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NREL: Untapped potential exists for blending hydropower, floating PV

Hybrid systems of floating solar panels and hydropower plants may hold the technical potential to produce a significant portion of the electricity generated annually across the globe, according to an analysis by researchers at the US Department of Energy’s National Renewable Energy Laboratory (NREL). A paper on the work is published in the journal Renewable Energy.

The researchers estimate that adding floating solar panels to bodies of water that are already home to hydropower stations could produce as much as 7.6 terawatts of potential power a year from the solar PV systems alone, or about 10,600 terawatt-hours of potential annual generation. Those figures do not include the amount generated from hydropower.

For comparison, global final electricity consumption was just over 22,300 terawatt-hours in 2018, the most recent year for which statistics are available, according to the International Energy Agency.

This is really optimistic. This does not represent what could be economically feasible or what the markets could actually support. Rather, it is an upper-bound estimate of feasible resources that considers waterbody constraints and generation system performance.

—Nathan Lee, lead author


Rendering shows a schematic of a hybrid floating PV-hydropower system.

Floating photovoltaics (PV) remain a nascent technology in the United States, but their use has caught on overseas where space for ground-mounted systems is less available. Previous NREL work estimated that installing floating solar panels on man-made US reservoirs could generate about 10 percent of the nation’s annual electricity production.

So far, only a small hybrid floating solar/hydropower system has been installed, and that is in Portugal.

NREL estimates 379,068 freshwater hydropower reservoirs across the planet could host combined floating PV sites with existing hydropower facilities. Additional siting data is needed prior to any implementation because some reservoirs may be dry during parts of the year or may not be otherwise conducive to hosting floating PV.

Potential benefits exist by coupling floating PV with hydropower. For example, a hybrid system would reduce transmission costs by linking to a common substation. Additionally, the two technologies can balance each other. The greatest potential for solar power is during dry seasons, while for hydropower rainy seasons present the best opportunity. Under one scenario, that means operators of a hybrid system could use pumped storage hydropower to store excess solar generation.

Funding for the research came from NREL’s Laboratory Directed Research and Development Program.


  • Nathan Lee, Ursula Grunwald, Evan Rosenlieb, Heather Mirletz, Alexandra Aznar, Robert Spencer, Sadie Cox (2020) “Hybrid floating solar photovoltaics-hydropower systems: Benefits and global assessment of technical potential,” Renewable Energy, Volume 162, Pages 1415-1427, doi: 10.1016/j.renene.2020.08.080



Solar on the upper pond reduces evaporation in pumped hydro.
They used energy to get the water up there, don't want to lose it.


Yes it is a very good synergystic idea with benefits more than the sum of their part. A good solution for California where there is so many reservoir and sun and wind.

Albert E Short

However, I don't see them sitting in the Niagara River as a viable option


I'm for using all these spaces for solar power; but, it seems to me that rooftops are underutilized, especially in states like Florida where the Republican politicians work more for the utilities and status quo than the people and economic, logical change.


You can get 2-axis solar with very high utilization by building giant floating lily pads the rotate about vertical axis, and with each panel inclination controlled by pneumatic or water hydraulic control for horizonal axis control. Low cost 2-axis solar, free land, reduced evaporation, no curtailing, ...


Check out the Robert Moses Niagara Power Plant on Wikipedia.
" The pump-generating plant in the Lewiston Dam is atypical, in that the dam was constructed not to control the flow of water in a natural river, but rather to contain a man-made 1,900-acre (770 ha), 22-billion-US-gallon (83,000,000 m3) upper reservoir (named the Lewiston Reservoir)." It is a variant of pumped storage hydro.

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