Prairie Solar

Instead of using gravel or turf grass under and around solar arrays, prairie solar establishes ground cover with a diverse array of long-lasting native and perennial plants. This approach is also known as “pollinator-friendly solar” (PFS) and makes a big difference as solar projects grow. To reflect the broader benefits from such prairie restoration, we refer to this mainly as “prairie solar.”

Pollinator populations have experienced alarming declines for years, which is a source of public and agricultural concern. When solar farm fields are carefully planted to consistently provide blooms across the seasons they attract pollinators of all types including native bee species, honey bees, butterflies and hummingbirds and enable them to survive and thrive. The ground cover provides many other benefits, as well.

Perennial plants establish deep root systems which not only hold soils in place and increase water infiltration, but allow the plants to re-sprout each year. They also drop seeds that germinate new plants. As a result, they are largely self-sustaining and there is no cost for annual plantings.

Experts recommend using prairie plants native to the region as these are best adapted and integrate better with the local ecosystem. You can learn more about native plants here.

The potential contribution for increased pollinator habitat is substantial with thousands of new acres of solar development on the horizon. This can be done while reducing costs and environmental impacts and benefiting local communities and farms.

Cooperatives Lead Pollinator-Friendly Solar

Rural electric cooperatives are leading the way in pollinator-friendly solar in the United States, but it has been deployed in Europe for years. The first known U.S. prairie solar project was by Minnesota’s largest electric cooperative, Connexus Energy, installing PFS at their headquarters for their first solar project in 2014.

Since then, the concept has become increasingly popular with cooperatives and now is taking off across the country. Cooperatives, in particular, adopt pollinator-friendly solar because it serves the cooperative principle of “Concern for Community,” which is reflected in prairie solar and in the many other benefits of prairie restoration.

Prairie Restorations, Inc. has been a leader in restoring prairies since 1970 and has led the way throughout the growth of this concept. ELPC visited with Prairie Restorations staff at their headquarters and learned directly from them how they approach prairie solar (see the video section for more).

Ron Bowen founded Prairie Restorations, Inc in 1970 to restore land to native, pre-European settlement habitat, and is President of Prairie Restorations, Inc. He captured the unique moment for prairie solar:

“We’re talking about thousands of acres across the country that can provide energy and electricity – that’s fabulous. But, it can also provide habitat for pollinators and of course pollinators can have widespread benefits. So we have a great opportunity for a win-win here, let’s go, let’s do this, let’s not miss the boat, we need to, we really need to make it happen.”

See the video section for interviews and expertise.

Prairie Restoration: A Proven Concept

The restoration of land back to native habitat is a well-established practice, dating back to the first known restoration project at the Curtis Prairie in Madison, Wisconsin in 1934. Since then, thousands of acres of prairie have been restored in multiple states. Prairie restoration has developed as a beneficial business practice over the past 40 years as firms have gained comprehensive knowledge and experience in successfully restoring native plant communities.

The very market forces that drive their business growth (soil and water conservation, ecological values, pollinator protection) provide practical appeal to local neighbors of solar farms. Fortunately, solar farm developers have several mature and successful businesses available to assist them when choosing native landscapes over less sustainable options.

Pollinator-friendly solar offers the chance to become even more efficient and productive by combining two established practices: solar power and prairie restoration.

Solar Beekeeping

Another quickly growing practice is to add beekeeping to solar farms with blooming prairies. Bee populations can better survive when there is more abundant habitat that is free of pesticides. This is a further example of how solar and agriculture can coexist successfully and beneficially on the same site.

Establishing Prairie Solar

Establishing pollinator-friendly ground cover that will last over time requires consulting with prairie restoration experts. It is important that the plantings be properly planned to establish the new plants successfully. Prairie restoration experts evaluate the site and vicinity, test soils, select plants and carry out the establishment plantings, subsequent plantings and check-ups.

Mike Evenocheck, Director of Sales & Marketing for Prairie Restorations stresses that the first two to three years of pollinator field establishment require the most work:

“During the first couple years these plants really focus on the below ground growth working on the root systems. During that time period you can have a lot of weeds move in, pioneering species that tend to want to take over and crowd out the prairie that’s developing. So, we employ a variety of techniques to control those weeds. Namely, the first growing season, it’s mowing — coming to the site about three times a year.”

