Huge solar farms floating in the ocean could be used to convert carbon dioxide in seawater into methanol, a fuel that can power airplanes, trucks and other long-haul vehicles. That's the takeaway from provocative new research suggesting that such "solar methanol islands" could curb our reliance on fossil fuels that belch harmful greenhouse gases into the atmosphere.
"This is just one of the many things we should be doing to control climate change, along with having better insulation in our homes, having higher efficiency in car engines and driving electric vehicles," said Bruce Patterson, a physicist at the University of Zurich and co-author of a paper about the research published June 3 in the journal Proceedings of the National Academy of Sciences. "This is just one piece of a mosaic."
The floating solar farms described in the paper would consist of clusters of about 70 circular solar panel "islands" covering an area of roughly one square kilometer (0.4 square mile). Electricity produced by the panels would be used to split water molecules into hydrogen, which would then react with CO2 extracted from seawater to produce methanol.
Patterson said a single floating solar farm of the sort he envisions could produce more than 15,000 tons of methanol a year — enough to fuel a Boeing 737 airliner on more than 300 round-trip flights between New York City and Phoenix. "We'd mostly want to use the fuel in airplanes, long-haul trucks, ships and non-electrified railroad systems," he added.
Methanol burns more cleanly than fossil fuels, and Patterson said the carbon dioxide that its combustion releases into the air would eventually return to the ocean, where the floating solar farms could reuse it. "Over about a year or a year and a half, it'll end up in equilibrium again," he said. "We'll be able to take it out of the ocean and complete the cycle."
But Mark Jacobson, a professor of civil and environmental engineering at Stanford University who was not involved with the study, said the proposed solar farms wouldn't get to the root of the climate crisis.
"Some people think the only problem in the world is to reduce carbon dioxide, but that's not the problem," he said. "The problem is air pollution, energy security and carbon emissions. You have to solve all three of those problems together. This is a solution to a very narrow aspect of the problem, so to me, the idea is misplaced."
Jacobson called using solar farms to produce methanol a "roundabout way of doing things," particularly since methanol is not a widely used fuel source. "Floating solar is a good idea, but just for producing electricity," he said. "With this fuel conversion, it's a fuel that we don't really need. There are a lot more efficient uses for a solar panel."
Patterson acknowledged that the farms wouldn't be a "silver bullet" in the fight against climate change. But especially for commercial air travel, he said, methanol from the farms would be a helpful alternative to jet fuel. "We have to do something like this if we want to save the planet but still be able to fly airplanes," he said, adding, "We have to do everything we can to save the planet, and this will hopefully be a small part of it."
Floating solar farms would work best in regions with ample sunlight, moderate wave action, low risk of severe weather and depths shallow enough to allow the farms to be tethered to the ocean floor, he said. Candidate locations include in the Persian Gulf, the Red Sea, off the coasts of Spain and Australia, and parts of Southeast Asia.
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