Solar panels on ag lands maximize their efficiency

Sheep graze under the 35th Street Solar Array at Oregon State University. 

A recent study by Oregon State University (OSU) showed land productivity could be increased when combining sheep grazing and solar electricity production on the same land.

In a paper titled Herbage Yield, Lamb Growth and Foraging Behavior in Agrivoltaic Production System, published in Frontiers in Sustainable Food Systems, the two-year study is believed to be the first to investigate livestock production under agrivoltaic systems—when solar energy production is combined with agricultural production.

Conducted on the university’s grounds in Corvallis from 2019 and 2020, researchers compared lamb growth and pasture production in pastures with solar panels and traditional open pastures. The plots with solar panels had four panels and arrays, creating half partially shaded and the other half fully shaded areas. In spring 2019, a pasture seed mixture was over-drilled into the existing pasture to improve pasture production and forage quality.

Weaned Polypay lambs (2.5 months old) were used at a stocking rate of 60 lambs in 2019 and 50 lambs in 2020 in both the open and solar pastures. The lambs had free access to a mineral supplement and fresh water in portable water troughs connected to a permanent water supply in both fields.

The findings of the study concluded:

• The lambs gained almost the same amount of weight—4.23 and 4.19 ounces per head per day on solar panels and open pastures, respectively, in 2019; and 4.58 ounces per day but dropping to 1.79 ounces later in the grazing season in 2020.

• The daily water consumption of the lambs in the two pasture types in spring 2019 was similar during early spring, but lambs in open pastures consumed more water than those grazed under solar panels in the late spring period. There was no difference observed for water intake of the lambs in spring 2020.

• Over the two years, solar pastures produced 38 percent less forage than open pastures. Researchers noted that the solar pastures showed higher forage nutritional value and lowered dry matter content than open pastures.

• On average, lambs spent 43.5 percent of their time grazing under solar panels. However, there was a difference in the time of day, with half of their grazing activity under the solar panels in the morning and noon. The number dipped to 29 percent in the afternoon. The lambs spent over 90 percent of their idling and ruminating time under the solar panels.

• Overall, the return from grazing was $1,046 per hectare (one hectare equals 2.47 acres) per year in open pastures and $1,029 per hectare per year in pastures with solar panels.

“The overall return is about the same, and that doesn’t take into account the energy the solar panels are producing,” said Serkan Ates, an assistant professor in OSU’s Department of Animal and Rangeland Sciences and a co-author of the paper. “And if we designed the system to maximize production, we would likely get even better numbers.”

The same group of researchers conducted an earlier study published in January that showed using land for both solar power and agriculture could provide up to 20 percent of total electricity production in the U.S. The paper states it would require an area of roughly 13,000 square miles or 1 percent of current U.S. farmland to meet the goal. The researchers estimate the cost of the agrivoltaic arrays would be $1.12 trillion over a 35-year project life and the payback period would be roughly 17 years. After the projected 35-year project lifespan, the solar arrays would produce $35.7 billion in annual revenue.

Agrivoltaics provide a “rare chance for true synergy: more food, more energy, lower water demand, lower carbon emissions, and more prosperous rural communities,” said Chad Higgins, an associate professor in OSU’s College of Agricultural Sciences and the senior author of the paper.

The researchers plan to do another study quantifying the forage and lamb production from three different pasture types under solar panels. The university has plans to install a solar farm on five acres at the North Willamette Research and Extension Station.

The American Solar Grazing Association (ASGA) announced earlier in May that it received funding from the New York State Energy Research and Development Authority for a two-year project to collect and analyze data on the agricultural, economic and environmental impacts of commercial beekeeping and sheep grazing on solar sites. ASGA is currently accepting applications for solar participants and the study will start in 2022. — Charles Wallace, WLJ editor

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