Tag Archive for: AgriSolar

SETO Announces Funding Opportunity for Agrivoltaics 

“The U.S. Department of Energy (DOE) Solar Energy Technologies Office (SETO) announced the Solar with Wildlife and Ecosystem Benefits 2 (SolWEB2) funding opportunity, which will award up to $11 million for research and development, technical assistance, and stakeholder engagement activities that improve the compatibility of large-scale solar (LSS) facilities with wildlife and facilitate the dual use of land for agricultural and solar energy production. 
 
SETO expects to make three to eight awards under the SolWEB2 notice of funding opportunity (NOFO), each ranging from $1 million to $3 million.” – energy.gov 

DOE Funding Opportunity Announced for Small Businesses 

“The U.S. Department of Energy (DOE) released new funding for the Small Business Innovation Research and Small Business Technology Transfer (SBIR/STTR) Phase I program for Fiscal Year 2025. The SBIR/STTR programs are competitive funding opportunities that encourage U.S.-based small businesses to engage in high-risk, innovative research and technology development with the potential for future commercialization. See the Solar Energy Technologies Office’s (SETO) SBIR/STTR funding notice for details on SETO topics.” – govdelivery.com 

University of Hawaii Completes Agrivoltaics Research 

“The University of Hawaiʻi’s Office of Sustainability and College of Engineering participated in a tour of the Hawaiʻi Agriculture Research Center (HARC) Agrisolar project in November. The event highlighted the intersection of renewable energy and agriculture, offering students a firsthand look at an innovative approach to sustainable land use. 

The HARC Agrisolar project, established in collaboration with AES Corporation, Longroad Energy, and Clearway Energy Group, spans a 230-acre solar farm in Mililani. Underneath the panels, researchers have successfully cultivated crops such as lettuce, strawberries, radish and poha berries since the project’s inception in June 2022.” – Hawaii.edu 

Czechia Passes Legislation for Agrivoltaics 

Czechia has introduced new legislation for deploying agrivoltaics. The law, effective from the start of this year, builds on initial measures introduced in May 2024. 

The newly approved measures permit agrivoltaics to be installed on six crop types, including vineyards, hopyards, orchards, tree nurseries, crops in containers and truffle areas.” – PV Magazine 

By Stacie Peterson and Chris Lent, National Center for Appropriate Technology

Agrivoltaics is a practice defined as the co-location of crops and grazing under and adjacent to solar photovoltaic panels. The concept of agrisolar co-location goes beyond photovoltaic solar and includes other solar energy production that is not photovoltaic, such as solar thermal. Solar thermal is a term used to describe a technology, such as a crop dryer or solar water heater, that converts the energy from the sun into thermal energy. This thermal energy can be used to heat, dry, and distribute air, water, or heat transfer fluids. Solar thermal principles can be employed in crop drying, processing, and storage, and in water-intensive operations, like dairies.

In addition to solar photovoltaic energy production systems, solar thermal energy production is a great way to collect and utilize solar energy. In concentrated solar thermal (CST) production, energy from the sun is concentrated by mirrors, lenses, and parabolic dishes or troughs that reflect the heat energy to a collection point called a receiver. The accumulated energy is then used to power an electric generator. CST systems are often associated with utility-scale electric production; however, CST also has potential applications in commercial water heating, water desalination, and manufacturing. In agriculture, smaller-scale solar thermal systems can be used for crop and grain drying, food processing and drying, greenhouses, and to heat process water for dairies, such as the Winton Cone Optics system shown in in the photo below and described later in this section.

Winston Cone Optics Solar Thermal System.  Photo: Winston Cone Optics

Solar Thermal Crop Drying Overview

The sun has been used to dry crops for preservation for millennia. This natural drying process exposes agricultural products to the sun and wind and continues to be used in certain regions to preserve crops because of its low cost and simplicity. It is limited by natural conditions that affect drying, including hours of sunshine and precipitation, which can lead to inconsistent and low-quality results. Sun drying can also be a lengthy process, leaving the crop susceptible to insects, animals, and birds.

Solar thermal drying is a method of dehydrating food crops and grains using solar energy. It’s an environmentally friendly and energy-efficient technique that harnesses heat from the sun to remove moisture from agricultural products and preserve them for periods of storage. Grains, fruits, vegetables, herbs, meat, and fish are some of the agricultural products that are dried to preserve their quality and for use in a variety of value-added products.

