The rising number of solar panel setups showing up in the country is good news for renewable energy supporters, but it may also be positive for livestock producers. A study published in the journal PLOS One from an Oregon State University College of Agricultural Sciences team of researchers finds that grasses favored by sheep and cattle thrive in the shade of a solar array installed in a pasture on campus.

These results suggest that locating solar panels on pasture or ag fields could boost crop yields, according to Chad Higgins, corresponding author of the study and an associate professor in the OSU Department of Biological and Ecological Engineering. Higgins notes there are some plants that are “happier in shaded environments. The amount of water that went into the making of those plants is tremendously smaller than in an open field. You get double the yield, less water and all the solar energy.”

SHADE AND GRASSES: Sheep graze under the 35th Street Solar Array at Oregon State University. 

The idea of “double cropping” ground for both solar photovoltaic power and conventional agriculture is known as agrivoltaics and dates to the early 1980s. Ground-mounted solar arrays typically aren’t placed on farms with the intent to grow crops.

Higgins explains that the difference in this research is that the solar array was installed without the intent to influence plant production. “It was by accident. Nobody engineered this system. Now we’re trying to develop a deeper understanding of how we can engineer the system to be technically feasible, environmentally sound and economically viable,” he adds.

Solar at work
OSU has solar project sites in Corvallis covering 10 acres that have the capacity to generate 2.6 million kilowatt-hours of power annually. This study looked at the 35th Street Solar Array installed in 2013 on the west side of campus.

Higgins and his colleagues noticed green grass growing in the shade of the panels. In May 2015, they installed microclimate research stations that recorded mean air temperature, relative humidity, wind speed, wind direction and soil moisture. By August, the instruments revealed the areas under the panels maintained higher soil moisture throughout the three-month period.

Higgins notes that the result was striking. The areas under the array produced double the amount of plant material than the unshaded areas, including an increase in the nutritional value of plants. And there was a significant increase in late-season plant growth.

Higgins shares his thoughts on the process: “It’s like a tortoise and a hare race. The plants that experience the full brunt of the sun use their water resources as quickly as possible. They grow to the extent they can, and then they die. On the other hand, the plants in the shade take sips of water because they are less stressed, and they keep chugging along.”

The next step is to test the impact of panel placement on certain high-value crops suitable to shaded conditions.

The study is part of a larger effort to understand links between energy, water and food systems, Higgins said. He is founder of the Nexus of Energy, Water and Agriculture Laboratory at OSU. The research team included Elnaz Hassanpour Adeh, a doctoral candidate in OSU’s water resources engineering program; and John Selker, an OSU Distinguished Professor. Both are in the Department of Biological and Ecological Engineering.

Source: Oregon State University