Case Study: Mauntel’s Solar Sheep

Written By: Alex Delworth, Clean Energy Policy Associate; Center for Rural Affairs

Just off the campus of Maharishi University in Fairfield Iowa, sits a 1.1-megawatt (MW) solar farm. Beneath the panels, a flock of sheep and their newborn lambs are grazing, while beginning rancher Emily Mauntel and her Australian Shepherd Ziggy stand back and admire their work.

Solar farms pose a considerable opportunity for multipurpose agricultural uses in rural spaces. Iowa has seen a rapid increase in solar project development the past two years. According to the Solar Energy Industries Association, the industry is expected to add another 1,304 MW—a 250% increase over current installed capacity—during the next five years. Depending on the type of technology installed, this could mean between 6,520 and 13,040 acres of land will be used for solar production. With proper local siting, these projects will be required to plant and maintain native vegetation underneath the panels. This increase in open pasture presents a unique opportunity to combine traditional land uses with renewable energy development, such as pollinator habitats or open grazing for livestock. An opportunity Emily has already begun benefiting from.

Originally from Michigan, Emily relocated to Fairfield to attend Maharishi International University. While completing a three-month internship at a goat farm in Oregon as part of the university’s Regenerative Organic Agriculture certificate program, her interest in livestock grew. After the internship, she remained in Oregon for another year, working for various livestock operations and gaining experience in the industry. In late 2021, she moved back to Fairfield to work on the university’s vegetable farm and help her peers in their respective livestock businesses.

Emily Mauntel holding a solar-grazing lamb. Photo: Emily Mauntel

One day she and a friend were driving past a large solar array in Minnesota and noticed how the infrastructure was perfect for sheep grazing. They knew about the array in Fairfield, which is owned by the university and operated by Ideal Energy, a local solar company. She contacted the solar company to pitch the idea first and gained their approval before approaching the university. Both parties were ecstatic because the university had been looking for somebody to graze livestock and Ideal Energy saw an opportunity to avoid spending about $5,000 for annual landscaping, according to the company. Emily said the two parties came to an agreement that she would graze the array, which provided her an opportunity to access pasture in exchange for landscaping the solar farm. With this agreement, Emily benefited by not having lease payments for the time her sheep were on the farm, saving her approximately $360 per month according to Iowa State University’s land lease estimates, or about $2,520 for 2022.

Sheep grazing under solar array. Photo: Emily Mauntel

Once Emily had approval, she and her friend went into business together and purchased a 30-head herd of sheep from an auction in Texas. In May 2022, 29 ewes and one ram were dropped off on the six-acre, 1.1-MW solar farm. Before purchasing the herd, she surveyed the land and determined that, given the amount of growth on the site, she would be able to graze five sheep per acre. That is two more than usual because of how lush the plant life was on the property. The site was planted with a mix of flowering prairie species, including clover, fescue, broad-leaf plantain, and others, which served as a good food source. The sheep were allowed to roam freely throughout the solar array, something Emily said worked well. Overall, she believes rotational grazing would have been more efficient but would have required a larger investment due to the cost of a moveable fence.

Emily with her herd. Photo: Emily Mauntel

What makes this story especially interesting is that the agribusiness model directly addresses two major issues beginning farmers face—access to land and infrastructure. A 2017 survey by the National Young Farmers Coalition found that land access was the number one issue their respondents faced. Young farmers, according to the survey, are also the most inclined to rent, which makes finding land with the right infrastructure more difficult.

The Fairfield solar site’s infrastructure made the land even more attractive to Emily. She said it had sufficient fencing to hold her sheep and keep out predators. Due to the required native vegetation management, it also had plenty of food for the sheep, which means she never had to supplement food for them, except a mineral feed mix for nutrition. A water source to fill up the livestock troughs and an access road straight up to the gate also proved beneficial. Considering all of these factors, Emily was able to cut a lot of costs throughout the process.

Newly energized by the experience she has gained through solar grazers and managing her own livestock, Emily is now looking to return to the West to continue ranching. She and her business partner plan to sell their herd. Emily hopes to see the solar grazing model continue on the site, saying it has been a perfect opportunity for her to gain experience in the industry, and she believes it will be a great opportunity for the next person, as well.

