INSIGHT: IS HYDROGEN THE TRANSPORT FUEL OF THE FUTURE?

Many energy commentators believe that hydrogen is the transport fuel of the future. But are fuel cells the answer to the yachting industry’s dependence on fossil fuels?

Moored in her home port of Saint-Malo in Brittany, the 30-metre, hydrogen-powered catamaran Energy Observer is a hive of activity. It’s mid-February and the first energy self-sufficient vessel using renewable sources to produce hydrogen from purified seawater is just days away from embarking on a round-the-world voyage that will last four years. 

Having already racked up over 18,000 nautical miles since her launch in 2017, by the time you read this the floating smart-grid laboratory will be en route for Tokyo and the Olympic Games before moving on to California.
                                       

Over the winter Energy Observer’s array of green energy technologies underwent a series of technical tweaks. A second fuel cell specially developed by Toyota and based on the same system in its hydrogen-powered car, the Toyota Mirai, was added to provide the vessel with an extra 114kW of power. 

The photovoltaic cells covering the deck and superstructure have been upgraded in collaboration with Solbian and the 202m2 of solar panels now provide an output of 34kW. The fixed pitch propellers have been replaced with automatic variable pitch props by Brunton to reduce drag, increase boat speed and enhance the generation of hydrokinetic power.

The 12-metre tall OceanWings developed by Van Petegehem and based on the wing sails of America’s Cup trimarans were already in place, but the deck fittings, mechanics and automatic management software have been improved. The vessel is also fitted with two battery packs of 50kWh each, which are mostly used for peak shaving and can provide 10 hours of ‘get home’ power in an emergency.

“Of course, these improvements still have to be thoroughly tested at sea,” says Hugo Devedeux, the development engineer on the project and a permanent crew member. “But even using the new fuel cell at 50 percent for optimised efficiency give us around twice the net power when you consider the original fuel cell was just 22kW. That meant there were times when we struggled with the wind on the nose and 20 per cent left on the batteries.”

The tantalising attraction of hydrogen is that when consumed in a fuel cell to generate electricity, the only emissions are heat and water vapour. No greenhouse gases (GHGs) and no particulates. Energy Observer harnesses green electricity from solar and hydrokinetic sources to electrolytically split water molecules (H2O) and release the hydrogen, which is fed into a fuel cell to produce energy in an electrochemical reaction to power the vessel and onboard services. The heat produced during the process is recycled to provide hot water and onboard heating. 

The first fuel cell predates the first combustion engine, but the success and efficiency of the latter has largely confined hydrogen technology to space exploration and submarines. Until now. The urgent need to combat climate change and global warming has refocused attention on hydrogen as arguably the most viable path to decarbonisation and securing a more sustainable energy system. Indeed, Pierre-Etienne Franc, initiative secretary of the trade group Hydrogen Council, believes “The years 2020 to 2030 will be for hydrogen what the 1990s were for solar and wind.”

Fuel cells are no longer a technology of the future: we now have cars, buses, trucks, trains and even aeroplanes powered by hydrogen fuel cells. Ship builders are also responding to GHG-reduction regulations targeting marine traffic. Yachting has been slow to relinquish its love affair with fossil fuels and even slower to pick up on the potential of fuel cell technology, focusing instead on hybrid solutions with batteries. Lithium-ion batteries can provide zero-emission propulsion for smaller vessels that operate with short duty cycles, such as small passenger ferries and lake service boats, but their power density and weight limit their use as a primary power source for large yachts.

Let’s be clear: fuel cell propulsion is still very much in development and there are considerable obstacles to overcome before fuel cells can rival batteries on yachts, let alone diesel engines. One of the principal challenges associated with using hydrogen as a transport fuel is that it is difficult and expensive to store. If a fuel-cell car were to store the 1kg of hydrogen needed to drive 100km at atmospheric pressure, for example, the gas tank would have to be 11m3 in size. That’s why cars use compressed hydrogen gas, squeezing about 5kg into a carbon-fibre reinforced tank at 700 bar. Clearly, even a small displacement yacht requires much more fuel, and hence storage space, than a family car.

