirected generative models that use a layer of hidden variables to model a distribution that has as input a set of visible variables Larochelle and Bengio (2008) . RBM are widely used to compose deep belief networks (DBN) extracting characteristics from a dataset through unsupervised training ( Hinton and Salakhutdinov, 2006 ). As it will be explained further in Subsection 2.3 , the network used in this work has an initial layer with 6 neurons that, after normalization, gets to 55 neurons in the visible units and at least 55 neurons in the hidden unit. The main strategy here is to use this approach aiming at finding a solution to the distribution of energy consumption problem with solar panels in our autonomous sailboat, the F-Boat. Our current proposal is inspired by our previous project ( Júnior et al., 2013 ; Negreiros, 2019 ), whose main objective is the development of an autonomous vessel for collecting and monitoring environmental data. This is an open project, with complete documentation that can be found on our web repositories ( LAICA, 2015 ; Negreiros, 2019 ). The focus of the project is to develop a long-endurance autonomous system, satisfying quality criteria for being qualified as sustainable and with environmentally friendly energy generation.

The current project version named F-Boat is an evolution of previous USV projects that our research group has developed, such as the N-Boat 1 ( Júnior et al., 2013 ) and N-Boat 2 ( Negreiros, 2019 ). F-Boat is a twin, new version of N-Boat 2 with updated architectural design and equipment. It is also an autonomous unmanned vessel (a sailboat USV) as seen in Figure 1 With respect to the planning of missions, they can be established using our multi purpose platform regarding some restrictions. The main one is mission duration, which should be determined based on how many hours or days without solar charging the vehicle will face and if the electrical engine propulsion will be required. Considering the worst situation, with no sunlight, the theoretical endurance is 62 h without using the electrical motor (navigation only with sail and rudder). The endurance is 11 h if using the electric motor on a continuous basis, in the case of no wind situation, for example. Knowing that, it is possible to stay for a long time on the water without charging, and with the batteries recharging when necessary, which is provided by the solar panels. The two boats are self-sufficient considering their current set of electric and electronics, being satisfactory to date. However, our main issue in this paper is related to future power consumption, as the emergency electrical motor and other eventual payload devices would be embarked, which may eventually increase said consumption. In this case, planning on future available energy and defining what equipment or device will function, must be done based on an estimation of said production. In this newer version, in addition to the sensors necessary for autonomous navigation, other more dedicated sensors are used, such as the stereo camera Zed that has a 16 m range ( Ortiz-Fernandez et al., 2018 ) for very short forward-visual sensing and a 360°camera for larger-range visual sensing. Both sensors allow the robot to perceive its immediate environment and find short-range obstacles. We notice that the depth information provided by the ZED is useful only in the short range (16 m and less). In general applications, the idea is to complement the depth information with a LIDAR, however, we have not bought it at the time that this article has been written. Nonetheless, we are working on accurate detection algorithms for the short range based on the Zed information, in order to guarantee that the boat stops when some obstacle is detected just on its front. At the moment we are also working with computer vision and AI approaches using the 360 camera, which can be applied for larger depth distances. All of these sensors generate a massive amount of data that are locally processed by an embedded processor based on an nVidia Xavier board. Part of the data is locally saved for future analysis and comparison with a simulator that has been implemented ( Paravisi et al., 2019 ). This data can also be sent to a ground control station (GCS), which is an option for mission updates or telemetry (we use the Mission Planner for that). We initially intended to use this high-performance processing board as a kind of a single board computer (SBC), for communication with the GCS and managing all boat resources and systems, besides visual data processing. However, due to real-time restriction, we are studying the possibility of using another board as the SBC, since visual processing may complicate the real-time implementation aspects of the system. Hence, the general contribution of the project is a step forward for solving the several challenges faced when developing a sailboat robot, beginning with the boat’s architectural design and construction itself, including solutions for autonomous sailing navigation, image processing, obstacle detection, and control issues.

F-Boat hull with its solar panels.

With this general objective of the project in mind, the energy management is treated as the specific focus of the contribution of this paper, which resides on describing reliably and ecologically correct solutions to both sailboats’ energy problems. We propose a particular solution that involves the use of offgrid energy production based on solar panels to maintain the more complete as possible set of components operating, such as the emergency electric motor and other actuators, processors, and cameras. Hence, it is necessary to make an intelligent use of the scarce energy resource, aiming at an autonomous, sustainable, and ecologically correct system. Having this focus in energy management, the practical contribution that we propose here is a set of rules that are implemented for setting up what are the devices that can operate given certain weather conditions to the sailboat, including emergency cases. This management is implemented by way of using a Boltzmann machine ( Bu et al., 2015 ; Passos et al., 2020 ). Therefore, our main contribution is this methodology to predict energy production from solar panels in the near future, to increase the sustainability of the sailboat through better energy management and thus reducing the navigation problem induced by negative power input (consuming more than it produces). Our current results demonstrate the use of Boltzmann machine to forecast the expected future energy production as a solution to improve energy autonomy of mobile platforms.

Some theory on sailboat projects are introduced in the following Section, in which we will also describe the basics an Boltzmann Machine, that will be the intelligence approach behind the vehicle’s energy resource. Then, we provide the energy generation system followed by the use of Boltzmann Machine approach, with a experiment on energy management and our final discussions.

2 Background Issues Related to Autonomous Sailboat

A sailboat that intends to operate at the sea gives up important challenges that are brought by physical environmental phenomena such as waves, wind, water salinity, and temperature, among others. Most of these phenomena can be represented by dynamic variables, which is one natural alternative for building, analyzing, and comparing techniques for autonomous sailing. In order to better understand, also for design and implement a fully autonomous sailboat, it is necessary to gather some multidisciplinary contents. In this section, we get into some of these, with important issues related to the energy management, architectural design of our sailboat, and details of Boltzmann machine energy management solution.

2.1 Renewable Energy Sources in Sailboats

The usage of renewable sources, such as the sun, wind, tides, among others are important ways for enhancing energy autonomy in future vehicles ( Dupriez-Robin et al., 2009 ). In this direction, the use of wind propulsion is an important solution for surface water autonomous vehicles (USV or ASV). However, to ensure that a sailboat is an electrically self-sufficient platform, since all onboard electronics require one or more energy sources, considerations must be taken regarding the total energy required and how much operating time will be spent on the missions. Rechargeable batteries are typically used as primary sources for energy storage. It is essential to consider on-site energy production using some self-sustaining model. On vessels, there are several ways to obtain energy. One of the most used is solar panels, which is an excellent alternative energy source for embedded systems in general ( Raghunathan et al., 2005 ).

Solar panels are devices that convert energy from solar radiation into electrical energy. However, depending on factors involving the panels’ nature, such as direct radiation, hours of sunlight, and temperature, substantial variations in the amount of energy produced by these mechanisms can occur. It is necessary to use a charge controller, which stabilizes varying energy ranges. As occurs in any transformation process in nature, a part of the energy is lost. Thus, the price of this transformation is a decrease in the energy efficiency rate of the system as a whole.

It is important to mention that choosing a sail-powered vessel is a strategic and main point of long-range monitoring projects. Since we choose well-designed energy sources and also use well-defined consumption strategies ( Kanellos, 2014 ; Khan et al., 2017 ; Vu et al., 2017 ; Letafat et al., 2020 ), sailboats are able to achieve full autonomy, acting independently of human beings, as long as they are programmed for the task. A fully autonomous robotic sailboat does not need to stop for recharging or refueling ( Hole et al., 2016 ). In cases of semi-autonomy, recharging strategies during the mission must be considered and planned ( Waseem et al., 2019 ). The architectural design adopted in our sailboat is described next.

2.2 N-Boat and F-Boat Behavioral Architecture

As aforementioned in the Introduction, F-Boat is an upgrade from the previous autonomous sailing boat called N-Boat. Both of them are implemented inspired on the behavioral architecture namely subsumption ( Brooks, 1986 ), which constantly processes and executes routines of the different layers. With this approach, the basic actuation and sensing commands never cease to be executed. The basic idea of the architecture is that more basic and instinctive behaviors controls (robot survival) prevail over more sophisticated and unnecessary behaviors. In order for this to be orchestrated by a resource management algorithm, each behavior has a weight, allowing them to be ranked. It is noteworthy that behaviors below a given behavior are not suppressed, however, the behaviors above can be suppressed. Figure 2 illustrates the implementation of this approach. For example: Navigation control has a more critical processing weight than Obstacle avoidance . Thus, in extreme cases, the Obstacle avoidance behavior routine is suppressed by the processing of Navigation control routine. But it is important to understand that even in this case the PID + control behavior is still processed because it has even more priority.

Basic architecture of N-Boat and F-Boat inspired in the subsumption architecture.

The architecture represented in Figure 2 shows weights for each behavior, on the left. These weights should be constantly adjusted to adapt in real-time to the environment changes. The machine learning model, which is inserted in the left of Figure 3 , is responsible for this update. Nonetheless, as the marine environment (wind, tides, weather, swells, among others) is highly dynamic, there is a great need for the weights of these behaviors to quickly adapt. Furthermore, each behavior can use machine learning, in its own context, to improve its performance. As illustrated in the blue boxes next to each behavior. For example, in the rudder control, the P, I, and D gains can be adjusted by using the ML. In cases where regular algorithms are not able to perform this task in the required time, the option of using TEDA-Cloud Bezerra et al. (2016) is listed as an alternative. For instance, if data processing can be made available online, it is possible to establish a window in which the signals can be processed with a greater degree of dynamicity ( Bezerra et al., 2016 ).

