Hydrogen is heralded as the next fuel in the energy transition, but as boatbuilders gear up to bring the new high-pressure gas on board, availability, economy, and the true ecological gains remain in question.
My investigation into the feasibility of hydrogen as a propulsion fuel was personal. An environmentally conscious liveaboard on a 60‘ (18.4m) sailing yacht with plans for future chartering, I set out to answer the question: Can I replace my boat’s twin 120-hp diesel engines with electric motors powered by a hydrogen fuel cell?
The short answer is yes but at great cost and without any certainty about certification and insurance.
And then there are the broader questions: Will it be wise in terms of fuel economy, safety, ease of operation, and maintenance? Will it yield a substantial reduction of carbon emissions?
It’s clear from product and market development that some boat designers and builders are betting on positive answers to those questions. They’re not the only ones.
Big engine manufacturers and energy companies are pursuing projects and cooperative partnerships to develop a hydrogen infrastructure and hydrogen engines for road transport as well as sea transport and yachting. Here are just a few examples.
In a desert in Oman, there’s a plan for a solar plant to produce 25 gigawatts (GW) of electric power used to create hydrogen. This green hydrogen plant is being developed by the Oman state oil company OQ, Hong Kong–based green fuels developer InterContinental Energy, and Kuwait-government-backed renewables investor EnerTech.
Shell Oil Company is investing in developing and testing fuel cells to propel a ship chartered to supply one of the oil giant’s facilities in Singapore. Sembcorp Marine of Singapore will develop and build the fuel cells. The newly built Penguin Tenacity, a 184‘ (56.1m) Ro-Ro ship, will be retrofitted next year to demonstrate the use of hydrogen fuel cells as an energy source for large-ship propulsion.
And here’s an application of hydrogen in recreational boats: In 2009, the European Union funded a pilot project called Future Project Hydrogen with Frauscher Boats in Austria. The yard converted the battery for 4-kW electric motor in one its 600 Riviera runabouts to a fuel cell with a high-pressure hydrogen cartridge. The idea was to swap an empty cartridge for a full one in a matter of minutes, or refuel from a dockside hydrogen pump. The proof-of-concept prototype was a success—Frauscher claimed a range of 80 km (50 miles), but that’s as far as it went.
Smoothing Renewable Energy Peaks and Valleys
The worldwide transition in energy production is shifting more to renewable sources (chiefly of electricity). More large-scale wind- and solar-power plants are being built. While they reduce carbon emissions, the facilities pose a new problem: too much energy is available on sunny and windy days, and there may be shortages at other times. Because actual energy production can’t be easily throttled up and down as in a conventional power plant, these renewables require storage as a buffer between supply and demand. This from the Wall Street Journal in December 2020: “In the spring of 2020, as the state of California was setting records for its solar power generation, it was forced to curtail that output due to limitations on what the grid could handle. Yet by August, California was instituting rolling blackouts as extreme heat caused electricity demand to soar. In order to rely on renewables, excess power needs to be stored.” But even the most efficient batteries will not efficiently store energy for long periods; and the frequently cited option of water pumped uphill to reservoirs in the mountains and flowing down big pipes at high speed to power turbines requires a lot of space, site-specific infrastructure, and energy that is lost in the process.
Industry giants like Mitsubishi Heavy Industries see hydrogen as a solution that can be produced anywhere. Once stored in high-pressure tanks, the element can contain energy potential for a long time, and it can be produced fairly efficiently with surplus power from renewables. That’s why energy providers, including some big oil companies, are preparing for a hydrogen infrastructure.
By capturing the fluctuating temporary overcapacities of renewable energy sources to make hydrogen, this fuel really will be zero emission. With significant specialized infrastructure on its way, and sourcing from renewable energy facilities being built or already installed, hydrogen is poised to become a competitively affordable energy carrier. “Decarbonization has to be affordable for it to be sustainable,” said Thomas Bohner, CEO of Mitsubishi Power Europe. That’s just the kind of thing an aspiring green yacht owner likes to hear.
