sailboat energy transformation

Solar power

Electric boats.

• electric boat

I drove a rare solar-electric yacht to test clean-sea propulsion, here’s how it went

While we at Electrek often tend to focus on electric vehicles taking over roads, it’s important to remember that our inevitable abandonment of fossil fuels stems to all modes of transportation, whether it’s by land, air, or even the sea . I recently had the opportunity to set sail on Sunwater Marine’s Ramblin’ Rose , a 40-foot sailing yacht powered by solar panels and electric propulsion. It’s one of the only vessels of its kind on the West Coast.

Sunwater Marine is a San Diego-based nautical transportation company with a keen focus on spreading the benefits of renewable energy and electric propulsion to sea dwellers.

It was founded by president James Richmond in 2020, amid the global pandemic. Richmond had a little more free time to search for a boat for blue water cruising to which he could add solar.

James has been sailing for over 50 years, and has nearly 40 years of experience in the renewable and energy-efficiency industry.

He soon found a 2015 Leopard 40 Catamaran and initially planned to simply add solar panels for an electric range and an energy-efficient water maker.

However, James soon discovered viable options for electric propulsion, and began researching the possibility of converting his new yacht to be be solar-electric.

The result is the Ramblin’ Rose , a catamaran that can haul 12 passengers and sleep up to nine. It also happens to be one of the only solar-electric yachts in the West Coast.

I got the chance to take the solar-electric yacht out of beautiful Coronado and test the technology out myself.

The Ramblin’ Rose solar-electric yacht

As previously mentioned, Sunwater Marine’s Ramblin’ Rose is centered around a Leopard 40 catamaran, built by Robertson & Caine in South Africa. Richmond then put an additional $100k into a renewable energy conversion, equipping the yacht with solar panels, and electric motors.

While the original catamaran came with some traditional solar panels, Richmond’s experience in renewable energy told him that would not suffice for his solar-electric yacht.

He added lighter and more flexible solar technology from Sunflare , the first company to successfully mass-produce thin, durable CIGS (copper indium gallium selenide) solar panels.

The Sunflare panels on the Ramblin’ Rose operate individually with their own bypass diode, so if one is shaded (by the sail for example), the rest still work.

Richmond also separated the solar panels into three separate zones, so if one side of the boat is shaded, the other two are still harnessing the sun’s power back into the boat’s batteries.

He also showed me how durable these advanced solar panels were, as I was able to walk around on top of them without worrying about breaking any glass or ruining them.

The panels help charge the electric yacht’s battery packs while out sailing and indicate to the captain when they are doing so.

Electric propulsion and battery packs

To help power this vessel in and out of the marina and on the sea, Sunwater Marine’s president researched electric propulsion systems around the world, and decided that OCEANVOLT was the best option.

The solar-electric yacht now features two OCEANVOLT 15 kW ServoProp sail drives , utilizing unique propeller blades that can change pitch to optimize efficiency and even regenerate power.

The software controlled variable system adjusts the pitch of each of the propeller blades automatically, so that the power generation and output are always optimal. This is much more efficient than traditional fixed propellers.

The electric propulsion is powered by a 48 volt system, meaning it’s safe to touch without electrical shock (an ideal situation for maritime fun).

Each electric motor on the yacht is powered by a bank of 12 Lithium Iron Phosphate (LFP) batteries on each side, 24 total. The batteries provide 21 kWh of power on each side of the vessel, 42 kWh in total.

Richmond explained that he positioned each battery pack eight inches off the bottom of the boat, too, so if any water were to come in, the batteries would still be OK. Furthermore, the captain showed me backup storage of eight additional batteries should anything go awry at sea.

The status of each and every battery is monitored 24/7 by a supervisory battery management system (BMS) that will shut the battery bank down, should any individual battery begin to malfunction. Fire is not something you want on a boat, despite being surrounded by water.

Additionally, the system was implemented to safely operate minimal electric functions under any conditions, so if the electric yacht were to tip over, there would still be power to send a distress signal.

Thoughts on the future of electric propulsion

After manning the helm of the the Ramblin’ Rose , there is a lot to be excited about for the future of electric propulsion at sea , especially on a gorgeous yacht.

The ride itself was eerily smooth and quiet compared to diesel motors, with zero vibration throughout the boat. If you didn’t look back and see the wake of the electric motors, you might not even notice the yacht was being propelled.

There is a lot of potential in electric propulsion, especially as it pertains to propellers than can remotely change their angle like the OCEANVOLT ServoProps. This makes reversing the electric yacht in particular, much easier for captains compared to fixed props built to push forward.

The ability to set sail and regenerate power from the propellers is also a huge perk and pairs nicely with the advanced solar panels. Plus, you always have shore power as a backup when you’re in a pinch.

From what I’ve seen, the biggest hurdle looking ahead will be battery capacity, and providing enough stored energy to power the electric propulsion systems on the yacht.

The solar panels do help a lot, but it’s a relatively slow process. Smaller, lighter battery options will be crucial for longer distances at higher speeds at sea someday. In the meantime however, we still have sun and wind to pick up the slack.

Currently, the range and top speed are still limited by this lack of surplus energy below deck. We didn’t take the Ramblin’ Rose above 7.5 knots (~8.6 mph) because we didn’t want to burn through all our battery life (that was also in respect to the charter setting sail after us that day).

The solar-electric yacht still has diesel motors onboard for emergencies, but Sunwater Marine’s founder agreed with me that we’d like to see a day when those motors are not needed at all. Unfortunately, the technology is not quite there yet.

Luckily, people like Richmond and Sunwater Marine are using their knowledge and resources (and personal funds) to figure this stuff out for the masses, while spreading the word about electric propulsion. It has become a genuinely viable option at sea, even if it is only in support of other forms of propulsion like sailing for now.

If you’re ever visiting the San Diego area, I highly recommend reaching out to Sunwater Marine and chartering the Ramblin’ Rose , or one of the other solar-electric yachts Captain Richmond is working on.

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Scooter Doll is a writer, designer and tech enthusiast born in Chicago and based on the West Coast. When he’s not offering the latest tech how tos or insights, he’s probably watching Chicago sports. Please send any tips or suggestions, or dog photos to him at [email protected]

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Yachting World

• Digital Edition

The future of yachting: Smart technology for your next yacht

• Toby Hodges
• May 14, 2020

Could hydrogen-powered yachts be built from rocks or plants in the next decade? Toby Hodges investigates yachting’s eco future

It’s becoming abundantly clear that to meet greenhouse gas emissions targets set out in the 2016 Paris Agreement, we’ll need to adopt some radical changes in all lifestyles. Thankfully sailing is, by its very nature, a green activity. In fact, if you wanted to live as carbon neutral a lifestyle as possible, move onto a yacht and go sailing! But for how much longer will we be able to buy glass reinforced plastic boats, powered by diesel engines ?

When you consider the energy, materials and waste in composite boatbuilding, it can paint an ugly picture. Ironically, the best way forward might be to revert back to building wooden yachts with hemp ropes and cotton sails, but that is perhaps not the most practical answer to supplying today’s global boating demands.

However, researching this feature has filled me with optimism. There are brilliant minds working in the marine industry and many fascinating solutions for alternative materials and power sources. So how might eco-tech change boatbuilding in the next ten years and what will your next yacht look like?

This hydrogen electric cat is midway through build at Daedalus in North Carolina

The simple solution

Technology will continue to make yachts ever simpler to operate. The ability to go daysailing easily will be critical for an increasingly time-poor generation, while powerboaters drawn to the eco credentials of sailing will seek an intuitive format, in yachts that are easy to rig, dock and manage.

Boatbuilders are progressively incorporating greener propulsion and sustainable power sources, and are turning to natural and recyclable materials. Whether they are regulated to do so or not, this is a logical step to take, especially if we, the buyers, demand a more ethical product.

In the next decade we’ll certainly see a marked increase in the use of 3D printing in boatbuilding. Already employed for custom parts, this technology could be used to build hulls and decks – printed structures with natural fibre skins surrounding them could eliminate the need for wasteful moulds.

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There are already bodies in place concentrating on the reduction of waste and energy use in boatbuilding, while promoting recycled and low-impact materials. 11th Hour Racing is doing commendable work here. The common boatbuilding technique of using hand laid-up polyester certainly looks increasingly endangered.

Search for speed

The most effective way to minimise your carbon footprint afloat is to sail, so there is a strong argument for choosing performance yachts , which can harness the wind more efficiently. Large yachts and catamarans have an advantage too as they provide the deck space to host numerous solar panels and the speed to incorporate regenerative propulsion.

During its research for the Outremer 4E project, and new 55, Grand Large Yachting found that the usage of a yacht accounts for a much higher carbon footprint than its build. If you are able to sail in five knots of wind, then you can sail 95% of time in the Mediterranean, it says (data from western Med June-September).

Outremer’s 4E prototype will be used by cruising guru Jimmy Cornell for his next circumnavigation

To achieve this performance requires minimising weight, but what are the best alternatives to using the traditional high strength-to-weight ratio synthetic fibres such as glass and carbon?

Basalt fibre has long shown promise and is being used by new French catamaran brand Windelo to build its hulls, with PET (recycled plastic bottles) cores. Basalt is transformed from volcanic rock (with minimal CO 2 emissions), so the fibres are particularly resistant to heat and are recyclable.

However, it is the fibres from plants that could offer the most potential for boatbuilding. Flax in particular, the plant from which linen is derived, looks like becoming one of the most effective alternatives for use in high-strength composite applications.

Natural promise: Linen fibres are derived from quick-growing flax plants

Boats from plants?

The flax-based products of Swiss company Bcomp have already been used effectively in motorsport bodywork and snow skis for their combination of stiffness and vibration damping.