Case Study: Far Niente Winery

Photo courtesy of Far Niente Winery

By Anna Richmond-Mueller, NCAT Energy Analyst

At Far Niente Winery, respecting the land and all it provides is just second nature. Since 1979, their winemakers have been coaxing award-winning wines out of the grapes grown on their Napa Valley estate, but in 2005 began embracing their role as environmental stewards through their sustainability practices related to farming, winemaking, and renewable energy generation. Located on the Martin Stelling Vineyard in Oakville, Far Niente’s floatovoltaic system is at the forefront of the winery’s commitment to those sustainable practices and ethical winemaking.  

When Far Niente decided to go solar, they faced challenges both unique and common to the agricultural world. Where many businesses may have chosen to place panels on the roof of their buildings, Far Niente’s old stone winery building is on the National Register of Historic Places, making it impossible to do so without violating regulations. Installing ground-mounted panels immediately around the heritage building was not an appealing solution either. After doing the math and realizing they would need to install over 2,000 panels to hit their energy production goal, they were faced with a tough choice: remove established cabernet sauvignon vines or get creative and take a risk. “Taking two acres out of cabernet production really hurts,” says winemaker Greg Allen. “By looking to the pond, it allowed us to maximize how many grape vines we were able to keep and still meet our goal.” These challenges ultimately culminated in the decision to build the world’s first grid-connected floating solar array, despite the lack of real-world success stories of floatovoltaic arrays at the time.  

Developed by Thompson Technology Industries and installed by SPG Solar, the ambitious project went live in April 2008. A total of 1,000 Sharp 208 polysilicon panels were installed over the vineyard’s pond, covering just shy of a full acre. The panels rest atop pontoons anchored to the pond’s banks via marine-grade cabling attached to concrete columns. This setup allows the pontoons to rise and fall with changing water levels throughout the year. Rounding out the vineyard’s solar system are 1,300 ground-mounted panels adjacent to the pond. The system was originally installed with a 500-kilowatt central inverter, but that was replaced after 10 years with 12 SolarEdge string inverters. Together at peak output, the arrays generate roughly 407 kilowatts total with about 177 kilowatts coming from the floatovoltaic system alone. 

Photo courtesy of Far Niente Winery

Unsurprisingly, building such a system comes with a substantial financial commitment. The project’s total cost was $4.2 million upon completion, with an estimated payback period of 12 to 15 years. Fortunately, the net cost for Far Niente was significantly less, thanks to a $2.80/kW self-generation cash rebate from Pacific Gas & Electric, as well as a 30% federal tax incentive and accelerated depreciation tax benefit. The winery worked with Banc of America Leasing and Capital on a seven- year lease as well, which included a buyout option that would allow them to be the sole owners of the system. Far Niente did opt to purchase the array at the end of the seven years, and reports that the system paid for itself at around year 14 of operation.  

With all the energy generated by the system, the winery is able to cover about 80% of its annual energy requirements, but that is far from the only benefit. The floatovoltaic array saves almost a full acre of viable land from being sacrificed for additional ground-mounted panels. Since this part of the vineyard is foundational to the winery’s cabernet sauvignon program, all that preserved space equates to thousands of dollars of bottled cabernet sauvignon revenue saved each year.  

Additionally, there’s reason to believe that the panels’ positioning on top of the pond leads to increased efficiency when compared to the ground-mounted panels. Greg Allen has taken the surface temperature of the panels and found that those on the floating array can measure up to 5 degrees Fahrenheit cooler than their land-based counterparts. Because photoelectric conversion improves in cooler environments, keeping the solar panels at a lower temperature will increase the energy production efficiency when compared to the warmer panels on land.  