Hydrogen Motors and Fuel Cells
With sources for hydrogen fairly assured, I turned to just how it could be applied to power my boat’s propulsion and onboard electrical system. Again, I looked for assurance from some big industry players investing in hydrogen fuel cells and combustion engine technologies. The engine manufacturers I found all speak of their green ambitions, but they are in it for the business and see commercial opportunities in developing hydrogen technology.
Daimler Truck and Volvo Group recently created cellcentric GmbH & Co. KG in Germany to develop hydrogen fuel cells to power long-haul trucks. Most likely, the marine division Volvo Penta will benefit from that development as well. In Japan, Kawasaki Heavy Industries, Yanmar Power Technology, and Japan Engine Corp. are jointly developing hydrogen-powered marine engines. Rolls-Royce Power Systems, a supplier of ship and larger yacht engines, is testing a 250-kW hydrogen fuel cell in its demonstrator plant in Friedrichshafen, Germany, using polymer electrolyte membrane (PEM) low-temperature fuel cell technology. These hydrogen fuel cells deliver the highest power output per weight and volume of the fuel. Compact and lightweight with high power output sounds promising to me as a boat owner, and the fuel cell’s ability to start cold and immediately generate power also adds versatility. However, upon closer inquiry it’s clear none of these technologies is ready for prime time, and most are several years from broad commercial availability.
Hydrogen Fuel Cells on Large Yachts and Tenders
Actively involved in the development technology of hydrogen as a green fuel since 2005, and anticipating client demands and expectations, German superyacht yard Lürssen designed and engineered a modular-fuel-cell-powered yacht. Now the yard has a client who wants it. Methanol will fuel the yacht’s combustion engines but will also continuously reform into hydrogen to run a fuel cell alongside the combustion generators. Along with a battery bank, the fuel cell—developed by the national research-and-development project called Pa-X-ell—is sized to allow the yacht to stay at anchor running all desired household functions for 15 nights, or to travel 1,000 nautical miles with no carbon emissions. Since 2009 Lürssen has been part of Pa-X-ell, upon which the yard seeks to capitalize with its first hydrogen yacht. (Other partners include Carnival Maritime and Meyer Werft.) Besides the fuel cell, the company Freudenberg is to engineer and construct the machinery to reform methanol into hydrogen. The aim is to develop and test a hybrid-energy system with a new generation of polymer electrolyte membrane (PEM) fuel cells (or proton exchange membrane fuel cells) for yachts and seagoing passenger vessels.
Likewise, French yard Fountaine Pajot, builder of sailing and power catamarans, plans to offer a hydrogen fuel cell for onboard electricity when at anchor for its Samana 59 (17.98m) catamaran. Diesel engines will propel the boat, but electricity will be supplied by the REXH2 fuel-cell generator, developed by the French company EODev (Energy Observer Developments) together with Toyota Motor Corporation. The car manufacturer engineered it as a range extender for electric vehicles, but the lightweight, compact generator—88.18-lb (40-kg) machinery fitting within 35.31 cu ft (1m³)—offers 70 kW for any electric application. Because the generator runs without noise or vibrations and has only water vapor as exhaust, silence can be enjoyed at anchor, Fountaine Pajot reasons.
The big cat will use the same technology that EODev applied previously in the battery- and hydrogen-powered superyacht tenders of the new brand Hynova, which exhibited a prototype November 2020 in Monaco. Hynova will rely on a REXH2 fuel cell to generate electricity for an extensive battery pack to power the electric-propulsion motors. The two batteries have a 150-kW capacity each, combined with 80 kW from the fuel cell. At low speeds, the fuel cell will charge the batteries to power the engine. To reach the top speed of 25 knots, batteries and fuel cell together will power the engines, reducing the range. The tender will carry 49.6 lbs (22.5 kg) of hydrogen in four pressurized tanks of 350 bar. Retail price for this yacht was not disclosed. It’s no accident that this 40‘ (12.19m) open boat is presented as a superyacht tender, targeting an audience for whom money is not an issue. To this middle-class green-aspiring skipper, the undisclosed costs and obviously early days of technology development and adoption give me pause.
It’s important to note that while some components and technologies have been developed for the yacht projects above, and some of these boats have been built and sea-trialed, none has sold and been tested in active service.
I wanted to look at other hydrogen options still in the research-and-development phase but actually powering boats on the water.