Evenocheck explained that higher maintenance activities end in the third or fourth years when the field is mature and can out-compete weeds and invasive plants. Then, “the maintenance needs start to wane.” At the same time, solar developers operate on tight schedules; they need to build the solar facilities and get them fully operational, including effective ground cover, without delay prior to project commissioning. Fortunately, the process to establish pollinator-friendly solar integrates well with solar site development.

Evenocheck explains how the solar array construction and prairie establishment can proceed together on-schedule: “The challenge with these native landscapes is they’re not instantaneous. That’s why we put down annual crops to stabilize the soil and provide quick ground cover while the native roots take hold.”

Pollinator Solar Standards

Establishing native and flowering vegetation has broad public appeal, but it’s important that “pollinator-friendly solar” lives up to its name. While many sites are carefully cultivated, others might be established on the cheap with an eye toward the short-run, providing little or no pollinator benefit.

The degree of benefit to pollinator populations from a given site varies due to a number of site characteristics including plant mix, pesticide use on adjacent fields and the amount of flowering throughout the year.

To maintain credibility and confidence in the pollinator-friendly solar concept, a number of states have established voluntary standards and scoring for pollinator habitat. University entomologists (“bug experts”) develop scoring systems and sites must pass a certain score threshold to attain pollinator-friendly status.  An example of the Minnesota scorecard can be found here. This approach ensures that any solar development claiming that it is pollinator-friendly actually delivers the benefits it promises, and avoids “greenwashing” (making false claims to gain environmental credibility).

Other approaches are possible; Stearns County in Minnesota now goes beyond scoring and standards to require wildflowers and native grasses be planted on solar farms to provide pollinator habitat.

Farm-Friendly Solar Builds Community Acceptance

Land use choices, such as development of utility-scale solar, affect local communities and foster much discussion. Often, solar farms require local or state permitting where the public gets an opportunity to see the plans and to comment on them. As the solar farms introduce a change to the local landscape they tend to attract local interest and, at times, opposition.

Farm-friendly solar strategies increase local acceptance of new projects by integrating the solar farm into the landscape in ways that bring multiple benefits and complement other land uses.

The addition of pollinator-friendly fields which are often pleasing to the eye, or bucolic solar pastures which provide local farmers income opportunities, can build local support and confidence that the facility is being built with respect for the community.

Collen Hollinger of Prairie Restorations, Inc. works on planning native landscaping in solar projects and has seen first-hand the effect of pollinator fields on local acceptance:

“A solar array is really a great neighbor. Once it’s installed, and that can take three months, …, you’ve got these panels and they are silent and then you have underneath it this beautiful example of native habitat. In much of the Midwest, 98% of our original prairie has been replaced by agriculture. We’re now creating a patchwork quilt of pollinator habitat among these many solar arrays, and we don’t yet know or realize the tremendous impact we’ll have. It’s likely to be transformational.”

Cost Comparisons

The selection of ground cover for a solar farm has a number of effects on the costs for project construction, maintenance and the land’s legacy value after the solar project. Prairie solar fields differ from traditional land cover like turf or gravel and affect a variety of costs, both directly and indirectly.

Cost comparisons should reflect lower maintenance costs after the first 3 years. Typically in the third or fourth year above ground growth overtakes weeds, reducing costs for mowing and weed suppression substantially. To avoid delay in completing the solar array installation, short-lived annual crops are also planted in the first years to establish ground cover for the site.

Maintenance costs such as mowing are significantly reduced after the third year for solar farms with native prairie vegetation. After three years the roots of prairie plants grow deep into the earth, some over six feet, supporting the above-ground portion of the plant to flourish and out-compete other plants. As an additional benefit, reduced mowing reduces dust buildup on panels, which lowers maintenance costs even further.

Plants with deep root systems allow water to infiltrate at a greater rate than with either gravel or turf grass. This provides a more economical alternative to other stormwater management costs for the site, such as creating basins or drainage channels, addressed in more detail in this section.

Fields planted with flowering prairie plants or forage for livestock grazing (solar pastures) also provide a more appealing aesthetic for passersby. When the view of farm fields changes from row crops to fields of solar panels, this can result in community opposition. Incorporating blooming prairie plantings however, can help reduce this opposition which can otherwise cause delays and raise development costs. In fact, it can even generate support for a solar farm!

Site permitting and preparation costs for solar pollinator habitat are often lower than traditional site development strategies. The largest cost reductions come from avoided grading and soil screening.