Case Study: A Pollinator-Friendly Solar Site in Minnesota that Manages Stormwater.

By Briana Kerber, Fresh Energy

As we continue to deploy clean energy across the United States, more attention is being paid to how best to develop clean energy projects at the pace and scale that the climate crisis requires, while also ensuring that we are taking care of the sites and communities that host those projects. That’s where a national project from the National Renewable Energy Laboratory (NREL), Great Plains Institute (GPI), Fresh Energy, and the University of Minnesota comes in. Funded by the U.S. Department of Energy’s (DOE) Solar Energy Technology office, the Photovoltaic Stormwater Management Research and Testing (PV-SMaRT) project is using five existing ground-mounted photovoltaic (PV) solar sites across the United States to study stormwater infiltration and runoff at solar farms.

Jake Galzki, researcher at the University of Minnesota, measures water infiltration and runoff at Connexus Energy’s Ramsey Renewable Station site. Photo: Aaron Hanson

Together, the five sites represent a range of slopes, soil types, geographical locations, and PV configurations that will help solar developers and owners, utility companies, communities, and clean energy and climate advocates better understand how best to support solar projects and the host communities in which they are built, in particular lowering the costs of clean energy development while ensuring protection of the host community’s surface and ground waters.

On the banks of the Mississippi

With black-eyed Susan flowers dotting its expanse, the Minnesota site stands out among the five sites in the project. Situated on 18 acres of county-owned land near the Mississippi River in Ramsey, Minnesota, 30 miles northwest of the Minneapolis-St. Paul metro area, Connexus Energy’s Ramsey Renewable Station is flanked by an RV service center to its east, a highway to the north, and a specialty vegetable farm that grows pumpkins and peppers on the project’s west and south sides. Thanks to a partnership with the team at Bare Honey, a Minnesota-based honey producer, the site hosts beehives, too. The 3.4 megawatts of solar panels face south, in a two-in-portrait configuration on a fixed-mount racking system. Throughout the array, the panels are 24-36″ above the ground at the lowest edge.

Blanketed with sandy soil, the Connexus site was seeded with a pollinator-friendly vegetation mix throughout the array and open areas. And the pollinator-friendly aspect was the lynch pin in garnering community support. Pollinator experts and ecologists testified this wouldn’t be just any solar development—it would be a seasonally blooming, low-growing meadow, giving work opportunities to local seeders and apiaries as well as providing ecological benefits to the nearby crops surrounding watershed. Between the sandy soil and the ground cover, when it rains—or even pours—any excess water is channeled into the ground. And that has significant meaning for researchers, solar developers, utilities, and clean energy advocates alike.  

The Minnesota PV-SMaRT site, developed by Engie Distributed Solar for Minnesota’s Connexus Energy. Photo:Aaron Hanson


Designing solar sites for extreme weather

Part of the process of planning out or conducting analyses on clean energy developments like solar farms is to test how well the site will hold up against an extreme weather event, like a flood. Engineers and researchers utilized three different design storms, essentially model storms of various magnitudes, to test Ramsey Renewable Station’s response and evaluate rainfall and soil moisture as well as determine how fast excess water would soak into the ground.

Through these models, the PV-SMaRT research team discovered that, against three design storms—two-year frequency storm, 10-year frequency storm, and 100-year frequency storm, the most intense of the three—all stormwater was channeled into the soil by the deep-rooted vegetation. Using both an InVEST modeling framework and a 2D Hydrus water model, University of Minnesota (UMN) researchers involved in the PV-SMaRT project, including Aaron Hanson and Jake Galzki, led by UMN professor Dr. David Mulla, have been able to keep tabs on the site, monitoring data from moisture sensors and comparing numbers from the site to those of other PV-SMaRT locations.

In fact, the team found that if they wanted to observe a runoff response, they had to actually reverse engineer the site to provoke one. For example, if the team conducted a model of the site in which vegetation suffered due to heavily compacted soil, then they could observe a runoff response. But, in virtually every other scenario, the combination of the diverse, deep-rooted pollinator-friendly vegetation and sandy soil ensures that all excess water soaks directly into the ground. In the research team’s eyes, that made the Connexus Energy Ramsey site a prototype for the rest of the PV-SMaRT project.

Benefits for the site and the study

And Brian believes that those involved in stormwater permitting at solar sites can learn something from the Ramsey example. “As a result of this study, stormwater permitting at sites such as this can be predictable and transparent to both the city or county and the developer,” he says, “reducing soft costs for solar developers while ensuring good water quality outcomes for regulators and habitat co-benefits for local communities.”

Vice President of Renewable Energy at GPI, Brian Ross notes that the site is important because it serves as a sort of bookend for the project: “It is a site that requires only ground cover green infrastructure in almost any circumstances. Comparing this site to our other project sites is incredibly useful. The characteristics at play at Connexus Energy’s Ramsey solar site point toward the potential capacity of a solar farm to mitigate not only the site but also contribute to broader watershed management.”

