Solar-paneling canals would not only produce renewable energy for use across the state, it would run the water system itself. “By covering canals with solar panels, we can reduce evaporation and avoid disturbing natural and working lands, while providing renewable energy and other co-benefits,” says environmental engineer Brandi McKuin of the University of California, Merced, and the University of California, Santa Cruz, lead author on the paper.Ironically enough, the performance of solar panels falls as temperatures rise. In a solar cell, photons from the sun knock electrons out of atoms, producing an electric current. When a panel gets too hot, that puts electrons into an already excited state, so they don’t create as much energy when dislodged by photons. Spanning panels over canals would, in a sense, make them water-cooled, boosting their efficiency. “And additionally,” McKuin adds, “shade from the panels mitigates aquatic weed growth, which is a major canal maintenance issue.”
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Bales and McKuin calculated all of this by incorporating a variety of models. Evaporation rates, for instance, came from hydrological models. They folded in climate models, too, to predict how the state will warm over the coming years. They got so granular that they also calculated how the cooling effect of the canal water would improve the panels’ generating efficiency.
Ultimately, they landed on a potential annual savings of 63 billion gallons of water across California. But they also took into account the human benefits of such a project, which are more nebulous. For example, many farmers pump their water with diesel generators. If solar panels provided that energy instead, that could cut local emissions, thus improving air quality. “You can look at the economic costs, but you can also look at the social benefit,” says Bales.