Paul Riley, a composites expert now marketing Bcomp products for marine use, says that flax is lighter than glass fibres, with similar stiffness and significantly lower cost than carbon fibres, yet with up to 75% CO 2 savings. “I think we’ll see this coming into mainstream yachting in the next two to three years,” he says. “Manufacturers need to take a stand and switch to less environmentally impactful materials, which will also provide improved health and safety for their workers.”

Flax grows from seed to crop in eight weeks, rarely needs irrigation, and chemicals are not required. Thus far it has been used by German yard Greenboats, including on the 2016-built GreenBente 24, and superyacht builders Baltic Yachts. News that Gurit, global leader in composite material supply, will be the worldwide distributor for Bcomp, could lead to a broad adoption by marine manufacturers.

A Tesla Model S electric race car clothed in Bcomp flax composite bodywork

Visitors to the Düsseldorf Boat Show this year may have seen the potential of this fibre on the Greenboats stand. Its Judel/Vrolijk-designed Flax 27 daysailer became a test-bed for numerous natural and recycled materials. The hull is made from flax and bio resin with a PET core, the deck from cork.

Greenboats’ founder Friedrich Deimann told me how frustrated he became with using composite materials, especially coming from a wooden boatbuilding background. “It takes five times as much energy to produce glassfibre than linen fibre,” Deimann reports, showing me the plants from which he built his beautiful clear-coated daysailer.

Greenboats has been using Flax or Natural Fibre Composites (NFC) since 2010. And it minimises the use of moulds by using a stitch-and-glue technique to build panels. Deimann’s company shows what is possible, but he admits a lack of trained personnel and the costs of small-scale production are the current issues.

The Greenboats Flax 27 daysailer has a hull made of linen fibre and bio resin with a core of recycled plastic bottles

Another is resin control. “You can’t use hand lay-up with flax because it’s a natural material, and without compression the fibres can absorb a lot of resin,” says Deimann. “By vacuum-infusing the resin, you compress and control it.” Vacuum-infusing resin brings its own environmental issues because the plastic used in the bagging process creates a significant amount of landfill. Some boatbuilders have already found a clever solution here in reusable silicone bags.

But the resin itself still remains an issue for chemists to solve. Pure bio resins exist already, but for the high-performance epoxies required in boatbuilding the natural content might only be around 30%. Entropy resins, bio-epoxies used in marine, snow and surfboards for example, are manufactured by replacing petroleum-based carbon with renewable plant-based carbon – by-products from the agricultural industry.

Recyclable boats

Elsewhere, yards have been forging ahead with various technologies that offer a cleaner end of life potential. The hull of the mini 6.50 raceboat Arkema 3 was made from a recyclable thermoplastic composite using Elium acrylic resin, for example, which can be ground down and reused to manufacture new parts. And many RS dinghy hulls are made from rotomoulded and recyclable polyethylene.

Meanwhile, the benefits of using high-tech timber construction are clear for all to see thanks to Spirit Yachts . Its strip-planked technique makes for a very stiff, lightweight structure, with hulls made from largely renewable materials. Indeed, the beautiful new Spirit 111 flagship is being labelled as one of the most environmentally friendly superyachts ever.

Managing director Nigel Stuart has instigated a network of green initiatives at the Ipswich yard and in its yachts. The Spirit 111 includes energy-saving appliances throughout, including ultra-efficient hydraulics and genset, and a regenerative propulsion system for its Torqeedo electric drive.

And it is this latter element – power – that will surely be the primary focus for making cruising yachts greener in the coming decade.

Going electric

Torqeedo and Oceanvolt have led this drive so far, with Volvo Penta now ramping up its electromobility technology. And although Torqeedo has already delivered 100,000 electric drives, this represents only a small fraction of the market, according to CEO Dr Christoph Ballin.

“So far, only about 1.3% of marine propulsion systems are electric… we need to put the foot down and do more,” he states. Over the next decade, Ballin sees serial hybrid power as the optimum solution for yachts, systems that involve a large battery bank with a mix of solar and hydro power generation. This reduces the CO 2 footprint by around 90%, but with the safety net of a ‘diesel range extender’ – a compact generator, says Ballin.

Moonwave is a Gunboat 60 recently refitted with the latest generation of Torqeedo’s Deep Blue electric drive system

Such a system caters for normal sailing and living requirements using only battery power. “The role of the generator is reduced from providing everyday energy for living on board (heating, cooking, washing, aircon) to emergency use, if you will. And the role of the combustion engine for driving the boat is completely eliminated.”

But what about hydrogeneration? Combined with enough solar panels, surely this will enable us to dispense with fossil fuels on board altogether? “I fully agree, hydrogeneration in terms of using the propeller to create power under sail is one thing that is here to stay,” Ballin believes.

ZF steerable saildrives are being integrated with Torqeedo systems for hydrogeneration

But it is dependent on the speed and size of the vessel. He points out that if you have a fast boat you can generate all the electricity you need while sailing: “We have a customer with Gunboat 60 which generates 10-15kW”.

Battery storage

“The limitation here,” points out Ballin, “is how much energy you can store in a battery, because of the energy density that batteries offer.” Torqeedo’s Deep Blue technology and use of BMW’s i3 high voltage lithium-ion batteries gives it an edge on competitors.

But is the reliance on lithium boat batteries as a ‘clean’ source of energy storage simply solving one problem by adding another? The questionable mining ethics surrounding the cobalt used in many lithium batteries has been widely reported and the question of battery recycling still remains unanswered.

Ballin foresees supply chains becoming more ethical from a human rights standpoint. He explains that BMW is now controlling the entire supply chain for its batteries, including sourcing the raw materials, to avoid inhumane working conditions.

This makes for another whole topic, as does the recycling issue, to which Ballin alludes to the potential for a second life for marine batteries in powerwalls and energy storage before they go into any recycling for cobalt extraction.

“We are in front of the largest mobility revolution since the introduction of combustion engines,” Ballin states. “We have to live with the fact that the stages in this transformation programme are all imperfect – and will be for more than ten years.”

Looking ahead, Ballin sees three key scenarios for what is possible for climate neutrality on boats: battery electric vehicles; hydrogen-power; and synthetic fuels. “The rule for sailors I think will be that wherever battery electric vehicles are feasible those are the preferred ways to go forward.

“If battery electric vehicles do not give you enough power, which is almost always the case for oceangoing vessels, then you can go to hydrogen for example… It will become mainstream to have a climate-neutral range extender.”

Hydrogen power

So could hydrogen be the holy grail of energy for yachts? Hydrogen fuel cells work by converting hydrogen (from seawater) to positive and negative electron charges. So far this process has been used as an energy source only by a few pioneering vessels, including Energy Observer , the first energy autonomous hydrogen boat to circumnavigate. And Race for Water , a solar and kite-powered multihull carrying a conservative amount of hydrogen (200kg) in 25 bottles, is currently three quarters of the way round the world.

Solo racing sailor Phil Sharp has been demonstrating a hydrogen fuel cell in place of a diesel engine to generate power aboard his Class 40 OceansLab . He believes larger scale commercial shipping and marine craft can adopt the technology to reduce their carbon emissions to zero.

For leisure yachts, however, hydrogen fuel cells are not yet economically feasible. Torqeedo’s Ballin explains the practical limitations: “The energy density of hydrogen per kg is a lot better than petrol or diesel, but the volumetric energy density is about 1/13th of diesel.” This means much larger fuel tanks are necessary – although these volumes can be reduced under pressure.

That helps to explain why hydrogen has been adopted by only a handful of (large) yachts thus far. A pioneer of the technology is Daedalus Yachts, which is midway through building the first hydrogen-powered superyacht. “Over the past two years we have conceived and developed not only a complete hydrogen electric marine propulsion system but also a clean energy micro grid with the only emissions being oxygen and pure water,” says Daedalus’s founder Michael Reardon.

The overview of the Daedalus renewable energy and power system

The 88ft catamaran is being built to full commercial survey for world cruising for visionary Stephan Muff, who created the technology for Google Maps. The Daedalus electrolyser (which converts water to hydrogen) is the same as has been used in US spaceships and NATO submarines, so the North Carolina company is quietly confident it’s onto a reliable power source.

For the shorter term however, sailors should look to solar and battery technology, where we can assume continued improvements in efficiency and capacity for reduced costs. Building photovoltaic cells into biminis, decks, masts, and sails is already feasible.

Using sail power alone whenever possible is an obvious objective. But it’s the sailcloth itself that is arguably the most disposable component, particularly aboard racing yachts. Laminate sails with a Mylar membrane can’t be recycled, so many used sails go to landfill, or are abandoned in sheds and shipping containers.

OneSails 4T Forte membranes are recyclable sails that use STR stripes, a high modulus fibre produced by compaction of polymer to create a flat ribbon

Polyester/Dacron sails are largely thermoplastic so can be melted and reformed (although typically coatings such as melamine render this highly problematic). However, other than turning them into bags and accessories, what are the options for sails with synthetic fibres, high modulus yarns, which are notoriously difficult to chop up and repurpose?

OneSails has been ahead of the game here with its 4T technology. It uses a recyclable base polymer and replaces the glues and resins with heat fusion. The result is a composite single structure sail, which uses a low-stretch technology to avoid Mylar or taffeta, for a completely recyclable sail. “This technology is the only genuine sailmaking system that offers the opportunity for sailors to recycle ‘end of life’ sails,” says OneSails UK’s John Parker.

North Sails’ 3Di products also avoid Mylar film and the company is working to recover raw material from used sails to turn it back into polyester fibres. North’s commercial director Tom Davis, who has overseen its cloth business for the last 20 years, sees two key areas of development with greener sails. Firstly with the raw materials: “I will be very surprised in the next few years if materials going into sails aren’t substantially bio-based.”