Crop dryers can be distinguished by the source of energy used to operate them. Three types are fossil fuel dryers, electric dryers, and solar energy dryers. It takes 2.4 megajoules of energy to evaporate 1 liter of water and most dryers operate at less than 50% efficiency, therefore requiring large energy inputs (Dhumne et al., 2015). Because of the cost to operate fossil fuel-powered and electric crop dryers, solar crop dryers have gained attention as a cost-saving alternative. Small-scale solar dryers have been used around the world, especially in areas where fuel and electricity are scarce and there are favorable sun and weather conditions. 

Solar dryers are further categorized as either passive (using natural convection) or active (using powered convection). Within these two main types, there are three different designs for solar dryers: direct, indirect, and mixed-mode. All these systems have a solar collector component often made of glass or plastic, but it can also be a metal surface painted black to optimize solar energy collection. The solar collector absorbs sunlight and converts it into heat energy, which is then transferred to a drying chamber where food crops are spread in a thin layer to maximize exposure to the heated air.

One option for direct solar thermal crop drying is a greenhouse or high-tunnel structure with natural ventilation and screened tables and shelves inside to lay the product to be dried, as shown in the photo below. It is a best practice to add a solar-powered fan to force the circulation of air through the greenhouse or high tunnel.

Direct solar thermal crop drying of coffee beans. Photo: NCAT

A basic indirect solar dryer design, shown in Figure 1, includes an insulated box with a glass window that allows light in, a dark surface that absorbs light and radiates heat, an air inlet that allows cold air in, and an air outlet at a higher point in the dryer box that allows hot air, which naturally rises, out (Muhammad K., 2003). The heat of the sun, which is magnified in the solar dryer, and the natural movement of the air through the dryer work to dehydrate the crops placed in the dryer chamber. To avoid mold, a best practice is to clean the dryer chamber and remove condensation regularly. A solar-powered fan can also be incorporated into the design to lessen condensation and increase dehydration.

Figure 1. Schematic of a Solar Air Dryer. Graphic: NCAT

A variation on this design includes the incorporation of a fan, which can be solar-powered, and a drying chamber with crop trays that is separate from the solar collector (Figure 2). 

Figure 2. Schematic of Solar Air Dryer with Separate Drying Chamber. Graphic: NCAT

Grain Drying

Grains such as rice, soybeans, corn, and wheat are almost always harvested at a moisture content that is too high for safe storage of the crop. High moisture levels in stored grain lead to spoilage and mold-induced aflatoxins that can ruin the crop and be harmful to animals and humans (NTP, 2021). To prevent this, grain is sometimes dried through natural air drying where air is forced through the perforated bottom of a grain bin and up through the stored grain by a fan. This can work well when the ambient air conditions are dry enough to allow for moisture to be removed from the grain. When the ambient conditions don’t allow for effective natural air drying, a heater is used to help dry the grain. Most stored grain in the U.S. is dried this way.

Solar Thermal Buildings and Grain Bins

The metal roof and side walls of an existing or new building can be converted into a solar thermal collector. In this application, the existing metal on the south-facing side of a building is painted black, and wooden purlins are attached to accept a second layer of metal or a clear covering. A metal covering creates what is called a bare-plate solar collector and a clear covering creates a covered-plate solar collector (Figure 3). The solar-heated air is then ducted to an adjacent grain bin. In a similar manner, the bin where the grain is being dried and stored can be converted to a solar thermal collector (Figure 4).

Figure 3. Solar Thermal Building

Figure 4. Solar Thermal Grain Bin

Solar Thermal for Process Water

In agricultural operations that require a lot of hot water, like dairy farms, heating water can account for as much as 40% of energy costs. On farms like these, solar thermal water heating can be used to reduce energy costs. Solar water heaters, much like the crop and grain dryers described above, require a solar collector to capture the sun’s energy. Depending on the design, this energy is transferred directly to the water being heated or to a heat transferring fluid, like glycol, that is pumped through a heat exchanger to heat water.

Designs vary for solar water-heating systems, but the basic components are a collector, a heat exchanger, and a hot-water storage tank. A basic schematic of a simple solar hot-water collector in Figure 5 below shows the basic principles of solar hot water heat collection and storage. Like solar dryers, the heat from the sun is transferred through a transparent or semi-transparent medium, like glass, and reservoirs of water behind the medium collect and store the solar heat. This hot water is then used in farm processes.

