The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) has been studying the feasibility of floating solar photovoltaic systems to boost solar energy production nationwide. While the vast majority of solar installations in the U.S. have been large-scale, ground-mounted solar panels, NREL’s study, published late last year, found that floating PV on 24,000 man-made reservoirs has the potential to produce 10% or more of the nation’s electricity annually.

According to NREL, floating PV was first demonstrated in California 10 years ago but never quite caught on in the United States. With over 100 sites worldwide, only seven are in the U.S. The difference in popularity may be due in part to the fact that other countries have less land available to dedicate to solar panels. Jordan Macknick, NREL’s lead energy-water-land analyst and principal investigator of the project, suggested that land availability and price may begin to influence the growth of floating solar in this country as well.

Floating PV being installed in Walden, Colorado. Source: Dennis Schroeder/NRELFloating PV being installed in Walden, Colorado. Source: Dennis Schroeder/NRELAdvantages of floating PV include reduced evaporation and algae growth. The research team looked at where in the U.S. water evaporation losses are greatest and matched those areas with the solar resource potential to determine how this technology could be used for evaporation reduction.

In addition, the team identified areas with extremely high land values and those where solar installations bump up against agricultural needs as good candidates for floating solar. Combining floating PV with hydroelectric facilities is another way the team found to increase energy output and reduce costs by using existing transmission infrastructure.

NREL plans to continue studying the pros and cons of floating PV installations on man-made bodies of water. “We are exploring floating PV from a number of different angles, including negative tradeoffs. Despite providing benefits for reducing algae, it is unclear what types of impacts floating PV will have on other aquatic or avian species. We are also trying to understand other material and motion fatigue-related risks to the technology itself. Long-term maintenance costs are also an uncertainty,” Macknick told Engineering360. “We haven’t seen any major impacts on wildlife yet, but again it hasn’t been studied with the same level of rigor as with land-based PV systems.”

Other areas to be investigated, according to Macknick, include materials science questions such as the long-term impacts of water body soiling on PV and floating equipment for multiple water quality types, motion fatigue analyses of components, impacts of changes in microclimate temperatures and humidity levels on long-term system output, opportunities for flexible PV systems to be utilized, off-shore floating PV opportunities and bi-facial PV technology options. Policy and techno-economic issues such as further capital and O&M cost characterization of floating PV systems, long-term analyses of system performance, improved accounting of additional benefits and synergies of floating PV (including evaporation, algae, hydropower and aquaculture), as well as permitting and zoning challenges and barriers will also be studied.

The study findings were published in Environmental Science & Technology