Basic architecture combined with machine learning.

We notice that, with current embedded computing resources, there is the possibility that behaviors can be computed at the same time. Since many control cards already have more than one physical core in the processor and chips or GPU cards. Therefore, it is quite plausible that this architecture can delegate more than one processing at the same time, which means that is possible for the boat to compute the processing of an obstacle avoidance while analyzing the processing of a payload, or the running energy management system, based on the Boltzmann machine.

The integration of the energy management system based on the Boltzmann machine as a behavior in our basic sailboat control architecture allows us to implement the energy-saving strategy. Since the behaviors also have energy consumption grades, routines that consume energy may be suppressed. It is important to mention that our machine learning implementations allows to predicting these cases, minimizing the situations where these events may happen. The behaviors that can be turned off should be above the energy management system and behaviors that can not be turned off should be below it.

2.3 Restricted Boltzmann Machine

The data classification problem is intrinsically related to the recognition of patterns and regularities in a given database. In the context of learning systems, classifying data is considered a supervised problem. However, unsupervised approaches, such as the restricted Boltzmann machine ( Smolensky, 1986 ; Hinton, 2002 ) and autoencoders ( Bourlard and Kamp, 1988 ), have been applied as feature extraction tools to feed supervised algorithms such as artificial neural networks ( Haykin, 1999 ). Thus, semi-supervised techniques emerge, which have gained prominence in recent years.

The restricted Boltzmann machine (RBM) is a stochastic network widely used to compose deep belief networks (DBN) ( Hinton and Salakhutdinov, 2006 ). RBM can extract characteristics from a dataset through unsupervised training. Due to this, approaches that use RBMs to compose a DBN were developed as the first stage of a classifier based on artificial neural networks ( Salama et al., 2010 ; Tamilselvan and Wang, 2013 ).

The restricted Boltzmann machine ( Smolensky, 1986 ; Hinton, 2002 ) is essentially a stochastic network consisting of two layers: visible and hidden. The visible units layer represents the observed data and is connected to the hidden layer, which in turn, must learn to extract characteristics from this data ( Memisevic and Hinton, 2010 ). Originally, RBM was developed for binary data, both in the visible layer and the hidden layer. This approach is known as Bernoulli-Bernoulli RBM (BBRBM). Since there are problems where it is necessary to process other types of data, Hilton and Salakhutdinov ( Hinton and Salakhutdinov, 2006 ) proposed the Gaussian-Bernoulli RBM (GBRBM), which uses a normal distribution to model the visible layer neurons. In this section, the basic concepts related to the GBRBM approach will be described.

In RBM, the connections between neurons are bidirectional and symmetrical. This means that there is information traffic in both directions of the network. Furthermore, to simplify the inference process, neurons from the same layer are not connected to each other. Therefore, there is only a connection between neurons from different layers, so that the machine is restricted. Figure 4 shows an RBM with M neurons in the visible layer ( v 1 , …, v m ), n neurons in the hidden layer ( h 1 , …, h n ), where ( a 1 , …, a m ) and ( b 1 , …, b n ) are the bias vectors and W corresponds to the connection weight matrix. From here to the end of Section 2 , the set ( W , a , b ) will be called θ .

The RBM is an energy-based model, with the joint probability distribution of the configuration (v,h) being described by:

As the RBM is restricted, it does not have neuron connections between the same layer, the probability distributions of h given v and v given h are described by Equations 3 , 4 , respectively.

The Restricted Bolztmann Machine that we use here is implemented using Python, with the Numpy, Keras, and Sklearn library help. After training, this network is able to predict the future vessel’s dynamic consumption 24 h ahead. Here, we use data collected from previous missions by the F-Boat’s predecessor vessel (N-Boat), as the sensors provided data on wind position and intensity, tides, vessel instantaneous energy consumption, sail position, and rudder position. This information is used as input to the neural network, which begins its learning process by processing these data with a bias lower than 0.01%.

A simple Restricted Boltzmann Machine architecture.

3 Similar Projects (State of the Art)

Literature related to nautical autonomous vehicles is scarce when compared to other types of autonomous vehicles. At this point, we present the most relevant works related to the research topics of this one, mainly for comparison. As organizational criteria, all comparisons are described in Table 1 and their comments can be found in the following text. Notice that other types of vehicles appear in the table besides unmanned surface vehicles (USV), including autonomous underwater vehicles (AUV), and autonomous vehicles (AV).

Strictly related works.

Although the Sailbuoy team ( Sailbuoy, 2018 ) is known to be the first sailboat that completed the Microtransat challenge ( Microtransat, 2021 ) (June 2018), the achievement was not fully autonomous, being remotely controlled at some parts of the cross. Even still, it has proven to be a robust platform, staying for months at sea transmitting and receiving data. The authors point that their solution can be used in applications for measuring ocean parameters ( Hole et al., 2016 ), tracking oil spills, or as a communication relaying station.

Competitions are an important source of references in sailing robotics, as occurs in other robotic fields such as the world robot soccer competition (Robocup). Examples of international competitions related to robotic sailboats are the World Robotic Sailing Championship (WRSC) , derived from the Microtransat Challenge , which is a competition between autonomous sailboats aiming to cross the Atlantic Ocean. Other sailboats from Table 1 ( Stelzer and Jafarmadar, 2007 ) and also from the literature ( Alves and Cruz, 2008 ; Stelzer, 2013 ; Dahl et al., 2015 ) were developed to compete in this challenge.

Further, we select from Table 1 three examples of works dealing with energy management in autonomous sailboats. The first one ( Sun et al., 2021 ) deals with energy control methods for saving energy by improving the navigation system. The second ( Liang et al., 2021 ) tries to increase energy autonomy by changing the hull structure to carry more battery packs. The third and last topic ( Ou et al., 2021 ) is about optimizing energy by improving the use of the motor in hybrid sailboats (sail and engine).

Finally, besides having the two twin sailboats constructed, we also consider using another simulation environment that we have built based on the N-Boat specifications (last item of Table 1 ) ( Dos Santos and Goncalves, 2019 ; Paravisi et al., 2019 ). By using simulators it is possible to customize the same variables for different vehicles, as often as necessary. Simulated environments are a viable startup testbed that provides an initial performance for sailboat systems, tested in multiple environments, due to the aforementioned particularities and because of the number of scenarios that can be considered. For example, the Boltzmann machine can be implemented and tested in this environment, before practical implementation.

4 Power Generation System

Despite converting wind into kinetic movement, electrical energy is still required for the instrumentation that allows autonomous sailing, which is the emergency and maneuvering electric propulsion engine, the rudder and sail actuators, the onboard computer, sensors, and the payload. Currently, the N-Boat and F-Boat power generation systems are purely fed by solar panels and a bank of nautical batteries. Details of this generation, storage and other alternatives will be treated in the next sections. This current generation is what is needed for long-term missions ( Boas et al., 2016 ), which do not use the electric propulsion engine constantly. The main hypothesis of this work is to allow the use of the propulsion engine, without compromising the boat’s energy supply in these missions. Therefore, it is necessary to use a strategy that allows, at certain times, under certain circumstances, its use during short a period of time.

4.1 Energy Generation Approaches

Self-sufficient autonomous vehicles can generate energy in several ways. In this work, we are classifying the sources into renewable (ecological) and non-renewable. The renewable correspond to Hydraulic, wind, solar, geothermal, marine, biomass and biogas. The non-renewable are oil, natural gas, coal and nuclear. Although there are many possible sources to be shipped, few are feasible, those illustrated below in Figure 5 .

Energy generation approaches.

Renewable sources, in addition to being ecologically correct, allow for long-term missions. Several studies ( Wang et al., 2008 ; Waseem et al., 2019 ) demonstrate that this alternative ends up being one of the best choices, but requires strategies that guarantee a positive energy balance at the end. Since propulsion is the main energy consumption item of autonomous vehicles, there is a notable increase in energy autonomy between sailboats and other types of autonomous vehicles that are propelled by engines.

For a better hardware architecture understanding, we present the solution based on the N-Boat and F-Boat models. Figure Figure 6 illustrates all components that generate or consumes some type of energy in these vessels. An important point is an electric motor, which, as will be shown later on, its continuous use can compromise the entire vehicle’s autonomy. Therefore, the solution needs a strategy that only allows its use in special moments, such as poor wind conditions, return to base, emergency maneuvers, among other situations.

F-boat’s current energy generation model.

Our model uses a solar panel for electricity production. In the future, there is the possibility of using wind power generation and/or a mini-hydro generator. Solar production has some advantages and disadvantages. The main advantage is that it corresponds to the most efficient in terms of cost, generation, extreme weather conditions resistance, and ease of installation. However, there is a lack of moments where there is no source, such as nighttime or bad weather conditions. Another drawback is the large deck area required.