Figure 5. Simple Solar Thermal Water System (U.S. DOE, 2024)

As shown in Figure 5, solar thermal water systems often include a flat-plate collector. In this type of system, a flat metal plate is attached to metal tubes, which contain a heat transfer fluid that is used to heat water in a storage tank.  This type of systems works best for water that does not need to be heated higher than 200°F (U.S. Energy Information Administration, 2024). The main components of a flat-plate solar collector are:

  1. A black or dark surface that absorbs solar energy.
  2. A transparent cover that transmits solar radiation to the dark surface but prevents heat loss from the dark surface.
  3. Tubes containing heat transfer fluid connected to the dark surface. These are often called evacuated tubes because they are designed as a set of two glass tubes, with the air between the tubes removed, or evacuated. This vacuum is created to reduce heat loss. 

It is common to build a support structure with insulation around the plate and tubes. Figure 6 is a schematic of a basic flat-plate system. 

FIGURE 6. Schematic of a flat-plate solar collector with liquid transport medium. Graphic: NCAT

In the case of Winston Cone Optics, the evacuated tubes are paired with solar reflectors, as shown in the photo below. A schematic of their process is shown in Figure 7. They can heat water, create steam, and deliver process heat up to 350°F with this system.

Winston Cone Optics solar reflectors and evacuated tubes. Photo: Winston Cone Optics 

Figure 7. Schematic of Winston Cone Optics.  Graphic: Winston Cone Optics

Solar thermal flat-plate collectors heating a high tunnel Photo: NCAT

The photo above shows a solar thermal flat-plate collector array coupled with a high tunnel. In this system, the collectors provide heat for an in-ground hydronic heating system in a 30 X 96-foot-high tunnel. Inside the high tunnel, an insulated 500-gallon, in-ground solar storage tank is heated with the heat transfer fluid circulating through the collector panels. Water circulating through PEX tubing buried under the growing beds is heated from the storage tank via a heat exchanger delivering heat to the root zone of the crops. A back-up heater is used to heat the water for cloudy days when solar can’t be used.

Solar thermal provides an opportunity to harvest sunlight and use the energy tin crop drying, processing, and storage. Solar thermal works by collecting sunlight, converting sunlight to heat, and by transferring heat via airflow or heat transfer fluids. Projects can be as simple as a solar air dryer, or as complex as a concentrated solar heating system for a diary. By working with the sun, thermal energy can help make farm processes more efficient and environmentally friendly while saving significant energy costs.

CONCLUSION

References

Dhumne, L.R. V.H. Bipte, Y.M. Jibhkate. 2015. Solar dryers for Drying Agricultural Products. International Journal of Engineering Research. Vol. 3, S 2. (PDF) Solar Dryers for Drying Agricultural Products (researchgate.net)

Muhammad, Kamran. 2023.  Fundamentals of Smart Grid Systems. Academic Press. doi.org/10.1016/C2021-0-02193-3

National Toxicology Program (NTP). 2021. Report on Carcinogens, Fifteenth Edition.  U.S. Department of Health and Human Services, Public Health Service. Research Triangle Park, NC. 

U.S. Energy Information Administration. 2024. Solar thermal collectors. U.S. Energy Information Administration, Washington, DC.

U.S. Department of Energy. 2024. Solar Water Heaters.  energy.gov/energysaver/solar-water-heaters

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Experts Say Agrisolar Could Benefit Nova Scotia 

“Solar energy advocates believe agrivoltaics could have many benefits in Nova Scotia. There are now more than 10,000 solar installations in Nova Scotia, according to the non-profit group that’s trying to build up solar infrastructure in the province. That’s up from 8,000 this time last year and just 200 in 2018. ‘Farmers in Nova Scotia have been real leaders on the uptake of solar,’ said David Brushett, board chair of Solar Nova Scotia. ’There’s a real strong interest among the agricultural sector in solar.’” – cbc.com 

New Albania Law Recognizes Agrisolar Development 

“The Kuvendi – the Parliament of Albania – changed the Law on the Pasture Fund. Lawmaker Edona Bilali from the ruling Socialist Party of Albania submitted the bill, citing numerous requests for photovoltaic and wind installations. In the solar power segment, PV panels now need to be mounted at least five meters above the surface to allow cattle grazing.” – balkangreenenergynews.com 

Agrisolar Recognized on World Soil Day 

“Solar energy and agriculture are proving their relationship is a mutually beneficial one. As technology improves and more farmers adopt solar solutions, we can expect to see even more innovative applications emerge. Solar energy is ushering in a new era of sustainable agriculture. 