A further boon to resource management is the array’s potential to reduce evaporation rates — a crucial win for a vineyard operating in an area seeing increasingly higher temperatures and more frequent drought conditions. While Greg notes that there is no completed study yet, he says, “In my mind, I think that the panels decrease the amount of evaporative loss from the pond.” He adds that it is difficult for the winery to quantify the potential amount of water saved, since there are systems both pulling water from and pushing water to the pond at various times. Currently, the pond serves the winery in several capacities, including as a fire- and frost-protection system, irrigation source, and as the recipient of all process wastewater from the winemaking facility. Three wells intermittently feed the pond, as well. Greg states that there is an ongoing research partnership between the winery and University of California Davis that will hopefully shed light on the shading and water conservation benefits, as well as the ecological impacts of the array.  

When reflecting on the challenges the project presented, Greg says “Interconnection [to the grid] was a big one.” In order to meet their energy production goals, the entire system needed a 500-kilowatt inverter. The winery hit a roadblock with the project when they realized the main service transformer for the winery was only half that size. Far Niente’s utility provider requires that the main service transformer must be able to accommodate 100% of the energy produced by a solar system. “That spawned a massive project of its own,” Greg says, since the winery then had to replace their transformer to match the power rating of the inverter before they could bring the array online.  

As the system approaches 15 years of use, they are noticing more individual panel failures. Greg says that the panels installed in 2007 are no longer commercially available to replace the failed panels, but there is a silver lining. He estimates around five more years of operation with their current set up, and then the winery could begin to look at the possibility of a major system overhaul. Over a decade of research and development has greatly increased the efficiency of today’s panels, providing the possibility of cutting their solar array footprint in half while maintaining the amount of energy produced on-site. “We could regain substantial amounts of vineyards,” he says. Should the winery choose to overhaul their entire system in such a way, the future revenue from the potentially recovered vineyard space could fund the cost of the improved system. 

Photo courtesy of Far Niente Winery

Looking back, Greg says a big challenge has been on the operations and maintenance side of owning the arrays. “Our main job is making and selling wine, and suddenly we’re put in the position of having to – on a daily basis – verify that the system is functioning and then initiate troubleshooting” when it’s needed. He points out that in the beginning, no one at Far Niente was an expert at what essentially became running a small power plant, but they had to develop that expertise in order to keep the system operating. With the possibility of a new system installation on the horizon, Greg speculates that partnering with a third party on a power purchase agreement could be an ideal solution for Far Niente. A power purchase agreement is an arrangement that allows a solar developer to install, operate, and own a system on a customer’s land. The customer is then able to purchase the electricity generated by the system directly from the developer, often at reduced rates. “It means that we would have on-site generation of renewable energy that we use,” he says, “and we would rely on the experts to maintain the system while we focus on growing grapes and making phenomenal wine.”  

No decisions have been made yet as to whether Far Niente will pursue upgrading their system or move towards a power purchase agreement. Regardless of what path the winery will take in the coming years, Greg says they are really pleased with their decision to pursue onsite renewable energy generation and the overall performance of the solar arrays over the years. In particular, the winery’s ownership and staff have enjoyed being pioneers in the field of floatovoltaics. Far Niente’s years of renewable energy generation serve as an excellent example of how solar energy production can support a company’s efforts to implement sustainable measures while existing in harmony with agricultural operations.

Case Study: UMass South Deerfield Pilot Project

Photo: AgriSolar Clearinghouse

The South Deerfield dual-use array is a research facility built at the University of Massachusetts (UMass) Crop and Animal Research and Education Farm. The pilot project is the result of a team leveraging private, public, and governmental resources. Designed and constructed in 2010 by Hyperion Systems, a solar development company based in Amherst, Massachusetts, the UMass South Deerfield site is the oldest example of agrivoltaics in the United States. At the time, dual-use racking was not commercially available, so the Hyperion Systems team developed a custom solution. With guidance from UMass Amherst agronomist Dr. Stephen Herbert, the team began testing shading implications using 2x4s and plywood. The initial goal was to determine ideal shade conditions to grow hay grasses below the array while maintaining flexibility for future research opportunities.

Photo: Hyperion Systems

The array is fixed-tilt and south-facing with module heights ranging from 6 to 8 feet to the leading edge. The panels are spaced at a range of 2 to 5 feet (E-W) edge to edge, which supports a wide range of crop productivity investigation under varying panel configurations.