At Connexus Energy, Rob Davis, communications lead, points out that there was an overwhelmingly positive community response to the pollinator-friendly aspects of the project. “That’s why Connexus requires pollinator-friendly ground cover for all our solar sites, and it was especially important for this project due to the location near the Mississippi River and a specialty crop grower. The site’s soil and ground cover combine to easily handle heavy rainfall events,” he says.

Jake Galzki, researcher at the University of Minnesota, inspects soil and water monitoring equipment at Connexus Energy’s Ramsey Renewable Station site. Photo:Aaron Hanson

Rob notes that when the project was built, it did not have the advantage of accurate hydrological models for PV solar projects, which resulted in a requirement for grading that included carving a two-foot bump diagonally through the project. Thanks to insights from the PV-SMaRT study, Rob is confident that policy changes can be made to avoid grading in the future, as it unnecessarily disturbs the soil and creates an uneven surface for vehicles managing a site. In its place, Rob points to the high-performance vegetation, as it requires less grading and fewer stormwater containment basins and is therefore a much better use of limited maintenance funds.

Insights yet to come

Data and observations from the Connexus Ramsey site serve as a benchmark as the PV-SMaRT research team continues to gather insight about the four other project sites across the country. Overall, the findings from the Ramsey site further validate the project’s recommended best practices in exemplifying how we can lower the soft costs of clean energy development and of ongoing maintenance while protecting the host community’s surface and ground waters, create needed habitat, sequester carbon in the soil, and help craft a truly sustainable clean energy future that will benefit everyone for generations to come. Read more about ongoing validation of this foundational research via Great Plains Institute.

A version of this article was originally published via Fresh Energy. Read it here.

Case Study: Vermont Farmers Access Clean Energy

Farmer-members of Organic Valley, a farmer-owned cooperative representing nearly 1,800 family farms, can now access renewable energy options for their operations. In Vermont, solar development company SunCommon has created a program to help Organic Valley farmers access and implement solar energy. SunCommon provides the financing and ownership options for solar array installation so that farmers have no upfront costs while offsetting their energy usage and receiving credits on their utility bills.

Photo Courtesy of SunCommon and Choiniere Family Farm

SunCommon offers a variety of system sizes, ranging from smaller systems to meet the needs of a single farm to community-scale systems that can power a farm plus 40 to 50 homes. The company has so far assisted 75 farmers in Vermont and New York implement solar energy, including the Choiniere Family Farm in Highgate, Vermont, which had farm infrastructure that they were planning to retire from production because of its depreciation. When the opportunity to install solar became available, the Choiniere family happily signed on, since the Organic Valley investment made the project low-risk. It turned out to be a good decision: the Choinieres were able to revive the barn by installing solar panels on the roof, which adds overall value, and turn the barn into a new milking parlor. SunCommon helped this family farm install panels that can produce 115,500 kWh each year, saving them $20,000 annually.

Photo Courtesy of SunCommon and Choiniere Family Farm

Organic Valley is the largest farmer-owned organic cooperative in the United States, with over 100 farmer-members in the state of Vermont. This program is currently accepting new Organic Valley farmers to participate. If you are in Vermont or New York and want to take advantage of reduced costs through solar energy generation with no upfront costs, follow this link to learn more.

Case Study: Saffron and Solar Farms

The North American Center for Saffron Research and Development is conducting a multi-year study of saffron crops grown under and adjacent to ground-mounted solar arrays. The study, which began in 2015, includes two years of field data from the iSun solar field (formerly Peak Electric) in Burlington, Vermont.

Researchers established the saffron corms in three locations within the solar field: in the aisles; directly under the solar panels; and around the perimeter of the arrays. These three locations include both raised beds and in-ground planting methods.

Saffron is a perennial crop suitable for sunny locations in arid and semi-arid regions. It is relatively resistant to cold. Yields typically increase for three years after planting, often increasing exponentially between the second and third years. Saffron is a high-value crop, with values ranging from $19-$55/gram retail. It is also a hand-harvested crop, making it well-suited for agrivoltaics.

In the first year of the field trial, the saffron yield was low, as expected for newly planted saffron corms, with a higher yield in the raised bed plots. The second year of the trial produced higher-than-average yields, with some plots producing yields three times higher –than averages. 

Highest yields occurred in the lots located in the aisle and around the perimeter of the solar panels, with yields of 17 pounds of saffron/acre, which would be equal to $192,775/acre at an average price of $25/gram. 

The plots directly under the solar panels did not show this increase in production. These plots showed a 30% decrease in yield, indicating that the area under the panels is not an ideal micro climate for saffron production. Figure 1 shows the average yield of the harvested saffron per acre during the field trial.

Figure 1. Average yield of harvested saffron per acre during 2019 and 2020. (Ghalehgolabbehbahani et al., 2022)

Research will continue at this facility and the AgriSolar Clearinghouse will plan a field trip for the public in the fall of 2022. The annual report for this study is available in the Information Library here.