As we mark World Soil Day (Dec. 5), it’s also worth celebrating that it is also a transformative force to be reckoned with in farming!  Here are 5 key ways that solar energy is revolutionizing farming practices around the world.” – earthday.org 

By Anna Richmond-Mueller, NCAT Energy Analyst 

Known as the “Sunshine State,” it’s easy to see why solar energy production should be right at home in Florida. The state is also one of the country’s top agricultural producers, raising billions of dollars worth of specialty crops and livestock each year. Agrivoltaics seems like a natural fit and a potential option for farmers and ranchers looking to diversify their revenue and support the growth of renewable energy in the state. At Fiddlehead Farms, owners Walter and Sharon Liebrich are embracing that potential, working hard to bring an agrisolar pilot project and educational space to life in Tallahassee.   

Walter’s interest in agrivoltaics is deeply rooted in his passion for renewable energy. In 1998, Walter was the High School Florida State Champion in Policy Debate when the yearlong topic debated the pros and cons of increasing the use of renewable energy in the U.S. Then in 2004, he earned a Master’s degree in Public Administration from the Askew School of Public Administration at Florida State University. At the time he was in graduate school, connecting a solar project to the grid was an opportunity largely limited to big businesses and utilities. His thesis advocated for solar net metering and interconnection policies for individuals and small businesses in the state, something that wouldn’t be in the Florida statutes until 2008. After earning his degree, Walter went on to work as a Senior Policy and Budget Analyst in the Governor’s Office for 15 years before transitioning into the solar industry. He is also on the Board of Directors for ReThink Energy, a local nonprofit dedicated to community outreach and education for Floridians as the city moves towards its clean energy goals. Through his work with ReThink Energy, Walter joined the Tally 100% Together Coalition and helped to pass a unanimous city commission resolution in 2023, committing Tallahassee to 100% renewable energy by 2050.  

The Liebrich Family.

Walter and Sharon both share a passion for farming and gardening, as well. After meeting in 2009, they started pursuing those passions together by cultivating an edible landscape at their home, with the goal of having their child pick the vegetables for that night’s dinner right in their own backyard. The 0.3-acre primary residence in midtown Tallahassee is home to many varieties of citrus, blueberries, blackberries, fig, pears, mangos, kiwi, avocado, pineapple, peaches and more. They also have a year-round seasonal garden comprised of anything from broccoli, kale, and arugula to tomatoes, peppers, and squash. They began their apiary work in 2019, successfully cultivating bees to help support the worldwide food shortage. By 2023, their impressive dedication to renewable energy and specialty crop production led them to set their sights on a new goal: creating an agrivoltaic community solar project.  

Around the same time, the Tallahassee City Commission unanimously adopted the 100% renewable energy resolution, and Walter and Sharon poured their entire life savings into the purchase of a 5-acre piece of property adjacent to a new public park and cypress preserve in Tallahassee. Their vision for the newly purchased land includes a 1-megawatt agrivoltaic array that would provide locally grown produce for the community, while also helping bring the city closer to its 100% renewable energy goals. However, before that vision can come to life, they must overcome some regulatory barriers for solar in the City of Tallahassee. “Anything from 100 kilowatts to 75 megawatts is all basically regulated under the same umbrella, which is extremely cost-prohibitive,” Walter explains. Projects in this size range are required to undergo thousands of dollars of grid and impact studies before an array can be built. Fortunately, thanks to all his volunteer work with ReThink Energy and Tally 100%, Walter has cultivated a network of professionals in the city and utility, who all want to see his vision become a reality. He understands the importance of building bridges further from home, as well. From the National Renewable Energy Laboratory to the Florida State Director of the Office of Energy, Walter continues to make connections that will be vital in the project’s success. He continues to work with city officials towards a positive change in the regulations for mid-size projects, as well.  

The solar aspect of the pilot project might still be in the early stages, but there’s already a lot happening at the site on the agricultural front. The unkept land was mostly filled with invasive species and heavily vining plants when Walter and Sharon bought it. Clearing invasive species, wild vines, and other biomass on-site is necessary for the project’s implementation. That doesn’t mean that the site will be clear cut and bulldozed, though. Instead, selected areas will be cleaned up while others will remain largely as they are. Any brush and invasive trees that do need to be removed are being used to create biochar, which Walter then uses to construct the raised beds for the row crops. Kale, broccoli, peppers, tomatoes, squash, pineapple, banana, and kiwi will all make an appearance throughout the year. The site is also home to wild sparkleberries and persimmon bushes. These plants will be incorporated into the site’s agricultural production by grafting their close, more familiar cousins onto the existing bushes. Japanese Fuyu persimmons will be grafted onto the wild persimmon bushes, and blueberries will be grafted onto the sparkleberries. Once the plans for solar panels are solidified, they will be built around and above the raised beds and bushes already in place. 

