Case Study: University of Delaware Agrisolar Research 

As we strive for climate change solutions, competition over land for food production or clean energy production is an emerging challenge to address this challenge, demonstrations of systems that produce energy and food on the same land are needed to usher in solution-scale adoption of these practices. A new research project at the University of Delaware (UD) will study the results of growing food crops underneath uniquely designed PV solar arrays. SolAgra Corporation will oversee the installation of two solar arrays at the UD Newark and Georgetown campuses. Once built, these sites will have the potential to demonstrate just how symbiotic solar energy and agricultural production can be. 

Professors Steven Hegedus, UD Department of Electrical and Computer Engineering, Gordon Johnson of the Plant and Soil Sciences Department, and Emmalea Ernest, Agriculture Program Leader, will work with their students to investigate the potential benefits to food crops grown beneath the PV arrays. All the preliminary engineering studies for the project are completed and approved, and construction is on track to be completed by the start of the growing season in April 2024. UD will fund the installation of the solar arrays and the initial crop plantings underneath. Further funding from the US Department of Agriculture and the US Department of Energy is being pursued to sustain a multiyear study of the sites. 

Barry Sgarrella, founder and CEO of SolAgra, said he developed the raised solar platform that will be used in the UD project to “help farm families be more profitable and to slow the trend of farmland being consumed by commercial development.” The SolAgra Farming Array™ will consist of elevated array segments with 15.5 feet of clearance to accommodate the tallest agricultural equipment. The racking will be assembled and the solar panels installed at ground level and then hinged into an upright position. 

 The panels will track the sun to increase energy production by as much as 15% and, when needed, they can be rotated so the panel edge is perpendicular to the sun to allow the maximum amount of sunlight to hit the crops below, a function Sgarrella calls CounterTracking™. This, coupled with the unique ability to shift the entire array east or west, called DynamicShifting™, will deliver varying degrees of sunlight or shade to crops planted below as needed. The rows of solar modules will be installed on 11.25-foot centers, a relatively dense panel row spacing for agrisolar cropping applications.  

Dynamic Shifting allows the entire array to move side to side for the least amount of shading possible.

Each array segment will be 35 by 45 feet and is designed to hold enough solar panels to produce 17 kW of electricity. The array segments will be modular and can be scaled up to much larger size arrays. Each research site at the UD project will contain two array segments totaling 68 kW of installed solar panels. The two systems will be identical except that the array installed on the Newark campus will house bifacial solar panels to study how much electric production can be gained from light reflecting off the crops and ground back to the underside of the panels. Sgarrella stated that the cost to install a segment is comparable to other raised-platform solar arrays of the same size, and costs would decrease for larger installations as economy of scale is achieved.  

According to Professor Hegedus, part of the research will involve looking at crop production at different shading levels. Photo saturation is the point at which plants cannot efficiently utilize more sunlight in the photosynthesis process and once the crops are at that point, it makes sense to utilize the light for energy production. The crops that will be included in this study are strawberries, tomatoes, peppers, and lettuce and were chosen because of their high market value. The flexibility of the SolAgra Farming Array™ design will allow the researchers, through controls on their smart phone or tablet, to provide full sun, full shade, or anything in between based on individual crop needs. The results can then be used to help develop shading schedule algorithms that can control the system for different crops. 

Sensors will be used to measure direct and diffuse illumination under the panels, soil and air temperatures, humidity, and crop temperatures to start quantifying crop benefits. It’s expected that the soil in the shade of the panels will retain moisture and that the crops will require less irrigation, which has been shown as a benefit of agrivoltaic cropping systems in other research.  

The researchers will also orient the panels horizontally to test the system’s ability to protect crops from severe weather like rain or hale. Even in this horizontal “umbrella” position, the panels will be able to produce 80% of their rated power. The benefits of protecting crops from damaging hail and heavy rain are evident, but many crops could benefit from the protection and shade control this system could offer. For example, this system could protect against sunscald, which can affect most crops in the right conditions and render them unmarketable. And, if grape growers could control sun levels, they could affect the acidity and sugar levels of the grape, which is very important in wine production. Many crops could benefit if growers could protect them with a solar panel covering, especially as weather conditions become more extreme. 

An umbrella effect is created when the solar panels are placed in a horizontal position and shifted over the top of each crop row.

Professor Hegedus believes that one of the biggest indirect benefits of proving this type of agrisolar system is that opposition to large solar installations on farmland might dissipate once neighbors realize that farming is not being replaced by solar panels but rather augmenting with an additional layer of income. He said, “farming is just carbon-based solar energy so now we’re combining two different ways of harvesting that energy.”  

The project’s researchers will be challenged by the quantity of data gathered from multiple sensors over a nine-month growing season at two locations. Advanced data analytic techniques will be necessary to organize and effectively interpret all the information. Future work will utilize the results from the study to form shading schedules that are tuned to each geographic and climate region to accommodate sun angle changes and local weather conditions so that the technology can be effectively utilized by farmers. 

