BOSTON HARBOR — If you closed your eyes, you’d likely not notice the 35-ton boat approaching.
As the Energy Observer, a self-sufficient, hydrogen-powered catamaran puttered around the harbor on a morning in early May, it hardly made a peep. Its electric motors whizzed softly, mixing in with the slosh of wake and the percussion of ropes against fiberglass.
Launched in 2017 in France, the Energy Observer operates as a mobile clean energy laboratory and as a demonstration of its onboard technologies. This includes desalination of ocean water, production of hydrogen gas to power the engine, solar and mechanical power generation, and the storage of all that energy. No gas or diesel is used to make the boat go.
Crew members describe the vessel as part testing-ground, part proof of concept, and part educational space. As the ship has traveled the globe, the crew invites passengers — students, journalists, and researchers — on board to show off a clean future that’s already technically possible.
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Global shipping, powered largely by diesel fuel, contributes roughly 3 percent of the world’s greenhouse gas emissions that cause climate change. The limitations to transform the sector remain cost, scale, and inertia.
After a quick jaunt around Boston Harbor by the Energy Observer, a voice came over the intercom. “Captain speaking,” said Marin Jarry, who stood at the helm. “Close your seat belt, we are turning.”
Luc Bourserie, systems engineer, laughed at Jarry’s instruction, with nothing to hold onto within reach on the upper deck. Beneath him, hundreds of solar cells wrapped the fiberglass hull.
The Energy Observer, as Bourserie explained with a wide smile, is covered in more than 2,100 square feet of solar panels, including some that are bifacial, meaning they can collect solar energy on both sides at once: capturing solar energy from the sky directly and reflected off the waves. At peak efficiency, that’s enough to produce more than 33 kilowatts of electricity, most of which is stored in batteries below deck, and used to power the operations of the boat.
The catamaran also sports a pair of wing-like sails designed to take the load off the electric motor when wind is sufficient. While the sails themselves do not create power, they allow the motor to spin freely and generate electricity from the boat’s motion — similar to hitting the brakes in an electric car, Bourserie said.
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All told, Bourserie said, the Energy Observer can store two megawatt hours of energy, but loses about half of that energy as heat when it’s converted to electricity. (Still, that’s enough energy to power a typical family home for a month.) The heat generated in the conversion process is used elsewhere on board, for example to keep the crew warm inside the cabin.
The roughly 30-meter catamaran also desalinates seawater for general use, and then solar energy powers electrolyzers used to split water into oxygen and hydrogen atoms. Hydrogen gas is then stored in eight tanks to power the engines.
Beatrice Cordiano, an onboard climate scientist, said one of the biggest hurdles to implementing hydrogen storage widely is the initial cost of the equipment, especially electrolyzers.
“At the moment, it’s a niche technology, so it costs a lot,” she said of the electrolyzer. “And you need a way to [power] it. You need a lot of solar panels, you need a lot of wind turbines.”
Sergey Paltsev, deputy director of the MIT Joint Program on the Science and Policy of Global Change, said he admires the effort onboard the Energy Observer, but that a larger implementation of the onboard technology is not currently viable for larger vessels.
“Yes, it will work for this small catamaran, but if you’re going to take a look at those huge cruise ships, or huge container ships, or huge tankers, that’s a very different requirement, in terms of how much power you need to have,” said Paltsev.
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He noted that the roughly 8 kilograms of hydrogen produced by the ship’s electrolyzer each day is a fraction of the energy these larger vessels consume.
“A typical container ship uses 8 million [megajoules per day], so one would need about 7,000 of these electrolyzers (if they work every day),” Paltsev wrote in an email.
Still, Paltsev said the Energy Observer, with years of sailing completed, is a good proof of concept for hydrogen storage. Though he does not anticipate a major transition to hydrogen power in the next few years, he said, “We need to keep those options on the table.”
Bourserie said sailing the open ocean, with its harsh storms and currents, allows the onboard technology to be tested and proven in extreme conditions. That helps determine the limits of the technology.
During their time in Boston, crew members met with students and researchers, sharing thoughts and findings about making the transition to clean energy. Bourserie, who grew up in France and studied engineering with a focus on energy, said he was partly drawn to the project by its emphasis on cultural exchange.
“It’s a big part of what we do,” Bourserie said. Part of the ship’s purpose is “to arrive [in new countries] and to create discussions about energy transitions.”
On Wednesday, the vessel is scheduled to begin crossing the Atlantic Ocean, stopping in St. Malo, France, before arriving in Paris in time for the Summer Olympics.
That will be Cordiano’s first trans-Atlantic crossing. Standing on the upper deck, she hypothesized that the vessel could sustain itself for around a month and a half before needing to dock.
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“I’m not super worried, even if we are really offshore,” Cordiano said. “I rely on this system. I have seen that it works.”
After the Paris Games, the boat will be decommissioned, concluding a voyage that will have visited more than 40 countries and spanned more than 62,000 nautical miles.
Daniel Kool can be reached at daniel.kool@globe.com. Follow him @dekool01.