In the present project, we adopted a panel with the current-voltage graph shown in Figure 7 .

Current × Voltage curve for a photovoltaic panel.

The generation of electrical energy in a photovoltaic arrangement is intermittent and is strongly determined by cloudiness and temperature. These factors cause the operating point, which leads to the extraction of maximum power from the photovoltaic array to change constantly. Thus, tracking this Maximum Power Point (MPP) continuously is a way to ensure greater efficiency in energy conversion, as can be seen in the figure Figure 7 .

To control the battery charge, a charger controller is necessary. This equipment can find the perfect current and voltage ratio, charging the battery bank with maximum efficiency.

PWM, which stands for Pulse Width Modulation, is a charger controller that keeps a battery fully charged through high-frequency voltage pulses. Thus, this driver allows to check the battery charge status and adjust the sent pulses. This type is more used in the market as it has a lower price than an MPPT driver.

MPPT stands for maximum power point tracking and is a charger controller that looks for the best power point of the module or solar panel. Enabling the system to make the maximum power the panel has to offer and also can monitor energy production and reduce system losses. This type of driver is more expensive than the previous one, but it promotes greater efficiency than the PWM controller.

In Figure Figure 8 , it is possible to see a schematic diagram that reflects an alternative configuration on the N-Boat and F-Boat. For reasons of energy efficiency, the MPPT load driver is directly connected to the power distribution. As the electronic arrangement was designed with maximum system robustness and reliability, power output is connected directly from the battery bank, being much safer than installing through the charge controller mentioned beforehand. Therefore, the boat can still be powered by the battery bank with a remaining charge. Here we also mention the necessity of using a general circuit breaker and a fuse box (with one for each compartment) guaranteeing maximum safety.

MPPT regulator connected directly to power distribution.

4.2 Electric and Electronic Components

In Figure 9 it is possible to visualize the F-Boat packages diagram. It features all of the vehicle’s electrical and electronic components in a structured way, including also related documents, classes, diagrams, and packages. Each package is better described below.

F-Boat’s package flow diagram.

The energy package, which is the main focus of this work, contains the entire set of equipment responsible for the generation, storage, and distribution of energy throughout the vessel. The sail package contains the components responsible for controlling the sail angular position and the rudder, as its name suggests, involves the components responsible for controlling the vessel’s rudder. Computers are the devices responsible for all planning and data processing on the vessel. The communication package contains all components related to both internal (between all internal components of the sailboat) and external (communication with the shore base) communication. Motorization package relates all necessary hardware to motorize the sailboat, used in specific situations. Sensors are responsible for capturing the necessary data for both monitoring and general movement of the sailboat, working together with the cameras that are used for image acquisition, responsible for the computer vision tasks of the vessel.

4.3 System Consumption

Using solar panels, the production is enough to keep, during a short time, the sailboat system working without a lack of energy. Of course, without using the electric propulsion motor. The Boltzmann machine will be used for days when there is no full sunlight and/or massive use of electric propulsion is required. In these cases, the boat will need to turn off some modules and behaviors for it to survive these moments. This same strategy could be used to further increase their autonomy, if necessary, as will be described later in this work.

As each battery has 111 A/h and the boat has 4 batteries of these embarked, the total of available amperage is 444 A/h. In practice, this may go to lower values, as these batteries may not be 100% charged, addicted, or the battery life can vary from its use and falling. Anyway, it is possible to assume, for a theoretical environment, that this available power is sufficient for the tests. Considering the consumption labeled in each equipment manual, as shown in Table 2 .

Calculated energy consumption.

The same table ( Table 2 )shows the components expected energy consumption, which is informed by the datasheet or by laboratory tests carried out in previous experiments. Notice that, in the table, some of the items are labeled as fixed or variable. This is because some of them stay turned on throughout the entire mission, so their consumption is often identical to reported in the datasheet. However, other components have a consumption relative to their use. Such as the sail winch, which is only used when it is necessary to trim the sail. Taking into account the minutes that were turned on and relating it to the total consumption hour, so that it is possible to estimate an initial of the vessel’s total energy consumption.

5 Energy Management Experiments With RBM

Even though sailboats use wind as their main source of energy for their movement, electrical energy is still necessary for directing the sail and the rudder and also for their other components. As the production and storage of this energy resource is limited and scarce, therefore, a system that distributes energy efficiently and safely inside the vehicle is necessary. Besides, a strategy is essential to make intelligent use of this resource. With that in mind, we designed our vessel so that in the case that the solar panels stop producing energy, it is still possible to make severe use of the battery banks during the next 48 h, without completely discharging. This happens at night, for example (a 12 h period, considering Natal, Brazil). This is to say that the boat would still have remaining energy when the solar panels start recharging again. If the recharging does not happen accordingly, the boat will completely stop all systems.

That alone enables an ability to perform long missions, in case of regions with restrictions on the periods of day and night. Besides, protocols and consumption strategies were programmed, checking this energy consumption process. For example, on a given mission, it is possible to stay closer to the theoretical route, at a higher energy cost. However, it is known that performing fewer maneuvers reduces the sailboat consumption, but the actual accuracy on the theoretical route would also decrease. Another example would be to make little use of image processing in certain open sea locations. Leaving this feature to places with already pre-mapped obstacles or in places full of ships traffic. In addition to the embedded technology, all of this raw and processed data is sent to a command base ashore or a nearby support vessel. These data are displayed via a user-friendly platform that allows data tracking, route changes, strategy changes, and manual control of the sailboat for extreme situations. Besides these exemplified strategies can and should be taken into account, they are not the main subject of this work, as here we discuss the possibility energy estimation. Actually, the application of solar panels systems for ships depends on many factors mainly: 1) Solar radiation availability in ship’s operation areas; 2) existence of sufficient and adequate deck area to accommodate the solar panels; and 3) techno-economic efficiency of a solar panels system that includes energy efficiency, fuel oil rates, and investment costs.

Hence, in order to simulate the behavior of the system for the sailboats, we implemented and tested it through a Boltzmann Machine using data collected from the electrical and electronic components of the N-Boat hardware architecture, such as described above. The implemented system aims to show a solution to find a better way to use the distribution of energy consumption with solar panels in our autonomous sailboat F-Boat, which contains a saving/rescuing engine. Through sensors and data obtained directly from the charge controller, the proposed system monitors and manages component power control through a relay system. The system also connects to two modules: computers, where it can change the energy operation of some of its components depending on the current state of charging the batteries, and to the vessel’s communication package, which can send data to the external monitoring application.

We use the Boltzmann machine neural network with restrictions to predict the vessel’s energy consumption in a 24-h range. For this forecast, we designed the network to read data provided by sensors on the vessel itself, thus using external natural phenomena, winds, tides, lighting density, angle of incidence of sunlight. As navigation aids, we can predict the vessel’s energy consumption with and without the use of solar panels.

The Restricted Boltzmann machine neural network is fully developed using Anaconda, Spyder 5 platform which is an open-source cross-platform integrated development environment for scientific programming in the Python language. This development is aided by Numpy (2021) , Keras (2021) , TensorFlow (2021) and Scikit-Learn (2021) libraries, which are open source neural network libraries written in Python. They are capable of running on top of TensorFlow, Microsoft Cognitive Toolkit, R, Theano, or PlaidML. These tools are designed to allow quick experimentation with deep neural networks, focusing on being easy to use, modular and extensible.

Hence, we implemented a neural network code using standardized techniques to facilitate the implementation of the learning process with the network. The Boltzmann machine has libraries already created and tested by other researchers, so we can focus on information and data collected in the research, by using these standard techniques. Most of them have their repository on the Github site and in some cases, such as Tensor-flow, it has its own library for research with official forums of participating developers their difficulties and successes in designing architectures using these techniques. Our network has an initial layer with 6 neurons that receive input tide data, wind speed and direction, vessel battery voltage, average motor consumption, and consumption of the actuators. After normalization, we get 55 neurons invisible units and more than 55 neurons in hidden units, connected similarly to the network presented in Figure 4 , which process the data in 7 h and 28 min with 4,903 iterations of epochs. As result, we obtain an estimated consumption of the vessel in the range of 24 h.

The graphs in Figure 10 show the results generated by our experiments. The green line is the consumption data that we calculate by taking data from the N-Boat’s real electrical and electronic components ( Table 2 ). Notice that it is not the online (real-time) consumed value of a true mission, however it is very close to it as we use the real values of the equipment and devices consumption to calculate it. The yellow line is the data calculated for the N-Boat if using a solar panel. The red line is RBM’s predictions without a solar panel, which were later placed under the real consumption data (calculated from N-Boat electric and electronics) to understand if it was correctly estimating the real value. The blue line is the RBM estimates with the solar panel data.

Results for estimated consumption of the sailboat on a 24 h duration simulation, with data extracted from the N-Boat sailing experiment.

We notice that for the experiments shown in Figure 10 , we estimated the recharge of the panels in operation by way of using mathematical calculations based on the MPPT charger controller actual parameters. Nowadays, we are already working on the implementation of sensors for collection of this kind of data in the newer version of our project, the F-Boat. So, the real consumption value will soon have the real value given by these sensors and the estimated value of consumption with the solar panel given by using the neural network.