In the face of climate change, well-designed agrisolar systems may give farmers a better chance to stay in business. Having the ability to protect crops and to control the shade levels could optimize production while at the same time producing revenue from solar power production, keeping farmland in production and profitable. Applications of this technology will be studied at UD in the coming years over the course of this project.  

Photos courtesy of Solagra.

Case Study: Hawai’i Agriculture Research Center

Crops growing under solar panels at the Hawai’i Agriculture Research Center. 

By Anna Richmond-Mueller, NCAT Energy Analyst  

In Mililani, Hawai’i, a one-acre agrivoltaic research and development site run by the Hawai’i Agriculture Research Center (HARC) is working to grow fruits and vegetables for their community, while also discovering which crops grow best locally in an agrivoltaic setting. This agrisolar project is just one of many ways HARC has been working to foster and improve agribusiness in Hawai’i for over 125 years. The overarching goal of the project is to determine how to develop novel agricultural production systems for replication at commercial scale, while simultaneously increasing the productivity and profitability of agrivoltaic sites in Hawai’i.  

Nestled within a larger 230-acre solar system consisting of bifacial auto-tracking panels, the site is a collaboration between HARC, Longroad Energy, AES Corporation, and Clearway Energy Group, which owns the array. HARC researchers believe that agrivoltaic projects require research and development in the local environment to determine optimal infrastructure design, crop selection, and agronomic practices. With this in mind, agricultural construction and environmental monitoring began on-site in 2021. 

By June 2022, preparation for the first planting of crops underneath the panels began. Researchers treated the area for weeds, disked compost into the soil, and installed four lines of dripline irrigation in each raised bed. A total of eight 180-foot beds were constructed, containing 14 different crops for initial trialing: radish, daikon, melons, kabocha squash, broccoli, cauliflower, bush beans, eggplant, poha berries, bunching onion, lavender, strawberries, sweet potato, and dryland taro. While most of the plants were successfully cultivated, researchers considered the 2022 growing season to be a screening process that allowed them to choose which crops they will plant on a larger scale in the coming years.  

In addition to the in-ground plantings, hydroponic lettuce trials were also conducted in four commercial-scale troughs between the rows of solar panels. Five lettuce varieties were chosen based on what is most popular in commercial markets in Hawai’i . By December 2022, eight cycles had been harvested and yield data collected for detailed analysis as part of an ongoing graduate school thesis project at the University of Hawai’i .  

Agrivoltaic projects like this have the potential to help meet both energy and food production needs for the state, while simultaneously optimizing land resources. HARC has successfully demonstrated that agricultural activities can be conducted on solar sites with minimal impact to existing operations and will hopefully expand their research beyond a single acre plot in the coming years.  

Photo courtesy of Hawai’i Agriculture Research Center. 

Case Study: Colorado State University Rooftop Agrivoltaics 

A variety of chile pepper plants grow under solar panels on the roof of Colorado State University Spur campus.

Written for the AgriSolar Clearinghouse by Allison Jackson, Colorado Agrivoltaic Learning Center

Sitting atop the brand-new Hydro Building at Colorado State University’s Spur campus is one of the world’s first agrivoltaic rooftops. The 46-kW array is a southeast-facing fixed array. Half of the array has monofacial monocrystalline panels, while the other half has bifacial panels. The roof’s infrastructure was completed in April of 2023 followed by crop planting later that month. Dr. Jennifer Bousselot is an assistant professor of Horticulture and Landscape Architecture at Colorado State University and the lead researcher for the rooftop agrivoltaics site. There are a variety of experimental plots planted under each panel type, along with a control plot in the open sun, which includes performance experiments on chile peppers, medicinal herbs, leafy greens, and sown meadow plots.  

Dr. Jennifer Bouselot showcasing the sown meadow garden on the CSU:Spur Terra building.

Being situated on a rooftop comes with even more challenges than a typical agrivoltaic site. The wind loads on a roof make it challenging to install a tracking system, and the solar array requires membrane penetrations at every post or a ballast system under the soil substrate to ensure that the panels are secure. Irrigation is also trickier as green roofs have a well-drained substrate. This makes drip irrigation ineffective as water moves too quickly through the substrate profile for roots to absorb the water. The costs to locate agrivoltaics systems on rooftops is substantially increased due to higher engineering costs and the difficulties of moving and installing all the materials high in the air. 

Medicinal herb and chile pepper experimental plots under the monofacial solar panels.  

It is obviously early days for this agrivoltaics site, but some differences were already evident. Based on measurements, available light was higher under the monofacial panels than under the bifacial panels. In the chile pepper experiment, the agrivoltaic plants had reduction in chlorophyll concentration (due to less light), but also a reduction in stomatal conductance (a proxy for water use). The chile pepper plant height was also affected; the plants were up to 5 cm shorter in the open sun as compared to under the panels. The same also held true for the leafy green experiment, —the leafy greens (like kale, chard, arugula, spinach, and lettuce) under the solar panels were larger as compared to the full sun. The plants in the shade reached higher and created larger leaves to collect the necessary amount of sunlight.  