Students Experimenting with Hydrogen
The prize-winning Solar Boat Team from Delft Technical University in The Netherlands explored hydrogen as a propulsion source in the 2021 project Hydro Motion. Students from different courses collaborated to refit their 2019 prize-winning solar foiling trimaran to be powered by hydrogen to compete at the Monaco Energy Boat Challenge in July 2021. After a successful first race, the boat’s electrical system was damaged, forcing the boat to be withdrawn from competition. Their concept, however, remains interesting. A battery serves only to compensate for the time it takes the fuel cell they developed to throttle up. Their research and the solutions they found provide good insight into the dynamics of hydrogen propulsion.Maritime Technology student Gerard Wiegersma, the project’s structural and hydrogen development engineer, explained the setup for the hydrofoil boat. “We have a 30-kW [40-hp] brushless electromotor to drive the boat. It has an energy efficiency of 98%, so we use almost all of the energy potential from the hydrogen for propulsion. To get the foiling boat going, we will need a lot of energy—about 45 kW [60 hp]. This is delivered by the fuel cell together with a battery. Once we fly, the fuel cell delivers enough energy to keep the boat going—about 10 kW [13.4 hp]. At foiling speed, we will go about 18 knots. We will take 7 kg of hydrogen to complete the race.” While the fuel cell delivers a maximum of 30 kW, it can continuously run at 10 kW. “Efficiency of our fuel cell drops quickly when we push it to maximum power output,” Wiegersma said. The student team created automatic integration with the battery so that peak loads—when the boat drops off its foils in a big wave—will be handled by the battery instead of pulling extra power from the fuel cell.
The maximum efficiency of a fuel cell may be 85% to 90%, largely depending on its integration with batteries. If batteries handle peak loads in electricity demand, the fuel cell can continuously run at maximum efficiency. Fuel cells do not react instantly to throttle commands. It takes some time, typically 10 to 30 seconds, before the output is adapted to the new demand. That’s why a fuel cell/battery combination is always required in vehicles.
Safety is a big concern with hydrogen. It is the smallest and lightest element, so it can easily leak from gas lines. It is highly explosive and carries a lot of energy potential. “Safety requirements are basically the same as with natural gas,” Wiegersma said. If hydrogen gas escapes, “it will rise in the atmosphere 25m [82‘] every second. Ventilation upwards is always needed. We made a watertight compartment for the fuel cell. A fan pumps air into it to create pressure. The compartment is ventilated, and the pressure will blow out any leaked hydrogen gas.”
The Hydro Motion boat uses 350-bar (5,076-psi) pressure tanks, the lower of the two industry standard pressures. For automobiles running on hydrogen, the standard is 700 bar (10,000 psi) so they can carry the hydrogen needed for an acceptable range within the car’s limited space. All the pipes, nozzles, and connections must be certified for such high pressure.
Zero Emission Demonstration
At Next Generation Shipyards in Lauwersoog, in the far north of The Netherlands, yard director Albert Keizer embraces the potential of hydrogen as a fuel for medium-size ships. “My goal is to transform the port of Lauwersoog into the first totally hydrogen-powered seaport,” Keizer said. “The fishing vessels and small coasters that dock here could very well use hydrogen fuel cells and electric motors to sail the distances they do. Using solar panels and windmills, we could produce our own hydrogen locally to fill up the ships. Of course, the renewable power from the sun and wind will also be used for lighting and heating of the port buildings and powering the dockside equipment.”
Keizer acknowledges that in commercial shipping, certification by class societies is mandatory. His first step is demonstrating the safe and reliable use of hydrogen aboard the 72‘ (21.95m) yacht Ecolution, launched in 2010. This sailboat was conceived by and built for the Dutch former astronaut Wubbo Ockels, who wanted to sail the world and demonstrate zero-emission liveaboard sailing. The steel boat is equipped with two Aerorigs. When sailing, the freewheeling propellers generate electricity. With the battery pack fully charged, the boat should be able to get in and out of harbors and anchorages on the electric engines without ever starting a diesel generator. The foundation Wadduurzaam, now operating the yacht, took the next step in demonstrating zero-emission sailing by replacing the diesel generators with fuel cells. “It runs wonderfully,” Keizer said after the first test sails. “The fuel cell performs as expected. It evens out the voltage on the battery poles and assists well to meet the demand of power at changing loads. The amperes required from the battery pack show a flattened-out curvature. We see that for 1 kg of hydrogen, we generate about 16 to 19 kWh of electrical power.”