With its partner, Steelhead Composites, Daedalus has built the world’s only certified hydrogen containment vessel

And secondly, with what he terms the ‘back end’: “A very high percentage of the total acreage of sailcloth in all areas will be repurposed/recycled.” Again, he sees the quickest changes happening with polyester and reports that North is already using recycled PET films, which are chemically indistinguishable from oil-based film.

Davis has been impressed by the speed of the technology in these areas. “In the sailcloth/making business, we’re not big enough to be producing new yarn or filaments – that’s really a petrochemical level business. But we are the beneficiaries of the technologies those companies develop.”

So in the case of high modulus yarn products, North is working with a company that is producing a bio source for the monomers that become polymers and then become high performance yarn and fibre. “So instead of pumping oil out of the ground and converting it to plastic, they’re starting with trees and ending up with very high performance plastics,” Davis explains.

Positive thinking

It goes without saying that future yachts should be well insulated, durable and with very low energy loss and consumption. Battery banks and renewable regeneration will mean there’s little requirement for fossil fuels. Water filtration in and out of the boat is increasingly important. For those who spend long periods aboard, the growing energy efficiency of watermakers means there is simply no call to ship bottled water. Self-sufficiency rules.

The dissolving print your anchor leaves in the sand should be the only evidence a yacht ever leaves behind! I’m confident the next decade will bring a tidal wave of innovation in the marine sector. And with the right collective mindset, the future is indeed bright – it’s exciting and it’s green.

First published in the April 2020 edition of Yachting World.

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The revolutionary boat powered by the ocean

The Philippines’ traditional three-hulled boat is being redesigned, to draw its power not from fossil fuels, but from the energy of the waves.

We were standing in the pouring rain at Sabang Port, waiting for our turn to board a bangka (a traditional Filipino boat) that would take us to the entrance of the Puerto Princesa Underground River, which runs beneath a cave in Palawan, an island province on the western part of the Philippines. At last our bangka arrived, a trimaran with bamboo outriggers either side of its main hull.

The trimaran is a common sight on Philippine waters. The country pioneered this design in its early warships, then adopted it for its traditional sailboats and fishing boats. As an island nation, the Philippines relies on watercraft – boats, ferries and cargo ships – to transport people and goods across its more than 7,000 islands. But its fleet of cargo and passenger ships are one of the biggest contributors to the country’s greenhouse gas emissions. In 2012, transportation accounted for the second largest source of greenhouse gas emissions in the country’s energy sector , after heating and electricity.

Globally, 9% of all transport emissions came from international and coastal shipping in 2010 . That’s a small figure next to the 72% that came from road transport, but it puts shipping on a similar level to aviation, which made up 10.6% of transport emissions. And with the volume of world sea trade projected to grow at a rate of 3.8% a year to 2023 , emissions from the shipping industry are likely to increase too, unless the growth in sea traffic can be uncoupled from emissions.

A new design of ship in the Philippines is hoping to pose a low-carbon alternative to the country’s usual bangka, by working with the power of waves rather than against them. The ship is a hybrid model, using multiple internal combustion engines for initial propulsion but switching to wave energy while cruising in open waters.

This seacraft is the brainchild of Jonathan Salvador – a marine engineer and owner of shipbuilding company Metallica Marine Consultancy, Fabrication and Services – who was inspired by the conventional bangka’s design.

“The outrigger’s job is to provide stability so the bangka doesn’t tip sideways,” Salvador says. “But I also noticed that each time a wave hits the outrigger, the outrigger constantly reacts to the upward and downward movement of the wave. What if we can convert this reaction – this kinetic energy – into electrical energy?”

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The way wave energy works will be familiar to anyone who has waded in sea waters. At times, the waves are strong enough to push you back to shore or tall enough to push you over. “Waves have a lot of momentum, and it’s that momentum you feel when you’re out in the water,” says Bryony DuPont, professor of mechanical engineering at Oregon State University. “Wave energy uses that momentum, sometimes as-is and you just need the motion of the waves, and sometimes we capture that momentum and force it through machinery that generates electricity.”

The hybrid trimaran has this machinery – a wave energy converter – in the form of hydraulic pumps integrated into its outriggers. As the pumps move through the waves, they harvest the momentum of these waves, converting their kinetic energy into electrical energy, which will then be fed into a generator that will supply electricity to the ship. The electricity then provides propulsion via a motor. The more waves the trimaran encounters, the more power it can produce from those waves.

Construction of the hybrid trimaran started in 2018 and was set for completion by early 2020, in a collaborative effort between the Metallica shipbuilding company and the Aklan State University. But a typhoon in 2019 delayed the project and community quarantines enforced this year due to the Covid-19 pandemic resulted in a skeletal workforce at best and brought the project to a standstill at worst. Despite these difficulties, the team is aiming to finish building the ship by the end of 2020, with a three-month sea trial scheduled for the first quarter of 2021. The vessel is expected to be capable of carring 100 passengers, four vans and 15 motorcycles.

The hybrid trimaran’s use of wave energy could be a significant step toward reducing the need for environmentally damaging fuels such as diesel in the Philippines. And with wave energy offsetting gasoline use, Salvador and his team aim to bring down the vessel’s carbon emissions by a third compared with the most modern large-scale shipping lines .

The wave energy converter would also benefit from the ship’s traditional trimaran design. “Wave energy requires motion of one part of the system relative to another,” says Rob Cavagnaro, a mechanical engineer at the Marine Sciences Laboratory of the Pacific Northwest National Laboratory in the US. “Having outriggers that can heave – or move up and down – relative to the central hull may be well-suited for this purpose.”

Moreover, waves are energy-dense; in other words, they can be ferociously powerful. At coastlines, waves can reach power densities of 60–70 kilowatts per metre in areas with deep waters . In the UK and the US, for example, the average wave power density is between 40 and 60 kW per metre . “If we can translate that energy into other useful forms, we can do a lot with very little,” DuPont says.

But converting the high-force, low-speed motion of waves in an efficient way can be a challenge. “There may be many sources of loss along the way, from friction in the hydraulic systems to heat in the electrical generator,” Cavagnaro says. The engineering challenge that remains is to minimise these losses.

Another hurdle would be designing a wave energy converter small enough for the ship’s dimensions. “Wave energy converters generally develop more power the larger they are, but if they’re so large that the waves can’t move them, then can’t effectively harvest momentum,” DuPont says.

Even so, a private company in Boracay, a popular tourist island in the country, has already expressed interest in operating the ship once it’s launched, says Rachel Habana, a senior scientist at the Philippine Council for Industry, Energy and Emerging Technology Research and Development, which oversaw the trimaran’s development. “We envision the future of public sea transport in the Philippines to be safe and green with less emissions, and we see the trimaran bringing that vision to life,” she says.

But as yet the hybrid trimaran is still a prototype. “Because we have new technology for the vessel, we need a technology verification step before we can go for full-scale commercialisation,” says Yasmin Tirol, project leader and campus director of Aklan State University’s College of Fisheries and Marine Sciences. “We already conducted some test modelling for the wave energy converter, but we have to look into its actual performance and optimise it.”

Cost is another issue. Funding for the project is at 76 million Philippine pesos (£1.2m; $1.5m), but Salvador estimates commercial-level costs to reach 250 million Philippine pesos (£4m; $5m) or more per ship. To keep expenses low, at least 80% of the trimaran’s parts are sourced locally, while the entire manufacturing and assembly process is done within the country. Staying local also opens up opportunities for improving the skills of the shipbuilding and ship engineering workforce in the Philippines, and allows smaller shipbuilders and the country’s large workforce of seafarers to participate.

Salvador refers to the current trimaran as a “series one” prototype, with plans for more ambitious series two and three versions that will use wave energy to help the engine create more power, or even fuel the vessel entirely. But this might be a difficult feat given the considerable power demands of large modern ships. “The power available in waves interacting with the ship may not be enough to meet the full energy needed for propulsion,” says Cavagnaro. “It would also depend on how large and long the waves are – the highest-energy waves are ones that would not be comfortable to move through.”

Wave energy powered vessels are a nascent technology, and it’s still to be seen which is the best way to draw power from the sea. For instance, the Autonaut, an unmanned surface vessel, uses foils to harvest wave energy for propulsion . Meanwhile, the most common design concept for wave-powered boats uses fins that move like dolphin kicks or a whale’s tail to propel the boat forward. All these have yet to go mainstream or be applied to larger seacraft.

But for any boat navigating the choppy waters between the islands of the Philippines, it is a tantalising prospect to turn that churning energy into forward motion. The hope is that this abundant, clean resource will become as widely used at sea as its more mature renewable energy counterpart: the wind.

“I think anyone who has surfed or swam in the ocean or been on a rocking boat has contemplated the immense power of ocean waves,” DuPont says. “It’s thrilling to see brilliant ideas stem from that spark of inspiration – from being connected to the ocean.”

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Regenerative Electric Propulsion

Imagine a sailing vessel meeting energy needs through regenerative power..

By combining technologies from the 19th and 21st centuries—skipping over the petroleum era—Matthew Turner will become a unique teaching tool that can inspire appreciation for past boat building designs while utilizing innovative technology solutions to construct a truly green sailing ship.

The basic regenerative electric propulsion concept is simple. Instead of diesel engines, the ship is propelled by AC electric motors directly connected to the propeller shafts and drawing energy from large battery banks. When the ship is sailing, the energy of the passing water causes the propellers to rotate, which, in turn, causes the electric motors to become generators that re-charge the batteries onboard. Significant electrical energy is created as sailing speeds increase.

New advances in propellers, electric propulsion/regeneration motors, battery technologies and electronic controllers make this possible and are available today.

Matthew Turner can, in fact, operate on a carbon-neutral basis. Energy to run our ship will come from regenerative power under sail, which can be fueled with bio-fuel, and dockside charging from solar panels and wind generators. The dockside solar will be facilitated by the US Army Corps of Engineers at their Bay Model facility, which has recently been outfitted with a rooftop solar array that generates 540 kW/h.