Chamomile plants in agrivoltaics system (left) versus full sun application (right).

The flowering of the medicinal herb plants seemed to be delayed for the agrivoltaic plants as opposed to the full sun plants, as seen in the photo above. On the positive side, the pigment content (a measure of potency) of the herbs was slightly higher in the agrivoltaic plants. It is only partially through the first growing season, with still more data collection to be completed, but it is interesting to note some of the early results.  

Incorporating agrivoltaics on rooftops presents an innovative synergy of renewable energy and sustainable agriculture. These sites can make urban spaces not just consumers of resources, but also active contributors to both energy and agricultural production. By harnessing the power of the sun through solar panels while simultaneously cultivating edible and useful plants, this innovative approach can maximize land utilization, reduce urban heat island effects, and foster local food production.  

Photos courtesy of Allison Jackson, Colorado Agrivoltaic Learning Center.

Chiktopia: Solar Grazing with Automated Chicken Coops 

By Allen Puckett, NCAT Technical Writer 

August 2023 

In Ballground, Georgia, Jeffrey Whitmire and Chris Ayers, owners and operators of Chiktopia, are making use of an innovative solar technology that allows them to automate pastured poultry production while also practicing regenerative agriculture. Whitmire and Ayers, both students at the University of Georgia, produce and use fully automated solar-powered chicken coops on their operation, which they also sell to other farmers. In addition, Chicktopia provides regenerative grazing services to farmers. 

These solar-powered chicken coops assist in building the topsoil (regenerative agriculture) using chickens. The self-moving, automated chicken coops makes spreading manure and flock rotations much easier for farmers and results in healthier soil with a higher level of organic matter. Chiktopia suggests that automated equipment such as these solar chicken coops are mandatory for regenerative agriculture in the future.  

“At Chiktopia we believe sustainable farming practices are not only what are best for the planet but are also what create the happiest animals and the healthiest food. We help farmers minimize labor and maximize management. 

Our automated chicken coops use renewable energy systems, which automate the majority of the labor in the pastured-poultry process. Whether it be for broilers or egg-layers our coop will help save you time and labor.” – Chiktopia 

Chiktopia aims to help build a more resilient food system across the United States using pasture-raised poultry, says Whitmire. 

The Regenerative Process 

If a farmer wants a section of land to be converted into a regenerative crop farm, Chiktopia provides that service and process. The first step in the process is to put egg-laying hens on the land in the mobile, solar-powered coops. Once the hens are rotated through the whole pasture, dairy cows are then put on the land to spread more manure. This last step of the grazing process allows the soil to sustain more vegetation through increased microbe quality and carbon sequestration. This improvement in soil health is known as regenerative grazing.  

Traditional Chicken Coops 

A traditional chicken coop is made of steel and must be manually lifted or moved using a handle or trailer hitch on one end. This requires much more manual labor than having an automated coop. Moving these traditional coops causes the pasture to be damaged when chickens spend too much time in one spot. The mobility of the new solar-powered coop keeps the chickens from destroying the pasture and allows the organic matter in the soil to regenerate. 

Solar-Powered Chicken Coops 

The solar-powered chicken coops are equipped with an automated temperature-control system, automated chicken feeder, sun-tracking solar array system, automated pressurized watering system, automated egg collector, and even heat lamps for young chicks. These coops have a traditional hitch for farmers who might prefer moving the coop with ATVs or trucks, but they can also be easily moved with a handheld remote control. 

When the coop moves, the birds don’t seem to mind at all. On the outside of the coup is an electrified perimeter fence that keeps the chickens in and predators out. When the hens are first put on a specific site, they spend a couple days in the coop getting comfortable with the new location, says Whitmire. They are then let out of the coop into the fencing area where they can roam. 

The floor of the mobile coop is lined with plastic netting that allows the bird manure to fall to the pasture below. Feeders are aligned on the two sides of the coop above the netting where the birds tend to spend most of their time. When they aren’t feeding, there is a ladder in the center of the coop that allows the birds to get up near the ceiling and roost on installments designed for chicken roosting.  

These automated, solar-powered chicken coops are available to order on  Chiktopia’s website. Depending on the needs of the farmer and the design of the coop, costs can vary, ranging from $8,000 to $20,000. One coop created by Chiktopia houses up to 400 birds. 

Predation Prevention and Shelter  

These coops provide effective predation prevention. The sturdy cover provided by the coop protects hens from hawks and other predatory birds when they are inside. The coop’s design also reliably provides protection from harsh weather and other conditions that may make the birds uncomfortable or unsafe. 

“We keep our birds protected through using strong materials on the coop and an electrified fence. Solar panels also reflect light at raptors.” – Chiktopia  

Future Improvements 

Chiktopia plans to make improvements to their coops, including a rainwater diverter that puts water directly into the watering tank that will be available to the chickens.  

