Sharing the power of the sun

MORRIS, Minn. — To help farmers optimize land use, diversify revenue, conserve resources and improve animal welfare, researchers at the University of Minnesota’s West Central Research and Outreach Center have been investigating the use of agrivoltaics. Agrivoltaics refers to the practices that combine agricultural production with solar energy on the same land, such as grazing dairy cattle under solar arrays.

Attendees of the Midwest Farm Energy Conference June 16-17 at WCROC near Morris learned about green ammonia as a farm fuel, agricultural robots, electric tractors and WCROC research on agrivoltaics.

Brad Heins, a dairy professor in the Department of Animal Science at UMN, did the agrivoltaics presentation. He shared benefits of the practice, such as how it can strengthen farm productivity.

“Our goal is to really improve the environment and farm resilience,” he said.

According to the Minnesota Department of Commerce’s Division of Energy Resources, dairy farms across the U.S. consume between 400 and 1,700 kilowatt-hours per cow each year. The majority of this energy comes from fossil fuels.

Hoping to find a solution to lower fossil fuel and energy usage, researchers at WCROC installed a 30-kilowatt solar panel system in a pasture in 2018. Standing around eight feet above the ground, dairy cows stand, graze and relax underneath the panels. Today, the panels remain standing, calming concerns about cows destroying them.

“(The panels) look exactly like they did when we put them up eight years ago, and the cows still like to go underneath there, graze underneath and use it for shade protection,” Heins said.

To uncover how the cows interacted with the solar panel systems and determine if there were any effects, 24 crossbred cows were placed into two testing groups: shade from panels or no shade. Researchers used several types of sensors to monitor lying and standing behaviors, activity, water intake, body temperature and more.

Results found that shade from the solar array reduced heat stress in cows by lowering their body temperatures by half a degree during the afternoon, while increasing water intake — potentially improving milk production. Additional research also uncovered that cows with access to shade had lower activity levels due to lying under the panels and being less stressed.

“The other cows that didn’t have access to the shade were panting and moving all over the place, trying to dissipate their heat, so it does show that we can reduce heat stress on these animals,” Heins said.

A half-megawatt solar panel system was later installed for dairy heifers at WCROC, along with virtual fencing to manage the pasture borders.

“(The system) provides lots of good opportunities as you drive by Highway 59 for people to see that you can have cattle and solar existing together and not causing a lot of issues with the public or farmers,” Heins said.

Different forages, grasses, fruits, vegetables and crops were also planted underneath panels to examine growth. Heins said some kinds, like orchardgrass and tall fescue, grew very well — perhaps even better than if they were fully in the sun.

“We think that the panels were preventing evaporation of the moisture from the soil underneath,” Heins said. “It was providing shade to the soil and allowing it to keep the moisture in and allowing the grasses to do much better.”

Heins and a team of researchers also developed a mobile solar shade power station. The system, designed for rotational grazing, was built on an old header trailer and powered by a generator and batteries with the panels being able to fold and extend. As cows move to graze, the station, pulled by a truck, can follow the herd, providing shade and collecting energy.

“(The station is) all battery powered, so we can store the solar energy in the batteries, and we can actually power the electric tractor that we have, and we could power electric fences or irrigation,” Heins said.

Agrivoltaics can provide a range of benefits, not only for farmers, but for their land, crops and livestock.

“(Farmers considering agrivoltaics) need to work with the developers and start small,” Heins said.

When it comes to the future of agrivoltaics, according to an article co-authored by Heins and published in the Journal of Animal Science last year, future research on agrivoltaics will focus on reproductive performance, long-term effects on milk, fat and protein production, body weight, health and well-being.