Day-to-day operations are designed to minimize energy and water use with a waste management system that will repurpose, recycle and reduce waste. By using LED lighting, induction cooking and low energy navigation and appliances, the Matthew Turner will use less than 50kWh per day. The vessel can produce enough clean energy in a day of sailing to sustain the vessel’s needs.

HybriGen Benefits:

• Power is delivered on-demand to support propulsion or auxiliary power, or both simultaneously
• Variable speed genset and lithium-ion battery banks eliminate under-loading of the engine and wasted fuel
• Reduced operating time of diesel generators also allows for reduced maintenance
• Electric traction motors and batteries allow for completely silent and emission-free cruising
• Flexible, tablet-based diagnostics and control system allows for powerful, yet easy-to-use system operations and monitoring
• Isolated propulsion system in each demihull provides complete redundancy

Read more about BAE’s HybriGen Power and Propulsion here

Yachting Monthly

• Digital edition

The true carbon cost of sailing – and why going electric could be less green than you think

• Theo Stocker
• February 7, 2024

New research reaches some surprising conclusions about which propulsion systems might actually have the lowest carbon footprint. Theo Stocker digs into the numbers

A white sail on a blue sea. What could be cleaner than that?’ Sailing nerds might recognise this quote from the all-time greatest sailing film, Wind . Or maybe that’s just me. Anyway, it’s easy to assume that drifting around with the breeze has little impact on the environment, let alone the global climate. But that assumption may be further from the truth than you think.

Certainly, the marine industry is tiny compared to other emitters of greenhouse gases, but it still registers on the scale. Recreational boats account for less than 0.1% of global greenhouse gas (GHG) emissions, specifically 0.7% of transportation carbon dioxide (CO₂) emissions in the United States and 0.4% of transportation CO₂ emissions in Europe.

Those numbers sound small, but then consider that there are estimated to be 50 million recreational craft globally, with as many as one million new boats being added to that number every year. New research has now been published by the International Council of Marine Industry Associations (ICOMIA) as they seek to plot a way forwards for the leisure marine industry.

The rather bleak headline is that if you want to move away from fossil fuel propulsion, you could easily generate a larger rather than smaller carbon footprint, whether you’re looking at biofuels, hydrogen, electric or hybrid propulsion systems.

The good news, however, is that the devil is in the detail. Make a few compromises to things like range and performance, conduct an honest appraisal of how you actually use your boat, and utilise new and emerging technologies, and you can reduce your boat’s carbon footprint, whether you’re buying a new boat or not.

John Kerry, with his granddaughter, signing the 2016 Paris Agreement on behalf of the US. Photo: Xinhua / Alamy Stock Photo

Paris climate agreement

The Paris Climate Agreement, a legally binding international treaty that seeks to limit global temperature increase to 1.5°C above pre-industrial levels, requires signatories to reduce global carbon emissions by 43% by 2030.

While the marine leisure industry might be a tiny proportion of global emissions, it is still a contributor. Given recent protests against superyachts and the perception of sailing and boating as an elite, luxury pastime, ICOMIA wanted to be able to work with regulators to reach policy decisions based on data rather than emotions, assumptions or ideologies.

Article continues below…

There was, however, a ‘vacuum of data’ and while regulators, companies and customers were all trying to take positive steps environmentally, there was very little cold, hard evidence guiding them, leaving potential for flawed choices and the potential dismissal of the best options for reducing the marine industry’s carbon footprint. To fill this void, they commissioned the most detailed research project ever undertaken on the subject in the marine industry.

The result of the project is the 550-page report Pathways to Propulsion Decarbonisation for the Recreational Marine Industry. So far, the report and its data has been shared with the European Commission Department of Growth, the US Dept of Energy and Governments in the United Kingdom, Spain and Sweden.

Infrastructure for new technologies to be adopted is an essential part of assessing their carbon footprint. Photo: Scharfsinn / Alamy Stock Photo

ICOMIA set out to create a robust and holistic analysis of the full environmental impact of all currently available propulsion technologies for recreational vessels under 24m (80ft).

It was to consider the full-life ‘cradle-to-grave’ impact of building, using and disposing of leisure craft. The report covers first-of-its-kind primary research study from Ricardo, a leading global engineering consulting firm. The resulting data took two years to compile and was subject to thorough peer reviews in an attempt to make this the most robust data possible.

ICOMIA’s aim was not to make a pronouncement on what technologies are green or not, but to provide benchmark data against which governments, boat builders, technology developers and you, the sailing public, can make informed choices.

The study covered nine types of vessel up to 24m, including inflatable tenders with small outboards, runabout day motor cruisers, fishing boats, pontoon boats (a large sector in the US), personal watercraft, sailing yachts, inland waterways craft, large displacement motorboats and performance motor yachts.

Steve Bruce, UK MD for ePropulsion, is sceptical about ICOMIA’s report. Photo: Scharfsinn / Alamy Stock

The study was broken down into six steps: exploring the decarbonisation options; conducting a Greenhouse Gas Life Cycle Assessment (LCA) to ISO 14044 and 14067 standards including the manufacture, use phase and end of life for energy converters and energy carriers; assessing the total cost of ownership of each system, including purchase, operation and maintenance; analysing the implications of life expectancy, maintenance, performance, safety and availability of each system; analysing the infrastructure implications, before ranking the suitability for each craft type and usage case.

The report is still pretty broad brush strokes, and there are plenty of caveats to the findings. How and where boats are used, what technology is installed, and the supply chains in each of those products have an impact, and ICOMIA says that it is keen that the data acts as a baseline for people to innovate around and find ways of cutting emissions in every part of a boat’s lifecycle.

Even so, some are sceptical about the report. Steve Bruce, Managing Director (UK) of electric engine manufacturer ePropulsion said, ‘I have to say I am extremely disappointed.

It would appear to me that the report has been written with a bias against electrification and has failed to consider several relevant factors, such as the ability to re-purpose and ultimately recycle batteries.

‘It also seems to be based on facts that do not appear to be in line with what we are being told by boat users in our daily conversations, so I would like to better understand precisely where the report writers have decided to select their data from and why.

‘The small amount of hours they suggest boats are used for does not correlate with the actual use profiles we are being asked to support.’

From a user point of view, electric propulsion has many benefits over combustion engines. Photo:

What the research doesn’t do

The report’s authors were keen to emphasise that they were not aiming to stymie certain solutions, but rather to identify the real-world use cases in which these systems are the best to choose, and to highlight where more development and investment is required.

They also noted that the research focuses on propulsion systems, while there are a whole host of other areas in which a pleasure vessel could reduce its carbon footprint, from building materials and manufacturing processes to supply chains, shipping, and disposal. Similarly, how a vessel is used will have a big impact.

ICOMIA CEO Joe Lynch explained, ‘This isn’t to tell people what to do but to help them make the best decision for their use case and allow industry to find solutions, by providing a set of data. It is a point in time study for most popular types of vessel currently in use. We hope to expand this out to more use cases and more emerging technologies, such as foiling, in due course, and aim to turn the work into a more usable life cycle analysis tool as a basis for solid decision making to help decarbonise the marine industry.’

The research did not interrogate the use of recycled goods, for example repurposed pre-used car batteries, or the re-engining of existing yachts, and nor did it pit one type of vessel against another.

It also didn’t give weight to local considerations, such as the need to reduce pollution or noise in ecologically sensitive environments, or increased user enjoyment or a reduction of maintenance.

‘This is a decarbonisation report rather than a usability report,’ said Lynch. ‘There are many other reasons to choose electric-based criteria such as noise, smell, cost, maintenance and so on,’ acknowledging the focus is very much on the global carbon emissions of a vessel’s lifecycle.

Electric cars have a very different set of parameters, meaning they are more able to offset the additional carbon emitted in their manufacture. Photo: Kenny Williamson / Alamy Stock Photo

Cars vs Boats

One of the big assumptions the report seeks to interrogate is that because electric cars, or ‘battery electric vehicles’ (BEV), are thought to be the most environmentally friendly solution for land-based transport, the same will apply on the water. The problem is that there are vast differences between cars and boats, according to the data.

For a start, propelling a boat over a set distance takes roughly 10 times more energy than it takes to move a car. Then you’ve got the fact that most cars are used much more regularly and for longer periods than cruising boats.

This means that of a car’s total lifetime carbon footprint, less than 20% of it is in its manufacture, with almost 80% in its usage – energy supply, exhaust emissions and maintenance – and a bit in its end-of-life disposal. For a boat, the research shows that while some yachts are heavily used, many lie idle for great chunks of time, and they arrived at an average annual usage of a sailing boat’s engine of just 24 hours a year, based on data from engine manufacturer service records and data from the US Environmental Protection Agency.

For the various kinds of motorboats, this increases to between 35 to 48 hours a year. Only a commercially operated rental jet ski had an average use case of over 100 hours a year.

Proportionately, as much as 50% of a boat’s lifetime emissions come from its manufacture, 10% from scrappage and 40% from its usage (and even less when it comes to sailing boats). This gives you a much shorter lever with which to balance out carbon already emitted with a reduction of carbon in usage.

Small dinghies are now frequently powered by electric motors. Photo: Benjamin Sellier

Supply chain carbon

The research analysed the carbon contribution, or global warming potential (GWP), of each stage in the supply chain and lifecycle of each propulsion system, for each of the vessels being considered.

It assumed a like-for-like comparison of energy storage and range, rather than the ‘optimised’ systems referred to later. While these vessels would not be usable in the real world, it made it possible to compare the carbon footprint of equivalent processes within the supply chain.

In the figures given, an inflatable dinghy using an electric outboard can eliminate around 40% of its total GWP from its usage emissions (energy, tank to wake) alone, compared to the petrol-driven baseline. However, this has to offset an almost three-fold increase in its raw materials (propulsion) carbon footprint and a manufacturing footprint that is around two-and-a-half times higher.

