Iowa agrivoltaics—growing broccoli, beekeeping and solar panels

A recently completed 1.3 MW solar project underlines that Iowa State University and Alliant Energy are eager to evaluate the feasibility of agrivoltaics on solar farms.

By Tony Kryzanowski

There’s a lot of buzz about the new 1.375 megawatt (MW) Alliant Energy solar farm located on 10 acres of Iowa State University (ISU) property near Ames, Iowa.

It partially has to do with the bees that will be husbanded on the property as both honey producers and pollinators for a variety of potential cash crops that will be planted in and around the solar array.

The site has been designed and developed for agrivoltaics research and demonstration, with the hope of developing and showing how solar power generation and agricultural production can share the same land base. Concerns about potential agricultural land being taken out of production for solar farms are being widely expressed, and the renewable power industry is looking for ways to address these concerns. One way is to share the land with agriculture.

ISU researchers will track the response of various crops in and around this infrastructure and study the practicality of trying to produce a cash crop in the midst of a solar array. This is said to be the first, utility-scale agrivoltaics site in the Midwest and was made possible by a $1.8 million, four-year grant from the U.S. Department of Energy. This was the largest grant approved under this Department’s program.

“We nestled the project between other teaching farm facilities at ISU,” says Nick Peterson, Strategic Partnerships Manager at Alliant Energy, “because the solar farm is going to be another teaching asset for the university to be able to teach agrivoltaics, to do research, and to demonstrate how sustainability and agriculture can mix together.” 

According to the university, “project results may help guide further decisions on the economic, energy and safety considerations of marrying large-scale solar projects with agricultural production on farms.”

The $4.2 million Alliant Energy solar farm features 3,300 bifacial solar panels and is the first completed in the state under the company’s Customer-Hosted Renewables program. This program features solar installations of between 500 kilowatts and 2.25 megawatts where a landowner receives an annual lease payment as compensation for the use of their property to generate solar power. The ISU array will generate enough renewable power to supply about 200 homes and in addition to an annual lease payment, it will also generate renewable energy credits for the university to offset a portion of its carbon emissions. Alliant Energy and ISU have signed a 20-year lease agreement for the use of the land.

“This program doesn’t burden the landowner or customer with capital costs and it allows us to put more renewable energy back on the grid for all of our customers,” says Peterson.

Alliant Energy supplies power primarily to rural customers in Iowa and Wisconsin. It has a sustainability goal of eliminating all coal from its generation fleet by 2040 and achieving net-zero carbon dioxide emissions from the electricity it generates by 2050 as part of its Clean Energy Blueprint program.

The power generated by the ISU solar farm will be added to Alliant Energy’s overall power generation portfolio of which 52 percent comes from renewables—primarily from 1300 MW of installed wind power in Iowa. More recently, the company has turned its focus more toward solar power generation with four separate utility-scale projects providing a combined output of 400 MW expected to come on line in Iowa by the end of 2024.

	The Iowa State University solar array will generate enough renewable power to supply about 200 homes and will also generate renewable energy credits for the university, to offset a portion of its carbon emissions.

 In neighboring Wisconsin, Alliant Energy has 400 MW of wind power installed and is in the process of placing nearly 1.1 gigawatts of solar power into service, spread across 12 projects.

Originally envisioned as just a solar farm owned and operated by Alliant Energy, thanks to the Department of Energy funding, the ISU site has become a ‘living laboratory.’

Peterson says discussions about the solar project and the potential to include agrivoltaics evolved as part of the power company’s longstanding relationship with ISU, such as its 60-year relationship with the university’s electric power research centre. He says that the company was aware that the university had a goal of moving more toward sustainability and was interested in renewable energy. So locating a solar array with an agrivoltaics element seemed like a natural fit at its current location, which is part of the animal science teaching and research farms managed by the College of Agriculture and Life Sciences and its Department of Animal Science.

Discussions about the solar project and the potential to include agrivoltaics evolved as part of Alliant Energy’s longstanding relationship with Iowa State University, such as its 60-year relationship with the university’s electric power research center.

