Researchers say they have determined a way to make agrivoltaics — the process of growing crops underneath solar panels — more efficient. They found that red wavelengths are more efficient for growing plants, while the blue part of the spectrum is better for producing solar energy. Solar panels that only allow red wavelengths of light to pass through could enable farmers to grow food more productively while generating power at the same time.
Previous studies have found that agrivoltaics can reduce the amount of water required for crops, since they're shaded from direct sunlight. Researchers at Michigan Technological University determined in 2015 that shading can reduce water usage by up to 29 percent. Majdi Abou Najm, an associate professor at University of California, Davis' department of land, air and water resources, told Modern Farmer that by splitting the light spectrum, crops can get the same amount of carbon dioxide with less water while shielding them from heat.
The researchers put the idea to the test by growing tomatoes under blue and red filters, as well as a control crop without any coverings. Although the yield for the covered plots was about a third less than the control, the latter had around twice the amount of rotten tomatoes. Abou Najm noted that the filters helped to reduce heat stress and crop wastage.
For this approach to work in practice, though, manufacturers would need to develop translucent solar panels that capture blue light and allow red light to pass through. Matteo Camporese, an associate professor at the University of Padova in Italy and lead author of a paper on the topic, suggested that translucent, carbon-based organic solar cells could work. These cells could be applied onto surfaces such as glass.
There are other issues, including the fact wavelength-selective agrivoltaic systems may need to account for different crop types. Harvesting those crops efficiently might require some out-of-the-box thinking too. Still, the research seems promising and, with a growing global population, it's important to consider different approaches to using our resources more productively.
“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. “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.”