Biochar raised beds.

Looking ahead, Fiddlehead Farms hopes to make a positive impact on both local communities and the agrisolar research community. Most of the food grown at the site will be donated to Second Harvest of the Big Bend, a nonprofit fighting food insecurity in the region. When it comes to research, Walter understands the importance of having test sites and welcomes collaborations with universities, research institutions, and solar companies. He hopes to install a variety of racking types, tracking abilities, and panel heights across the site. Fiddlehead Farms is also a nonprofit organization, and anyone interested in becoming involved in the project is encouraged to reach out to Walter and his team at fiddleheadfarmstlh@gmail.com.  

It’s easy to see the decades of passion and vision behind Fiddlehead Farms. Pilot projects play an important role in showcasing the potential for agrivoltaics to truly make a difference in local communities. Whether it’s providing locally grown food to those in need or working with public officials to make positive changes in renewable energy policy, Fiddlehead Farms is poised to do it all for the Tallahassee area. “From the beginning, I’ve understood the importance of building all kinds of bridges. National, state, and local – even the friends that we’ve made here with the neighbors at the site,” Walter explains. Fiddlehead Farms is the next step in bringing those people together and strengthening the resiliency of the local community.  

All photos courtesy of Walter Liebrich. 

As agrivoltaics gain traction across the United States, research on barriers and opportunities for co-locating agriculture with solar is expanding. The SCAPES solar research project, led by the University of Illinois Urbana-Champaign, has received funding from the U.S. Department of Agriculture to study how to efficiently co-locate photovoltaic and agricultural systems in various biogeographical regions. As part of this research, the project team created a survey to better understand the strengths, weaknesses, opportunities, and threats of such co-location. 

Your voice matters! Please take 15 minutes to complete this survey. Your participation is greatly appreciated and will contribute to the success of our research. Your insights can impact future agrivoltaic considerations. We encourage all industry representatives to participate. 

Access the survey here: redcap.healthinstitute.illinois.edu/surveys/?s=4YFMYDLELE47C4EH   

Or use the QR code below: 

Agricultural Land Usually Remains in Agriculture After Solar and Wind Development  

“As [agrisolar] development has expanded, some communities have raised concerns about the local effects of solar and wind projects. USDA, Economic Research Service researchers recently studied how solar and wind development affects land cover near wind turbines and solar farms.  

Researchers examined the land cover in the three years prior to and following installation and found that cropland or pasture-rangeland usually stayed in the same land cover even after the addition of solar or wind development.” – ers.usda.govhttps://www.solarpowerworldonline.com/2024/07/avangrid-hires-5000-sheep-for-grazing-on-two-solar-projects-in-the-pacific-northwest/ 

WINAICO Develops New Solar Aquaculture Module 

“This year, the company will launch the AQUA salt-resistant double-glass module series, featuring double-layer coated glass with excellent density and light transmittance, POE encapsulation technology, highly waterproof seal performance of junction box, and apply a thicker oxidized film coating to shield the aluminum frame from corrosion.  

After more than 15 years of operation in Taiwan and the worldwide renewable energy market, WIN WIN Precision Technology has demonstrated expertise in customizing solar modules for island climates, its solar brand WINAICO holds exclusive patents for the wind-resistant and water drain valve designs.” – prnewswire.com 

Illinois Farmer Successfully Adapts to Solar Grazing 

“[Trent] Gerlach’s family had been raising corn, soybeans, and livestock since 1968, and like many farmers, they leased farmland in addition to working their own land. And when the owner of one of those leased parcels decided to work with Acciona Energia to help site its High Point wind and solar farm, Gerlach initially was not enthusiastic. 

‘The thought of taking productive farm ground out of production with solar panels was not, in my personal opinion, ideal,’ he said.  

But Gerlach was determined to make the best of the situation. 

Ultimately, that meant a win-win arrangement, where Acciona pays him to manage vegetation around the 100 MW array of solar panels that went online in early 2024. Gerlach does that with a herd of 500 sheep. 