Using sustainable marine fuel caused a far bigger increase in the craft’s total footprint, in which the energy well-to-tank actually doubled the craft’s footprint.

For sailing yachts, there is a proportion of the vessels’ total GWP that is attributed to the hull and structure’s raw materials that is several times higher than that of any of the propulsion systems’ raw materials, including electric, though manufacturing impacts are significant.

Mineral extraction and the processes involved are a large part of batteries’ carbon footprint

By far the worst option for a sailing boat was hydrogen, where the well-to-tank impact of the fuel accounted for 40% of the vessel’s total GWP, giving a hydrogen-propelled vessel a carbon footprint twice the size of a fossil fuel-propelled boat.

Both electric and hybrid systems’ GWP were 50% higher than the baseline, with much of this coming from raw materials, manufacture, and surprisingly, maintenance, given electric systems’ almost maintenance-free usage, due to the necessary replacement of the batteries (estimated life span of 12.5 to 15 years).

Even sustainable marine fuel had a higher total impact by about 12% before use-case optimisation, due to a higher energy well-to-tank impact.

Darren Vaux, President of ICOMIA, says, ‘There is a lot of carbon in the supply chain of the batteries, and because there is such low utilisation of hours, it’s very hard to offset. Sailing craft life is long, so the batteries have to be replaced during the course of its life because they don’t have the same longevity.

‘The fascinating thing is that electric motors’ torque profile, lack of noise and all of that are absolutely ideally suited for marine. The challenge is the energy storage, both in terms of the energy density, and also the life of the batteries and the carbon embodied in them from most battery manufacturers.

‘Where manufacturers who operate in a country where they have a high green-energy mix, and a supply chain for manufacture in a factory with a very low carbon footprint, then there’s a competitive advantage to say, “I’ve got a battery that has a very low carbon footprint,” and that will address some of the carbon issue. The energy density of batteries is still significantly lower, but this may be satisfactory in some cases.’

Fitting any kind of alternative propulsion to runabout day boats like this RIB requires a significant compromise.

Realistic comparisons

The five power systems weighed up were all systems that use existing technologies currently available commercially. These were: conventional petrol or diesel internal combustion engines (ICE) as a baseline; sustainable fuels used as drop-in alternatives for fossil fuels in ICEs; hybrid fuel (fossil/sustainable) and electric systems; battery electric drives, and hydrogen ICE or fuel cells.

In order to calculate the life cycle assessment of vessels equipped with the various alternative propulsion systems, it was unrealistic to substitute in systems that provided like-for-like power and range.

As Patrick Hemp, ICOMIA technical consultant explained, ‘We get a lot of questions around the bottom-up approach and why H2 ICE and Battery Electric needed to be optimised. The main reason Ricardo had to do this was because the current baseline speed/range is simply not possible with Hydrogen ICE or Battery Electric (too much weight and volume) and hence, a downsizing was required.’

Fitting any kind of alternative propulsion to runabout day boats like this RIB requires a significant compromise

Runabout motorboat

As an example, a small runaround motorboat may have a typical range of 14 hours and 166 miles. To give the same range in a single duty cycle (one tankful or battery charge) with hydrogen propulsion, fuel storage would need to be around 430% larger than the ICE system and would be 350% heavier, giving the boat a displacement 56% greater.

With electric propulsion, the volume of the batteries for this range would be 360% larger and 820% heavier, with a vessel displacement 133% heavier.

In the calculations, the researchers decided to optimise the power system so that it could still fulfill the way most people use the boat, but with a propulsion system as close to the mass, volume and performance of the existing system as possible.

When aiming to achieve a range of 3 hours and 35 miles for the same small motorboat – a reduction of around 80% – a hydrogen system that was 61% larger and 13% heavier with a displacement increase of just 6% was achievable. For electric power for the same range reduction, the system was 23% larger, while being 81% heavier, with a displacement increase of 16%.

A sailing yacht has a huge fuel-free range if sailed, but most cruisers rely on auxiliary propulsion to keep making progress when conditions don’t suit. Photo: Richard Langdon

Sailing vessel

The calculation for a sailing boat used a baseline of a boat running on diesel, though the HVO fuel figures are identical. With a 21kW / 28hp engine and 70L fuel tank, the boat has a range of 24.5 hours and 147 miles, and there is no increase to mass, volume or displacement for either diesel or HVO.

Change to a hybrid electric drive system running a 21kW / 28hp ICE engine, with a 21kW electric drive. The fuel tank can be reduced slightly to 59L for the same range, but the system volume increases by 69% and would be 137% heavier, increasing the boat’s displacement by 6%.

For an electric or hydrogen system, the systems were specified to a range of 4 hours / 24 miles at an equivalent 6 knots, a reduction in range of around 84%.

The electric system, with a 21kW motor needed a battery capacity of 49kW, which resulted in a system that was actually 18% smaller than the baseline, though it was 61% heavier, and resulted in an additional 3% displacement.

Hybrid Marine specialises in diesel-electric parallel hybrid systems built around new Beta and Yanmar engines

The hydrogen-powered boat, with 21kW engine, had high-pressure fuel tanks to hold 3.7kg of hydrogen. This system was 49% larger than a standard engine and tank, and was 12% heavier, adding just 1% to the boat’s displacement.

Alternative propulsion systems were optimised in this way to enable realistic life cycle assessment comparisons to be made. Looking at the data then, sailors are free to make choices about whether they would be more happy to accept compromises to range, performance, the amount of space on board, and displacement, as well as cost.

Unsurprisingly, the report found alternatives are more expensive than the status quo, albeit within an enormous range. Electric systems as specified in the optimised use cases were 40% to 250% more expensive, 85% to 200% more for hydrogen, 25% to 115% more for hybrid, and 5% to 45% more for using sustainable drop-in marine fuel alternatives.

Large numbers of yachts remained unused or very lightly used, leading to just 24 engine hours a year on average

How much do boats get used?

While ‘battery electric on-road automotive vehicles’ (BEV) reduce CO₂ emissions by between 50% and 70% relative to conventional fossil fuel engines over their lifetime, the initial CO₂ created during the production of an electrical vehicle (EV) can be at least 50% more than a conventional ICE vehicle due to raw materials and the energy intensive process of creating the battery.

This means it takes an electric car 100,000 to 150,000km (62,000 to 93,000 miles) to get the break-even point where it is starting to have a positive impact on carbon emissions, which might take 3-5 years of fairly heavy use.

This also takes into consideration the fact that drivers’ range expectations have, on average, been reduced, so that one battery charge on your car will take you about 60% of the distance your old diesel or petrol car would have done. The cost, size and weight of the batteries would be prohibitive for a like-for-like range, and the environmental cost – mostly attributed to the batteries – would also be even higher.

For boats, those with very high use cases, and where small batteries with limited range can be specified, such as ferries and other commercial vessels, some of the new technologies really do add up in a similar way to cars. But the average leisure cruising yacht (though not, for example, a liveaboard cruiser), has just 24 hours of engine use a year, over its 45-year life span, according to the data.

Diesel engines remain the lowest impact propulsion to manufacture and install, but the emissions from the supply and use of them needs to be reduced

If this seems crazily low, marine surveyor Ben Sutcliffe Davies explained, ‘When I go to survey a vessel, I’m often amazed at how few hours have been put on the engines. It’s rare to find a yacht that’s done much over 50 hours in a year.’

Certainly, many boats will be used far more than the assumptions in this report, but there are also many boats that sit sadly idle, used for a handful of days or hours over the summer. The ‘use case’ of any boat is one of the key deciding factors in what propulsion technology will be the greenest option, and it’s worth remember that this report aims to look at the majority average rather than outliers.

In order to get to the ‘break even’ point on an average GRP cruising yacht, where the new propulsion system’s reduced usage emissions have compensated for its increased manufacturing emissions, you will need to do 60 hours of electric motoring a year (compared to 24 hours average), every year for its 45-year life span.

To get to a point where you have cut your emissions by 50% – the benchmark in the automotive industry – you will need to increase your usage by 600% above the average, or 168 hours of motoring a year on your electric engine. The figures are almost identical for a hybrid system.

Liveaboard and long-term cruisers clearly have a much higher use case, giving them longer to offset carbon with alternative technologies. Photo: Crew Eastern Stream

For a hydrogen system, which has a manufacturing footprint slightly lower than that of battery systems, the break even point comes sooner, with a modest 52% usage increase (36.5 hours), but with a slightly higher carbon footprint in use, a 50% reduction in emissions compared to a diesel engine will take a whopping 192 hours of motoring a year.

Surprising findings

Once the use cases and optimised propulsion systems have been taken into account, for many recreational sailing yachts that match the assumed use case, opting for electric propulsion in a new yacht or converting a used boat to hydrogen, hybrid or electric propulsion will be worse for the environment than sticking with a fossil fuel internal combustion engine (ICE).

For most vessels and average use cases, the best way of reducing environmental impact for the time being is to retain conventional ICE engines, but switch to sustainable synthetic or biofuels such as hydrotreated vegetable oil (HVO) or e-petrol, the report claimed.

Doing this in a sailing yacht will, over the vessel’s 45-year lifespan with an average annual usage of 24 hours, reduce the vessel’s global warming potential by around 35%, compared to using fossil fuels in an ICE engine. The same benefit applies to both new boats and the numerically more significant existing fleet of boats already in use. Switching to electric or hybrid propulsion may in fact increase the vessel’s global warming potential by over 35%.

If you can find somewhere to buy HVO biofuel, this will be simplest way to immediately cut your carbon

Of the nine vessel types analysed, electrification was only the greenest option for a commercially operated personal water craft used for 156 hours per year over a 12.5 year lifespan. The highest impact of going electric was for a displacement motorboat, used for 48 hours a year over 45 years, where the global warming potential went up by over 80%.