5.1 Results Discussion

With the collected data, our objective is to define the success rate of a mission related to energy failures. Using maritime currents, wind speed, solar luminance rate, among others, and measuring how much natural energy can be transformed into mechanical energy, we can estimate the success of a mission. We chose to use a neural network so that it can re-establish the calculations in case a natural phenomenon occurs suddenly, a tide change or a storm that changes the wind or reduces the sunlight, for example. Some questions appear that are already answered or that we will work on in the short time. The first one is what are we looking at here? We are looking for a system that can be used to eventually help save energy and keep the sailboat alive (running). Second question is how far ahead can we predict energy consumption? This is one of the parameters that serves as input to the Boltzmann machine. We should guarantee for this time the minimum of 48 h as set in the N-Boat and F-Boat initial design. With this time, some rescuing action can be taken.

Yet the model needs to train for 7 h and 28 min in order to generate a useful output, however with transfer learning this time can be diminished. In practice, we believe that the mechanism can be implemented in the SBC embarked, which are nVidia boards Xavier, for online learning and changing the output parameters in certain situations. We believe that this will produce a usable system which can give predictions in real time. At this time the mechanism is only suitable for offline use. Thus, what we are generating is not a forecast or prediction of energy consumption, but a model of actual data given by N-Boat (our first sailboat) data. This simulation uses data from a real mission that it performed in Natal, Brazil, in normal weather conditions. In such an experiment, the boat basically used sail and rudder to perform some maneuverings. A last question is how would we use this? This is not fully operating in our real sailboats yet. However, from these initial experiments and tests we could devise a way for the sailboat to manage without human intervention and decide if certain equipment can be turned on or not during a long running mission. Next step, in a very short time, is to put all of these running inside the F-Boat, which is operational at Guanabara bay, Niteroi, Brazil ( https://youtu.be/mvJdl09Jazo ).

6 Conclusion and Future Work

We verified the use of the Boltzmann Machine as a prediction tool for helping the management of the energy in our autonomous sailing boats projects, and achieved some expected responses. The association between renewable and continuous energy generation with an energy management strategy using the Boltzmann machine indicates positively in this direction. Our results show that using artificial intelligence is a possible direction of research towards defining a strategy for energy monitoring, in order to further suggest decisions such as sail movement, the best path to the target and the correct start/stop times for the electric propulsion engine.

Besides the results obtained in the simulation using the Boltzmann machine showed some evidence of a solution to the intelligent energy use problem in the sailboat, a series of future work are still necessary in order to further provide better results on this subject. Actually, more work is already planned to be done on this project in order to improve the current one, such as the introduction of other forms of sustainable energy generation (wind and hydro generation), system monitoring through specific sensors for the entire solar panels, providing more precise information related to charging rate, battery bank charge, battery temperature, charge controller errors, among others. Still, a more effective survey of component energy consumption through bench and field testing in various work modes is required.

Acknowledgments

Thanks to CAPES, Brazil, for grants of AN and LG (Pro-Alertas); CNPq, Brazil, for grants of LG and EC; FAPERJ and CNPq Brazil for grants of EC; and NVIDIA.

Data Availability Statement

Author contributions.

AN : Conceptualization, Methodology, Formal analysis and investigation, Writing—original draft preparation; WC : Conceptualization, Methodology, Formal analysis and investigation, Writing—original draft preparation; AA : Conceptualization, Methodology, Formal analysis and investigation, Writing—original draft preparation; DS : Conceptualization, Methodology, Formal analysis, Writing—original draft preparation; JV : Conceptualization, Methodology, Writing—review and editing, Supervision; DD : Conceptualization, Methodology, Formal analysis and investigation, Writing—original draft preparation, Funding acquisition, Resources, Supervision; EC : Conceptualization, Methodology, Formal analysis and investigation, Writing—original draft preparation, Writing—review and editing, Funding acquisition, Resources, Supervision; LG : Conceptualization, Methodology, Formal analysis and investigation, Writing—original draft preparation, Writing—review and editing, Funding acquisition, Resources, Supervision. In addition, all authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

This work is partially supported by CAPES Brazil under grants 001 and 88881.506890/2020-01, by CNPq Brazil under grants 311640/2018-4 and 309029/2020-1, FAPERJ grant E-26/202.922/2019 and by NVIDIA.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