“Our birds have never been happier, and collecting eggs has never been easier! Daily movements are easy because the coop moves itself.” We were not able to move our birds on pasture before we had an automated Chiktopia coop.” – Chiktopia customer 

Battlefield Lavender Farm: Solar Powered Processing

By Chris Lent, NCAT Agriculture Specialist

The concept of agrisolar—the use of land for solar electric and agricultural production—is becoming a popular idea. It captivates the imagination to think of the many ways we can use a limited land base to produce…

Read more

Shaker Village of Pleasant Hill Solar Grazing in Kentucky 

By Allen Puckett, NCAT Technical Writer

In Harrodsburg, Kentucky, a flock of sheep is successfully grazing on a solar array at the E.W. Brown Farm, thanks to a collaboration between Shaker Village of Pleasant Hill and LG&E. This operation is Kentucky’s largest solar farm, consisting of 44,000 solar panels on 50 acres.  

Shaker Village’s flock grew from 125 Shetland sheep to more than 200 sheep—with 15 ram and ewe lambs born in Spring 2023, and more expected in the near future.  Of these 200 sheep, more than 50 moved to the Brown Solar facility in April of 2023. 

Photo credit: LG&E

Utilizing sheep on the solar array is not only more environmentally friendly, but it will also save the company and its customers money in the long-term by offsetting the cost of using traditional (gas-powered) lawn mowers. Managing vegetation with sheep is also safer than using traditional mowers and weed eaters beneath and around solar panels, according to the E.W. Brown farm. 

“By using sheep to graze what is Kentucky’s largest solar farm, instead of lawn mowers, we’re being more environmentally friendly and holding down maintenance costs for our customers,” said Aron Patrick, director, Research and Development. “What started as a research project is laying the foundation for sustainably integrating more solar generation into our portfolio, and we hope the unique way we’re managing it can be a model for solar sites around the world.” – https://lge-ku.com/sheep  

Photo credit: The Harrodsburg Herald

Shaker Hill uses Shetland sheep, a heritage breed, on the E.W. Brown solar site. This breed originates from the highlands of Scotland and was common in the 19th century when the Shakers occupied the Pleasant Hill area. This allows Shaker Hill to connect their farm story directly to the Shaker’s agricultural history. Also, importantly, Shetlands are a smaller breed of sheep, and their size allows them to access the hard-to-reach areas of the solar arrays, whereas a larger breed might not be as efficient in maintaining vegetation growth. Shetlands are also known for their resilience in poor forage conditions, long life span and natural lambing ability.  

“We’re happy to provide a green and sustainable way to help care for our neighbor’s land,” said Shaker Village farm manager Michael Moore. “Our farm gravitates toward heritage breeds, like Shetlands, that were raised by the Shakers of Pleasant Hill. This allows us to connect our farm story directly to the agricultural history of this region.” 

The 50 sheep moved to the site in April 2023 will graze throughout the spring, summer and fall, and then they will be transported back to the Shaker Village Farm for the winter months.  

Photo credit: LEX Today

There are also two Anatolian Pyrenees cross-bred dogs on-site that aid in protecting the sheep from predators. The guardian dogs live with and provide protection to the flock year-round. The team at Shaker Village manages the daily care of the dogs. 

The successful partnership between Shaker Village, LG&E has inspired the launch of the children’s book, Levi the Lamb’s Big Day. The book follows a sheep named Levi as he grazes a solar facility. The book was written by LG&E and KU manager of Technology Research and Analysis, Aaron Carter, and is available for purchase online or at the Shaker Village Gift Shop. 

Photo credit: WDRB

Shaker Village also has a “ewe tube” camera, where people can watch a live feed of the solar array. You can watch the sheep graze the facility here.  

Case Study: Winston Cone Optics and Dairy Processing 

Winston Cone Optics’ installed pilot system on the roof of a dairy barn in California.

By Anna Richmond-Mueller, NCAT Energy Analyst

Thanks to the increase of solar photovoltaic sites in recent years, agrivoltaics has started to work its way into the public eye as a means of bridging the gap between land use for agricultural and energy production. By co-locating energy production with sustainable agriculture, the land that solar arrays occupy can continue to produce crops, provide forage for grazing animals, or even serve as a pollinator habitat for bees. Beyond photovoltaics, the broader umbrella of “agrisolar” also encompasses concentrated solar-thermal power (CSP), which can help decarbonize the agricultural processing space. Winston Cone Optics (WCO) in Merced, California, is at the forefront of this effort, helping dairy farmers reduce their propane consumption by using CSP to heat water for equipment sterilization.  

WCO’s CSP system was developed at University of California, Merced under the guidance of Dr. Roland Winston. The technology utilizes nonimaging optics, which allows the system to function in a stationary position. Compared to photovoltaic tracking systems – which adjust the solar panel’s angle throughout the day to follow the path of the sun – WCO’s system requires less upkeep and fewer parts, while simultaneously achieving 50 to 60% efficiency. The solar collectors pair nonimaging reflectors with evacuated tube receivers. These receiver tubes house a selectively coated fin that absorbs the concentrated thermal energy. As the fin increases in temperature, pressurized water is circulated through the tube and into a heat exchanger where the hot water can be passed into the hot water system. 

