Under a clear, sunny sky in Ames, the chirps of crickets and chorus of cicadas create a soft background for the mechanical creaking of solar panels and whirring of inverter boxes.
“It's no different than your computer at home when you're plugging away on Facebook and the fan starts going there,” said Nick Peterson, the strategic partnerships manager at Alliant Energy. “But as you can hear, the birds sometimes are enjoying the man-made forest that we’ve created for them here.”
This past summer at the Alliant Energy Solar Farm at Iowa State University, professors and students have worked under the din of wildlife and technology to tend to vegetables, fruits and boxes of beehives.
What is agrivoltaics?
The project is part of a U.S. Department of Energy-funded study on agrivoltaics, or the practice of using land under and around solar panels for agricultural purposes, such as cultivating pollinator gardens, growing food crops and grazing livestock.
Since the same qualities that make land attractive for harvesting solar energy — being flat and sunny — also make it ideal for farmland, the two industries can often be in competition for land. However, a team of researchers at ISU is determined to prove a dichotomy does not have to exist.
In 2023, over 75% of all land in Iowa used for farming was dedicated to growing corn and soybeans. According to an ISU Agricultural Policy Review from last year, some of the strongest opposition to solar energy in Iowa stems from concerns over land use.
“[We’re] trying to convince folks that solar isn’t taking away from farmland,” said Suzanne Slack, an associate professor of horticulture at ISU and co-principal investigator who oversees fruit production on the site. “You can still farm under solar — it’s just a little bit different.”
The 10-acre site in Ames is bolstered by a four-year $1.8 million grant from the Department of Energy. It is one of six agrivoltaic projects to be awarded the FARMS grant in 2022.
“The ability to put solar all across the country is going to help decarbonize and we have to go to farmland for that,” said Katie Hendrickson, chief of staff for the Office of Energy Efficiency and Renewable Energy at the Department of Energy. “Being able to co-locate solar on agriculture land, whether that's grazing, especially crops like we're seeing today, pollinators — we can't get there without working with our farmers.”
In Ames, researchers are trying to show how agriculture can work on a solar farm by mimicking a real life scenario with three stakeholders — a landowner, utility company and farmer. In this study, those parts are played by ISU, Alliant Energy and the faculty and student workers.
“We're trying to demonstrate if those three groups can come together and do what you see here today, which is get multiple benefits out of a single piece of land,” said Matt O’Neal, a professor of entomology, plant pathology and microbiology at ISU and co-principal investigator.
How does it work?
A team of engineers, horticulturists, sociologists, entomologists and economists at ISU are working together through a public-private partnership with Alliant Energy. The project has been in production since 2020, but 2024 has been the first year of testing plants in the ground. So far, the team has grown broccoli, bell peppers, summer squash, grapes, raspberries and honey berries on the 1.375 megawatt solar farm.
The three vegetables selected were chosen on input from farmers they work with from the Iowa Specialty Crop Growers Association, according to Ajay Nair, chair of the department of horticulture and principal investigator on the project. With broccoli — a cool season vegetable, the squash growing in early summer and the peppers full season, researchers are able to maximize the time they can observe the plot.
Sensors monitored by faculty from the department of engineering are positioned under the panels and in the soil to measure temperature, moisture and irradiance — or the level of solar radiation in a given area.
While the crops are growing, researchers track data such as plant height, stem diameter, leaf number and number of flowers. After harvesting the produce, they track data on the number of produce, its diameter, marketability and quality.
For Nair, he sees promise in agrivoltaics to produce higher quality vegetables, namely in peppers where sunscald is common.
“Hopefully, by growing peppers under the system, the impact of that sun will be lessened,” Nair said. “Peppers are a great crop to show and replicate here, because this is a standard crop which many of our fruit and vegetable growers grow, so there's nothing new for them to learn or technique-wise.”
And, for Nair, it doesn’t hurt that he has a personal penchant for the produce.
“You already see a pattern here that I like grilling because you have summer squash, you have bell peppers,” said Nair. "I mean, throw them on a grill — amazing.“
Nair said the microclimate under the panels is cooler and more moist than the microclimate outside the panels. This shift in temperature and moisture can create more ideal conditions for grazing livestock and safer conditions for workers, something that has already been attractive to the students on the farm.
“They really like the shade,” said Slack. “That’s one of the reasons our strawberries look so beautiful. They were willing to put that extra effort because they really liked the site.”
The added moisture and shade under the panels is especially beneficial for growing crops in the face of climate change.
“We're expecting to see more extreme weather conditions — hotter, drier conditions,” O’Neal said. “And yeah, we need irrigation but we're going a long way in producing an environment that is going to potentially be more conducive for crop production.”
The future of agrivoltaics
The vegetation can also reduce heat stress on the panels and make them more efficient. However, the project is not without its obstacles.
Increased humidity can lead to increased fungi growth, and the horticultural researchers have found common pests such as squash bugs and cucumber beetles on their crops. However, they have also observed fewer instances of Japanese beetles on grapes and raspberries grown under the panels than ones grown in the control plot.
Planting native plants and pollinator mixes can also support bee populations and boost biodiversity, enriching farmland typically used for monoculture crops.
“To some extent, the grass — especially true with our pollinator mix — is a way to provide habitat and forage for wildlife,” O’Neal said. “There are some wildlife that we could tolerate out here, and some that really need a perennial source of habitat and food that the typical ag landscape doesn't provide, so there's some opportunities, not only to farm but also to conserve wildlife at a solar facility.”
In the future, researchers hope to test the farm’s produce for its nutritional quality, evaluate if the panels can protect against early season frost and attract involvement from other departments, including the animal science department.
Despite the ISU agrivoltaics farm being the first of its kind in Iowa, Slack said agrivoltaics have worked successfully across the world, including in Europe, the Caribbean and some parts of Asia. One of the largest hurdles to adoption in the U.S. is education.
“I guess the biggest roadblock is people don't know about it — so [we’re] just trying to spread the word that this is a thing,” said Slack.
