Federal reservoirs could play a crucial role in meeting the United States’ growing need for renewable solar energy, according to a recent study published in Solar Energy. This research, conducted by Evan Rosenlieb and Marie Rivers, geospatial scientists at the U.S. Department of Energy National Renewable Energy Laboratory (NREL), and Aaron Levine, a senior legal and regulatory analyst at NREL, provides new insights into the potential of floating solar panels installed on federally owned or regulated reservoirs across the country. This is the first study of its kind to precisely quantify the energy that could be generated by floating solar projects on these water bodies.
The Huge Potential of Floating Solar Panels
The findings of the study are impressive. Reservoirs in the U.S. could host enough floating solar panels to generate up to 1,476 terawatt hours (TWh) of energy annually. To put that into perspective, this is enough power to supply roughly 100 million homes each year. This is what Rosenlieb refers to as the technical potential—the maximum energy that could be generated if all of the reservoirs identified had floating solar panels installed at full capacity.
It’s important to note that this represents an optimistic upper bound, as practical, economic, and environmental limitations would undoubtedly prevent the full development of every identified reservoir. Still, even if developers could harness 10% of this potential, it would make a significant contribution to the country’s energy needs.
While the study identifies the energy-generating potential of these installations, Rosenlieb and Levine are quick to acknowledge that human and wildlife activities on or around certain reservoirs have not been fully factored into the initial study. For example, the impact of recreational boating, fishing, and the presence of aquatic ecosystems might limit the extent of solar panel installations at some locations. However, both Rosenlieb and Levine have stated their intention to investigate these factors in more detail in future research.
Accurate Data for Better Planning
What sets this study apart is its use of highly precise geospatial data to identify specific reservoirs suitable for floating solar. This new, detailed data provides far greater accuracy than previous studies in quantifying the potential for floating solar projects across the nation. By using geographical mapping tools and algorithms, the research team was able to pinpoint which bodies of water are best suited for solar energy generation. This level of accuracy will help developers plan more effectively, taking into account the topographical, environmental, and logistical factors that affect feasibility. Developers and energy planners will also be able to tailor their projects based on location, considering factors such as proximity to transmission lines, electricity demand, and local regulatory constraints.
Rosenlieb and Levine’s approach differs significantly from earlier efforts that lacked such granular data on which reservoirs are most suitable for floating solar technology. Floating solar panels, also known as floating photovoltaic (FPV) systems, are buoyant solar arrays that float on the surface of water bodies, harnessing the energy of the sun without requiring land. This eliminates the competition with other land uses such as farming, housing, or industry. By utilizing available water surfaces—such as those on federal reservoirs—these projects allow for solar energy generation with minimal impact on terrestrial ecosystems.
Advantages of Floating Solar Panels
Floating solar panels offer several clear advantages compared to conventional land-based solar installations. The most obvious benefit is the efficient use of space—these systems don’t require clearing land and can be placed on existing water bodies without disrupting agriculture or urban developments. In fact, the installation of floating solar panels has the added benefit of shading water surfaces, which helps reduce evaporation, a crucial advantage given increasing concerns over water scarcity in many parts of the country.
Additionally, the cooler temperatures of the water help to keep the solar panels operating more efficiently. Solar panels are generally more efficient when they’re cooler, and the ambient temperature of water helps regulate this, leading to better overall performance.
The Lack of Large-Scale Floating Solar in the U.S.
Despite these advantages, floating solar is still an emerging technology in the United States. Levine points out that, while the technology has gained significant traction worldwide, in the U.S., “we haven’t seen any large-scale installations, like at a large reservoir.” To date, no floating solar projects in the country have exceeded 10 megawatts (MW). However, this doesn’t mean that floating solar hasn’t been tested or implemented in smaller capacities. In fact, several countries, including China, Japan, and South Korea, have already seen substantial floating solar projects of over 1 GW (gigawatt) in total capacity.
The researchers believe that large-scale floating solar plants will eventually become a crucial part of the U.S. energy landscape, especially as other sources of renewable energy, such as land-based solar, face space limitations. Floating solar offers an opportunity to tap into unused water areas, allowing for the generation of clean energy without interfering with other uses.
Evaluating Suitable Reservoirs
The researchers not only identified the total potential energy capacity of floating solar projects in the U.S. but also provided insights into the characteristics needed for a successful installation. Some reservoirs are more appropriate than others due to various physical and logistical factors that could make certain water bodies better suited for these systems. Factors such as depth, topography, water temperature, and wave activity were considered. Reservoirs that are relatively shallow, low-maintenance, and calm provide ideal conditions for installing floating solar panels. Others, however, face challenges.
For example, some areas with frequent shipping traffic could pose logistical issues. Large wakes created by boats or cargo ships could damage the infrastructure required to keep the floating solar panels in place. Additionally, severe water temperatures or deeply sloped waterbeds could further complicate installation.
Yet there are several locations in the U.S., particularly in hydropower reservoirs, where the conditions for floating solar panels are favorable. Hydropower could be particularly compatible with floating solar, as these reservoirs already serve a function in energy production. By adding floating solar technology to such facilities, energy generation could become even more reliable and resilient.
One particular advantage of using hybrid energy systems that combine both solar and hydropower is that these technologies complement each other. Hydropower is intermittent—it depends on water levels in the reservoir—while solar energy could continue to generate power when water levels are low due to drought or other disruptions. In this way, solar could step in when the hydropower plant is unable to operate due to depleted water levels. Furthermore, in some cases, pumped storage hydropower projects, which rely on two reservoirs at different elevations, could provide additional capacity for installing solar panels without impacting existing ecosystems.
The Path Forward for Developers
Looking to the future, Rosenlieb, Levine, and Rivers intend to take their research a step further by examining additional factors critical to the successful implementation of floating solar power across the U.S. One area of focus will be determining how much it might cost to develop specific sites—whether certain locations would be prohibitively expensive due to complex regulations, land ownership disputes, or environmental concerns.
Another important consideration will be how best to navigate the regulatory environment—particularly at the state and federal levels—as developers look to build on federally managed or regulated land.
In addition to identifying suitable locations on existing reservoirs, the researchers also plan to expand their work to examine potential opportunities in smaller water bodies, such as estuaries, and even more unconventional options like ocean sites, where solar panels might be installed on large-scale floating platforms that can harness both water and sunlight.
Conclusion: A Key Component of the U.S. Energy Future
The new study on floating solar presents significant potential for the renewable energy sector in the U.S. By tapping into the power of federal reservoirs, floating solar could play an important role in decarbonizing the energy grid, meeting growing energy demands, and mitigating the effects of climate change. With its advantages in space efficiency and water conservation, floating solar offers an innovative solution that could pave the way for more sustainable energy production in the years to come.
As the country continues its transition toward a more sustainable energy future, floating solar could provide a critical, yet often overlooked, piece of the puzzle. While large-scale installations may be years away, the foundation for success is already being laid, with extensive data and research providing the roadmap for the future. The next step for developers and researchers alike is to convert this technical potential into real-world, impactful projects that will help power the United States in a clean and sustainable way.
Reference: Evan Rosenlieb et al, Floating photovoltaic technical potential: A novel geospatial approach on federally controlled reservoirs in the United States, Solar Energy (2024). DOI: 10.1016/j.solener.2024.113177