If your vessel, its systems, their manufacture, and your usage don’t match the averages used in this report, then the life-cycle assessment might reach different conclusions, particularly if your usage is higher than average, but it’s worth considering the lifespan emissions when making these decisions.

How we choose to build, propel, and dispose of boats could be limited if their climate impact isn’t addressed

Conclusions

The research concluded that renewable diesel fuel, specifically hydrotreated vegetable oil (HVO) ICEs can provide the largest global warming potential (GWP) reductions compared to existing ICE propulsion, but only if the fuel is produced using waste feedstocks so that it’s not taking resource away from global food production, and gives the marine industry the greatest chance of decarbonising by as much as 90% by 2035 without compromising a vessel’s range or performance.

That’s all very well, and marinas with existing fuel supply infrastructure should be able to adapt easily, but it would require a huge increase in the supply of HVO in order to facilitate that change, and that capacity just isn’t there at the moment. As the report notes, ‘There is considerable uncertainty over the availability of these fuels through to 2035, and caution must be taken to guarantee that e-fuels are produced using low-carbon electricity sources and biofuels are produced with low GWP feedstocks.’

It also concludes that because electric-only systems ‘may have a higher GHG contribution from raw materials and manufacturing than conventional propulsion systems’, vessels that have low-usage cases are unlikely to ‘yield a reduction in greenhouse gases’ over their lifespans. Boats that are in frequent and prolonged use may be more likely to reach the break-even point, while hydrogen and hybrid systems may, in some cases, be the greenest option.

ICOMIA is now working on making a full life-cycle assessment tool available to the industry so that boats and use cases can be examined on a case by case basis. The report is a snapshot of the LCA for each type of boat, and a series of assumptions made about its usage.

ICOMIA President Darren Vaux, explains, ‘These use cases should cover the majority of the market, but there will be outliers that don’t fit these use cases. We are trying to move the dial on meeting the Paris Agreement for decarbonisation of the marine industry. At the moment, the only thing that will get us there is drop-in HVO fuels.

‘We need to focus policy-makers’ minds,’ Vaux continues. ‘We’re building infrastructure for electric vehicles, but we also need an infrastructure for the supply of sustainable fuels. We also want to challenge innovation, to encourage the industry to use the data-set as a challenge, with a clear focus on what the supply chain carbon impacts are.

‘Our data-set is the majority case, but that leaves room for boat builders to find ways around it, to say, “We’re better than that.”’

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Watch CBS News

Take a tour of the Energy Observer, a sailboat running on 100% renewable energy

By Alecia Reid

April 12, 2024 / 6:11 PM EDT / CBS New York

NEW YORK -- A sailboat running on 100% renewable energy has made its way around the world for the last seven years and is now in New York City until Earth Day.

CBS New York's Alecia Reid got a tour of the vessel.

The Energy Observer is a decommissioned racing catamaran, now refitted with solar panels covering the entire vessel, in addition to innovative technology. It's a step towards a greener, more sustainable, low-carbon future.

"What we're trying to show to people is that a mix of renewable energies is the best option," boat swain George Conty said.

The floating lab is the first self-sufficient, zero-emission vessel. The crew of five uses renewable energy and hydrogen technology to power the boat as they sail around the world. The initial energy comes from the sun and wind.

"The excess, we store it in batteries. Then when the batteries are full and we still have some sun, instead of just losing this energy that arrives on the boat, we produce hydrogen to continue storing this energy in the form of gas," on-board system engineer Luc Bourserie said.

Engineers are constantly testing the technology to ensure it works. The hope is that any part of the prototype can be used as an inspiration to others searching for ecological sustainability.

"We have proof that the technology works," said Beatrice Cordiano, on-board scientist and climate energy expert. "The concept is quite simple, you just have to deploy a lot of renewable energy capacity."

It's definitely tight quarters living on the boat year-round, but the crew has a decent-sized kitchen that they make good use of.

"And sometimes we don't, and make salads. We adapt," Bourserie said.

People interested in touring the Observer can win a chance at the Earth Day Festival in Union Square on April 14. The vessel will remain in New York City until April 22 before heading to the Summer Olympics in Paris.

Alecia Reid is an award-winning, Emmy-nominated reporter for CBS News New York. She is a sustainability and social justice advocate; passionate about giving a voice to people who may not otherwise be able to tell their stories.

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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 )

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• Zhi Yung Tay 1 &
• Dimitrios Konovessis 2  

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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.

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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

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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.

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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

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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.

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This boat will make its own fuel on a round-the-world voyage

Remember Solar Impulse 2 , the solar-powered plane that circumnavigated the world in July 2016? This could be the ocean-going equivalent. In a bid to prove the effectiveness of hydrogen as a renewable fuel, Victorien Erussard and Jérôme Delafosse will sail around the world in a boat powered by the gas – made from the elements they encounter on the way. “The problem is that 95 per cent of the hydrogen that you use already is made out of fossil energies,” says Delafosse. “We will produce hydrogen onboard from the ocean, we will clean and purify the water and then we will electrolyse it and then compress it in tank storage.”

The Energy Observer, which sets sail from Paris in May 2017, is an ex-racing catamaran that can generate hydrogen from 130 square metres of solar panels, two wind turbines, a traction kite and two reversible electric motors. Explorer Delafosse, 45, and Erussard, 37, an experienced offshore racer, partnered with French research centre CEA-LITEN to develop the technology. “When we are over-producing energy, when we have a lot of wind and sun, the idea was not to waste this energy and to just keep it on board,” says Delafosse. “Hydrogen is the best way to do this because it's very light and the efficiency of hydrogen is three times more than just fuel.”

The Energy Observer has hydrogen tanks instead of a battery, so even though it weighs 30 tonnes, it is nearly three times lighter than MS Tûranor PlanetSolar , the last solar powered boat to circumnavigate the globe. In theory it can also go three times faster – a potential top speed of 42 knots – although in practice Delafosse expects it to cruise at eight to 10 knots. However, whereas the PlanetSolar went round the world in 18 months, the sponsor-funded Energy Observer team expects to take six years, at a cost of €4 million (£3.42 million) per year.

Why so slow? Because Energy Observer is set to make 101 stops, showcasing the potential of renewable energy at stop-offs around the world. “We can use this technology in hotels, in houses, in cars… the idea is to be less dependent on the network,” Delafosse says. “It shows how fast things can happen: as it did in London at the turn of the last century with [moving from] horses to cars, it will happen with renewable energy.”

This article was originally published by WIRED UK

• The Odyssey
• The Innovations

At the outset, Energy Observer is the name of a boat, self-sufficient in energy, with zero emissions, zero fine particles, zero noise, as well as being a symbol of our awareness raising and our ambitions at the service of ecological transition.

We designed her to prove that entirely decarbonised, decentralised and digitised energy is possible, that such a virtuous circle is achievable. Her on-board technologies, combining multiple sources – solar, wind and hydro power – and forms of storage, batteries and above all hydrogen, prefigure tomorrow’s intelligent energy networks (smart grid), which can be reproduced on a grand scale, everywhere and for everyone.

Outdoor views.

Energy Observer sailing towards in Hamburg

Energy Observer in Svalbard

Energy Observer has arrived in Saint-Malo for the end of its European Odyssey

Energy Observer sailing towards Helsinki

Energy Observer's solar pannels

Inside views

Energy Observer Inside view

Energy Observer living area boat

Energy Observer Inside boat piloting

Energy Observer living room boat

Energy Observer Inside boat bedroom

Hydrogen, keystone of the Energy Observer system

To date, hydrogen is renewable energies’ best ally. The most abundant chemical element in the universe, lightweight and boasting an energy density that is 3 times greater than traditional fuels, it enables excess surplus energies to be stored and their irregularity to be offset. If Energy Observer were to store her energy using solely traditional batteries, she would weigh twice as much!

Today, the 63kg of hydrogen stored on board Energy Observer provides 1MWh of electricity, equivalent to the average electricity consumption (including electric heating) of a 4-person household for one month and 10 days.*

In the 63 Kg of hydrogen, the fuel cell provides 1 MWh of electricity, but also 1 MWh of thermal energy that can be used for heating and hot water.

Though maritime and terrestrial mobility is satisfying the ever-increasing demands for power, speed and reliability, today hydrogen is the only energy vector offering a credible alternative to fossil fuels with no impact on the environment.

Via on-board testing of an energy system based on a mix of renewable energies and hydrogen produced aboard, we are paving the way forward for multiple terrestrial and maritime applications, which can be replicated on the scale of a user, a district or a town.

*This example is based on a household living in a house of about 140m2 at an altitude of 1000 m with a heat pump system.

Clean energy sources

The adaptability of sustainable energy systems is based on a combination of technologies, which enable energy to be produced from nature without damaging it: sun, wind, waves and currents. Our process of continuous innovation, enables us to experiment with new technologies every year, test them and sometimes give up on them where the results prove inconclusive. For solar energy, our team trialled the first bi-facial, heterojunction photovoltaic panels designed by the INES (National Institute of Solar Energy), right up to the latest flexible or vertical and invisible panels supplied by Solbian.

For wind energy, having initially trialled traction kite systems and vertical-axis wind turbines, since 2019 we’ve been developing automatic propulsion wings with the VPLP architectural firm: OceanWings®. New, automatic variable pitch propellers have also been tested since early 2020 with a view to enhancing the performance of the on-board hydro-electricity produced using the power of the ocean current. The selection criteria still remains the same: these innovations must be able to be replicated and adapted and satisfy the multiple application and mobility challenges, so that one day it becomes accessible to all.

