Posted on 8 January 2024 by Guest Author

This is a re-post from Yale Climate Connections by Rachel Goldstein

Just southeast of Phoenix, over 150 miles of canals sit uncovered in one of the hottest and driest regions of the country. The Gila River Indian community’s solar panel project, which would cover some of those canals with solar panels, could be the start of a new wave of such solar projects, known as floatovoltaics.

A new study by an international team of researchers shows just how useful wide-scale floatovoltaics could be. They calculate that covering 30% of the surface of 115,000 reservoirs globally could generate 9,434 terawatt hours of power a year. That’s more than twice the energy the entire United States generates annually and enough to fully power over 6,200 cities in 124 countries. 

As the climate crisis intensifies, a prolonged megadrought coupled with water overuse has depleted water resources in the American West, hurting the ability of hydropower generators to provide the electricity needed for growing air conditioning demand during extreme heat. The region must quickly find ways to generate more energy while also conserving water, especially in the Colorado River watershed where water supply is being lost through evaporation in two of the largest U.S. reservoirs feeding hydroelectric plants, Lake Powell and Lake Mead.

That’s where floatovoltaics come in. Floating solar panels already have been successfully deployed for large-scale projects in Asia. The solar panels are mounted on structures that sit atop lakes, reservoirs, canals, and remediation ponds, to name a few examples. They combine both shading infrastructure to prevent evaporation and panels to generate carbon-free power, both desirable features for drought-stricken areas that also need more carbon-free power.

“The electrical system is really no different than a rooftop system or a ground mount system,” Chris Bartle, director of sales and marketing at Ciel & Terre USA, told WIRED magazine. “We’ve taken essentially old technology from the marina world — docks and buoys and whatnot — and applied that to building a structure that an array of solar panels can be mounted to. It’s really as simple as that.”

By using the otherwise open surface area of a lake, floatovoltaics do not have to find suitable parcels of land that are not already being farmed or supporting sensitive ecosystems. Another big advantage: The solar cells can float on reservoirs that feed into hydroelectric dams and are already located near massive transformers and transmission facilities that can accept large amounts of electricity. This helps floatovoltaic developers avoid siting challenges and costly interconnection upgrade fees.

Still, the technology is fairly nascent, with under 50 megawatts of facilities operating in the U.S. Installation costs and maintenance logistics are about 25% higher than ground-mounted solar projects. Developers must balance key criteria to ensure predictable cash flow and limited risk since current tools and strategies in the development pipeline are not always equipped to work with floating solar.

Over the next decade, the global compound annual growth rate for floating solar is projected to rise 15%, according to a recent report by Wood Mackenzie, which puts the comparable growth rate for the U.S. at about 13% over the next decade. Regions with high land costs and high solar demand, such as California and New Jersey, are expected to lead development due to favorable economics for unique siting opportunities, as well as favorable policy. New Jersey already hosts the largest floating solar array in North America, an 8.9 megawatt facility that covers a reservoir located next to a water treatment facility.

New Jersey isn’t exactly facing a water scarcity crisis, so the technology would be even more welcome in Arizona or New Mexico, which would benefit from the water retention along with the electricity. Pilot programs in the area include the Salt River Project, in which a major electric utility is teaming up with researchers at Arizona State University. The Turlock Irrigation District in central California recently embarked on Project Nexus, which will deploy solar panels over open irrigation canals in one of the nation’s most critical (and water-constrained) agricultural areas.

Good policy could help floatovoltaics break through its early market stage in the U.S. and overcome cost and logistical concerns. New Jersey’s SREC-II incentive program provides an additional incentive to solar projects that aren’t built on scarce available land. This benefits floating solar projects as well as rooftop, carport, and canopy projects, helping the Garden Statbecomeng a solar energy leader.

Southwestern states have plenty of cheap, available land, but these rural areas still face permitting and interconnection challenges. State lawmakers and regulators should find ways to incentivize floating solar, particularly on their reservoirs and tributaries that could feed existing transmission lines. More projects could seek funding from the Bipartisan Infrastructure Law, like the Gila River Indian Community in Arizona did to install floatovoltaics on their canals on the Colorado River. New funding opportunities are particularly important for government-owned projects on reservoirs or municipal water treatment facilities that are unable to benefit from tax credits.

Poor understanding of floatovoltaics in the U.S. by players such as insurance agencies and companies that develop the design is making the development of this technology more expensive and time-consuming than it needs to be. Still, each element of floating solar systems relies on existing and provable technology that has been successfully deployed at scale in other countries. U.S. companies and government entities have every incentive to explore the massive untapped potential of floatovoltaics. They just need to dive in.

Rachel Goldstein is a research and modeling manager at Energy Innovation Policy and Technology LLC®, a Yale Climate Connections content-sharing partner.