Schematic drawing of the dairy’s system. 

When WCO was looking for a pilot site, they learned of a local dairy building a fully automated freestall barn just down the road from their headquarters. They reached out to the farmer and offered to install their system in an effort to cut down the farm’s propane costs. Funding from California Energy Commission helped finance the project, which totaled around $50,000 not including labor. In October 2022, a 91-square-meter array mounted on the roof of the barn began pre-heating water for milking equipment sterilization. The system preheats 1,000 gallons of well water from 70 to 180 degrees Fahrenheit each day and collects it for use at any time in a hot water storage tank. It integrates seamlessly into the existing propane-fueled heating system, which now acts as a backup system to heat the water on cloudy days when the solar system can’t fully handle the demand. The system’s cost per kilowatt is almost half of what the farmer currently pays for propane, and it has reduced on-farm consumption for water heating by 70%. 

Close-up of the concentrated solar system on the barn roof. 

As farmers continue to search for ways to lower their operating costs and decrease their reliance on fossil fuels, WCO’s robust and uncomplicated system is an attractive solution showing great promise. The team emphasizes the adaptability of the system, as the modular collectors can easily be scaled up or down to meet the needs of a wide variety of processes. The modules are able to be installed on both flat and angled surfaces, making them easy to place on almost any rooftop and avoid taking up valuable ground space. The installation time is also impressively quick. The team first recommends conducting a thermal energy audit to ensure the building is properly insulated, followed by a period of time tracking the energy needs of the building’s current system. Once an understanding of the energy load has been established, the team knows how to size the CSP system properly for the process’s demands. Then, it may take as little as a few weeks to install the new system. Looking forward, the WCO team is excited to continue their work in the dairy space and hopes to expand their portfolio of sites across a variety of farms both big and small.  

Photos courtesy of: Winston Cone Optics 

Solar Shepherd in Massachusetts: Solar Grazing 

By Allen Puckett, NCAT Technical Writer 

July 2023 

The Solar Shepherd provides grazing services in Brookfield, Massachusetts, with 75 sheep that graze a solar array site owned by SWEB Development, a European clean energy firm. This beneficial partnership was born when SWEB reached out to Solar Shepherd for grazing services after seeing their solar-grazing sites on social media. Learn more about the partnership in the AgriSolar Clearinghouse’s video How a Shepherd and Solar Developer are Joining Forces to Grow Sheep, Clean Energy. 

Solar Shepherd’s founder and owner Dan Finnegan is a third- generation sheep farmer in eastern Massachusetts. His history working in a corporate environment led him to think more about what was important to him—the land, local farming, and clean energy. While he likes raising sheep, there wasn’t enough acreage for it to be profitable without agrisolar sites. 

“It wouldn’t be enough to produce a living for a family,” he said. “This is more than a hobby-farming operation. With solar grazing, we dramatically expand our flock. We work hard to be competitive with landscapers on these sites. The grazing fees mitigate the costs and pay down the investment to take the show on the road (transporting sheep to solar sites). We’re used to farming out the back door, and now we have sites spread hundreds of miles apart. The grazing fees make that cost affordable.”  

“I saw a solar array built on a lambing pasture, and a landscaper showed up with a tractor and started mowing up the solar arrays. He was going about 30 mph with a batwing sprayer and was mowing the rows and hosing down the panels around the arrays. I was thinking, they should just put the sheep down there and let them graze,” Dan recalled. 

Solar Grazing Site Specifications and Management  

The site is in a 15-acre array that produces 5 MW of DC and 3.375 MW of AC, enough to power approximately 1,100 homes. A landowner leases the land to SWEB, and SWEB hires Dan to graze the solar arrays with the sheep. The pricing is relatively the same as traditional mowing and gas-powered landscapers, but grazing sheep comes with many environmental benefits, such as enhanced landscape stabilization that directly benefits the solar companies. This stabilization includes deeper root systems on previously rocky terrain, improved turf health, and significant runoff reduction. 

Solar Shepherd practices rotational grazing on their sites, which allows more carbon in the soil and retains more moisture. “We see that impact very rapidly. There are some sites we had that, in just one year, the customer came to us and said, ‘I can’t believe the impact the sheep had on the vegetation sustainability. It was rocky before, and now there are deeper root systems, stabilized soil.’ Erosion is a big concern at the base of the panels. A direct benefit to the solar companies is stabilizing that ground,” Dan added. 

There’s also the “Fuzz and Buzz” – a solar seed blend used at the Brookfield site that benefits pollinators and sheep. It’s not as robust of a floral bloom, but the bees and sheep benefit greatly from this blend. A gas-powered mower removes all the vegetation on an array in a single day. The sheep take around a month to “mow” the same array. This allows valuable pollinator habitat to be left for the bees and birds. There’s good seed-to-solar contact, and the imprints from the sheep hooves allow the seeds to be captured in the soil. The sheep help the effectiveness of reseeding a site and some graziers will run the sheep back over the seeds to help stomp them down into the earth. 

