Solar Panels on Agricultural Land

Sheep graze below solar panels. Photo: Merrill Smith, U.S. Department of Energy.

George Harvey

In April, two reports on the use of solar panels on agricultural land appeared almost simultaneously. One was a press release from Fraunhofer ISE, “Agrophotovoltaics: High Harvesting Yield in Hot Summer of 2018” (Fraunhofer report). The other was the “Farmers’ Guide to Going Solar,” from the U.S. Department of Energy (DOE). They share a single main message, which is that farmers can benefit from having solar arrays on their fields, without necessarily reducing agricultural output.

The Fraunhofer report describes an experiment in which solar panels were placed over a field of potatoes. According to the report, the electric energy output of a hectare of land where solar panels were co-located with potatoes was 86% of what it would have been without a crop, because the panels had to be spread out a bit more, so fewer were installed.

While the solar output might be considered pretty good, given co-location, the data on potatoes was surprising. Potato production was 103% of what it would have been without solar panels. It appears that potatoes, and many other crops, do not need as much sunshine as they get. The solar panels prevented them from burning in the sun of a record-breaking hot summer, but reduced cooling at night, so they could continue night-time growth a bit faster than usual.

The Fraunhofer ISE report can be seen at http://bit.ly/FISE-Report.

The DOE report is aimed at farmers who are considering the installation solar panels. It has nearly twenty commonly asked questions, along with their answers. The material at the site is very easy to read.

Some of the questions are surprising. One, for example, asks whether the land under solar panels can be burned off each year. Unsurprisingly, the answer was negative.

Another question, asking what the benefits of co-location are, has a multi-part answer with its own surprises. For example, there is reduced legal risk for developers for solar arrays co-located on farmland, because the land is already disturbed, and so there is a reduced likelihood of environmental issues coming up.

Other facts presented in the DOE report are worth mentioning. Pollinator plants can be grown under solar panels for the production of honey, and when this is done, benefits can be had at any farm within three miles. It is possible to raise panels high enough that many pieces of standard farm equipment can function beneath them, though doing so costs more. Also, solar panels do not heat or dry up crops, and many crops, including lettuce, do well in the partial shade they produce.

The DOE report can be found at http://bit.ly/DOE-Report.