Solar Panels Over California Canals do Much More Than Just Generate Clean Power

Shade from solar panels installed above a small portion of a California irrigation canal reduced water evaporation by up to 70 percent, enhanced PV performance due to the cooler microclimate, and cut aquatic weed and algae growth by up to 85 percent.

Credit: Turlock Irrigation District

Those results are not what Project Nexus, a $20m state-funded pilot, set out to prove; the primary case was always about energy generation. But for a technology that costs more to build than ground-mounted solar, the water and maintenance results may be what make the economics work.

California operates approximately 4,000 miles of open irrigation canals, delivering water to farms and homes across the state. Project Nexus successfully demonstrated that 'over canal' panels can generate electricity and this test program was instigated after a 2021 study analysed the potential benefits of covering all 4,000 miles of California’s major open canals with solar panels. This modelling concluded that it could produce 13 gigawatts of generating capacity (about 50 percent of the new solar California needs to meet its 2030 renewable targets), and, by reducing evaporation, that 63 billion gallons of water could be saved each year - enough to serve 2 million people or irrigate 50,000 acres of farmland.

For canal operators, the question isn’t whether solar canopies generate power. It’s whether the total value of power generation, conserved water, land savings, and reduced weed maintenance justifies the additional cost over conventional solar. The argument is not quite settled yet, but, as one expert said: “We have to get to a hundred miles, and then it might take off.”