Solar grazing includes running three main operations: a sheep farm, a trucking company (as you move the animals), and a commercial landscaping business. “It’s more than just opening the gate, throwing the sheep in there, and driving away. There are always some sites that require things outside the lines,” said Dan.  

Dan’s partner, border collie Reggie, has been vitally important in effectively managing the sheep on solar sites. In the trucking operation, sheep are loaded in and out of trucks over and over, and that requires collecting them from one site to another to be loaded into the trucks.  

Reggie is immensely valuable in this process. She rounds up the sheep quickly, whereas it would take multiple human workers significantly more time. She is vital to effective time management (and cost, if you consider paying multiple workers to round up sheep all the time). Reggie moves the sheep around the array in accordance with rotational grazing practices. 

Grant Incentives in Massachusetts 

Massachusetts does have a grant program for dual use of solar (Massachusetts SMART Initiative), but it is “written in such a fashion that it can be difficult to be profitable,” said Dan. The grant does not apply to sites that already exist, and it requires panels to be built 10 feet off the ground. Solar Shepherd has not received this grant and has also not yet grazed an array that fits the 10-foot grant requirement.  

Livestock production is diminishing in Massachusetts and what’s left is small-scale vegetable farming. Dan speculates that the state is writing laws for solar development incentives with this in mind instead of grazing sheep under solar panels. 

Community Response 

“The community loves what we’re up to,” said Dan. “We had about 500 comments (on the recent video featured on CBS) and all of them were loving what we are doing. There are a few political comments. So, grazing sheep on solar might bring some unification from a political perspective.”  

He also added that, “At least half the time I show up, there is a family there outside the gate at the fence watching the sheep. People are wanting to bring kids out to the sites to see the sheep. I’d like to do a program where people can come see them. We would love to host a solar event. We’re going to bring some sheep to town off the hill in Brookfield so people can see them and interact with them. I have a dream of bringing a bus load of kids out here to see how bees, sheep, and everything all come together.” 

Since the Brookfield location is an ancient hay site where indigenous peoples managed the land when colonists first arrived, not damaging the vegetation or compacting the soil during the solar array installation was very important. This priority to minimize damage to the land could have a positive impact on community support for a solar site, particularly on ancient farmland or similarly valued sites. Communities like to see that a (solar) development company cares about the land and the process of development. 

Considerations for New Sheep Graziers 

New sheep graziers or those thinking about getting into sheep grazing on solar sites should consider a couple of things throughout the process. Educating themselves on what’s happening on the solar array is very important. “They don’t have to be engineers,” says Dan, “but they should understand what’s happening and what the potential dangers are and keep themselves and animals away from those areas. Stay out of areas where you might think ‘I should have an electrician in there.’ These are areas that contain things like cable trays and equipment pads.”  

Don’t move forward with grazing a solar site if you haven’t walked the location and examined it for suitable conditions for your sheep. If construction techniques did not leave a space where you would feel comfortable leaving the sheep, such as poor wire management or dangerous or sharp edges on array components, it may be a good decision to decline grazing in that location.  Dan says the sites he turns down are for animal welfare reasons. There might not be enough nutrition on the site, but it is usually wiring management. A good perimeter fence can also make a site more ideal for sheep.  

Operating a grazing operation on your own property requires having a plan for food and water delivery, as well as for avoiding predation. A plan should be in place for responding to issues that may arise on the site and with little notice. Solar Shepherd has a 24-7 hotline for such issues. 

For fencing, Dan prefers to use electric netting, which provides effective  protection from predators. Coyotes prefer to go under the fence rather than over it, and considering such nuances in predator-prevention strategies can help design a fencing system that is most effective for your area and your circumstances. Hiring people who think from the sheep’s perspective is important, says Dan. Fortunately, he has not had any issues with predation to his sheep.  

The Future of Solar Shepherd and Solar Grazing 

The future of Solar Shepherd is looking bright. It originally took the company approximately one year to get hooves on the ground at a solar site. Now it only takes about a week or two. “I feel great about the solar grazing future and Solar Shepherd. The sales pitches are getting shorter and shorter. The world is becoming aware of this subject. Five years ago, it was, ‘You’re doing what?!’ The last pitch I gave was an hour-long presentation. I got 15 minutes into the meeting, and people said, ‘It’s great; we are ready to sign.’” 

Maces Pond: Agrisolar Wild Blueberries

By Chris Lent, NCAT Agriculture Specialist

Not far from the town of Rockport, Maine, Paul Sweetland of Sweetland Farms, LLC has been tending wild blueberries since he was a young boy. On one field that he has been farming since the late 1990s, there is more than blueberries being produced. Solar panels have been installed over about 11 acres of wild blueberry plants in the first project in Maine to collocate solar electric production with wild blueberry cultivation. The project was developed by BlueWave, a Boston-based solar development company, and installed by CS Energy in the spring and summer of 2021.  

