In 2018, Europe’s extreme drought cut crop yields, but potatoes beneath German solar panels produced 11% more

In the scorching summer of 2018, Europe was sweltering under one of the worst droughts the continent had faced in decades. Rivers ran so low that freighters were left stranded, while farmers in Germany watched their whole wheat, maize, and sugar beet fields shrivel up in the weeks before harvest. What happened next was unusual. In a trial field near Lake Constance in southwest Germany, while crops in the open faced trouble because of the heat, the potatoes growing under the shadow of solar panels not only survived the weather but actually performed 11% better than those growing in the sun.

The numbers are verified from a 2021 peer-reviewed study titled “Agrivoltaic system impacts on microclimate and yield of different crops within an organic crop rotation in a temperate climate,” by Weselek et al., in the scientific journal Agronomy for Sustainable Development. The researchers studied crops growing both under and beside an experimental "agrivoltaic" system, meaning solar panels installed in such a way that they do not obstruct any agricultural activities below them.

The logic is simple


Solar panels provide shade. Shade translates to lower exposure of bare soil to the sun, and thus, lower evaporation of water. Higher retention of moisture means higher availability of water that can be absorbed by the roots of the crops during the dry spell in summer. As the study's authors explain, the potato is a type of crop that benefits from extra water because it is a tuber, a swollen underground stem that stores water and nutrients. That's why, during that drought-stricken summer, the potatoes grown in the shade of the panels had an advantage the sun-exposed potatoes lacked.

It should be noted that it is not only in Europe where such effects are observed. A pioneering research conducted in 2019 by Greg Barron-Gafford, a geographer from the University of Arizona, revealed that growing chiltepin peppers and tomatoes near the solar panels in the Sonoran Desert increased the yields and saved irrigation water while cooling down the panels, which in turn provided additional electricity generation. All of it is recorded in the paper “Agrivoltaics provide mutual benefits across the food–energy–water nexus in drylands,” published in Nature Sustainability.

Why should this matter

Agrivoltaics is one of the rare adaptation concepts that are not just mere theory. The InSPIRE program, an initiative by the United States’ Department of Energy’s National Renewable Energy Laboratory, has been testing agrivoltaics on the ground for years. Their synthesis report has identified operating agrivoltaics sites in over two dozen locations across the country, from Colorado to Massachusetts, this isn't a distant clean-energy dream, but something that has already been running on American farmland for several years.

The part one shouldn't ignore

The very same German scientists also discovered that in a regular, non-drought year, the potato yield beneath the solar panels was lower than usual, as the sun is the raw material of photosynthesis, and if there is less of it, there will be less production of energy.

The 11% boost was tied specifically to the drought conditions of that trial period; in an average year, the study found the shaded potatoes actually underperformed instead of outperforming their sun-grown counterparts. Additionally, wheat grown in the same experiment showed very little production under the panels. Moreover, setting up an elevated solar farm above farmland requires a lot more money than a regular one.

So is this the future or just a nice anecdote?

Somewhere in between, perhaps. It certainly won’t be agrivoltaics alone that will solve America’s problem of water-stressed agriculture, but it is one of the few instances where the provision of clean energy and agricultural output aren’t at odds for the same plot of ground; instead, they share space and even assist each other at times.