Raspberry crops grow under solar panels at an agrivoltaic farm in the Netherlands on July 12, 2022. FRANCOIS WALSCHAERTS / AFP via Getty Images
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As the world grapples with the climate crisis and transition from fossil fuels to renewables, crops and clean energy are increasingly sharing the same land, and agrivoltaics — the growing of crops beneath the shade of solar panels — is expanding.
Now, scientists are looking into how to harness the sun’s light spectrum in a way that can improve the efficiency of agrivoltaic systems in areas with arid farmland.
In a new study, scientists at the University of California, Davis (UC Davis), discovered that the blue part of the light spectrum is more efficient for solar energy production, while the red part of the spectrum is better for plant growth, a press release from UC Davis said.
The study, “Not All Light Spectra Were Created Equal: Can We Harvest Light for Optimum Food-Energy Co-Generation?” was published in the journal Earth’s Future.
“This paper is a door opener for all sorts of technological advancements,” said associate professor at the Department of Land, Air and Water Resources at UC Davis Majdi Abou Najm, who helped author the study, in the press release. “Today’s solar panels take all the light and try to make the best of it. But what if a new generation of photovoltaics could take the blue light for clean energy and pass the red light onto the crops, where it is most efficient for photosynthesis?”
A computer model for photosynthesis and transpiration that accounted for varied light spectra was developed by the scientists for the study. The response of plants like basil, strawberry and lettuce to differing light spectra was reproduced by the model in a lab. The scientists found that the red spectrum could be perfected for food growth and the blue spectrum could be filtered to generate solar energy.
“From a plant perspective, red photons are the efficient ones,” said Abou Najm, as Modern Farmer reported. “They don’t make the plant feel hot.”
Agrivoltaics improves land use efficiency by putting solar arrays — a collection of multiple solar panels — between crop rows. The panels shade fruits that are sensitive to heat, as well as leafy vegetables, while the temperature underneath the solar panels is lowered by the plants’ transpiration, which improves the performance of the solar cells.
“We cannot feed 2 billion more people in 30 years by being just a little more water-efficient and continuing as we do,” Abou Najm said in the press release. “We need something transformative, not incremental. If we treat the sun as a resource, we can work with shade and generate electricity while producing crops underneath. Kilowatt hours become a secondary crop you can harvest.”
As the amount of usable land on Earth dwindles due to climate change, the more knowledge we have of how light spectra variations affect plants the better humans can develop agricultural systems that balance water use, sustainable land management and food production.
“By 2050, we’ll have [an additional] two billion people on this planet, and we’ll need 60 percent more food, 40 percent more water and 50 percent more energy,” Abou Najm said, as reported by Modern Farmer. “[W]e’re optimizing an endlessly sustainable resource. If a technology kicks in that can develop these panels, then the sky is the limit on how optimized we can be.”