Oregon State Uni Researchers: Agrivoltaics Benefits Land & Animals

In a paper entitled ‘Herbage Yield, Lamb Growth and Foraging Behavior in Agrivoltaic Production System’, published in Frontiers in Sustainable Food Systems, researchers at the Oregon State University present a comparison between lamb growth and pasture production from pastures in agrivoltaic systems and traditional open pastures over 2 years in Oregon. They conclude from the experiment that the allowing lamb grazing to occur alongside PV power production has several advantages for both activities.

This project was conducted in spring 2019 and 2020 at a 1.4 MW agrivoltaic facility on the university campus. The PV system is east-west oriented and the panels are placed at a height of 1.1 MW from the ground, with a 6 m distance between the panel rows. The facility’s area was divided into three 0.2-hectare blocks and each block was arbitrarily assigned to the grazing under solar panels and grazing in open pasture fields. The soil type was a combination of Woodburn silt loam, Amity Silt loam and Bashaw silty clay. The paper notes that in solar pastures, the distance between solar panels was 6 m, providing 3 m fully shaded and 3 m partially shaded areas. Each solar pasture contained four solar arrays and four solar panels. Thus, these pastures had 50% open (partially shaded) and 50% fully shaded areas.

The lambs’ foraging behaviour was monitored by visual scanning at five-minute intervals from 8 a.m. to 4 p.m. and herbage mass was measured in each plot. Measurements on land-use efficiency for total annual herbage and lamb liveweight production, were also taken. The scientists state that to calculate the net returns from the onsite grazing activity, they averaged the daily liveweight production in 2019 and 2020, multiplied by the average number of grazing days across both years, and assumed an average price of $316.19 per hundred kg weight based on the USDA average price of lambs in 2018.

It was observed from the result of the experiment that the annual forage yield in solar pastures was lower compared to open pastures. The reason behind is, as per the authors, was poor production in fully shaded areas. However, it was also noted that solar pastures showed higher forage nutritive value, which offset the lower herbage mass, leading to similar lamb liveweight gains in both the solar and open pasture fields. While 45% of the lambs’ grazing activity took place in shade directly under the solar panels, this percentage increased to 96% for its ruminating and idling activities.

Interestingly, the per day water consumption by lambs was similar for both solar and open pasture field during early spring, and lambs in open pastures consumed more water than those under the PV system in the late spring period. The scientists found no difference in water intake of the lambs in spring 2020, and believe that the shade created by solar panels can be more beneficial to animal welfare and water consumption in hot and arid regions. They argue that agrivoltaics systems may alleviate the need of artificial shelter provision to livestock, also reducing the initial infrastructure cost in pasture-based livestock production.

The scientists concluded at the end of their experiment that the return from grazing was $1,046 per hectare per year in open pastures and $1,029 per hectare per year in pastures with solar panels. According to them, the overall return is about the same, and that doesn’t take into account the energy the solar panels are producing.

This research was funded by the Agricultural Research Foundation (ARF) of Oregon State University. The authors include Alyssa C. Andrew, Chad W. Higgins, Mary A. Smallman, Maggie Graham and Serkan Ates.