Photo: Hyperion Systems

For the first five years of the array’s existence (2010 to 2015), the field beneath the panels was used for cattle grazing. The beef cattle enjoyed the shade provided by the modules during the warm summer months and were able to scratch against the racking posts without damaging the array. The electrical components were housed in protective conduit to ensure animal and farm labor safety. Dr. Herbert found that the grass underneath the panels, the variable group, grew 80 to 90% of the yield compared to the grasses in full sunlight, the control group. What’s more, the team found that if the modules were raised above the cattle’s head height and the structure was built beyond the minimum local building code requirements, the racking could withstand interference from large grazing animals.

Photo: Hyperion Systems

Since 2016, the array has been used for crop research. UMass South Deerfield has been a part of the NREL InSPIRE Project for three rounds (2016 to 2019, 2019 to 2022, and 2022 to 2025). Various crops have been studied during this time, primarily broccoli, bell peppers, kale, and Swiss chard. Other crops such as snap beans were grown for one season. In addition to crop trials, diverse layout configurations have also been explored. This includes growing the crops north to south and east to west directly beneath the modules, and in full sunlight between the panel rows. It’s clear from Dr. Herbert’s research that the crops under the panels benefit from the shade provided during drier growing seasons, like in 2016 and 2020, where the variable group did as well or better than the control group in full sunlight.

Photo: Hyperion Systems

The UMass South Deerfield dual-use array is a landmark project in the history of agrivoltaics in the United States. It continues to provide valuable insight into the viability of crop co-location in New England and beyond.

Photo: Hyperion Systems
Photo: Hyperion Systems

Case Study: Joe Czajkowski Farm

The Joe Czajkowski Farm project will be a commercial agrivoltaic array in Hadley, Massachusetts, set to be completed in time for the 2023 growing season. The project was developed through a partnership with Joe and Hyperion Systems, Amherst, Massachusetts, which has a long history in agrivoltaics. The farm’s dual-use array will serve as an excellent example of a medium-scale solar site that works for both the farmer and the land.

Farm owner Joe Czajkowski is a third-generation Hadley farmer. He produces on more than 400 acres across the Pioneer Valley. The farm practices both organic and conventional farming, contributing to the local food system by providing produce to institutions and retail outlets, including UMass Amherst Dining Services, Springfield Public Schools, Trader Joe’s, Whole Foods, and numerous local restaurants. Czajkowski’s produce reaches Boston almost daily, and their squash noodles can be purchased up and down the East Coast.

Czajkowski has been growing on this specific parcel for over two decades, rotating a variety of crops, including beets, broccoli, tobacco, and corn silage, among others. While the parcel is used annually, it is not one of their most productive fields. The site is set back from the roadway, has an existing farm access road, and features screening trees from neighbors. Combined, these conditions make the site an ideal space for an agrivoltaic system.

The project will consist of a 450-kW DC solar array on 2.2 acres. Comprised of 850 modules, the array will utilize single-axis tracking. Modules will be 10 feet above the ground when the modules are horizontal. These system specifications meet the Massachusetts SMART Program guidelines for agrivoltaics. The rows will be spaced 26 feet post to post, allowing for equipment to make two or three passes between the post rows, depending on the farming activity. In the first year, Czajkowski intends to grow broccoli underneath the array. He will rotate crops in the second year and plans to grow zucchini squash.

The array is part of a UMass Amherst-led research project that will assess crop productivity, soil health, and microclimatic conditions. The project has been awarded funding by the U.S. Department of Energy’s Solar Energy Technology Office. Data will be gathered by scientists from UMass and American Farmland Trust.

As an innovative business owner and farmer, Czajkowski is looking forward to the research opportunity with his alma mater UMass Amherst. The dual-use array will increase the farm’s economic viability by diversifying operations. Czajkowski is excited about the opportunity to be an energy provider for his community.