Energy Observer's solar panels

A legendary race boat

Built in Canada in 1983 by the naval architect Nigel Irens, under the supervision of the sailor Mike Birch , she was christened “ Formule Tag ”. In 1993, with Sir Peter Blake, the boat became “ENZA NEW ZEALAND” and won the Jules Verne Trophy, securing a round the world sailing record under sail of 74 days, 22 hours, 17 minutes and 22 seconds. In 1998, she became ROYAL & SUN ALLIANCE with the first female crew in the world to make a Jules Verne Trophy attempt headed by Tracy Edwards.

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by Peter Brown, Anthony Abbatiello, and Susannah Anfield

Voices of transformative leadership

• 15 minute read
• September 16, 2024

Four leaders reflect on what it takes to drive transformational change in healthcare, humanitarian aid, energy services, and the military.

Back to Transformation

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In our work with business leaders, we find widespread understanding that the world economy is undergoing a profound reconfiguration in the face of climate change, technological advancement, and shifting geopolitics, among other forces. Yet executives also tell us that day-to-day pressures make it hard to create the space they need to fully consider the implications for the reinvention their organization needs—or for the capabilities they need to develop as individuals to lead at this extraordinary moment.

To understand more about the role of leaders in catalyzing change, we asked four participants from PwC’s Leaders Solving for Tomorrow program—drawn from across the private, public, and social sectors—to share their stories and reflect on the unique challenges of leading transformation in the context of a world in flux. What follows are highlights from these conversations.

To guide the dialogue, we focused on the five differentiators of “ transformative leadership ,” which form the subheadings in this article. When practiced consistently, these differentiators underpin a capability for leading ongoing transformation—that is, a capacity to continually reinvent what an organization does and how it functions. They are relevant to anyone, from C-suite executives to frontline leaders, who wants to drive large-scale change.

Four leaders solving for tomorrow

Susanne gellner, joseph kamara, andy mitchell, manoj patel.

Chief Financial Officer, E.ON Sweden

Germany-based E.ON is one of Europe’s largest operators of energy networks and energy infrastructure and a provider of innovative solutions for its 47 million customers. As chief financial officer of E.ON Sweden, Gellner is responsible for finance, regulatory affairs, and procurement at a time when the energy system in Sweden and globally is undergoing a profound transformation in the face of climate change, electrification, rapid growth of renewable energy, and concern for energy security. These same forces are driving E.ON Sweden to transform its infrastructure, operations, and organization.

Regional Director, Humanitarian and Emergency Affairs, World Vision East Africa

World Vision is a humanitarian nonprofit with more than 34,000 staff members working in nearly 100 countries to improve the lives of vulnerable children through emergency relief, economic development, and advocacy. In more than 20 years with World Vision, Kamara has worked in Uganda, Mozambique, Swaziland, Australia, and Kenya. Born and raised in Uganda, he holds a PhD from Western Sydney University, and is passionate about reimagining economic development, public health, and humanitarian relief to meet the challenges of the 21st century. 

Deputy Director and Capability Sponsor, Royal Navy

The Royal Navy is the principal naval warfare branch of the British armed forces with a fleet of more than 70 ships ranging from aircraft carriers to patrol boats, and around 30,000 active service personnel. As capability sponsor, Andy Mitchell leads teams designing all aspects of the future navy, looking sometimes decades ahead to consider the capabilities the service will need, and creating the change programs to deliver them. Mitchell joined the Royal Navy in 2023 following 25 years as an engineer, project manager, and program manager in the defense industry. 

Chief Transformation Officer, Southern Cross Healthcare

Southern Cross Healthcare is a large, private healthcare provider in New Zealand. The for-purpose organization provides elective surgery through New Zealand’s largest network of owned and joint venture hospitals, as well as rehabilitation, physiotherapy, mental health, and workplace health services. Patel joined Southern Cross in 2022 as chief transformation officer with a mandate to reimagine clinical experiences for patients and their families. He holds a medical degree from the University of Auckland and an MBA from Harvard Business School, and is a Fellow of the Royal Australasian College of Medical Administrators.

Make sense of the world

The complex and interrelated challenges that organizations face demand that leaders pay close attention to the external environment, engage with a wide range of stakeholders, and articulate a clear and compelling worldview that creates shared understanding and a sense of urgency.

S+B: We often hear from leaders that we are in a unique moment, with the external environment becoming increasingly challenging. Does this ring true? And what does it mean for your role as a leader?

JOSEPH KAMARA:  Anyone who works in East Africa will tell you that climate change is a huge driver of humanitarian needs. Disasters are becoming more frequent and more intense. Historically, we faced a drought maybe every ten years. Now it is every three years. Just before the declaration of the covid-19 pandemic, we had massive floods, followed by desert locusts that destroyed about 5 million hectares of cropland across the region. And then, just as the communities were starting to recover, a drought started. And with covid-19 impacting supply chains, transportation, and productivity, it was clear we were going to have a significant food crisis. So, we have no respite. It is one thing after another.

Then, of course, we face armed conflicts—4 to 5 million refugees and 12 million internally displaced people across the region. And that was before the Sudan crisis broke out in 2023. The number of people displaced is huge. Usually, it is the poor people who are hit the worst. Once agriculturalists lose their livelihoods, their ability to produce is gone, and some will be forcibly displaced. Conflicts at the global level also hurt us. The conflict in Ukraine caused the global oil price to skyrocket, which translated into higher cost of living: higher prices for transportation; for commodities; for fertilizers; for imported wheat, rice, cooking oil. In Somalia and Sudan, people depend on wheat, and the price of bread became impossible.

The reality is that these issues are interconnected, and they reinforce one another. To be effective at creating resilience, it’s not enough to respond to a crisis, you also need to take a long-term perspective. My role is to remind my colleagues: “Wait a moment. Yes, we are going to respond here, but what were the causes? What are the forces at work we should be thinking about?” We may not have the resources to address every cause, but we can understand more clearly the potential impact of what we are doing. I encourage my coworkers to think broadly, to think beyond what they see today, beyond the immediate crisis we are responding to, and look at the long term.

S+B: Does this resonate with your experience in the healthcare sector, Manoj?

MANOJ PATEL:  I remember a moment when we were coming out of the pandemic. A lot of people were leaving the healthcare sector because of covid-19. We had extreme weather events across the country—unprecedented flooding in Auckland, and storms in Christchurch that damaged our hospital. We had a shooting event close to our head office in downtown Auckland. We were already on high alert because of cyberattacks on health organizations in New Zealand. And in the middle of all this, we were trying to gear up as an organization for a bright future.

At a certain point, I started to realize that these were not one-off events. This was the pattern of today. We are going to be constantly facing crunchy issues, and, quite frankly, we need to set ourselves up to expect them. We were doing a great job of marshaling resources to deal with each situation, and the opportunity for the longer term was to adopt a mindset and capabilities to deal with this constant cycle of events—as well as maturing our ambition as an organization.

S+B: Andy, how do you approach making decisions in the face of so much uncertainty?

ANDY MITCHELL:  We need to make decisions based on where we think the world is heading. In the underwater battle-space, we have a requirement to act out to 2110 with our current nuclear submarine fleet, let alone any new craft we bring in. I think Jeff Bezos had it right when he said that you should ask yourself what won’t change, and build a strategy around that. In our case, we know that data is going to become more prevalent, along with computer processing and networking. We know that climate change is an issue we are going to need to deal with. So, it’s about making logical decisions based on what you know will be true, what you can infer, and what you are prepared to bet against.

Set radical ambition

After creating a shared understanding of the issues, transformative leaders set a radical ambition. They focus on a major problem that their organization is uniquely positioned to solve. They encourage the organization to stretch to the limits of what is feasible, and give people confidence that the objective can be achieved.

S+B: A radical ambition stretches people in new ways, so it’s important to focus on something deeply rooted in the purpose and values of the organization. Given that challenging environment you have described, Manoj, what was the radical ambition that Southern Cross Healthcare set out to pursue?

MANOJ PATEL:  Our ambition starts with our obligation as a for-purpose health organization that doesn’t have corporate ownership, which is unique in private healthcare in New Zealand. We can take long-term decisions that would be more difficult for a conventional, privately owned player. Our transformation journey really began when our board challenged us to step up to this opportunity.

We decided we needed to be ambitious around how we support the patient as a whole—transforming clinical pathways and the experiences that patients and their families go through. Healthcare is often transactional. If a patient is unwell, they see a general practitioner. If they need imaging, they get an X-ray or MRI. If they need a specialist consultation, they get a 20-minute appointment with a specialist. But what if a medication or a procedure isn’t funded? If the patient can’t pay for it themselves, they won’t get it. What if the patient needs to take six months off work after surgery? Nobody is paying for that, so it’s a burden on the patient. What if a patient can’t look after their children because they are going through oncology treatment? The social and psychological impact on the family isn’t funded or supported.

So, the opportunity is to look through the patient’s eyes at what’s important to them. It is about taking a bio-psycho-social approach: What’s the main biological issue? What’s the psychological impact on mental health? What are the social, family, and work aspects of the situation? Stepping back, a lot of things need to change to realize this ambition. We need to work with funders, work with the clinicians who are part of today’s journey, work with clinicians with different specialties who aren’t part of today’s journey, and work with commercial interests. We need to understand the challenges faced by different segments of the patient population. And we need to enable our own organization and our core beliefs along this journey.

S+B: Joseph, how do you articulate the need for radical ambition within World Vision?

JOSEPH KAMARA:  The problems we are confronting are enormous, and they are not going to end. The needs are going to grow. So, what can we do differently? Because if we don’t do things differently, we will become irrelevant. This is my drive: What are the alternative ways of doing business, of helping people, of easing pain? Sometimes I say to colleagues: “Imagine you are standing on a cliff. There’s no bridge to the other side, and you can’t go back. You need to leap. Is this what you are going to do? What is going to drive you? How are you going to overcome your fears, overcome the obstacles, and get across?”

