A recent National Renewable Energy Laboratory (NREL) study estimates that floating solar installations on federally controlled reservoirs could generate between 861 and 1,042 GWdc of power. This contribution represents nearly half of the U.S.’s solar capacity requirements to achieve a decarbonized energy grid by 2050.

The potential energy output varies based on factors such as reservoir floor slope and minimum water volume thresholds, emphasizing the importance of site-specific evaluations.

Developable reservoir areas range from 2% to 81% of surface area, highlighting the need for localized analyses instead of generalized assumptions about floating solar feasibility.

The southeastern United States and the southern plains states—specifically Texas, California, and Oklahoma—have the highest potential capacities because of their extensive large reservoir networks. Estimated system sizes range from projects of 10 kW to installations of up to 76.6 GWdc, with a median capacity of 123 MW.

Source: NREL

Floating solar projects have experienced significant growth since their global capacity first surpassed 10 MW in 2014. The country’s total floating solar capacity reached over 13,000 MW by 2022, with an annualized growth rate of 142%.

These systems offer multiple advantages over traditional ground-mounted solar installations. Floating solar panels benefit from higher efficiency due to water’s cooling effect. Co-locating these systems with hydropower facilities also enables hybrid energy generation to enable increased efficiency.

Floating solar panels also reduce evaporation by covering the reservoir, potentially benefiting arid and draught-prone regions. Countries such as South Korea have integrated floating solar into their renewable energy strategies. However, research into its overall role in global energy systems remains in the early stages.

Assessing Technical Potential

The technical potential of floating solar refers to the maximum feasible capacity, considering physical and technological constraints.

NREL’s study applied advanced geospatial methods to evaluate floating solar capacity on federally controlled reservoirs managed by the U.S. Bureau of Reclamation (USBR), the U.S. Army Corps of Engineers (USACE), and the Federal Energy Regulatory Commission (FERC). Unlike previous studies that relied on generalized assumptions about waterbody suitability, the new research incorporated detailed site attributes such as water depth, surface currents, and dam proximity.

The study analyzed data from the National Hydrography Dataset (NHD), USACE, USBR, and FERC, creating a comprehensive inventory of 1,052 reservoirs. Specific exclusion criteria were applied to ensure accuracy. The study excluded areas with sub-1 m water depths since they cannot support floating solar systems.

Buffers were applied to inlets and outlets with surface currents exceeding 2 m/s to prevent damage to the mooring systems. A 100-meter safety buffer was set up around dams for maintenance needs and to avoid regions with high currents.

Reservoirs in regions with average monthly low temperatures below -15°C were excluded because ice floes and heavy snow loading could pose significant risks to the floating solar panels.

Limitations and Future Directions

The study acknowledges certain limitations.

The analysis relied on modeled bathymetry data, which, while comprehensive, may lack the precision of detailed site-specific surveys. The study also did not account for regulatory, social, and environmental constraints that could influence the feasibility of these projects in real-world scenarios.

Further research is required to address these gaps, including methodology expansion and criteria refining. Such research could include natural waterbodies, estuaries, and offshore environments, as well as adjust exclusion thresholds, including those related to cold climates or water volume assumptions, to better align with the characteristics of individual reservoirs.

Incorporating considerations for recreational, ecological, and social factors would also provide a more comprehensive understanding of the practical challenges and opportunities associated with floating solar projects.

According to an earlier report published by NREL, floating solar could play a critical role in the Association of Southeast Asian Nations’ regional target of 35% renewable energy in the installed power capacity by 2025.

According to another NREL report, the addition of floating solar projects on top of water bodies that already have hydropower stations can annually generate around 7.6 TW of clean energy from the solar photovoltaic systems alone.