Case Study: Texas Solar Sheep  

In partnership with Lightsource BP, Texas Solar Sheep grazes over 1,800 sheep on a solar site in Deport, Texas. These sheep are grazed in groups of 50 to 75, 250 to –270, and even 500, making Texas Solar Sheep one of the largest Agrisolar grazing operations in the United States.   

All 1,800 sheep are grazed and managed on one solar site, which has 18 individual pastures. The sheep are grazed year-round on the same site. The area gets maybe one snowfall a year, which is not a huge issue for them, as the solar panels provide good protection from elements for the sheep. The farm may buy one stockpile of hay for the winter if they feel it is necessary as a precaution, but stockpiling food is not a great concern on this operation.  

No mowing duties are required on this site, thanks to responsibly managed, rotational grazing of the sheep. There are many weeds that sheep will not eat, so they must be manually removed. After some time, if those weeds can be removed from the site, then there is no need for mowing or the use of gas or diesel-operated maintenance equipment. Graziers mowed this site four times in 2021 and have not mowed at all in 2022 as of the end of September.  

J.R. Howard, owner of Texas Solar Sheep, says it is important for new graziers to know that the client of this operation is the solar site, and the grazier is providing a service to replace mowing on the site. The sheep-grazing service has been shown to provide significant benefits to the solar site, including enhancing the health of the turf, reducing runoff from rainfall, and providing crucial shade relief to both the grasses and the sheep during drought periods like those seen in 2021.  

Photo courtesy of Texas Solar Sheep

Healthy Turf Prevents Runoff 

The site has realized benefits from preventing rainfall runoff as a result of developing healthy turf. There was hardly any runoff after 3 inches of rainfall, due to the enhancement in turf quality from responsible grazing management, according to Howard. Healthy turf is a result of not overgrazing individual areas and managing proper sheep rotation. The sheep are not allowed to eat to the bare ground, resulting in what is known as a healthy turf that allows the land to capture and hold the water when it rains, resulting in less runoff and other associated issues. Howard said the land is back to looking like “normal land” and not “golf courses.” 

Shade Relief for Grasses and Sheep 

During the drought of 2021, the solar panels provided crucial shading for the grasses and the sheep. The grass between the panels that did not have shade did not do as well as the grasses that were getting shade from the panels. “The shade support really helped a lot,” Howard said.  

Sheep typically feed in the morning and then hang out in the shade during the day, which the panels provide plenty of. Unlike goats and cattle, sheep do not damage equipment by rubbing against it, climbing on it, or chewing on wires as some goats do. The sheep can be comfortable under the panels during the day with little, if any, threat of damage to equipment. 

Rotational Fencing  

One challenge that the operation has dealt with is constantly rotating the sheeps’ pasture, which needs to be consistent and on schedule. Limiting grazing to smaller areas more often, as opposed to one large area less frequently, is ideal. However, this approach requires fencing that must be moved regularly. The operation requires “cross fences” to break large blocks of land into smaller pastures. Moving fences is one of the most consistent tasks of the operation, but it is manageable.

 

Photo courtesy of Texas Solar Sheep

Breeding for Agrisolar Conditions 

The solar company allows the sheep owners to breed lambs when they want. The sheep live on the solar site from birth until they are sold or pass away. The sheep are also checked by a veterinarian at various times during their life cycle on the site. Owners breed sheep on site, to “get the ewe they want,” Howard said.  

This selective breeding process is an attempt to breed a sheep genetically superior in parasite resistance than previous generations of sheep. These sheep would be specifically resistant to parasites during the lamb phaseand the lactating ewe phases of their life, which are often when farmers struggle with parasites infecting their sheep. Due to the selective breeding process on this site, the sheep will be more resilient to the conditions they experience in Texas, which includes hot temperatures and prolonged, wet conditions. 

Although Dorper sheep, which originated in South Africa, are genetically capable of handling hot temperatures, they are being breed with Katahdin and St. Croix to enhance their genetic capabilities further—making them the most ideal sheep for agrisolar operations in these climate conditions. 