• Alaieri F., Vellino A. (2016). “ Ethical Decision Making in Robots: Autonomy, Trust and Responsibility ,” in International Conference on Social Robotics (Springer; ), 159–168. 10.1007/978-3-319-47437-3_16 [ CrossRef ] [ Google Scholar ]
• Aldegheri S., Bloisi D. D., Blum J. J., Bombieri N., Farinelli A. (2018). “ Fast and Power-Efficient Embedded Software Implementation of Digital Image Stabilization for Low-Cost Autonomous Boats ,” in Field and Service Robotics (Springer, 129–144. 10.1007/978-3-319-67361-5_9 [ CrossRef ] [ Google Scholar ]
• Almeida R. (2016). Programacao de Sistemas Embarcados : Desenvolvendo Software para Microcontroladores em Linguagem C . Rio de Janeiro, Brasil: Elsevier. [ Google Scholar ]
• Alves J. C., Cruz N. A. (2008). “ Fast-an Autonomous Sailing Platform for Oceanographic Missions ,” in OCEANS 2008 (IEEE; ), 1–7. 10.1109/oceans.2008.5152114 [ CrossRef ] [ Google Scholar ]
• Bezerra C. G., Sielly Jales Costa B., Guedes L. A., Angelov P. P. (2016). “ A New Evolving Clustering Algorithm for Online Data Streams ,” in 2016 IEEE Conference on Evolving and Adaptive Intelligent Systems, Natal, Brazil (Los Alamitos, CA: IEEE Press; ), 162–168. 10.1109/EAIS.2016.7502508 [ CrossRef ] [ Google Scholar ]
• Boas J. M. V., Silva Júnior A. G., Santos D. H., Negreiros A. P. F., Alvarez-Jácobo J. E., Gonçalves L. M. G. (2016). “ Towards the Electromechanical Design of an Autonomous Robotic Sailboat ,” in 2016 XIII Latin American Robotics Symposium and IV Brazilian Robotics Symposium, Recife, Brazil (Los Alamitos, CA: IEEE Press; ), 43–48. 10.1109/LARS-SBR.2016.15 [ CrossRef ] [ Google Scholar ]
• Bourlard H., Kamp Y. (1988). Auto-association by Multilayer Perceptrons and Singular Value Decomposition . Biol. Cybern. 59 , 291–294. 10.1007/bf00332918 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Brooks R. (1986). A Robust Layered Control System for a mobile Robot . IEEE J. Robot. Automat. 2 , 14–23. 10.1109/JRA.1986.1087032 [ CrossRef ] [ Google Scholar ]
• Bu Y., Zhao G., Luo A.-l., Pan J., Chen Y. (2015). Restricted Boltzmann Machine: a Non-linear Substitute for Pca in Spectral Processing . A&A 576 , A96. 10.1051/0004-6361/201424194 [ CrossRef ] [ Google Scholar ]
• Byrnes R., MacPherson D., Kwak S., McGhee R., Nelson M. (1992). “ An Experimental Comparison of Hierarchical and Subsumption Software Architectures for Control of an Autonomous Underwater Vehicle ,” in Proceedings of the 1992 Symposium on Autonomous Underwater Vehicle Technology (IEEE; ), 135–141. [ Google Scholar ]
• Dahl K., Bengsén A., Waller M. (2015). Power Management Strategies for an Autonomous Robotic Sailboat . Robotic Sailing 2014 ( Springer ), 47–55. 10.1007/978-3-319-10076-0_4 [ CrossRef ] [ Google Scholar ]
• Dos Santos D. H., Goncalves L. M. G. (2019). A Gain-Scheduling Control Strategy and Short-Term Path Optimization with Genetic Algorithm for Autonomous Navigation of a Sailboat Robot . Int. J. Adv. Robotic Syst. 16 , 1729881418821830. 10.1177/1729881418821830 [ CrossRef ] [ Google Scholar ]
• Dupriez-Robin F., Loron L., Claveau F., Chevrel P. (2009). “ Design and Optimization of an Hybrid Sailboat by a Power Modeling Approach ,” in Electric Ship Technologies Symposium, 2009. ESTS 2009. IEEE (IEEE; ), 270–277. 10.1109/ests.2009.4906525 [ CrossRef ] [ Google Scholar ]
• Frost G., Maurelli F., Lane D. M. (2015). “ Reinforcement Learning in a Behaviour-Based Control Architecture for marine Archaeology ,” in OCEANS 2015-Genova (IEEE; ), 1–5. 10.1109/oceans-genova.2015.7271619 [ CrossRef ] [ Google Scholar ]
• Haykin S. (1999). Neural Networks: A Comprehensive Foundation . Hoboken, NJ: Prentice-Hall, 842. [ Google Scholar ]
• Hinton G. E., Salakhutdinov R. R. (2006). Reducing the Dimensionality of Data with Neural Networks . science 313 , 504–507. 10.1126/science.1127647 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hinton G. E. (2002). Training Products of Experts by Minimizing Contrastive Divergence . Neural Comput. 14 , 1771–1800. 10.1162/089976602760128018 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hole L., Fer I., Peddie D. (2016). Directional Wave Measurements Using an Autonomous Vessel . Ocean Dyn. 66 , 1087–1098. 10.1007/s10236-016-0969-4 [ CrossRef ] [ Google Scholar ]
• Jo K., Kim J., Kim D., Jang C., Sunwoo M. (2015). Development of Autonomous Car-Part II: A Case Study on the Implementation of an Autonomous Driving System Based on Distributed Architecture . IEEE Trans. Ind. Electron. 62 , 5119–5132. 10.1109/tie.2015.2410258 [ CrossRef ] [ Google Scholar ]
• Júnior A. G. S., Araújo A. P. D., Silva M. V. A., Aroca R. V., Gonçalves L. M. G. (2013). “ N-boat: An Autonomous Robotic Sailboat. ,” in 2013 Latin American Robotics Symposium and Competition, 24–29. 10.1109/LARS.2013.52 [ CrossRef ] [ Google Scholar ]
• Kanellos F. D. (2014). Optimal Power Management with Ghg Emissions Limitation in All-Electric Ship Power Systems Comprising Energy Storage Systems . IEEE Trans. Power Syst. 29 , 330–339. 10.1109/TPWRS.2013.2280064 [ CrossRef ] [ Google Scholar ]
• Keras (2021). Keras Ecosystem – Deep Learning for Humans . Web Page Available at https://keras.io/ . (Accessed on Nov 30, 2021).
• Khan M. M. S., Faruque M. O., Newaz A. (2017). Fuzzy Logic Based Energy Storage Management System for Mvdc Power System of All Electric Ship . IEEE Trans. Energ. Convers. 32 , 798–809. 10.1109/TEC.2017.2657327 [ CrossRef ] [ Google Scholar ]
• LAICA (2015). N-boat: Construction of an Autonomous Robot Sailboat for Monitoring and Collecting Data on Rivers and Oceans Interinstitutional Project UFRN-IFRN . Web page. Available at: http://laica.ifrn.edu.br/projetos/n-boat-construcao-de-um-veleiro-robo-autonomo/ . (Accessed on Nov 30, 2021). [ Google Scholar ]
• Larochelle H., Bengio Y. (2008). “ Classification Using Discriminative Restricted Boltzmann Machines ,” in Proceedings of the 25th International Conference on Machine Learning, Helsinki Finland (New York, NY: ACM; ), 536–543. ICML ’08. 10.1145/1390156.1390224 [ CrossRef ] [ Google Scholar ]
• Letafat A., Rafiei M., Ardeshiri M., Sheikh M., Banaei M., Boudjadar J., et al. (2020). An Efficient and Cost-Effective Power Scheduling in Zero-Emission Ferry Ships . Complexity 2020 , 1–12. 10.1155/2020/6487873 [ CrossRef ] [ Google Scholar ]
• Liang C., Ou R., Lin B., Ji X., Cheung R. C. C., Qian H. (2021). “ Design of a Battery Carrying Barge for Enhancing Autonomous Sailboat's Endurance Capacity ,” in 2021 IEEE International Conference on Real-time Computing and Robotics, Xining, China (Los Alamitos, CA: IEEE Press; ), 1438–1443. 10.1109/RCAR52367.2021.9517585 [ CrossRef ] [ Google Scholar ]
• Liu J., Hu H., Gu D. (2006). “ A Hybrid Control Architecture for Autonomous Robotic Fish ,” in 2006 IEEE/RSJ international conference on intelligent robots and systems (IEEE; ), 312–317. 10.1109/iros.2006.282422 [ CrossRef ] [ Google Scholar ]
• Memisevic R., Hinton G. E. (2010). Learning to Represent Spatial Transformations with Factored Higher-Order Boltzmann Machines . Neural Comput. 22 , 1473–1492. 10.1162/neco.2010.01-09-953 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Microtransat (2021). The Microtransat challenge . Web page Available at https://www.microtransat.org/ . (Accessed on Nov 30, 2021).
• Negreiros Á. P. F. d. (2019). “ N-Boat: projeto e desenvolvimento de um veleiro robótico autônomo ,”(Master’s thesis) Brasil. [ Google Scholar ]
• Numpy (2021). Numpy Ecosystem – the Fundamental Package for Scientific Computing with python . Web page Available at https://numpy.org/ . (Accessed on Nov 30, 2021).
• Olenderski A., Nicolescu M., Louis S. J. (2006). “ A Behavior-Based Architecture for Realistic Autonomous Ship Control ,” in 2006 IEEE Symposium on Computational Intelligence and Games (IEEE; ), 148–155. 10.1109/cig.2006.311694 [ CrossRef ] [ Google Scholar ]
• Ortiz L. E., Cabrera V. E., Gonçalves L. M. G. (2018). Depth Data Error Modeling of the Zed 3d Vision Sensor from Stereolabs . Elcvia 17 , 1–15. 10.5565/rev/elcvia.1084 [ CrossRef ] [ Google Scholar ]
• Ou R., Liang C., Ji X., Qian H. (2021). “ Design and Energy Consumption Optimization of an Automatic Hybrid Sailboat ,” in 2021 IEEE International Conference on Real-time Computing and Robotics, Xining, China (Los Alamitos, CA: IEEE Press; ), 1414–1418. 10.1109/RCAR52367.2021.9517339 [ CrossRef ] [ Google Scholar ]
• Paravisi M., H. Santos D. D., Jorge V., Heck G., Gonçalves L., Amory A. (2019). Unmanned Surface Vehicle Simulator with Realistic Environmental Disturbances . Sensors 19 , 1068. 10.3390/s19051068 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Passos L. A., De Rosa G. H., Papa J. P. (2020). “ Fine-tuning Restricted Boltzmann Machines Using Quaternion-Based Flower Pollination Algorithm ,” in Nature-Inspired Computation and Swarm Intelligence . Editor Yang X.-S. (Academic Press; ), 111–133. 10.1016/B978-0-12-819714-1.00019-1 [ CrossRef ] [ Google Scholar ]
• Raghunathan V., Kansal A., Hsu J., Friedman J., Srivastava M. (2005). “ Design Considerations for Solar Energy Harvesting Wireless Embedded Systems ,” in Proceedings of the 4th international symposium on Information processing in sensor networks (IEEE Press; ), 64. [ Google Scholar ]
• Sailbuoy (2018). Offshore Sensing: Sailbuoy - Unmanned Surface Vessel Sailbuoy Project: Long Endurance Unmanned Surface Vehicle for the Oceans . Web page Available at: http://www.sailbuoy.no/ .
• Salama M. A., Hassanien A. E., Fahmy A. A. (2010). “ Deep Belief Network for Clustering and Classification of a Continuous Data ,” in The 10th IEEE international symposium on signal processing and information technology (IEEE; ), 473–477. 10.1109/isspit.2010.5711759 [ CrossRef ] [ Google Scholar ]
• Saoud H., Hua M.-D., Plumet F., Amar F. B. (2015). “ Routing and Course Control of an Autonomous Sailboat ,” in 2015 European Conference on Mobile Robots (ECMR) (IEEE; ), 1–6. 10.1109/ecmr.2015.7324218 [ CrossRef ] [ Google Scholar ]
• Scikit-Learn (2021). Scikit-learn – Machine Learning in python . Web page Available at: https://scikit-learn.org/stable/ . (Accessed on Nov 30, 2021).
• Silva Junior A. G. d. S., Santos D. H. d., Negreiros A. P. F. d., Silva J. M. V. B. d. S., Gonçalves L. M. G. (2020). High-level Path Planning for an Autonomous Sailboat Robot Using Q-Learning . Sensors 20 , 1550. 10.3390/s20061550 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Smolensky P. (1986). “ Information Processing in Dynamical Systems: Foundations of harmony Theory ,”. Tech. rep. Colorado Univ at Boulder Dept of Computer Science. [ Google Scholar ]
• Stelzer R. (2013). Autonomous Sailboat Navigation: Novel Algorithms and Experimental Demonstration . LAP LAMBERT Academic Publishing. [ Google Scholar ]
• Stelzer R., Jafarmadar K. (2007). A Layered System Architecture to Control an Autonomous Sailboat. Towards Autonomous Robotic Systems (TAROS 2007) . Aberystwyth, UK, 153–159. [ Google Scholar ]
• Sun Q., Qi W., Ji X., Qian H. A. (2021). V-stability Based Control for Energy-Saving towards Long Range Sailing . IEEE Robot. Autom. Lett. , 1. 10.1109/LRA.2021.3057562 [ CrossRef ] [ Google Scholar ]
• Tamilselvan P., Wang P. (2013). Failure Diagnosis Using Deep Belief Learning Based Health State Classification . Reliability Eng. Syst. Saf. 115 , 124–135. 10.1016/j.ress.2013.02.022 [ CrossRef ] [ Google Scholar ]
• Tas O. S., Kuhnt F., Zollner J. M., Stiller C. (2016). “ Functional System Architectures towards Fully Automated Driving ,” in 2016 IEEE Intelligent vehicles symposium (IV), Gothenburg, Sweden, 19-22 June 2016 (IEEE; ), 304–309. 10.1109/IVS.2016.7535402 [ CrossRef ] [ Google Scholar ]
• TensorFlow (2021). Tensorflow – an End to End Open Source Machine Learning Platform . Web page Availableat: https://www.tensorflow.org/ . (Accessed on Nov 30, 2021).
• Valavanis K. P., Gracanin D., Matijasevic M., Kolluru R., Demetriou G. A. (1997). Control Architectures for Autonomous Underwater Vehicles . IEEE Control. Syst. Mag. 17 , 48–64. [ Google Scholar ]
• Vu T. V., Gonsoulin D., Diaz F., Edrington C. S., El-Mezyani T. (2017). Predictive Control for Energy Management in Ship Power Systems under High-Power Ramp Rate Loads . IEEE Trans. Energ. Convers. 32 , 788–797. 10.1109/TEC.2017.2692058 [ CrossRef ] [ Google Scholar ]
• Wang C., Xiao Z., Wang S. (2008). Synthetical Control and Analysis of Microgrid . Automation Electric Power Syst. 7 , 98–103. [ Google Scholar ]
• Waseem M., Sherwani A. F., Suhaib M. (2019). Integration of Solar Energy in Electrical, Hybrid, Autonomous Vehicles: a Technological Review . SN Appl. Sci. 1 , 1–14. 10.1007/s42452-019-1458-4 [ CrossRef ] [ Google Scholar ]