When the owner of this land, David Dicky, started receiving solicitations from solar companies to lease his land for solar development, he was interested. However, he didn’t want to see acres of wild blueberries destroyed in the process of constructing a solar array. After consulting with several solar developers, he began working with BlueWave because of their experience and openness to developing dual land use solar installations. Dual-use solar, also called agrisolar or agrivoltaics, pairs agricultural production and solar electric production on the same land. BlueWave, with input from Mr. Sweetland and Dr. Lily Calderwood, a horticulturalist at the University of Maine, developed a solar site plan that would protect the berry plants and research the impacts of the solar installation on wild blueberry production. After a nearly two-year permitting process, Bluewave and CS Energy began installation in early 2021, aiming to have the project finished by late spring to allow time over the summer for the blueberry plants to recover. 

Navisun, a Boston-based solar independent power producer, purchased the solar project from Bluewave in early 2021. They worked closely with the installer, the landowner, and Sweetland Farms to ensure that this agrisolar project was financially viable for everyone. Both Navisun and Bluewave have made a commitment to innovation and land stewardship in solar development and have actively pursued agrisolar projects like this one to fulfill that commitment. 

Bluewave funded research by Dr. Calderwood to study the effects of solar construction on the established blueberry plants. To do this, the construction area was divided into three sections. In one section, panels were installed using standard practices and equipment. In the second section, the crew was mindful of reducing passes with heavy equipment, sharp turns, and other practices that can rip and damage the ground and plants. In the third section, they used polyethylene ground-protection mats and were very careful about using the same access paths and minimizing equipment passes through planning and efficiencies. The construction crew went through training on these low impact techniques before construction began.  

Commercially managed low bush or wild blueberries are harvested in July and August and then the farmer either burns off or mows the plants in the fall. The following year, the plants are in a vegetative cycle building new growth. It isn’t until the following year that the plants enter a cropping cycle, the berries are harvested, and the cycles start over again. Construction on this project took longer than planned, leaving a shorter time for the plants to recover in the first year. Despite this, the blueberries in all three sections rebounded, with the section containing the most protected plants rebounding more quickly and with better vegetative growth in the first year. The plants produced almost no berries in the harvest year of 2022. Dr. Calderwood attributes this to the short time the plants had to recover in the year of construction and the shade from the solar panels. More will be known about how well the berries will produce under the panels as the study continues through the 2024 harvest . 

The solar array covers nearly 11 acres of land plus an access road and is sized to produce 4.7 megawatts of DC power. To date, power production from the system is higher than was estimated. The system consists of a combination of one-sided (monofacial) and two-sided (bifacial) panels on a fixed-tilt racking system. The height and row spacing of the panels follow conventional solar development design, with the upper height at about 8 feet and the space between the rows of panels also about 8 feet. To accommodate for deep snow in the winter, the height of the drip edge, which is the distance from the front edge of the lower panels to the ground, was increased from a typical 30 inches to 5 feet. This additional height slightly increased the cost of the system but is standard procedure for Navisun on projects located in high snow areas and had the benefit of creating some extra height for working the blueberry crop under the panels. Navisun indicated that the installation costs were slightly above market cost for this size system. 

Through Maine’s Net Energy Billing Program, the local power company allows Navison to create energy credits based on the solar energy generated at the site. Navison then offers and sells those credits to small commercial customers in the area. Navisun pays the landowner a lease payment for the acreage the solar array occupies and subleases the land under the panels to Mr. Sweetland, agreeing to pay him a stipend as the caretaker of those grounds for at least the first five years the system is operating. This stipend can help offset any losses to Sweetland Farms if there is a reduction in blueberry production under the panels and isn’t an extra expense for Navisun, as they would need to arrange and pay for grounds maintenance in any solar development. Sweetland Farms also has an agreement to pay the landowner a percentage of the gross income from the cultivation and harvest of wild blueberries on the site. This creative arrangement of leases, subleases, and payments is a way to ensure everyone involved is treated fairly and is happy with the financial aspects of the project. 

One challenge in dual-use agrisolar projects like Maces Pond is finding the balance between energy production of the panels and crop production under the panels. The partners involved in developing this project knew that energy production would be a focus but also wanted to protect and track the production of wild blueberries under the panels. The data collected from this research and lessons learned could inform future projects and open the door for other wild blueberry landowners in Maine to diversify their income from their property.  

Because the panel height and width between the rows of the array were not designed to allow for traditional farming equipment adjustments have been made to help work the blueberries under the panels. For example, an ATV is now used for any spray applications and a walk behind harvester will be used under the panels instead of tractor-pulled harvest equipment. Mr. Sweetland and others working under the panels learned to always wear a hard hat to avoid the risk of hitting their heads on the solar racking.  

