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Untapped potential exists for blending hydropower, floating solar 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 analysis by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).

NREL researchers estimate that adding floating solar panels to bodies of water that already host hydropower stations could produce as much as 7.6 TW of capacity a year from the solar photovoltaic (PV) systems alone, or about 10,600 TWh 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 TWh in 2018, the most recent year for which statistics are available, according to the International Energy Agency.

“This is really optimistic,” said Nathan Lee, a researcher with NREL’s Integrated Decision Support group and lead author of a paper published in Renewable Energy. “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.”

“Hybrid floating solar photovoltaics-hydropower systems: Benefits and global assessment of technical potential” was co-authored by Ursula Grunwald, Evan Rosenlieb, Heather Mirletz, Alexandra Aznar, Robert Spencer, and Sadie Cox.

Previous NREL work estimated that installing floating solar panels on man-made U.S. reservoirs could generate about 10% of the nation’s annual electricity production. Floating PV remains a nascent technology in the U.S., but its use has caught on in countries where space for ground-mounted systems is less available. However, so far, only a small hybrid floating solar/hydropower system has been installed, in Portugal.

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

Potential benefits of coupling floating PV with hydropower include reduced transmission costs by linking to a common substation. Additionally, the two technologies can balance each other because solar power’s greatest potential 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.

NREL is DOE’s primary national laboratory for renewable energy and energy efficiency research and development and is operated for the Energy Department by the Alliance for Sustainable Energy LLC.