“A major difficulty we face is that current maritime legislation – or rather the lack of it – limits compression to 350 bar as opposed to the 700 bar for cars,” says Laurent Perignon of Energy Observer developments’ maritime division. “This poses a problem because at 300 bar the hydrogen storage tanks on a yacht need to be around fourteen times bigger than equivalent diesel tanks and five times the weight. At 700 bar we could at least reduce the volumetric mass by half.”

Liquified hydrogen occupies less space and has a higher energy density than hydrogen gas, but it has to be stored at minus -253°C. Liquid hydrogen requires a complex (off-site) production plant, specially insulated tanks for storage and a lot of energy to maintain cryogenic temperatures. A very real risk is that the net energy provided by the liquid hydrogen would not offset the energy and expense it takes to produce, transport and store it.

Some of these issues are highlighted by Aqua, the 112-metre superyacht concept by Sinot Yacht Architecture & Design in collaboration with Lateral Naval Architects notable for its audacious design and liquid hydrogen propulsion (recent reports that Bill Gates had commissioned Feadship to build Aqua as “the world's first hydrogen-powered superyacht” were denied by Sinot). Lateral Naval Architects readily admit that technological readiness is at an early prototype level, but they fully recognise and support the need to transfer to alternative sources of fuel:

“There is a key theme here, and that is electrification,” says the UK-based studio. “We believe that electrification is the gateway to fully exploiting the use of future fuels, cleanly produced via renewable energy.”

Energy Observer produces its own hydrogen using electrolysis and renewable energy, but the industrial method is much less eco-friendly. Nearly all global hydrogen production is by steam methane reforming (SMR) that blasts natural gas with high-temperature, high-pressure steam. SMR requires fossil fuel input and leaves behind carbon dioxide as a waste product, so it is of little use for decarbonising the energy system.

Clean hydrogen made by electrolysis is now becoming more cost-competitive, helped by the plummeting cost of renewable energy, but as Lateral Naval Architects point out: “The most significant barrier to the realisation of a full hydrogen superyacht is not the onboard technology, but rather the practical availability of green hydrogen within a global distribution network.” 

Regulations and infrastructure are other hurdles that need to be resolved if hydrogen propulsion is to have any hope of taking off. The Energy Observer team is working with Bureau Veritas and Lloyd’s Register to establish a set of safety criteria that the yachting industry can work to: 

“It’s a classic chicken and egg dilemma,” says Perignon. “Without operational guidelines in place, there can be no hydrogen refilling stations in ports and marinas. As the situation stands at the moment, a vessel storing more than one tonne of hydrogen would not be allowed into a commercial port. We urgently need regulations that are in step with the technology, and vice-versa.”

The most realistic scenario today for implementing hydrogen fuel cells on a superyacht is to replace the diesel generators for servicing hotel loads, or the same generators in a hybrid set-up for low-speed auxiliary propulsion in zero-emission mode for manoeuvring in port or cruising protected waters where the use of diesel engines is prohibited. But these applications are likely to expand in the near future with the EU-funded group Hydrogen Europe predicting that hydrogen usage will become widespread by 2030. In this context, yachting has the opportunity to be in the first wave of pioneers. 

“We’re working with a private client on a new-build project with fuel-cell generators that should be ready in time for the 2021 Monaco Yacht Show,” says Perignon. “But what hydrogen propulsion really needs is other early adopters so the technology can move beyond the laboratory stage into real-life applications.”

In the meantime, the Energy Observer team is collaborating on a hydrogen-powered boat that will take part in the Solar Energy Boat Challenge in Monaco from 30 June to 4 July. The stripped-down, 12-metre prototype being built by Hynova Yachts in the south of France will be fitted with two Toyota fuel cells for a top speed of around 30 knots. After the event, the boat will return to the shipyard for fitting out as a luxury tender and will make its debut at the Cannes and Monaco yacht shows in September.

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