Ecolution’s electric motors are variations of those in city buses. Output is 55 kW [74 hp] permanent or 75 kW [100.5 hp] peak performance. Each of two fuel cells is set up to constantly generate 20 kW [26.8 hp] to charge the batteries and assist at high loads. Next Generation Shipyards chose to run the fuel cell at a little under half its peak capacity. Keizer: “This reduces wear and tear of the membranes. Also, running the fuel cell at lower air pressure will result in a better saturation.”
“The conversion of Ecolution was not an easy project,” Keizer said. Nor is it inexpensive; he has spent €750,000 ($854,580) to date. That sobering price tag would more than triple the value of my boat.
The aim of Next Generation Shipyards and Foundation Wadduurzaam is to get hydrogen certified as a propulsion fuel for commercial maritime use. “I want to sail for one more whole day,” Keizer said, “so I can make the final adjustments to system settings. Then I want an inspector from the Ministry of Transport to come and inspect the engineroom for safety, redundancy, and reliability.” He has subjected the project to an extensive risk assessment with 200 potential dangers addressed and solutions incorporated into the design. Acceptance tests at the Ministry, the Bureau of Maritime Certification (Bureau Scheepvaartcertificering, in Dutch), and eventually the classification society DNV GL will follow. If successful, Keizer’s vision of transforming Lauwersoog to a hydrogen-powered harbor may be realized.
Ready to Sail with Hydrogen
The importer Natural Yachts, near Next Generation Shipyards in the north of The Netherlands, offers a fuel-cell-powered motoryacht, but not with a hydrogen fuel cell…yet. The Northman 1200 (40.22‘/12.26m) is built by the Northman Shipyard (Wegorzevo, Poland). Together with its system integrator, Electric Ship Facilities, Natural Yachts engineered the Northman 1200 electric, powered by battery packs married to a methanol fuel cell. “The fuel cell technology for methanol is not very different from hydrogen fuel cells,” project manager Jurjen Poorting said. “We chose methanol because it is liquid at outside temperature and is widely available. However, a hydrogen fuel cell is surely possible. The technology to do it is readily available. We will do it at client demand.” While the fuel cell is assembled and the electrically driven yacht lies in the water, the two are not connected. Poorting: “My strategy is different from the one Next Generation Shipyards chose. I have all the components. I will show them to the certification agents and then follow their instructions on how to install the fuel cell into the yacht. This way, we will not have to dismount the whole system after the inspector has suggested some alterations. We want to make life simple for our clients. While we know and are able to demonstrate the safety and reliability of our propulsion system, we need to convince insurance companies and certification institutes. Once we have achieved that, our customers can enjoy silent cruising with a very long range before recharging or refueling.”
A Northman 1200 electric is available with various battery packs. The smallest, at 42-kWh, has a 55-km range at cruising speed; and the largest, 84-kWh, a 115-km range at cruising speed. The projected range with a fuel cell will be at least doubled. The retail price of the yacht with the large battery pack is €261,227 ($316,536); the price for the yacht with a fuel-cell range extender was not available.
To Convert or Not to Convert to Hydrogen?
So how about my quest as a liveaboard who wants to know if converting to hydrogen is viable?
I will wait a while.
Yes, the necessary technologies are proven in concept and are available as components in some cases. The Norwegian company TECO 2030 offers ready-made marine fuel cells that can deliver 400 kW each and are stackable to reach a total of 1.2 MW. However, integration and certification need to be addressed. Also, infrastructure for hydrogen distribution for boats will need to advance. European inland shipping is seeing many pilot projects with hydrogen-powered vessels along the Rhine, Meuse, and other rivers, so availability of hydrogen filling stations along those waterways will develop.
