And the potential is surprisingly large: Reservoirs could host enough floating solar panels to generate up to 1,476 terawatt hours, or enough energy to power approximately 100 million homes a year.
"That's a technical potential," Rosenlieb said, meaning the maximum amount of energy that could be generated if each reservoir held as many floating solar panels as possible. "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."
Levine and Rosenlieb have yet to consider how human and wildlife activities might impact floating solar energy development on specific reservoirs. But they plan to address this limitation in future work.
This study provides far more accurate data on floating solar power's potential in the United States. And that accuracy could help developers more easily plan projects on U.S. reservoirs and help researchers better assess how these technologies fit into the country's broader energy goals.
Floating solar panels, also known as floating PV, come with many benefits: Not only do these buoyed power plants generate electricity, but they do so without competing for limited land. They also shade and cool bodies of water, which helps prevent evaporation and conserves valuable water supplies.
"But we haven't seen any large-scale installations, like at a large reservoir," Levine said. "In the United States, we don't have a single project over 10 megawatts."
Previous studies have tried to quantify how much energy the country could generate from floating solar panels. But Levine and Rosenlieb are the first to consider which water sources have the right conditions to support these kinds of power plants.
In some reservoirs, for example, shipping traffic causes wakes that could damage the mooring lines or impact the float infrastructure. Others get too cold, are too shallow, or have sloping bottoms that are too steep to secure solar panels in place.
And yet, some hydropower reservoirs could be ideal locations for floating solar power plants. A hybrid energy system that relies on both solar energy and hydropower could provide more reliable and resilient energy to the power grid. If, for example, a drought depletes a hydropower facility's reservoir, solar panels could generate energy while the facility pauses to allow the water to replenish.
And, to build new pumped storage hydropower projects -- which pump water from one reservoir to another at a higher elevation to store and generate energy as needed -- some developers create entirely new bodies of water. These new reservoirs are disconnected from naturally flowing rivers, and no human or animal depends on them for recreation, habitat, or food (at least not yet).
In the future, the researchers plan to review which locations are close to transmission lines or electricity demand, how much development might cost at specific sites, whether a site should be avoided to protect the local environment, and how developers can navigate state and federal regulations. The team would also like to evaluate even more potential locations, including other, smaller reservoirs, estuaries, and even ocean sites.
The research was funded by the Solar Energy Technologies Office and the Water Power Technologies Office in DOE's Office of Energy Efficiency and Renewable Energy (EERE).