What type of energy transformation does a sailboat have?

A sailboat uses energy from the wind. I don't think this is really an energy transformation; movement energy from the wind is converted into boat movement.

Ye sit does

Add your answer:

What type of energy transformation does a radio signal have?

The radio signal itself, of course, is not an energy transformation - energy transformation means that energy is changed from one type to another. There is an energy transformation when the radio signal is created, and another one when it is absorbed.

Is KE turning into electrical energy called a transformation of energy?

Every time one type of energy is converted into another type of energy, you can call it an "energy transformation".

What type of energy is present in moving sailboat?

Mechanical, which is then converted to chemical.

What type of energy transformation of an electric fan?

Electric energy to kitenic energy

Is helicopters a type of energy transformations?

no. its an example of mechanical energy but its not an energy transformation

What type of energy transformation is Niagara falls?

potential energy

Do you have to have the same type of energy before and after an energy transformation explain?

No. If the energy type doesn't change then how can it be a "transform"?

What type of energy transformation changes the food you eat into energy to play soccer?

The energy transformation processes are provided and controlled by Biochemical Metabolism.

What type of energy transformation performs muscles?

It is chemical to kinetic energy.

What type of transformation is Niagara fall?

What is the type of energy transformation that occurs in the microwave.

electical energy is transform to heat energy

What type of energy transformation do maracas have?

The autobots are unable to answer this question.

Top Categories

• Vessel Reviews
• Passenger Vessel World
• Offshore World
• Tug and Salvage World
• Maritime Security World
• Specialised Fields
• Marine Projects World
• Small Craft World
• Tanker World
• Dry Cargo World
• Boxship World
• Aquaculture World
• Trawling World
• Longlining World
• Seining World
• Potting World
• Other Fishing Methods
• Regulation & Enforcement
• Feature Weeks
• Classifieds
• Book Reviews

VESSEL REVIEW | Sinichka – Electric commuter boats designed for Russia’s Moskva River

A series of three new electric monohull commuter ferries have already begun operational sailings on the Moskva River in the Russian capital Moscow.

Built by Russian shipyard Emperium, sister vessels Sinichka , Filka , and Presnya – all named after rivers in Moscow – are being operated by the Moscow Department of Transport and Road Infrastructure Development (Moscow Deptrans). They are the first units of a planned fleet of 20 vessels that will serve the capital city and other nearby communities. The new ferry system will be the water transport system to be operated on the Moskva River in 16 years.

Each vessel has a welded aluminium hull, an LOA of 21 metres, a beam of 6.2 metres, a draught of only 1.4 metres, a displacement of 40 tonnes, and capacity for 80 passengers plus two crewmembers. Seating is available for 42 passengers on each ferry, and the main cabins are also fitted with USB charging ports, wifi connectivity, tables, toilets, and space for bicycles and scooters. The cabin layout can be rearranged to allow the operator to adjust the distances between the seats and to install armrests of varying widths.

An open upper deck is also accessible to passengers and is the only area on each ferry where smoking is allowed.

The ferries are all of modular construction with each ferry’s wheelhouse, main cabin, and other structural elements being built as complete, separate components. This enables the ferries to be easily dismantled for transport to anywhere in Russia by rail and then quickly re-assembled within seven days.

The ferries are also ice-capable. Recently completed operational trials on the Moskva showed that the vessels can also easily navigate under mild winter conditions with broken surface ice, though year-round operations are planned for the entire fleet.

The ferries are each fitted with 500kWh lithium iron phosphate battery packs that supply power to two 134kW motors. This configuration can deliver a maximum speed of 11.8 knots, a cruising speed of just under 10 knots, and a range of 150 kilometres.

Emperium said the transfer of rotation of electric motors to the propeller is carried out by direct drive. As a propulsion installation, a pulling rotary propeller-steering column with double screws is used. The installation of double pulling screws, with similar power, allows an operator to increase the efficiency of the propulsion system to deliver a slightly higher speed or to reduce energy consumption. This arrangement also provides the ferries with enhanced manoeuvrability necessary for navigating in close quarters.

The batteries themselves have projected service lives of 10 to 12 years and are fitted with safety features such as built-in fire extinguishers and gas vents. Quick-disconnect features allow the batteries to be easily removed for replacement or maintenance.

Some of our readers have expressed disquiet at our publication of reviews and articles describing new vessels from Russia. We at Baird Maritime can understand and sympathise with those views. However, despite the behaviour of the country’s leaders, we believe that the maritime world needs to learn of the latest developments in vessel design and construction there.

Click here to read other news stories, features, opinion articles, and vessel reviews as part of this month’s Passenger Vessel Week.

Related Posts

Baird Maritime

Tags: Emperium Filka Moscow Moscow Department of Transport and Road Infrastructure Development Moskva River Presnya Russia Sinichka WBW newbuild

• Previous VESSEL REVIEW | Ferry Rokko – Second 194m Ro-Pax for Miyazaki Car Ferry
• Next Brighton man to be charged for illegal abalone haul

Baird Maritime , launched in 1978, is one of the world's premier maritime publishing houses.

The company produces the leading maritime new portal BairdMaritime.com , home of the world famous Work Boat World, Fishing Boat World, Ship World, Ausmarine, and Commercial Mariner sub-sites, and the industry-leading ship brokerage platforms WorkBoatWorld.com and ShipWorld.com .

Contact us: [email protected]

© Copyright - Baird Maritime

• Terms & Conditions
• Advertise with Baird Maritime
• Submit News/Leads

We've detected unusual activity from your computer network

To continue, please click the box below to let us know you're not a robot.

Why did this happen?

Please make sure your browser supports JavaScript and cookies and that you are not blocking them from loading. For more information you can review our Terms of Service and Cookie Policy .

For inquiries related to this message please contact our support team and provide the reference ID below.

• Bahasa Indonesia
• Slovenščina
• Science & Tech
• Russian Kitchen

Check out Moscow’s NEW electric river trams (PHOTOS)

Water transportation has become another sector for the eco-friendly improvements the Moscow government is implementing. And it means business. On July 15, 2021, on the dock of Moscow’s ‘Zaryadye’ park, mayor Sergey Sobyanin was shown the first model of the upcoming river cruise boat.

The model of the electrical boat with panoramic windows measures 22 meters in length. The river tram - as Muscovites call them - has a passenger capacity of 42, including two disabled seats. The trams will also get cutting edge info panels, USB docking stations, Wi-Fi, spaces for scooters and bicycles, as well as chairs and desks for working on the go. The boats will be available all year round, according to ‘Mosgortrans’, the regional transport agency. 

Passengers will be able to pay with their ‘Troika’ public transport card, credit cards or bank cards. 

The main clientele targeted are people living in Moscow’s river districts - the upcoming trams will shorten their travel time in comparison to buses and other transportation by five times, Mosgortrans stated. 

As the river trams are being rolled out, Moscow docks will also see mini-stations, some of which will also be outfitted with charging docks for speed-charging the boats.  

Moscow is set to announce the start of the tender for construction and supply in September 2021. The first trams are scheduled to launch in June 2022 on two routes - from Kievskaya Station, through Moscow City, into Fili; and from ZIL to Pechatniki. 

“Two full-scale routes will be created in 2022-2023, serviced by 20 river trams and a number of river stations. We’ll continue to develop them further if they prove to be popular with the citizens,” the Moscow mayor said .

If using any of Russia Beyond's content, partly or in full, always provide an active hyperlink to the original material.

to our newsletter!

Get the week's best stories straight to your inbox

• Face it: Moscow Metro to introduce FACIAL payment technology
• What does Moscow smell like?
• Riding Moscow’s train of tomorrow (PHOTOS)

This website uses cookies. Click here to find out more.

