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Video: Yes, you can sail around the world on solar power

The French research ship Energy Observer proves the concept. But shipping remains a decarbonization challenge.

Julian Spector
Julian Spector
5 min read
Video: Yes, you can sail around the world on solar power

Electric cars are picking up market share among landlubbers, but the notion of electric ships plying the high seas can seem unmoored from reality. But a proof of concept is already circumnavigating the globe.

A French research vessel dubbed the Energy Observer logged nearly 11,000 nautical miles in 2020, propelled entirely by renewable energy captured onboard. The former racing yacht is plastered with solar panels that fill up batteries and tanks of pressurized hydrogen. The ship travels on good old-fashioned wind power as well as an electric motor fed by batteries and hydrogen fuel cells.

Canary Media boarded the ship at anchor in Long Beach in late April and verified that it is no mirage. Years of testing honed its solar panels and auxiliary technologies to withstand the battering of briny waves and wind.

"On this boat, we just use the hydrogen that we have produced on board from the seawater for years now. We are fully autonomous," said general manager Louis-Noël Viviès. "We are not very fast, but we can go anywhere we want, with no limit."

The design is a long way from commercial mass production, but its technologies could play select roles in the shipping industry, which produces an estimated 3 percent of global emissions — and rising.

In the meantime, Energy Observer proposes a different way of thinking about sea travel: a voyage where you never seek a harbor to refuel, because you make your own fuel. And a sailing experience without the familiar stench of diesel exhaust and rumble of combustion engines intruding on the fair breeze and undulating vistas.

How it works

The hull of the Energy Observer is a sleek racing catamaran built in Canada in 1983. The 100-foot vessel was built for nimble yet sturdy performance — it set a round-the-world sailing record in 1993.

To that frame, the team added:

  • 32 kilowatts of solar capacity, covering 202 square meters. The installation includes bifacial and heterojunction panels designed with the Institut National de l’Energie Solaire, as well as anti-slip panels designed by Solbian using SunPower cells.
  • Pressurized hydrogen gas tanks to hold 62 kilograms, equivalent to 2 megawatt-hours storage. Half of that goes to electricity and half to heating.
  • A 100-kilowatt-hour lithium-ion battery, developed by Forsee Power for marine applications. That storage capacity is equivalent to a high-end Tesla.
  • Two hydrogen fuel cells: a prototype from the Commissariat à l’Energie Atomique, a French national laboratory, with 26-kilowatt peak power; and a REXH2 from EODev, based on the Toyota Mirai fuel cell. This one has 110-kilowatt peak power, but Energy Observer typically runs it at 60 kilowatts for better efficiency.
  • A pair of high-tech, self-adjusting sails that catch the winds when available, giving an old-fashioned renewable thrust.

"We test, we try, we torture all the components," Viviès said. "We want to push the boundaries of a smart grid."

The electric motor runs on power from the batteries or the fuel cells in a hybrid system. The batteries handle short, intense bursts of power, while the hydrogen systems allow for longer-duration power with a lighter footprint than batteries.

Hydrogen tanks offer lighter-weight energy storage than lithium-ion batteries. (Image credit: Julian Spector)

Speed is the trade-off

The anchor weighing down adoption of this technology is travel speed.

Energy Observer can maintain an average speed of 6 knots, or just under 7 miles per hour, Viviès said, which is comparable to a typical sailing boat. It can cruise faster, but that sacrifices "full autonomy," meaning the ship consumes hydrogen faster than it can be replenished.

By contrast, a combustion-powered ship can maintain high speeds, but "needs to refill and has no autonomy at all," he added.

Still, Viviès insists that Energy Observer never struggled with running out of fuel.

"You just adapt your consumption to what you have," he explained. "If you have a lot of energy, you can go fast and spend a lot of [energy on making] espressos, and the heater and washing machine."

If the tank is running low, the crew slows down on energy-intensive espresso production. Or drinks the espresso and slows down the ship. It's a dynamic process.

A challenge for translating the experience of Energy Observer into broader maritime applications, then, is how to spread the carbon-free approach when alacrity matters. Global trade doesn't stop for espresso breaks.

The batteries are isolated abaft in the pontoon as a safety precaution. (Image credit: Julian Spector)

Next steps for zero-carbon shipping

Energy Observer isn't going into mass production any time soon. But one goal of the project is to translate its findings into other ship designs.

The group is working on a larger yacht for delivery in 2024, capable of carrying 20 to 40 people at higher speeds than Energy Observer, Viviès said. But many more hands are grappling with the challenge of cleaning up ships.

"The challenge with decarbonizing maritime shipping is really about cost," said shipping decarbonization specialist James Mitchell, a director of the Center for Climate-Aligned Finance at research nonprofit RMI. "Bunker fuel is just so cheap—it's residual, it's left over."

The options vary depending on the type of ship, though. For local or "short sea" trips, electrified battery-hydrogen hybrids are already making headway.

"The smaller the ship and shorter the distance, the [better the] economics are going to work," Mitchell said.

Hydrogen, however, is not dense enough for deep sea shipping. Liquified hydrogen needs a roughly four times bigger tank than diesel to power a ship over the same distance, and compressed hydrogen tanks take up even more space, said Mikael Wideskog, director for sustainable fuels and decarbonization at Wärtsilä, which manufactures power systems for ships and the electricity sector.

The other problem with hydrogen today is that most of it is still produced in carbon-intensive ways, with large-scale "green hydrogen" facilities still waiting to be built. Biofuels, though, are in production today and already work with Wärtsilä engines, Wideskog noted.

Some analysts believe ammonia could be used in long-distance shipping, due to its greater energy density compared to hydrogen. Several groups will test ammonia-powered ships in the coming years.

But shipping needn't tread water until these newfangled propulsion systems fully commercialize. Options today include route optimization and energy-saving devices, Wideskog said. Ships can transition to cleaner fossil fuels on the way to biofuels and synthetic sustainable fuels, which currently cost up to five times as much as cheap fossil fuels.

"This results in a stepwise approach in reducing your carbon footprint, instead of just waiting for carbon-free fuels," Wideskog said.

(Article image courtesy of Energy Observer)

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Julian Spector

Julian reports on the rise of clean energy. He worked at Greentech Media for nearly five years, and before that he reported for CityLab at The Atlantic.