Some might say there is nothing new under the sun. Active players in the practice called “agrivoltaics” would beg to differ. Typically, while solar arrays placed on a farmer’s field generate power for a community, they
also take up productive farmland. With agrivoltaics, solar arrays have a dual purpose. They play an integral role in agricultural production and expand clean power generation.
First introduced abroad, you can now find U.S. farms using solar installations, mostly hosted, to help grow crops, offer grazing habitats for livestock or provide fertile pollination fields. In this dual land usage, farmers learn about the benefits of solar power while electrical contractors and other installers are educated about agricultural practices. While most U.S. installations are pilot programs, some are commercial ventures as players in agrivoltaics emerge, conferences gain traction and professional organizations form.
Michele Boyd, strategic analysis and institutional support program manager with the Solar Energy Technologies Office of the U.S. Department of Energy (DOE), understands how agrivoltaics are being used, what’s being learned and the need for repeatable results. She sees agrivoltaics as a potential, though partial, solution to address community concerns about solar farms displacing farmland. “Farming is tough,” Boyd said. “For some farmers, having their land used for solar provides a diversified revenue stream for bad crop years or maybe just a constant stream of income, especially when leasing the land for solar array installations. With agrivoltaics, you can continue farming where the arrays reside.”
The benefits to agrivoltaics can be multiple. Boyd shared initial studies that show the practice can reduce plant irrigation needs, especially in dry areas such as the desert Southwest.
“The plants underneath the panels receive shade, keeping them cooler, and the soil moisture evaporation rate is slower,” Boyd said. “Some research has shown lower water demands. What we don’t know is how beneficial this is in every situation across climates.”
She said that the most dramatic effect has been shown in Arizona, according to an April DOE article.
“There, the crops do better and require less irrigation under solar panels. In another paper out of Minnesota, there’s benefit, but less dramatic. Applications in Massachusetts show that in drought years, the crop yield is higher underneath the solar panels,” Boyd said.
Robust programs are ongoing, including pilot projects with the U.S. Department of Agriculture (USDA), which works closely with the DOE on agrivoltaics. A recent, major program funded by the USDA is underway at the University of Illinois at Urbana-Champaign. The SCAPES (Sustainably Co-locating Agricultural and Photovoltaic Electricity Systems) project is exploring how crops and panels interact, which crops benefit most, effects on crop prices and yields and more.
“We also think that there’s an economic benefit of cooling the panel, so it performs better. Maybe taking advantage of irrigation systems,” Boyd said.
Imagining a market
Sandbox Solar, a largely residential solar firm in Fort Collins, Colo., has added agrivoltaics as a service. The 26-person firm serves Denver and northern Colorado. Ian Skor, CEO and co-founder, introduced the use of 40% transparent photovoltaic (PV) panels to agrivoltaics research with Colorado State University.
Funded by a USDA grant, the use of the semitransparent panels improved production of peppers, tomatoes, lettuce and kale beneath the arrays. Skor said traditional panels allow maybe 5% of light through.
“In a semi-arid environment like Colorado, where heat and sun toxicity can be an issue for plants, the protection of the semitransparent panels lets enough light through to maintain ideal plant photosynthesis throughout the day, but also protects the plants from heat damage and high wind. We discovered better retainment of soil moisture underneath the solar panels, so more water savings, water conservation,” he said.
Skor explained that specialty crops required more hand work and some basic tractor use.
“We were able to manually tilt the panels vertically where we could get our tractors through and service the ground and then tilt the panels back over,” he said. “With arrays in any project, once you’re running the electrical over, say, 150 feet, you get into voltage drop issues. We made sure to size the wiring correctly and kept the array supports clean.”
Byron Kominek is the owner of Jack’s Solar Garden and its accompanying development effort in Longmont, Colo. The family-owned business has more than 3,200 solar panels to create a 1.2-megawatt community solar garden—enough to power over 300 homes. Jack’s bills itself as the “largest commercially active research site for agrivoltaics in the USA.”
“Our solar array was first and foremost built to maximize energy production on our land,” Kominek said. “The interest in agrivoltaics and deployment came later.”