• Share full article

Advertisement

Supported by

U.S. Seeks to Boost Nuclear Power After Decades of Inertia

Measures moving through Congress to encourage new reactors are receiving broad bipartisan support, as lawmakers embrace a once-contentious technology.

By Brad Plumer

Reporting from Washington

The House this week overwhelmingly passed legislation meant to speed up the development of a new generation of nuclear power plants, the latest sign that a once-contentious source of energy is now attracting broad political support in Washington.

The 365-to-36 vote on Wednesday reflected the bipartisan nature of the bill, known as the Atomic Energy Advancement Act . It received backing from Democrats who support nuclear power because it does not emit greenhouse gases and can generate electricity 24 hours a day to supplement solar and wind power. It also received support from Republicans who have downplayed the risks of climate change but who say that nuclear power could bolster the nation’s economy and energy security.

“It’s been fascinating to see how bipartisan advanced nuclear power has become,” said Joshua Freed, who leads the climate and energy program at Third Way, a center-left think tank. “This is not an issue where there’s some big partisan or ideological divide.”

The bill would direct the Nuclear Regulatory Commission, which oversees the nation’s nuclear power plants, to streamline its processes for approving new reactor designs. The legislation, which is backed by the nuclear industry, would also increase hiring at the commission, reduce fees for applicants, establish financial prizes for novel types of reactors and encourage the development of nuclear power at the sites of retiring coal plants.

Together, the changes would amount to “the most significant update to nuclear energy policy in the United States in over a generation,” said Representative Jeff Duncan, Republican of South Carolina, a lead sponsor of the bill.

In the Senate, Republicans and Democrats have written their own legislation to promote nuclear power. The two chambers are expected to discuss how to reconcile their differences in the coming months, but final passage is not assured, particularly with so many other spending bills still in limbo .

“If Congress was functioning well, this is one of those bills you’d expect to sail through,” said Mr. Freed.

Nuclear power currently generates 18 percent of the nation’s electricity, but only three reactors have been completed in the United States since 1996. Although some environmentalists remain concerned about radioactive waste and reactor safety, the biggest obstacle facing nuclear power today is cost.

Conventional nuclear plants have become extremely expensive to build, and some electric utilities have gone bankrupt trying. Two recent reactors built at the Vogtle nuclear power plant in Georgia cost $35 billion, double the initial estimates.

In response, nearly a dozen companies are developing a new generation of smaller reactors a fraction of the size of those at Vogtle. The hope is that these reactors would have a smaller upfront price tag, making it less risky for utilities to invest in them. That, in turn, could help the industry start driving down costs by building the same type of reactor again and again.

The Biden administration has voiced strong support for nuclear power as it seeks to transition the country away from fossil fuels; the Department of Energy has offered billions of dollars to help build advanced reactor demonstration projects in Wyoming and Texas.

But before a new reactor can be built, its design must be reviewed by the Nuclear Regulatory Commission. Some Democrats and Republicans in Congress have criticized the N.R.C. for being too slow in approving new designs. Many of the regulations that the commission uses, they say, were designed for an older era of reactors and are no longer appropriate for advanced reactors that may be inherently safer.

“Tackling the climate crisis means we must modernize our approach to all clean energy sources, including nuclear,” said Representative Diana DeGette, Democrat of Colorado. “Nuclear energy is not a silver bullet, but if we’re going to get to net zero carbon emissions by 2050, it must be part of the mix.”

Among other changes, the House bill would require the N.R.C. to consider not just reactor safety but also “the potential of nuclear energy to improve the general welfare” and “the benefits of nuclear energy technology to society.”

Proponents of this change say it would make the N.R.C. more closely resemble other federal safety agencies like the Food and Drug Administration, which weighs both the risks and benefits of new drugs. In the past, critics say, the N.R.C. has focused too heavily on the risks.

But that provision updating the N.R.C.’s mission was opposed by three dozen progressive Democrats who voted against the bill and said it could undermine reactor safety . The specific language is not in the Senate’s nuclear bill.

Even if Congress approves new legislation, the nuclear industry faces other challenges. Many utilities remain averse to investing in novel technologies, and reactor developers have a long history of failing to build projects on time and under budget.

Last year, NuScale Power, a nuclear startup, announced it was canceling plans to build six smaller reactors in Idaho. The project, which had received significant federal support and was meant to demonstrate the technology, had already advanced far through the N.R.C. process. But NuScale struggled with rising costs and was ultimately unable to sign up enough customers to buy its power.

Brad Plumer is a Times reporter who covers technology and policy efforts to address global warming. More about Brad Plumer

Scientists develop 'bubble-powered' autonomous tool to transform wastewater into clean energy: 'This is an interesting discovery'

A new innovative tool may help solve two pressing issues at once: water contamination and harmful pollution from dirty energy . 

In a press release, the Institute of Chemical Research of Catalonia (ICIQ) announced that a team of scientists developed autonomous micromotors that can convert the main component of urine into ammonia without generating any planet-warming gases.

The motors, which are shaped like a tube and made from silicon and manganese dioxide, are propelled by bubbles released during a chemical reaction. 

"This is an interesting discovery. Today, water treatment plants have trouble breaking down all the urea, which can result in eutrophication when the water is released. This is a serious problem in urban areas in particular," PhD student Rebeca Ferrer said in ICIQ's press release. 

As detailed by the National Oceanic and Atmospheric Administration, eutrophication begins when a water ecosystem is inundated with too many nutrients, like those found in urine.

This can lead to toxic algae blooms , the release of planet-warming carbon dioxide, and barren zones where underwater creatures are unable to survive.  

Meanwhile, a transition to clean energy is ramping up in a worldwide effort to limit the overheating of our planet to 2.7 degrees Fahrenheit above pre-industrial levels. 

Like contamination from urine, rising global temperatures have contributed to the degradation of marine environments , threatening a major source for the billions of people who rely on fish and seafood. 

More than three-quarters of heat-trapping gases released into our atmosphere are produced by dirty energy such as oil, gas, and coal. 

As the International Energy Agency pointed out , some methods of producing ammonia are energy-intensive, but researchers have been looking into it as an alternative fuel because it doesn't release carbon dioxide when burned.

ICIQ researchers said that they were able to obtain ammonia from urea by coating their micromotors in laccase, a chemical compound that occurs in fungi, plants, and bacteria.

The scientists, whose findings were published in the journal Nanoscale, concluded that their "bubble-powered micromotors" could forge a promising path to generating green-energy fuels. 

Before the technology can be used in water treatment plants or elsewhere, though, more experimentation is needed, including large-scale trials. 

"We need to optimize the design so that the tubes can purify the water as efficiently as possible. To do this, we need to see how they move and how long they continue working, but this is difficult to see under a microscope because the bubbles obscure the view," Ferrer explained in a statement for the institute. 

A method of machine learning from the University of Gothenburg is expected to help with that issue.

"If we cannot monitor the micromotor, we cannot develop it," said PhD student Harshith Bachimanchi, who studies physics at Gothenburg. "Our goal is to tune the motors to perfection."

Scientists develop 'bubble-powered' autonomous tool to transform wastewater into clean energy: 'This is an interesting discovery' first appeared on The Cool Down .

Official websites use .mass.gov

Secure websites use HTTPS certificate

A lock icon ( ) or https:// means you’ve safely connected to the official website. Share sensitive information only on official, secure websites.

• search    across the entire site
• search  in Executive Office of Energy and Environmental Affairs
• This page, Healey-Driscoll Administration Establishes Nation’s First Office of the Energy Transformation, is   offered by
• Executive Office of Energy and Environmental Affairs

Press Release  Healey-Driscoll Administration Establishes Nation’s First Office of the Energy Transformation

Media contact   for healey-driscoll administration establishes nation’s first office of the energy transformation, danielle burney, deputy communications director.

BOSTON — The Healey-Driscoll Administration today announced the establishment of the Office of the Energy Transformation (OET) and the appointment of Melissa Lavinson as its Executive Director. The Office will be housed within the Executive Office of Energy and Environmental Affairs and is charged with the hands-on execution of the clean energy transition, including ensuring the availability and readiness of electrical infrastructure, electric and gas transition coordination, and a just transition for impacted workers and businesses. Lavinson will also convene an Energy Transformation Task Force with industry, labor and supply chain representatives, among others, to accelerate cooperation and understanding of the current state of the energy transition in Massachusetts. This is the first position of its kind in the nation.   

“We are committed to equitably and fairly transitioning to clean energy. This means working closely with workers and businesses to set them up for success in an economy powered by clean energy,” said Governor Maura Healey . “Melissa Lavinson joins our team with close working relationships with the utilities and unions and will be able to build quick consensus as we make the transition away from fossil fuels. She’ll be able to translate our policy goals into real-world actions.”   

“We are at an inflection point where our policy vision needs to be translated into practical solutions,” said Lieutenant Governor Kim Driscoll . “Our new Office of Energy Transformation and the Energy Transformation Task Force will be able to execute on the important granular work of readying our electrical grid and supporting our fossil fuel workers over the next few years.”   