Photo courtesy of Texas Solar Sheep

What New Graziers Should Know 

New graziers should know that this is not a grazing lease with the solar company but, rather, a grazing service business. As a service business, people with sheep will have a customer that they are providing a service to. This requires graziers to spend more time on-site where they can correct issues quickly. If sheep get out of the fenced paddocks, graziers can get them back to their assigned areas quickly. Sometimes sheep pass away and need to be removed as quickly as possible. Being on-site allows for that. If sheep are sick, they can be attended to quickly. The grazier can also ensure that sheep have constant access to water.  

The solar company also benefits from having Texas Solar Sheep staff on-site regularly. “We are out there more than the solar folks, so we see issues for them, too. It has been an extra set of eyes for them on the solar equipment, so that has been a significant help for them, as well. If they see downed panels, damaged wiring, or even fires, they can report it quickly and get it taken care of,” said Howard. “There is a public eye on this stuff, so we want to make sure we are doing it right.”  

Howard stated that grazing is the future of utility-scale solar. It is important that the first few big sites get it right. With great partners like Lighthouse BP, Texas Solar Sheep has been able to scale up its operation, and is planning for larger sites for the future, meaning more sheep on more solar sites. 

Howard said the family farm had about 300 ewes and having the opportunity to partner with Lightsource BP has allowed them to have extra land to graze and scale up their operation. “We’re not a big landowner, and this allowed us to scale up a lot, to 1,800 ewes.” 

Case Study: Summit Plant Labs

Agriculture Type: Specialty greenhouse farming

Project Type: Small commercial net-metering agrivoltaic system

Project Size: 26.7kW-DC

Project Design: Solar fence structure, SolarEdge inverters, 72-cell bifacial solar panels

Location: Fort Collins, CO

Developer and Contractor: Sandbox Solar

Summit Plant Labs is a specialty crop farm using greenhouses and lab space to grow pristine crop starts, microgreens, and other specialty crops. In their greenhouses they noticed they were having detrimental edge effects where plants growing along the edges are exposed to higher sunlight, heat, and less moisture. They hired Sandbox Solar to create a strategic way to solve these issues using solar panels to create shade at the edges and generate power.

Sandbox Solar used its SPADE Agrivoltaic Design Tool to generate 3D visual renderings and irradiance simulations of the greenhouses. SPADE effectively provided the farm with the necessary information to determine the optimal design that would produce a significant amount of energy to offset their consumption while also providing effective shading tactics to solve the edge effects and improve their agricultural business.

Example output from SPADE – Agrivoltaic Design Tool

The system was installed in September 2022, led by project manager Danny Weaver. The Sandbox Solar team customized the racking system with Tamarack Solar Products and other custom-engineered products. The system is vertical with the top edge approximately 9’ high and bottom at about 28” above grade. The height is customizable, and the metal is galvanized to protect it from external elements. This bifacial solar fence was installed using concrete piers; however, rammed-steel profiles would be the preferred installation method for future projects. The vertical mounting of the panels allows for energy to be collected from the front and rear sides of the panel. The irradiant reflection of the greenhouse covering provides a boost in production during dawn and dusk. This agrivoltaic system can be applied to open fields and other applications.

The production profile is unique and ultimately could provide a means for balancing the duck curve, a name given to a typical energy demand profile throughout the day, where demand is highest in the mornings and evenings and lowest during the mid-day, giving the trend a duck-shaped appearance. Production and evaporation data is still being collected (as of October 2022).

Summit Plant Labs energy-production profile

For more details on this project, check out this video:

For more details on SPADE, visit the Sandbox Solar website:   

https://sandboxsolar.com/agrisolar-tools/

Case Study: Sandbox Solar Agrivoltaics Research Site at Colorado State University’s ARDEC South

All photos courtesy of Sandbox Solar

Agriculture Type: Specialty crop research farming

Project Type: Small commercial net metering agrivoltaic system

Project Size: 11.4kW-AC

Project Design: Solar pole mount structure, SolarEdge Inverter, 72-cell bifacial solar panels, 72-cell opaque polycrystalline solar panels, thin film 40% semi-transparent solar panels

Location: Fort Collins, CO

Developer and Contractor: Sandbox Solar

Sandbox Solar is a solar energy developer and Engineering, Procurement, and Construction (EPC) company located in Fort Collins, Colorado. The company installs over 1MW of solar annually and has conducted agrivoltaic research and development since 2018 in a joint effort with Colorado State University.