Reference

Ghalehgolabbehbahani et al., 2022. Saffron and Solar Farms: A Win/Win for Environment and Agriculture. North American Center for Saffron Research and Development, Burlington VT.

Monadnock Region Community Supported Solar Case Study

The Monadnock Region Community Supported Solar project in New Hampshire is bringing together farmers, investors, and champions with a goal of helping local farms realize the potential of the renewable energy economy.

Community-supported refers to a synergistic relationship between a business and consumers. Whether it be community-supported agriculture, community-supported fishery, or community-supported solar, this business model allows consumers to have access to a good or service closer to their community, usually one that is healthier and more affordable. This model also allows the local business to have greater security in its operation and be able to spread out fixed costs, usually in the form of “shares” from the consumer.

Here’s how it works. Farmers in the Monadnock region can purchase an electricity share and become a member of the Farmer Member’s Group. Participating farms enter into an operating agreement with Community Supported Solar for Farms LLC. During the LLC phase, farmers contribute by paying for a portion of the solar array installation, and they continue to use their local utilities as usual. Upfront costs are also funded by investors, making the share payments cheaper for the farmers. Community Supported Solar for Farms LLC will work with Cheshire County Conservation District (CCCD), which serves as manager of the LLC, and investors to take ownership of the array in six years through a buyout.

After the buyout occurs, the farmers group will own the system and each share will be net metered, providing free energy to those that have a share. Net metering takes unused power from the array and sends it back to the grid for later use or for others to use. This project utilizes group net-metering, which allows multiple electric meters at different locations to be bound to one solar array. Members of group net-metering benefit from solar energy without needing a solar array on their property. Each share is equivalent to 5,000 kWh of energy. The 90-kilowatt array has been built on host-member Sun Moon Farm in Rindge, New Hampshire, which also grows and sells produce within a community-supported agriculture model.

Photo Courtesy of Sun Moon Farm, Rindge, New Hampshire

The project will realize a host of benefits. Farmers who purchase a share support renewable energy and will benefit from stable, low-cost energy, and the project’s investors benefit from earning tax credits, renewable energy certificates (REC) funds, a state rebate, and extra income on electricity sales to farmers.

CCCD and the Monadnock Sustainability Hub serve as community champions for the project. The CCCD has secured a grant through the New Hampshire Charitable Foundation that will be used, in part, for system buyout in Year 6. CCCD will host a crowdfunding initiative in February 2022 to raise additional funds to lower share costs even more for farmers.

Learn more about the Monadnock Region’s efforts at https://cheshireconservation.org/solar as well as their crowdfunding initiative at https://monadnock.thelocalcrowd.coop/campaign/community-supported-solar-for-farms/.

Helical Solar Case Study

As with most inventions, necessity drove James McKinion’s design for the Helical Solar dual axis, bifacial solar panel array. In 2016, McKinion wanted to maximize the area above cut pine trees for solar energy. However, it soon became apparent that the cost of bulldozing and clearing tree stumps was cost-prohibitive. He decided to engineer a solution.

Helical Solar installation
Courtesy of Helical Solar

He developed and patented a solar array design and received of several Small Business Innovation Research (SBIR) grants to develop a rural solar solution that could be used with agriculture while lowing electrical cost. The design included a 13-foot solar panel mount height that allowed for cattle grazing, tall crops, and mid-sized tractors. It also ensured landowners would not lose arable land. The panels rotate to follow the sun, so the shade from the panels does not require shade-tolerant crops. All cables run several feet underground, to ensure protection from animals and comply with code, and all cables above ground are encased in array. The access box consists of a heavy steel case designed to withstand an accidental tractor collision.  

McKinion also faced the complexity of anchoring solar panels with a 10- foot screw pile. The cost of an excavator with a boom tall enough to auger the anchor piles far exceeds the energy savings. To address this, he experimented with work-trucks commonly used by municipalities and rural electrical cooperatives, known as Digger Derrick trucks. He then found further cost savings when he decided to ship pre-assembled solar panels and parts to electric utility companies and train them perform the installation with existing equipment and staff.

The design also addressed another rural co-op problem: the lack of reliability among solar installation companies. For example, the Utility Board in Arkansas did not want to recommend solar installers to their constituents because many were not available for troubleshooting and support after installation. Helical’s solution allowed the utility companies to install the system while also providing an interface that would give customers real-time information about the energy being produced.

Helical now has prototypes operating in five states, with plans to update older panels. Currently, they are nine 360-watt bifacial panels in the system equaling 3.24kW. McKinnon estimates that the bifacial panels produce 10% more energy than a rooftop system and that dual-axis tracking produces an additional 35% energy production. The newer panels will be 550-watt series panels for a 4.95kW system. With the total 45% gain from the dual-axis, bifacial set-up, McKinion predicts an output that would typically be seen from a 7.6 kW system. These systems are engineered to offset the energy consumption of a typical single-family home.