“The DPU’s order on the Future of Gas gave us the regulatory framework to end Massachusetts’ reliance on natural gas, and now it’s time to act,” said Massachusetts Secretary of Energy and Environmental Affairs Rebecca Tepper . “This is a transition for the consumer switching to electric appliances, for the worker being trained in the latest decarbonization technologies, and for our utility companies, which will need to adopt a new business model. We are establishing the Office of Energy Transformation with a dedicated team focused on transitioning our utilities and their employees to our clean energy future. Melissa Lavinson shares our urgency and commitment to an equitable transition. I know she will be able to hit the ground running and lead this new office with enthusiasm.”    

“I’m thrilled to join the Healey-Driscoll Administration and get to work bringing the benefits of the clean energy transition to every community in Massachusetts,” said Melissa Lavinson . “I’m looking forward to bringing together energy workers, businesses, and other stakeholders to develop practical and immediate steps we can take to equitably, affordably, and responsibly shift to a cleaner, more electrified, and fossil fuel-free future. Our office will tackle some of the most complex and important barriers to this transition and build meaningful consensus to meet this moment. It will take all of us, working together, to make this vision a reality.”   

The Department of Public Utilities’ groundbreaking order in Docket 20-80 confirmed that Massachusetts will move away from fossil fuels and its supporting infrastructure as quickly as possible toward electrification, including advancing targeted electrification pilots and expanding geothermal. The electric network is projected to be the primary energy delivery mechanism for the entire state by 2050. To achieve this vision, the Healey-Driscoll Administration recognizes the need for a dedicated team to focus on to real-world, daily impacts of executing the energy transition.   

The Executive Director of the Massachusetts Office of Energy Transformation will provide leadership in strategic planning, roadmap development, and stakeholder engagement to advance the transformation of the state's energy delivery ecosystem. In this role, Lavinson will focus on three key areas:    

• Electric Infrastructure: As residents make the switch to electric heating and vehicles, the OET will work to ensure there is adequate infrastructure, regulations, and supply chain in place to accommodate increasing electric load on the timeline outlined in the state’s Clean Energy and Climate Plans. 
• Electric and Gas Coordination: The OET will work with the electric and gas utilities to ensure a coordinated approach to the energy transition that maintains reliability, safety, and affordability.
• Just Transition for Workers & Businesses: Many companies and thousands of workers are dependent on fossil fuels such as natural gas, oil, and propane for their livelihoods. The OET will work with stakeholders to develop a roadmap to empower and prepare workers and businesses for the future, while ensuring the safe and reliable operation of energy infrastructure during the transition.   

To address these issues, Lavinson will convene an Energy Transformation Task Force comprised of representatives from utilities, business, labor, supply chain industry, municipalities, and other implementation partners to accelerate cooperation and understanding of the current state of the energy transition in Massachusetts and areas in which immediate progress can and must be made. In collaboration with the Task Force, Lavinson will develop a slate of near-term priority actions to address current barriers to the transition and a longer-term execution roadmap to help companies and individuals implement the transition. Such a roadmap would evaluate where and when new electric infrastructure is needed, gas infrastructure can be retired, and near-term transition projects, including geothermal and targeted electrification projects, can advance. Planning ahead and taking a coordinated approach will help contain costs and minimize impacts on ratepayers. Additionally, the OET and Task Force will develop and execute a transition plan for gas workers and gas-dependent businesses to set them up for future success and competitiveness.   

About Melissa Lavinson   

Melissa Lavinson joins the Executive Office of Energy and Environmental Affairs from National Grid, New England, where she previously served as Head of Corporate Affairs, leading National Grid’s state and municipal government relations, community and stakeholder engagement, media relations, municipal customer management, strategic communications, and the company’s Equity in Energy initiative and Grid for Good philanthropic program in New England. Previously, Lavinson was Senior Vice President of Federal Government and Regulatory Affairs and Public Policy at Exelon Corporation and Senior Vice President of Governmental and External Affairs for Pepco Holdings, Inc. (PHI), the parent company of Pepco, Delmarva Power, and Atlantic City Electric, which provide gas and electric service to Delaware, Maryland, New Jersey and the District of Columbia. Lavinson also spent more than 20 years at California-based PG&E Corporation, including as Vice President of Federal Affairs and Policy and Chief Sustainability Officer. Earlier in her career, she worked at MRW and Associates and in ICF Consulting’s Climate Change Practice. Melissa holds a bachelor’s degree in Economics from Hamilton College. She starts as Executive Director on May 1.   

Statements of Support   

Gina McCarthy, Former Advisor to President Biden  

“Establishing the Office of the Energy Transformation is innovative, necessary and continues Massachusetts' climate leadership. We need to really dig in and figure out how we are going to accelerate the move away from fossil fuels and electrify our economy. I applaud the Governor and Secretary for their foresight and for bringing on Melissa Lavinson to lead this new office. I have known Melissa for many years and I can honestly say she is committed, forthright, fair and unafraid to tackle the hard issues and do it in a way that brings people together. She is the right person for this role.”  

Mindy Lubber, CEO and President of Ceres  

“Melissa is a 'make it happen' professional. She is strategic and smart and knows how to tackle monumental challenges and find solutions. I have seen her tackle problems like high energy costs where she provided a one- stop-shop for consumers to get help on bills. And I have seen her elevate sustainability at utility companies to become the priority for their boards and CEOs. I can think of no person better than Melissa to lead the state’s energy transformation program. I applaud Governor Healey for making this a high priority for her administration.”  

Bradley Campbell, President of the Conservation Law Foundation  

“Governor Healey has made a brilliant choice in choosing Melissa Lavinson to lead a new Office of Energy Transformation, and the office is sorely needed to accelerate the clean energy transition.  The planning and policy changes needed to overhaul our energy systems and phase out fossil fuels are many, and Melissa has a clear-eyed view of the failings and headwinds created by the current utility business model. Both the Governor and the Legislature now need to work together to make sure this office has the resources needed to do the job.”  

Elizabeth Turnbull Henry, President of the Environmental League of Massachusetts  

“Managing our net-zero transition and modernizing our electric grid will require thoughtful planning, coordination, and stakeholder engagement. In creating the Office of Energy Transition, the Healey-Driscoll Administration continues to re-design state government to better tackle the climate crisis and build a team of talented experts to accelerate equitable decarbonization.”  

Chrissy Lynch, President of the Massachusetts AFL-CIO  

“The energy transition is a critical opportunity to both combat climate change and create family-sustaining careers. The workers building, operating, and maintaining our decarbonized future deserve union jobs with good wages and benefits, strong workplace safety protections, and career-long training, and our current energy workers and their families deserve a thoughtful and just transition. This new Office and Task Force will make sure that we are centering workers every step of the way.”  

John Buonopane, Sub-District Director at the United Steelworkers  

"The creation of this office and taskforce are a real opportunity for the state leaders to make sure that fossil fuel workers do not get left behind in the energy transition. We look forward to working with Melissa and Secretary Tepper to ensure we go about an energy transition that is just and responsible."

Michael Monahan, International Vice President of the International Brotherhood of Electrical Workers 103  

“Creating this office and picking a leader that is not a political figure, but someone that knows the sector, understands the challenges, and has the purview and ability to get things done is both smart and necessary. I give credit to the Governor and Secretary for recognizing this role is needed and putting Melissa Lavinson in it. Melissa understands the energy transition will not happen overnight and that it will require hard decisions, compromise, and a real focus on making sure that our brothers and sisters who keep our energy system safe, reliable and operating every day are at the forefront -- because without them, this doesn't happen.”    

Nicole Obi, President and CEO of the Black Economic Council of Massachusetts

“BECMA is keenly focused on supporting entrepreneurs entering clean energy industries and we are excited that the Commonwealth is launching a new office devoted to synthesizing the efforts of a broad set of climate-based stakeholders. Melissa Lavinson is an exceptional leader with a demonstrated commitment to championing innovative solutions and fostering an inclusive Massachusetts economy. I look forward to working with her in this new role to expand equitable opportunities for underrepresented firms and communities.”

Lisa Wieland, National Grid New England President

“Helping the Commonwealth achieve its climate goals, while keeping our energy services reliable, safe, and affordable, is one of our most important responsibilities. With two decades of experience in policy, energy, and environment coupled with her collaborative leadership and action-oriented approach Melissa is an excellent choice to help the Healey Administration make progress on these ambitious goals .”

Joe Nolan, Eversource Chairman, President and Chief Executive Officer  

“With a focus on cost-effective and equitable solutions that maximize the benefits of clean energy for environmental justice communities and all customers, Massachusetts is a national leader in its common-sense approach to decarbonization through the unprecedented energy transition that we are all undertaking together. Melissa Lavinson will bring a unique combination of expertise and experience collaborating with a wide group of stakeholders in multiple regions across all levels of government to EEA’s Office of Energy Transformation, and we look forward to working together as she helps to address the challenges of this transformation and advance the commonwealth’s decarbonization and energy equity goals.”

Executive Office of Energy and Environmental Affairs 

Help us improve mass.gov   with your feedback.

The feedback will only be used for improving the website. If you need assistance, please contact the Executive Office of Energy and Environmental Affairs . Please limit your input to 500 characters.

Thank you for your website feedback! We will use this information to improve this page.

If you would like to continue helping us improve Mass.gov, join our user panel to test new features for the site.