Sandbox Solar received a USDA Small Business Innovative Research Grant, Phase I. This grant funded the design and development of the novel agrivoltaic research plot located at Colorado State University’s Agricultural Research Development Education Center (ARDEC South) in Fort Collins. The system was installed in May 2019 and is comprised of repetition plots of various treatments for scientific significance. The system includes three plots of open-field control plots, three plots of 72-cell bifacial solar panels, three plots of 72-cell opaque polycrystalline solar panels, and three plots of thin film 40% semi-transparent solar panels.

What Have We Learned?

The research and development team has learned that many crops respond very well to partial shade conditions without hindering growth. The partial shade from the panels has led to increased soil moisture and decreased ambient temperature, allowing the crops to avoid heat and drought stress that they may experience in full sun conditions. Fort Collins’ semi-arid climate and intense UV radiation along the Front Range can be a challenging place for certain crops to grow.

The team is continuing to model and research various panel types and layouts. Within the next two years, they hope to find the ideal ratio of transparency to power generation. Thin-film and semi-transparent solar technologies are expanding and progressing every year, leading to new potential solutions.

How Was Last Year’s Growing Season?

The team collected a lot of data in 2021, including measurements of temperature, Photosynthetically Active Radiation (PAR), light, and soil moisture throughout the growing season. They also collected harvest data on peppers, tomatoes, lettuce, and kale. Results indicate that all of these crops performed very well in partial shade conditions.

Learn more about Sandbox Solar’s Agrivoltaic Research & Development here:

Case Study: Grafton Solar

At Grafton Solar, cattle are grazing nearby fields of squash and lettuce at the 150-year-old family operation known as Knowlton Farms. Located in Grafton, Massachusetts, this project is demonstrating how diverse agricultural production can be maintained underneath a 2MW community solar array and a 1.4MW of battery energy storage. 

BlueWave Solar developed 19 of the farm’s 300 acres for dual-use solar. The panels are elevated to 10’6” and the rows are spaced, allowing for farm machinery, livestock grazing, and crop and soil sciences to easily function within the array. Owned and operated by AES, Grafton Solar is: 1) supporting Knowlton Farms’ family tradition and viability; 2) serving as a research site trial for the U.S. Department of Energy Solar Energy Technology Office; and 3) powering local community solar subscribers. This is an extraordinary case study.

Grafton Solar is a product of innovative industry leadership and research partnerships. UMass Amherst, Solar Agricultural Services, and the American Farmland Trust have united forces to promote research and education opportunities on site. Valuable insights about soil health, micro-climatic conditions, and crop productivity will be drawn from Grafton Solar, which can inform broader efforts to co-locate specialty crops and cattle with solar in the U.S.

Landowner Paul Knowlton is especially excited about being about to return to his fields full-time now that the financial benefits of regenerative farming plus solar enhance his farm’s viability. Grafton Solar is showcasing how one solar project can create abundant and diverse benefits – inspiring industry innovation, generating critical empirical knowledge, and pioneering a new way to farm – all at once.

Below is an AES produced informational document on the Grafton Solar Site.

2022.10.03 Grafton Solar Handout_smaller fileDownload

Case Study: ENEL Green Power’s Lake Pulaski

Lake Pulaski is an agrivoltaic solar power plant site developed by Enel Green Power that spans over 68.2 acres in Buffalo, Minnesota. This site is one of 16 developed for the Aurora Distributed Solar LLC project in 2017, supporting pollinators, grazing, and an apiary. The layout consists of 34,668 panels at 315 watts each, spanning over 500 individual arrays. The total plant system size is 10.92MW (dc). Each panel has a SolTech single, horizontal axis tracker to follow the sun path and optimize production. This tracker was chosen over the more standard axis-pole trackers due to their ability to allow curves in the array installation to accommodate the rolling landscape. The developers strived to install the system with minimal land disturbance to maintain the landscape and reduce excavation, thus allowing the panels to move with the rolling hills. Panel height was design to be approximately 2.5 fee from the ground at the maximum tilt angle of 45o to allow grazing sheep to pass under without harm to sheep or panels. This sets the total height of each array at a maximum of 10 feet.

