A study by the National Renewable Energy Laboratory, which is part of the US Department of Energy, suggests that if floating solar panels are deployed on the more than 379,000 hydro reservoirs globally, the resultant hybrid systems could generate anywhere from 16% to 40% of the world’s demand for electricity. In a press release, the NREL says adding floating solar panels to bodies of water that are already home to hydropower stations could produce as much as 7.6 terawatts of potential power a year from the solar PV systems alone. That’s equivalent to 10,600 terawatt-hours of electricity annually. In comparison, global final electricity consumption was just over 22,300 terawatt-hours in 2018, the most recent year for which statistics are available, according to the International Energy Agency.
Actually, some researchers think that 40% number is more than a little optimistic. They suggest the number should be closer to 16% than 40%. John Sherwin, program director at the University of Central Florida’s Solar Energy Center, tells E&E News there are variables that need to be researched first, such as how solar panels respond to the stress of being on the water. In an e-mail to E&E News, he said “the actual potential [of solar-hydro pairings] would be more conservative and be on the middle to lower end of the range.”
One of the factors that make a combination of floating solar and hydropower appealing is that the solar side of a hybrid facility can tap into the existing transmission infrastructure that already exist at a hydroelectric site. Another benefit is putting solar panels over an area that has few competing uses. There are no trees to cut down or fields to repurpose. That alone should simplify the permitting process compared to a conventional ground mount solar system that may create land use issues.
Other advantages include allowing hydropower operators to conserve water during dry seasons while keeping electricity flowing from the site to the grid. Allowing transmission lines to tap into a second, intermittent source of electricity brings them closer to their total capacity. That in turn allow ssystem operators to claim a higher capacity credit because they would have more dispatchable electricity available at all times.
In places like the Southwest, floating panel arrays might also cut down on evaporation at reservoirs, says Nathan Lee, lead author of the study and a researcher for NREL’s Integrated Decision Support team. “This could be an option to explore in the U.S. to ensure that we have the generation we need, given hydropower’s availability,” Lee says. The technology also highlights a less contentious path for renewable growth as utilities and governments seek to cut down on carbon dioxide emissions.
The largest slice of the world’s technical potential would come from North America, the study finds. A separate study from NREL last summer found that about 10% of the America’s electrical power could come from floating solar installed just on man-made bodies of water alone.
Floating solar is not yet a thing in the US but that may be changing. Just last week, Duke Energy announced it has been selected to install a floating solar array at Fort Bragg, North Carolina. The 1.1 megawatt system is part of a $36 million energy and water conservation upgrade at the world’s largest military installation and is expected to save $2 million a year in energy expenses.
Floating solar is gaining in popularity in Europe, where the largest such facility outside of China was connected to the grid in August. Located in the Netherlands, it contains 72,000 solar panels covering 18 hectares of water and here’s the astounding part. It was constructed in just 7 weeks! The installation will provide electricity directly to about 7,200 homes in the area.
It’s interesting how many factors go into designing a floating solar installation. The solar panels used in the Netherlands project are glass/glass units that allow some light to pass through to the water below to the organisms living there. The inverters and transformers are also mounted on floats, which allows the array to be connected to the shore by just one cable, making for minimal disturbance of the surrounding flora and fauna. Apparently there’s more to engineering floating solar than covering aquatic surfaces with photovoltaic panels.
Whether floating solar plus hydro could provide 16% or 40% of the world’s electricity, putting the two together will clearly be an important part of decarbonizing the electrical grid.