Construction of the solar array began in April 2023 and it was fully operational early in 2024. Waldinger Corporation, headquartered in Des Moines, Iowa, was the EPC on the project, with the 3,300 bifacial solar panels provided by Heliene. The site features both a fixed-tilt and tracker racking system. The fixed-tilt array was provided by DCE Solar and the tracker array was supplied by Array Technologies. The site is equipped with 60 percent single axis trackers to 40 percent fixed-tilt racking. The three-string solar inverters used on the project were supplied by
Canadian Solar. Fairfield, Iowa-based, Ideal Energy provided electrical design services and Iowa
City, Iowa-based Shive-Hattery Inc. worked as the civil engineering firm.
Also Energy will track solar power production for Alliant Energy from the ISU project.

	The $4.2 million Alliant Energy/ISU solar farm features 3,300 bifacial solar panels and is the first project completed in Iowa under Alliant Energy’s Customer-Hosted Renewables program.

According to ISU’s agrivoltaics project plan, university graduate students will conduct research and undergraduate students will help raise bees, plant vegetables and fruits and create a pollinator habitat. The first crop of raspberries was planted last fall, with planting of all selected varieties moving into high gear during the coming growing season.

Ajay Nair, Professor of Horticulture and the lead principal investigator for the agrivoltaics research project at ISU, credits Alliant Energy for its willingness to work with the university to make solar array design adjustments to accommodate agrivoltaics, such as installing a portion of the racking at different heights of between 5’ and 8’ and installing the electrical wiring so it doesn’t interfere or is impacted by operating farm and gardening equipment on the site. In total, there are four different array heights on the solar farm.

“One of the things that we want to answer is what is the yield when we grow crops between and under the solar panels,” says Nair “So, what are the differences between open-field and agrivoltaic systems—are there more diseases, are there more insects, and so on?”

On the solar power project site, the focus will be on high value specialty crops familiar to Iowa growers to maximize income potential, given the limited land base. Crops selected included broccoli, summer squash, peppers, strawberries and raspberries.

“Everything was a real collaboration in the solar array design to allow ISU to better publish research that is going to have both an academic and a real-life use benefit,” Peterson adds.

The hope is that ISU’s findings will provide industry with tangible evidence as to best design practices to incorporate and maximize potential outcomes from such activities as agrivoltaics.

Peterson says that the use of bifacial solar modules was looked at from both a solar power and crop production perspective, even though they have largely now become the industry standard.

“The National Renewable Energy Lab (NREL) have research that shows that any kind of vegetation underneath the panels impacts energy production due to the plants cooling off those panels,” says Peterson. “We’re now getting into that next level of data of what kind of plants provide better energy production and ISU has been tasked to do that with its Department of Energy grant.”

Nair emphasizes that this project goes much further than studying the potential of growing crops in the midst of a solar array. Economists have been included in the research group to determine feasibility and which crops are the most profitable. “At the end of the day, it’s about the feasibility and co-existence,” he says. “Can we grow specialty crops within a solar farm?”

With that in mind, the focus will be on high value specialty crops familiar to Iowa growers to maximize income potential, given the limited land base. By highlighting these specific crops, Nair says there is also the potential to promote them among Iowa growers and possibly to grow their representation within the state’s basket of typical cash crops. So those crops selected were broccoli, summer squash, peppers, strawberries and raspberries.

A control site has been established next to the solar array site where these crops will be grown under open-field Iowa growing conditions. Their performance will be compared to the performance of identical varieties planted in both sunny and shady micro-sites established within the solar array infrastructure.

As an expert in horticulture crop production, Nair says researchers will be interested to find out if there are instances where some crops actually perform better, for example, in a shady environment. The state has been experiencing considerable heat of late so it is possible that the shade provided by the solar panels could actually reduce stress and improve production performance of some of the crops planted. But that remains to be seen.

Beekeeping, but not animal husbandry, will be part of this four-year research initiative.  opportunity to evaluate the ability and viability of honey production inside the fences of a solar array.

Peterson says the research being done at ISU is incredibly valuable to the renewable power industry as a whole, because if it is viable, agrivoltaics could become part of much larger utility-scale arrays. Also, Alliant Energy is investigating if there are other opportunities for the inclusion of agrivoltaics on its other solar farms under development.

 

Q1 2024