Agrivoltaics In Action: Solar Panels Help Habitats And Farms, Too

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An organized effort to stop rural solar development is still sputtering along, but the case for converting marginal farmlands into clean energy powerhouses is getting stronger. The key element is the emerging science of agrivoltaics, in which solar arrays are designed to rehabilitate disrupted soil into pollinator habitats, leading to increased yields on nearby fields. And, that’s just for starters…

The Field Of Agrivoltaics Is Growing

CleanTechnica has been spilling plenty of ink on agrivoltaics over the past few years. The fast-growing field is a step up from earlier iterations of rural solar farms, in which a simple ground cover of gravel or a monoculture of short vegetation like clover was considered an economical approach to treating the soil beneath the panels.

The cost of solar panels has plummeted since the early 2000’s, providing more leeway for solar developers to introduce new applications for the land beneath the solar panels (here’s our complete farm-to-solar archive).

We’ll get to some of the latest developments in a minute, but the first and most accessible version of agrivoltaics involves planting diverse native, pollinator-friendly species within the solar arrays.

The benefits of that approach have quickly caught the eye of eager farmland owners and solar developers, and agrivoltaics has become hugely popular in just a few short years. The growth is so substantial that solar manufacturers have begun to tailor panels and racking systems specifically for agrivoltaic development.

Where Are The Numbers?

Regardless of all the enthusiasm, the missing piece of the puzzle is hard data, and now here comes the US Department of Energy’s Argonne National Laboratory with the missing piece.

Argonne researchers have concluded  a five-year study of two agrivoltaic arrays in Minnesota, where the agrivoltiacs movement is particularly strong. They have just published the results of their study in the open access journal Environmental Research Letters.

The publication of the study results is extraordinarily timely. In a press release describing the study, Argonne takes note of the Energy Department’s Solar Futures Study, which estimates that the US will need to devote about 10 million acres of land for utility scale solar development in order to meet its 2050 decarbonization goals.

Coincidentally, practically to the hour that Argonne announced the results of its agrivoltaics study, the Biden-Harris administration announced an ambitious plan to consider opening up 22 million acres of federal public lands in the Western US for solar development.

That sounds mighty good on paper, but as the Argonne team cautions, if the goal is to restore and improve natural habitats, then previously undisturbed land is not particularly the best candidate for agrivoltaic development.

Instead, the Argonne study indicates that marginal farmland would be a better pick. That sounds pretty reasonable. After all, previously farmed land has already suffered the indignity of being stripped of biodiversity in favor of monoculture crops, complete with chemical treatments and other elements of modern industrial farming practices.

“Disturbed lands such as former agricultural fields are ideal locations to hold rows of solar panels compared to lands that have been previously undisturbed,” Argonne affirms.

Here Are The Numbers

As for the data, Argonne explains that the two solar arrays included in the study were planted with native grasses and native flowering plants near the beginning of 2018.

“From August 2018 through August 2022, the researchers conducted 358 observational surveys for flowering vegetation and insect communities. They evaluated changes in plant and insect abundance and diversity with each visit,” the lab notes, emphasizing the meticulous research that went into the study.

“The effort to obtain these data was considerable, returning to each site four times per summer to record pollinator counts,” explains study co-author Heidi Hartmann, who manages the Land Resources and Energy Policy Program of Argonne’s Environmental Sciences division.

All the technical details are available in the study under the somewhat whimsical title, “If you build it, will they come? Insect community responses to habitat establishment at solar energy facilities in Minnesota, USA.” Argonne also provides this handy summary:

“By the end of the field campaign, the team observed increases for all habitat and biodiversity metrics. There was an increase in native plant species diversity and flower abundance.

“In addition, the team observed increases in the abundance and diversity of native insect pollinators and agriculturally beneficial insects, which included honeybees, native bees, wasps, hornets, hoverflies, other flies, moths, butterflies and beetles.”

“Flowers and flowering plant species increased as well. Total insect abundance tripled, while native bees showed a 20-fold increase in numbers,” the lab added. “In an added benefit, the researchers found that pollinators from the solar sites also visited soybean flowers in adjacent crop fields, providing additional pollination services.”

Onwards And Upwards For Agrivoltaics

One key takeaway from the study is that rural solar development needs to consider whether or not agrivoltiacs can improve the environment in which native species can thrive. The answer seems pretty obvious when native habitats are restored to former farmlands, but other examples may not be as clear-cut.

Nevertheless, former mines and other former energy-producing sites can offer additional opportunities for agrivoltaic arrays. One particularly interesting example of agrivoltaics at work on former energy-producing sites is an agrivoltaic prairie restoration project under way at a former nuclear energy site in California.

Still, the Argonne lab anticipates that all else being equal, about 80% of ground-mounted solar development in the coming years could take place on farmland. That makes it all the more important to come up with agrivoltaic solutions.

As the lab sees it, devoting marginal farmland to agrivoltaic development can help improve yields at nearby prime farmland, by nurturing strong colonies of pollinators. That could offset any loss in yields from land devoted to solar arrays.

That’s all well and good, but the field of agrivoltaics is rapidly evolving to permit actual farming to take place within the solar arrays, making the whole issue moot.

A couple of examples to cross the CleanTechnica radar are tiltable solar panels that enable heavy farm machinery to pass between rows, and vertical solar panels that double as fencing.

Agrivoltaics could also have the potential to sustain entire agricultural sectors. Massachusetts, for example, is leaning on solar panels to help preserve its beleaguered cranberry industry.

Another interesting example is Vermont, where researchers are exploring the use of agrivoltaics to promote saffron cultivation, in an effort to provide small farmers with a high-value crop while gaining revenue from solar arrays, too.

As for the opposition to rural solar development, we wonder where all these people were when valuable farmland was, and continues to be, permanently taken out of cultivation by sprawling housing developments, corporate parks, fulfillment centers and other forms of non-farm activity.

Just saying.

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Photo (cropped): “A monarch caterpillar on a common milkweed leaf” at a solar array in Minnesota, courtesy of Argonne National Laboratory by Lee Walston.