Trialing different levels of care for the protection of the ground and berry plants during installation has shown that with the right methods the natural state of a site can be protected during the construction phase. With some planning and simple techniques, damage to a site’s ecology can be minimized. 75% of the wild blueberry plant is below ground in the root system so the tops can be damaged without killing the plant. All the berry plants rebounded after the construction phase, but those that were protected the most did the best. 

There is some concern among communities in Maine that solar development will destroy wild blueberry fields which can take 10 or more years to establish. When the landowner in this project decided to move forward with a solar development project on his land, he visited his neighbors to talk to them and they all have been supportive of the project. Mr. Sweetland believes that support was bolstered by proactively approaching the neighbors and by the agrisolar nature of the project, which allowed for the preservation and continued production of blueberries under and around the solar panels. 

Dr. Calderwood will continue to collect data on shade levels, soil temperatures, plant density, insect and weed pressures, blueberry bud and fruit counts, crop yield, berry size, and more through 2024. That research is funded through a Northeast SARE Novel Approach grant and more information on Dr. Calderwood’s research on this project can be found at the University of Maine Cooperative Extension: Wild Blueberry page.

Case Study: Boulder Housing Partners Triangle Solar Array

Written for the AgriSolar Clearinghouse by Allison Jackson, Colorado Agrivoltaic Learning Center

The Boulder Housing Partners Triangle Solar Array is one of the first solar arrays in the Boulder, Colorado, area that is solely dedicated to offsetting energy use for low-income residents. The array is a south-facing fixed array with the leading edge of the solar panels about two feet off the ground. Construction was completed in 2021, and the array will generate over 19 GWh of solar energy in the next 10 years.

This solar array was built on 3.8 acres of degraded, rocky soils with prairie dog burrows and overgrown weeds. It was not an ideal spot for agrivoltaics (co-location of photovoltaics and agricultural activities), but that is what makes the possibility of rehabilitating solar land so appealing. Byron Kominek, owner of Jack’s Solar Garden and executive director of Colorado Agrivoltaic Learning Center, and Duncan Gilchrist of The Nature Conservancy had ideas about repurposing the land around these panels. “If we can demonstrate the ability to grow vegetation in a south-facing fixed solar array built on some of the worst terrain you can imagine for agricultural activities, then we will know that agrivoltaics can work within any solar array site,” stated Byron Kominek. According to Duncan Gilchrist, “The Nature Conservancy’s interest in this project is to demonstrate a replicable model for agroecological land restoration within solar arrays that weren’t originally designed for agrivoltaics.”

Area that has not been altered. Photo: Colorado Agrivoltaic Learning Center

Area of the solar array with swales and perennial plantings. Photo: Colorado Agrivoltaic Learning Center

With no water source at this site, integrating agriculture into the semi-arid climate of Colorado is extremely difficult. So, in conjunction with the Drylands Agroecology Research, the landscape was altered utilizing permaculture ideas of slowing, spreading, and sinking rainfall to aid in water retention. A series of basins were dug and amended with compost at the leading edge of the solar panels to capture moist running off of the solar panels to sink the water deep within the soil’s profile. Having planted hundreds of hardy, drought-tolerant perennials, these basins will hopefully provide a repository of soil moisture for these plants during the driest months of the year. Utilizing the shade from the solar panels will also help slow evaporation from the soil and maintain a more even soil moisture.  

The land was terraformed in November of 2022 with a mini-excavator and shovels. Perennial herbs were purchased and planted within the basins at the leading edge of the solar panels in April 2023. Irrigation was provided only at the time of planting for the perennials to get established. Herbs that were planted include fennel, lavender, lemon balm, oregano, rhubarb, thyme, and wild licorice. These plants will be monitored by researchers from the Dryland Agroecology Research group to assess their survivability and vigorousness.  

Terraforming the land in November of 2022 with a mini-excavator. Photo: Duncan Gilchrist, The Nature Conservancy

One benefit of having people within solar arrays stewarding the land is that they can catch system problems before the solar array asset owner does. Be it damaged panels, unsecured wires, or inverter errors, these issues can be easily monitored and relayed to the asset owner. In the long run, this can save asset owners money in operations and maintenance costs and potentially reduce the chances of lost revenues. During an initial site assessment for the viability of this agrivoltaics research project, consultants noted that the system’s inverters were offline followed by a discovery that the entire system was. The solar array asset owner was rapidly notified to alert their O&M team only to find out that the O&M company no longer serviced this site. The team also noticed that a small tree had grown up between two panels, shading their solar cells. These findings by the assessment team helped the solar array asset owner get their system back online, helped avoid future lost revenues, and kept their system running effectively. 

With the wet spring and summer this year in Colorado, the perennials are growing and thriving. Hopefully, this project can be a model for retrofitting solar arrays and incorporating agriculture under the microclimates that solar panels provide. 

Planting perennial herbs within the basins. Photo: Duncan Gilchrist, The Nature Conservancy  

Bronze fennel plant thriving in the solar array. Photo: Colorado Agrivoltaic Learning Center