Showing how the panel height is appropriate to allow for sheep to graze under panels.
Solar tracking system with grazing sheep

The landscape is grazed once a year near the end of September for one month to reduce the need for mowing, save on labor and gas, and maintain a healthy soil chemistry. Graduate students at Temple University in Pennsylvania are conducting studies on the benefits of grazing, such as soil composition, a reduced mowing, and a reduction in spraying for weeds. Eight of the 16 Aurora project sites are grazed for research purposes. Occasional mowing is required if the area has a high-growth year. Minnesota Native Landscapes (MNL) developed the original native seed profile to help promote pollinator activity under the panels. The final seeding was completed by Westwood Professional Services. MNL also maintains the pollinator and native landscape. Bare-grounded spraying is used to kill off unwanted invasive species, such as thistle. These areas are then fenced off to prevent wildlife and sheep in the area. Soil samples are taken from sprayed and mowed areas for research. Lake Pulaski also promotes the bee population by allowing bee farmers to move their hives next to the site to help pollinate the area and grow healthier bees.

Lake Pulaski Native Landscape
Lake Pulaski Native Plant
Dustin Vanesse from Bare Honey holds up a hive panel covered in honey bees.

Lake Pulaski is not without maintenance needs. The enormity and complexity of the site requires technicians, plant experts, landscapers, and sheep farmers to ensure that the site function as designed. Enel Green Power does most of the technical maintenance, while MNL sprays and maintains the plants. The SolTech trackers require slightly more maintenance than pole trackers, and they can go offline due to storms, sheep knocking the sensors, and other natural causes. Background research is being conducted by ENEL to determine whether the tracking system is worth the extra maintenance. At the end of the site’s service life, which is typically 25 years, the developers hope to decommission the system and return the land to agriculture with richer soil than the gravel alternative and unharmed adjacent landscapes. The research from this site will help quantify the benefits that agrivoltaics can bring to both solar development and agriculture industries.

Case Study: Million Little Sunbeams

Million Little Sunbeams: Where tradition meets innovation. 

Massachusetts’ first operational dual-use solar system took root in the town of Monson, where Nate and Ania Tassinari aspired to reinvigorate their 3rd generation family farm. Designed and installed by SunBug Solar in 2020, the 250kW project, named “Million Little Sunbeams,” uses single-axis tracking technology combined with bifacial solar modules to optimize power production. But power isn’t the only priority at this site – the Tassinaris elevated the array 10 feet above ground to continue their tradition of producing hay to support Murphy Dairy Farm – their cousins next door. Million Little Sunbeams is showcasing how 1 acre of farmland can harvest the sun twice.

Nate Tassinari, Owner of the Million Little Sunbeams Solar and Hay Site

The true story about this site concerns how solar can be an integral part of farm viability. Haying isn’t easy nor incredibly profitable. Converting arable land to energy production undermines the future of farming. But innovators like Nate know it doesn’t have to be one or the other – if done right, solar can be leveraged to support farmers, rather than threaten them. Seeing the Massachusetts’ SMART program as an opportunity for revenue diversification and farmland preservation, Nate pioneered a plan to own both the solar system and the land underneath. Million Little Sunbeams does not involve a lease to a solar developer, but instead was designed to allow the Tassinari family to sell the excess energy to the surrounding community – a win for the family farm that has allowed it to stay in operation. 

Million Little Sunbeams Solar and Hay Farm in Monson

Million Little Sunbeams sets a great precedent for co-locating solar with hay. The University of Massachusetts Amherst is monitoring the hay production underneath the array, which can inform & inspire the development of similar sites in the U.S. This unique success story is exemplifying how innovation can preserve family farming tradition and enhance the value of land.