Installing floating solar systems on the surface of 761 federally managed reservoirs in the United States could generate at least half the solar energy the country will need to decarbonize its grid by 2050, concludes new research from the federal Department of Energy (DOE).
Of the 1600 gigawatts of solar estimated to be required to decarbonize the U.S. grid by 2050, 861 GW could come from floating photovoltaic (FPV) systems hosted by federal reservoirs, according to the “most conservative scenario” in a study just published in the journal Solar Energy.
Under ideal conditions, with every viable reservoir holding its maximum number of solar panels, FPV generation could hit 1,042 GW, enough to generate up to 1,476 terawatt-hours of electricity per year. This could power roughly 100 million homes, the DOE’s National Renewable Energy Laboratory (NREL) said in a release dated Jan. 17, three days before the Trump inauguration.
“That’s a technical potential,” Evan Rosenlieb, co-author and NREL geospatial scientist, clarified in the release. “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.”
While there have been past attempts to assess America’s floating solar potential, the NREL study is the first to zero in on the specific hosting potential (or lack thereof) of every federally owned or regulated reservoir in the country.
To make NREL’s initial cut, a reservoir had to be part of a hydroelectric project, a parameter reflecting the desirability of potential hybrid solar-hydro systems. Purpose-built for resilience, such systems could see solar panels continuing to generate electricity even as hydro faltered through periods of drought. Research elsewhere also indicates that floating panels can combat drought by slowing evaporation on reservoirs and other waterways.
Reservoirs that see heavy shipping traffic or are in regions that see winter temperatures dip below -15C were also excluded.
The remaining 859 reservoirs were assessed for depth and flow, and excessively shallow reservoirs and those with strong currents were left out. Steep-sloped reservoirs lacking a flat bottom were also cut, as this feature could damage FPV systems in times of low water.
“Area must be in a location that will still hold water at low waterbody volumes or be on a waterbody whose bathymetry (the underwater equivalent of topography) is flat enough so floats may be designed to be grounded,” write the authors.
Of the 761 reservoirs that made the cut as potential FPV sites, 57% could house between 10cMW and 1 GW of floating solar panels, with a median of 123cMW.cAnother 35 reservoirs could house between 3 and 10 GW of FPV, while the remaining 15 or so could see FPV installations in excess of 10 GW.
While FPV potential is “well-distributed throughout the country outside of the areas where the cold temperature cutoff removed potential reservoirs from consideration,” the southeastern and southern plains states have the largest potential capacity, with Texas in the lead at 137 GW.
The authors caution that their research effort is just a first step, although a critical one, to assessing the actual potential of FPV in America —an upper bound of potential that environmental analysis, for example, is likely to “further constrain.”
