As they’ve become cheaper and more efficient, electricity-generating solar panels have popped up all over the United States. But some experts say it would be better if new photovoltaic panels were placed not only on parcels of land and rooftops but also on reservoirs and other bodies of water.

Floating photovoltaic panels — or “floatovoltaics,” as some call the devices — could generate large amounts of electricity without taking up valuable real estate, experts say.

Solar panels generate about 1 percent of the nation’s energy needs. New research by scientists at the federal government’s National Renewable Energy Laboratory shows that floatovoltaics installed on just one-fourth of the nation’s manmade reservoirs would be able to generate about 10 percent of U.S. energy needs.

"This is a strong tool in the toolbox that we can utilize for expanding our photovoltaic portfolio in the U.S.," said Robert Spencer, a data scientist at the lab and the leader of the research.

The 10-percent figure may be a conservative one. The study only included reservoirs with nearby electric transmission lines and those used primarily for irrigation or hydroelectric power, and excluded all naturally occurring bodies of water.

"What this shows is that there's an enormous potential for floating photovoltaics," Joshua Pearce, an engineer at the Michigan Technological University in Houghton who wasn't involved in the work, said of the study. "And that's with [NREL's] absurdly conservative assumptions."

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The world’s first floating photovoltaic system was installed at a California winery in 2008, but the U.S. now lags other nations in the implementation of floatovoltaics.

Of the 100 or so floatovoltaic installations now in existence, only seven are in the U.S., mostly at wineries in California and water treatment facilities, including the Canoe Brook Water Treatment Plant in Millburn, New Jersey. Roughly 80 percent are in Japan, where limited land and roof space make water-based solar panels especially attractive.

Untapped potential

Floatovoltaics cost less to install than traditional land-based solar panels, Spencer said, in part because there’s no need to clear land or treat soil. And research shows that the natural cooling effect of the water below can boost the solar panels’ power production by up to 22 percent.

Floatovoltaics offer benefits beyond more efficient power generation.

By limiting air circulation and blocking sunlight that would otherwise reach the surfaces of reservoirs, the study noted, they can dramatically limit the amount of water lost to evaporation. In addition, they can help prevent harmful algae blooms, which produce toxins that can sicken people and animals and raise drinking water treatment costs.

“The biggest benefits to installing floatovoltaics would be seen in the arid southwestern states that are dealing with scarce water resources," Spencer said.

Many unknowns

But floatovoltaics come with potential downsides. Given the world’s limited experience with them, it’s hard to know just how well panels would perform over the long term. Nor is it clear how floatovoltaic installations affect local wildlife.

"This gap in our understanding is important to reconcile as floatovoltaics have enormous technical potential," said Rebecca Hernandez, an assistant professor of earth system science and ecology at the University of California, Davis, who wasn't involved in the study.

Spencer agrees. "The biggest barrier to floatovoltaics are all the unknowns," he said, adding that having floatovoltaics' huge potential now quantified will help motivate scientists to try to tackle these research questions.

But Pearce isn’t so sure such concerns will stop the quick adoption of floatovoltaics. "The dam will break, and when you have fairly decent-sized companies that have installed two to three floatovoltaic systems, that will pull in other companies," he said. "I think it'll only be a couple years before floatovolatics are commonplace."

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