Achieve promised outcomes

Having set a radical ambition, transformative leaders channel their organization’s energy toward delivering on it. They translate ambition into specific, measurable outcomes and create the structures and systems that enable the organization to go beyond business as usual. Transformative leaders also remain personally engaged as execution moves forward, fighting the organization’s natural tendency to settle for functional excellence as opposed to transformative change.

S+B: Organizations can be resistant to change—especially organizations that have been successful for a long time. Is this something you experienced during E.ON Sweden’s transformation journey, Susanne? And what changes did your leadership team make to help the organization reinvent itself?

SUSANNE GELLNER:  When I came into the business, we were organized by function—asset management, operations, and customer care. In the first phase of our transformation, even before energy transition was high on the agenda, we changed this. We moved to a structure with three business areas, each with full P&L responsibility. This was partly about breaking down silos and partly about introducing more business-mindedness into the culture. Our engineering culture remained critically important, of course, but the new structure enabled us to think end-to-end about customer journeys, for example. Although we didn’t know it at the time, it also put us in a position to pick up the pace for the phase we are now in.

Today, there’s real urgency to move fast and do things differently. The energy crisis arising from the war in Ukraine was a wake-up call, especially in our part of the world. The energy transition and electrification are accelerating. There’s a completely new flow, physically, in the grid, with solar and wind coming in and big, stable sources such as nuclear being phased out. So, we are learning to run the system differently, with better methods and new technology. That’s the physical part of it. In relation to customers, contracts are changing. We need to be able to accommodate more flexibility and have different business models for different customers. Again, the challenge for us as an organization is moving fast enough. It’s a major shift.

Here’s a very hands-on example: historically, if we needed a transformer, we would calculate precisely what we needed and then source it. Today, we might need to source 25 transformers in advance. We don’t know exactly where and when we are going to use them. But if we don’t order them now, we may not get them for years. So, in finance and procurement we need to convince ourselves to take that risk. And the engineers need to accept that they may not get exactly what they want, but it will be good enough. We need to think in different ways.

S+B: Beyond systems and processes, what works in terms of getting an organization aligned and committed to achieving the promised outcomes? Manoj, Andy, what’s your experience and advice?

MANOJ PATEL:  We are innovating to show what’s possible if we raise our ambitions. For example, we are working across different cancer streams to identify where things can be done better. We looked internationally at different models, and different technology options that enable pathways to diagnosis that are better designed around the patient experience. We are looking to develop pathways that empower people to better manage their health. The early results from the pilot are promising. We've been able to detect early-stage cancerous changes and therefore prevent cancer from developing in a group of people with an average age of 50. These are real people and their families whose lives changed based on the program we are developing.

This is a program and a story that transcends the business case. It’s not about ROI. It speaks to mission and purpose, which is especially important in the early stages of transformation. It gives people hope and belief that not only can you dream of a better future, but you can also achieve it.

ANDY MITCHELL:  You need to have a clear vision, a sense of the journey, a North Star you’re moving towards. Reinforcement is the key thing. People sometimes make fun of me because I mention the same few things over again—and it can be exhausting to keep doing it. But, over time, reinforcement works.

The other thing is learning to communicate in new ways. I grew up professionally in an industry where the people tended to have similar technical, commercial, or project leadership backgrounds. I was trained to discuss everything very logically. Now I’m interacting with people who have commanded warships, or battalions of soldiers or marines. They don’t necessarily communicate in the same way. Basically, I’ve come to realize that I’m quite good at communicating with a small percentage of the population. It’s something I’m working on.

Act as a catalyst

For a company to deliver outcomes that matter and address the challenges that today’s organizations face, a wide spectrum of skills must come together—not just from within the organization, but also from the wider ecosystem. Transformative leaders act as catalysts for coalitions, building trust and combining resources across teams and from other organizations. They are magnets for talent, defining the capabilities they need, finding and attracting diverse talent, and creating an environment in which people can thrive.

S+B: Susanne, electricity generation and distribution are in the spotlight due to the forces you mentioned earlier—energy transition, electrification, concern about energy security. What does this mean for how you engage some of your major stakeholders? 

SUSANNE GELLNER:  Remember that for a long time, this was a very stable industry. Dialogue with the regulator was about striking a balance between reasonable prices for customers and a sufficient return for us. There was hardly a conversation about energy security—or how to finance growth. Today, all this has changed. It’s a more complex set of relationships. It is more political.

Working with a regulator is not fast paced—that’s just the nature of the relationship. It’s not like a customer negotiation where one side or the other can walk away. We talk about long-term goals: What do we want to achieve within the energy industry? What do we need to do? And then the hard part: What is needed to make it happen? Also trying to find solutions together—solutions that are acceptable to us as a company and are also acceptable to the regulator. As a leader, to be honest, I’ve been forced to step out of my box. I’ve learned that one can do much more than one initially thinks, although it takes guts to step up and try to push.

S+B: Andy, how will the Royal Navy’s ecosystem change? Who do you need to work with as the Navy evolves, and how will you need to engage them differently?

ANDY MITCHELL:  Some things probably will remain the same. Our allies and the people we work with across government will be broadly similar. The ecosystem of industry partners may not change all that much. But how we will work together and the capabilities we will need will be very different.

We’re moving from thinking of the Navy as a collection of ships to thinking of ourselves as a network of maybe 10,000 nodes: ships, boats, planes, uncrewed systems, vehicles from the commando force, the Royal Marines, sailors. This is not a once-in-a-generation transition, it’s probably once in 100 years. The battleship-to–aircraft carrier transition was the last time we went through something this big in terms of changing the capabilities you need, the types of people you need, the range of disciplines, the processes, and so on.

So, if you squint, the future Royal Navy might look broadly the same. But the fabric underpinning it will be completely different. We’ve got missiles, we might have lasers. We might have different sensors. These things will have different supply chains. We’ll have trusted industry partners accessing live data from our ships. So, the ecosystem of how you work, what competencies you need, what competencies you need from your partners, what conversations you need to have, is all changing dramatically.

Power the engines

Reinventing your organization requires asking people to constantly step outside their comfort zone, which increases the risk of burnout. Transformative leaders consciously power their own engines so they can power the engines of others. They understand and act on what they need to do personally to remain energized and help make sure others don’t burn out by paying attention both to their own behaviors and to the organizational practices that structure how work gets done. They strive to maintain a growth mindset and understand that everyone involved in a reinvention—starting with themselves—needs to transform at least as much as the organization.

S+B: Leaders have a responsibility to look after their teams, yet if they do not look after themselves, they don’t have anything left in the tank to look after others. So how do you stack the odds in your favor? How do you remain energized?

MANOJ PATEL:  The tools that work best for me are self-reflection and writing. The challenge is finding sufficient regular time to do it, and I haven’t really done enough of late, if I’m honest. But taking regular time to think and to write helps me manage myself and the way I show up in different contexts. It allows me to contextualize what’s going on, reinforce what’s important to me and where I want to go, and strategize around the tools that will help me get there.

When it comes to the team, I’ve really tried to empower them to be the owners and champions of the patient experience, whether that’s in cancer care, orthopedics, or women’s health. Transformation in healthcare requires leaders who have a breadth of knowledge, experience, empathy, and networks across clinical streams. These leaders then need to drive change and equally support the entire organization to develop understanding, buy-in, and ownership. I see my team as champions of this journey.

JOSEPH KAMARA:  People have various sources of strengths. For me, spirituality is important. My spirituality helps me to reflect, to think, to calm myself down, and to remember that I have limitations. Then there is the radical ambition we spoke about. Like for most people in my organization, this is a vocation. I have a very strong connection to the work that I do. Then there is going into the field and seeing the results. This gives me joy. About a year and a half ago, I went to Northern Kenya and visited a family that had lost nearly all their livestock to drought. They used to have about 45 animals. They were left with six or so—very few. We could see the carcasses, the bones all around. And, before we left, our host slaughtered a goat for us. It was one of the toughest moments for me to accept his generosity. The man had lost everything, but he said, “If you visit my house, you cannot leave hungry.” My goodness. How can I go back and do more?

The authors thank Nadia Kubis for her contributions to this article.

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Peter Brown  is PwC’s Global Workforce Leader. Based in London, he is a partner with PwC UK.

Anthony Abbatiello  is the US Workforce Transformation practice leader. Based in New York, he is a principal with PwC US.

Susannah Anfield  is a member of PwC’s global leadership development team. Based in London, she is a director with PwC UK.

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Officials ID bodies found days after boat crash off Old Saybrook

Published september 7, 2024 • updated on september 7, 2024 at 7:32 pm.

Officials have identified the two bodies that were found on Friday after days of searching. The men had been missing since a boat crash off Old Saybrook on Monday night.

Department of Energy and Environmental Protection EnCon Police said they located the body of one man around 12:10 p.m. on Friday. They said search crews located the body of the other missing boater around 4:30 p.m.

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The men have been identified by DEEP as 25-year-old Ian Duchemin, of Oakdale, and 24-year-old Ryan Britagna, of Waterford. The Office of the Chief Medical Examiner will determine each of their cause and manner of death.

Nine friends were returning after spending Labor Day on Block Island when the 31-foot motorboat they were in hit a jetty around 9:15 p.m. Monday, according to DEEP officials.

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Christopher Hallahan, 34, of Westbrook, was found dead in the vessel , according to authorities. The Office of the Chief Medical Examiner determined that he drowned and ruled his death an accident.

Six other people who were on the boat were taken to the hospital and one of them is in critical condition, Connecticut Environmental Police Captain Keith Williams said Tuesday morning.

Officials believe that person was driving the boat, but they have not confirmed that.

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Officials said the people who were on the boat have ties to the local community.

The capsized boat was recovered from the river around 11:30 a.m. Tuesday.

Several agencies, including police and fire crews from several nearby towns, the State Police Dive Unit, and a helicopter from the U.S. Coast Guard station on Cape Cod have been involved in the search for the missing boaters for several days.

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