In my investigation, few prices for hydrogen systems were mentioned. Where they were, I found that to replace diesel generators with fuel cells, Next Generation Shipyards spent what could have built a new yacht. As the infrastructure and the number of fuel cells in use are likely to increase dramatically in the next decade, I could still be among the early adopters in, say, five years, when prices drop to general economic affordability. More hydrogen will probably be produced from zero-emission energy sources by then, and a greater choice of more reliable and efficient generators will be available.
About the Author: Freelance journalist Hans Buitelaar, who lives in The Netherlands, specializes in yachting and the maritime industry, focusing on technology and sustainable innovations.
Hydrogen is the smallest and lightest chemical element. Each H2 molecule comprises two atoms: two protons and two electrons. Because of its small molecular size, it is difficult to contain. And because the gas is highly explosive, for any practical applications it must be stored in a liquid form in high-pressure tanks. (At normal atmospheric pressure, hydrogen becomes liquid at –422°F/–252°C.)
Hydrogen can be made by the steam reforming process—heating water up to 2,012°F (1,100°C) or more, which produces a lot of carbon dioxide, often released into the atmosphere as pollution. Methane pyrolysis is another method of creating hydrogen, by cracking it from the high hydrogen-to-carbon-ratio methane molecules at high temperature in the absence of air and water. To create 1 ton of hydrogen requires 4 tons of methane and 5 MWh of energy to generate the heat needed for this process. The environmental cost of the resulting hydrogen depends on the source of energy for that process.
The more efficient way to create hydrogen from water is electrolysis, using electricity to separate the oxygen and hydrogen. Water electrolysis can be done at 122°F–176°F (50°C–80°C). Currently, the energy available in hydrogen after it is made through electrolysis is 70%–80% of the energy used to make it. The technology is evolving, and the industry is striving to reach 82%–86% by 2030. Electrolysis causes no pollution. If the energy used in the process is from a renewable source, the resulting hydrogen is a carbon-free fuel.
Note that because hydrogen provides roughly three-quarters of the energy used to create it, the efficiency of the final output depends substantially on the efficiency of the fuel cell and the drivetrain.
Fuel Cell Basics
Hynova Yachts, in France, explained its fuel cell in the simplest terms: Through electrification, water breaks into hydrogen and oxygen molecules. In the fuel cell, hydrogen meets oxygen, and in a reverse process, water and electricity are the result.
In more functional detail, it works like this: Pressurized hydrogen runs from its tank to the fuel cell, which is basically a series of proton-exchange membranes. The hydrogen atom, coming to the membrane, will divide into two protons and two electrons. The protons will pass through the membrane and at the other side join with oxygen molecules to become water. The electrons escape along a wire at the membrane as usable electricity.
Hydrogen in most fuel cells comes in a constant flow. Output is varied by allowing more or less air to flow into the cell. At optimum efficiency, the output will be about one-third the maximum capacity. At higher capacities, the efficiency, as a factor of electric power harvested compared to the electric power needed to create the hydrogen, is reduced.
As an example, the TU Delft foiling hydrogen boat described in the main text has a fuel cell with a maximum power output of 30 kW. The team uses the fuel cell at 10 kW, reaching a 98% efficiency of the energy potential in the hydrogen. At full 30-kW-power output, the fuel cell efficiency drops to less than 75%.
Range and Cost of Hydrogen
Hydrogen has an energy density of 120 megajoules/kg. For comparison: gasoline has an energy density of 47 MJ/kg, and diesel 44 MJ/kg. Note that a diesel or gasoline engine typically runs at about 20% efficiency, while a fuel-cell-powered car may typically run at 50% efficiency. The theoretical maximum efficiency of a combustion engine is calculated to be 58%. A hydrogen-fuel-cell automobile will typically consume 0.8 kg of hydrogen every 100 km. A modern efficient car might burn 5 l of gasoline every 100 km. The cost of 1 kg of hydrogen is about $11.50 (€10). The cost to go the 100 km will be $9. Five l of gasoline will be about $4.50 in the U.S., but about $9.50 (€7.65) in European countries.
Worldwide, it is already possible to find hydrogen at more than 400 fuel stations. Germany leads, with 100 filling stations. Numbers are expected to double every year from now on. Hydrogen can be bunkered using a standardized high-pressure gas nozzle that would fit tanks on cars and boats.