He said the agrivoltaics portion of the solar, which includes a driving path, switchgear and transformer metering equipment, constitutes five acres. Jack’s has partnered with the National Renewable Energy Laboratory in Golden, Colo.; Colorado State University; and the University of Arizona in the study of agrivoltaics. Jack’s also has commercial growers, namely Denver’s Sprout City Farms.
“The arrays are not height-adjustable, so we elevated our panels about 2 feet higher on two-thirds of our property and about 4 feet higher on another third,” Kominek said. “That represents 8-foot-tall arrays and 6½-foot-tall panels when they’re flat. The varied heights make weeding easier, give workers shade [and] allow you to run a tractor for planting and harvest, depending on the crop. Because the panels track the sun east to west, you need to be cognizant how the arrays are positioned and at what time of the day to allow tractor access. I have 31 rows of panels giving us plenty of time throughout the entire day to hit all of it.”
Kominek also serves as the executive director of the Colorado Agrivoltaics Learning Center, the nonprofit side of Jack’s Solar Garden, providing tours and education for students of all ages, community members and policy planners.
Different flavors of agrivoltaics
Sandbox Solar also has a commercial agrivoltaics customer, with a PV installation that shows a different way to deploy solar panels. The customer, Spring Hill Greens, based in Fort Collins, is a farm committed to producing sustainably sourced, disease-free microgreens, baby greens and baby herbs. All the plants are grown in rows of greenhouses.
Skor explained that the farm had rooftop solar panels on a research building. However, “The company doesn’t have the land space to accommodate a traditional ground-mount solar, but they wanted to achieve a 100% electricity offset,” Skor said. “So, we deployed bifacial solar panels arranged as a solar fence between greenhouses. Bifacial are dual panels; each side a solar panel. Between the solar fence and the rooftop solar, the power generated offsets 100% of the electricity for the farm.”
Skor added that each farm is unique in terms of what agrivoltaics solutions would be best.
“I think everyone’s looking for a one-size-fits-all approach right now at a lot of different scales,” he said. “The challenge for us is making a more repeatable model that is economical and scalable across many farms. It’s the mixture of sales engineering in terms of getting the best economic cost and return, but also the right design that works for the crop and the solar.”
Sandbox Solar’s SPADE Agrivoltaics design software, in its current beta version, allows the user to model any type of crop, PV configuration, climate and panel irradiance.
“It’s a tool to help users determine what crop type or what configurations would work best for them,” Skor said. “It also determines the microclimate for specific crops which is created underneath the solar panels.”
Other possible applications
Another agrivoltaics application is called solar grazing. There is an association called the American Solar Grazing Association based in Foxboro, Mass. Sheep are a preferred livestock for this application, and solar arrays offer shade and habitat for these farm animals to graze among the mounted PV—another dual use keeping farmland in play with fields that host PV arrays.
Pollinator-friendly solar is additional application. It involves creating a habitat full of native wildflowers that provide food for pollinators under and around solar arrays. Some of this habitat can develop naturally, but suppliers are developing soil mixtures that grow distinct flowers to attract bees, butterflies and other pollinators as part of this effort. The University of Vermont and others are currently studying this application.
Of note to the electrical contractor
Kominek encourages electrical contractors and engineers who get involved in agrivoltaics to understand how the design of a solar array that supports agriculture is different.
“There are three things that are important, in my opinion, for building an actual agrivoltaics ag system,” Kominek said. “One of those is wire management. To meet the 2017 National Electric Code, we put wire mesh underneath the solar panels to protect the wires from farm machinery. Part of that Code states when you’re putting your wires up and creating loops, any exposed wires need to be shaped so that water drips off the bottom edge of it. We also need to make space for livestock so they don’t get caught in the loops, or really interact with any components of the array installation. Cables are placed flush to the arrays as much as possible.”
Elevated PV and wires looped high up could resolve problems for livestock and machinery.
“Agrivoltaics is a different kind of installation,” he said.
Boyd added that benefits need to be calculated and quantified between farmer and solar provider. “Agrivoltaics is becoming commercialized,” she said. “We’re looking at how to help make this happen faster and ensure that those benefits have mechanisms for measurement to ensure success and make sure the projects are done well.”
Sandbox Solar / stock.adobe.com: hanaschwarz / Jack’s solar garden