Heavy rainfall, which can damage crops, also increases as the warmer atmosphere retains more moisture. “In times of intense heat or extreme rainfall, protecting plants in this way can actually benefit them,” said Madhu Hanna, an economist at the University of Illinois at Urbana-Champaign who also won funding from the new USDA. grant for agrovoltaics. “So that’s another factor we want to look at.”
Hannah will study what the ideal solar massif could be for a particular crop, for example, if it needs larger or smaller gaps between the panels to let in sunlight. Height is also a problem: corn and wheat will need higher panels, while shrub soybeans would do well with a more squat variety.
Thanks to these gaps, crops grown under solar panels do not bathe in darkness. But in general, the light is more diffused, which means that it is reflected from the surfaces before it hits the plants. This reproduces a natural forest environment in which all plants, except the tallest trees, hang in the shade, absorbing all the sun’s rays that pierce.
Barron-Gafford has discovered that a shady tree, like a forest under solar panels, elicits a physiological response from plants. To collect more light, their leaves grow larger than they would be if planted outdoors. He has seen this happen with basil, which would increase the yield of this crop. Baron-Gafford also found that pepper Potatoes, which grows in the shade of trees in the wild, produces three times more fruit in the agrovoltaic system. Tomatoes also grow more fruit. This is probably due to the fact that plants are less stressed by the constant bombardment of sunlight, to which they are not evolutionarily adapted.
But each culture will be different, so scientists need to test each to see how they react to the shadow. “For example, we probably wouldn’t recommend someone plant a summer pumpkin directly in the deepest shade, directly under a panel,” said Mark Wuchanski, a gardening scientist at Colorado State University who studies agrovoltaics and is testing this scenario. “The better place for this could be farther to the edges, where it’s more likely to get a little more sun, because in that case we saw a drop in yield.”
While creating the panels involves some upfront costs, they can actually make farmers money, as Cominec told Grist in this 2020 story before his panels were in place. They would produce energy to run the farm, and the farmer could sell any surplus back to the utility. And because some plants — like these salsa ingredients in Baron-Gafford’s experiments — will use less water, this can reduce irrigation costs. “If we can actually allow farmers to diversify their production and get more from the same land, it can benefit them,” says Hannah. “The presence of crops and solar panels is more beneficial to the environment than just solar panels.”
This type of installation also cools the solar panels in two ways: The water evaporated from the soil rises up to the panels, and the plants release their own water. This is great for the efficiency of the panels because they actually perform worse when they get too hot. They generate an electric current when the Sun’s photons kill electrons from the atoms, but if they overheat, the electrons become overexcited and do not generate as much electricity when they are displaced.