When we think of solar, we tend to picture shimmering expanses of panels spread across farmland or mounted on rooftops. But how about attached to a raft, floating atop a reservoir?
Floating solar photovoltaics, also called “floatovoltaics,” is an emerging technology that’s taken off in countries across Asia and Europe, especially near urban areas with limited space available for land-based solar.
It’s also an untapped resource for the U.S. clean energy transition, according to a new study by researchers at the Department of Energy’s National Renewable Energy Laboratory. They found that federally owned or managed reservoirs could hold enough floating solar to produce up to 1,476 terawatt-hours of clean electricity — enough to power about 100 million homes each year.
“We know we’re not going to be able to develop all of this. But even if you could develop 10% of what we identified, that would go a long way,” said Evan Rosenlieb, geospatial scientist and study co-author.
Even under the most conservative scenario the researchers considered, the potential of floating solar equals more than half of the solar capacity required for a fully carbon-free grid in the U.S. in 2050.
Besides minimizing land use, floating solar shades water bodies, which reduces evaporation and conserves limited water supply at reservoirs. Water also cools down the panels, making them up to 15% more efficient than land-based solar.
But so far, floating solar only makes up a tiny fraction of the U.S. solar market and is mostly limited to small-scale projects, including at a wastewater treatment plant in Healdsburg, California; a reservoir in Cohoes, New York; and a lake at the Fort Liberty military base in North Carolina. The country’s largest floating solar project is an 8.9-megawatt installation at a water treatment plant in Millburn, New Jersey.
Compare that with projects like Thailand’s 45-MW floating solar farm in the Sirindhorn Dam reservoir, or China’s massive 550-MW system that sits atop a body of water used for fish farming in the city of Wenzhou. “In the United States, we don’t have a single project over 10 MW,” said study co-author Aaron Levine.