Iowa State University Agrivoltaics project lead professor Ajay Nair picks strawberries at the Alliant Energy Solar Farm at Iowa State on Sept. 4, 2024. (Photo by Brooklyn Draisey/Iowa Capital Dispatch)
Solar panels shone in the light of a clear sky Wednesday morning, occasionally clicking as they followed the sun’s path. Tucked underneath and around the array’s structure were plants — peppers, strawberries, raspberries, and grapes; even the beginnings of prairie plants, grass and clover.
Bugs flitted about in the breeze, though honey bees were likely staying close to their apiary home near the solar array due to the coolness of the day, said Iowa State University professor Matt O’Neal. The bees and other insects pollinate the plants found at the Alliant Energy Solar Farm at Iowa State, where research is conducted into how agriculture and renewable energy production can coexist, also known as agrivoltaics.
The farm is a public-private partnership between the company and university, with both gathering data to learn how to better serve customers and growers.
Funded by a four-year, $1.8 million grant from the U.S. Department of Energy, ISU researchers are exploring how certain crops grow underneath solar panels compared to plots grown outside of the array, among other projects.
Katie Hendrickson, chief of staff at the Department of Energy’s Office of Energy Efficiency and Renewable Energy, visited the site Wednesday after speaking with researchers and engineers involved with the project.
Hendrickson said the Department of Energy has provided about $20 million to agrivoltaics projects across the U.S. She said ISU’s solar farm is proof that there are creative solutions available to marry agriculture, where the most available land is, and solar energy.
“Agrivoltaics, it brings jobs to communities, it diversifies incomes for farmers, so seeing this in action is really cool,” Hendrickson said.
Alliant Energy finished construction on the solar array last fall after entering into a 20-year lease with the university for the 10-acre plot of land in 2021, said Alliant Energy Strategic Partnerships Manager Nick Peterson. Interdisciplinary teams of ISU faculty and students began working on the land this spring, starting off a three-year cycle of planting and harvesting broccoli, summer squash, bell peppers, strawberries, honey berries, raspberries, grapes, prairie plants and grasses.
The site houses both fixed and sun-tracking solar panels, Peterson said, producing enough energy to serve between 200-220 households. They are affixed at different heights to create different climates underneath the panels, so plants grown underneath can be compared to one another and energy production can be measured and compared.
Agrivoltaics project lead professor Ajay Nair speaks with Department of Energy Chief of Staff for the Office of Energy Efficiency and Renewable Energy Katie Hendrickson on Sept. 4, 2024. (Photo by Brooklyn Draisey/Iowa Capital Dispatch)
O’Neal said there are three big questions that all of the research being conducted on the site is seeking to answer: what can be grown under solar panels that is both economically and environmentally sustainable, how do the microclimates created underneath the panels by the plants impact energy production and how can these practices be replicated at other sites.
ISU Agrivoltaics project lead professor Ajay Nair said the equipment and practices utilized by the teams handling the crops are the same as what a commercial grower would use.
“We are demonstrating that this is possible, that you can grow commercially on a sustainable scale within a solar array system,” Nair said.
The broccoli and summer squash have already been harvested, as well as strawberries and raspberries, Nair said, and they’ve started picking peppers. Data is collected throughout the growing season on everything from stem height and diameter to leaf and flower numbers. Once the harvest begins, researchers look at the yield, quality and marketability of the crops.
Sensors are also placed throughout the solar farm to measure data like humidity, soil moisture, air temperature and more.
Using the crops grown outside of the shade of the array as a control group, Nair said broccoli did better outside than under the panels, but the results were flipped for summer squash. Though they haven’t had the chance to collect data on the peppers yet, the plants under the panels are greener and larger. Nair said he hypothesizes that the yield will be better as there won’t be as many nonmarketable peppers due to sun spotting.
Still growing at the solar farm were strawberries, which assistant professor Suzanne Slack encouraged people to pluck off and eat if they wanted. The researchers have seen larger strawberries from the plants under the panels and fewer bugs, which they will study further next year.
Food harvested from the solar farm goes to the university’s Horticulture Research Station, as well as to local food pantries. Nair said they made sure to bring philanthropy into their work, as making money isn’t a part of the project.
Economic studies are also being conducted into the marketability of the crops coming from the solar array and whether people may be willing to pay more for items like honey that are part of a solar farm.
(From left) Alliant Energy Strategic Partnerships Manager Nick Peterson, Iowa State University professor Matt O’Neal and Agrivoltaics project lead professor Ajay Nair speak at the Alliant Energy Solar Farm at Iowa State on Sept. 4, 2024. (Photo by Brooklyn Draisey/Iowa Capital Dispatch)
The team will keep growing these crops for two more years, rotating annuals and keeping perennials where they are. They will also expand their plots to plant crops underneath the fixed panels for further research.
Having crops under the shade of solar panels can also help those cultivating and harvesting them, Nair said, as they will be more comfortable in their work. Peterson said the company and university are thinking about possible future partnerships in order to bring more people, especially underserved communities and those who lack access to land, into the project and into agriculture.
The microclimate underneath the panels is consistently cooler and wetter, O’Neal said, opening doors for better grazing land and providing habitats for wildlife that have lost theirs due to agriculture practices.
“There are some opportunities, not only to farm, but also to conserve wildlife at a solar facility, if we’re thoughtful about the type of plants that we put into this unique landscape feature,” O’Neal said.
There are challenges that come with growing crops underneath the solar panels, Slack said, including the creation of optimal conditions for fungal growth and diseases. Data is still being collected on the strawberries post-harvest, but one of the things they’re looking at is the post-harvest rot compared to those grown out in the sun.
Nair said growers are approaching the project with caution, but specialty crop growers are expressing interest in the results. For those who grow fruits and vegetables alongside crops like corn and soybeans, leasing land to a company like Alliant Energy to put in a solar array could bring in a new income stream without giving up land that could be used for growing.
“Now you’ve got dual use, you have an income from the lease and from the vegetables which you were already growing,” Nair said. “So those growers are particularly interested.”
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