‘It’s incredibly cost-effective — sheep don’t break down like a tractor; if a tractor blows a belt, you’ve lost a whole day of cutting,’ he said. ​‘These grasses grow wickedly fast, it’s that constant presence of the sheep that’s been super effective. It aligns with our sustainability goals.’” – canarymedia.com 

This publication intends to inspire critical thinking about the importance of social aspects in agrisolar projects. We highlight considerations related to cultural landscapes, social acceptance, and participatory planning and offer lessons learned from case studies and a Stakeholder Engagement Plan to empower project planners and stakeholders. The intended audience for this chapter includes project planners, community developers, solar developers, researchers, landowners, and community members. While broad, the intent is to provide background, context, and considerations for these different audiences and an approach to meaningful engagement.

Gary Paul Nabhan, PhD., Agroecologist, Borderlands Restoration Network 

When most Americans think of crop production, they tend to imagine crops growing in full sunlight to achieve their full potential for productivity. But over decades,there has always been crop production in shade habitats or constructed environments, as well. Indeed, much of the coffee and chocolate (cocoa) consumed as beverages has been grown under shade-bearing, nitrogen-fixing legume trees such as madrecacao  (Glyericidia sepia), a tropical tree with a dense and expansive canopy that protects understory crops from excessive heat and damaging radiation.  

Virtually all the food crops, forages, and medicinal herbs grown in North American agroforestry and alley-cropping systems are to some extent shade-tolerant. Many—like chile peppers—can comfortably tolerate a 35% to 50% reduction in photosynthetically active radiation (PAR) compared to open sunlight all day. They seldom suffer a yield reduction due to less sunlight in this range, especially from noon to 4 p.m. Iin fact, yields in some varieties are augmented, perhaps because a significant percentage of all arid, temperate, and tropical wild plants evolved to begin their lives under the shade of “nurse plants” and have evolved shade tolerance to varying degrees over millennia. More than 30,000 farmers in the U.S. were engaging in one or more types of agroforestry practices by 2017, when agrivoltaic practices first hit the American scene.  

Agrivoltaic pepper plants in Arizona. Photo: NCAT 

Benefits and Challenges of Solar and Crop Co-Location 

So, what kind of benefits do shade-grown crops receive, and what are the challenges of growing crops under any kind of shade, for both the trees and the solar panels? 

Benefits 

Let’s first look at the benefits. Shade reduces the amount of sunburn or sun scald that understory plants receive but particularly reduces the effects of damaging ultraviolet radiation. It also serves as a temperature buffer, reducing high summer temperatures by as much as 4°F to 6°F and keeping winter temperatures in crop canopies 2°F to 4°F warmer—in some cases, enough to avert premature freezes or to extend the frost-free growing season by as much as three weeks. With less direct sun, evaporation of water from the soil and transpiration from the leaves are reduced, and soil moisture stress may not be as severe.  

The flowers of crops abort less in cooler temperatures, and they also attract more pollinators. Plant desiccation is not only reduced, but the nitrogen content of the foliage also does not spike enough to trigger feeding frenzies by leaf-sucking or browsing insects. At the same time, the Brix levels—an indicator of how sweet and nutritious vegetables and herbs might be—is sustained at higher levels, adding to the value of the crop. 

Perhaps the ultimate advantage is that it buffers farmworkers managing or harvesting from severe heat stress and dehydration in hot summers, improving their harvesting efficiency and reducing their vulnerability to hazards and illness. In 2023 alone, 30,000 more outdoor workers in the U.S. succumbed to heat stress than in any other year in recorded history. Since hand-harvested crops are time-consuming, their harvesters are especially vulnerable. 

Thermal image showing farm worker under a solar panel with a body temperature of 80°F and an outdoor temperature over 100°F. Photo: NCAT 

Challenges   

The disadvantages of co-location are more obvious for some sun-loving plants than for others. If the canopy tree or solar panel “competes” for too much light, it will result in reductions in photosynthesis and yields, thereby impeding the growth of the underling. However, there may be more humidity retained in the under-panel microclimate that fosters fungal diseases and possibly leads to more plant damage from insects that thrive on the fungal environment. 

Crop height may be impeded, requiring more pruning or difficulty in harvesting. And of course, most mechanical harvesters of high stature are eliminated from use if panel are 5 meters (16.4 feet) or less in height. 

Lastly, the space under photovoltaic panels is economically and ecologically costly per square meter; the metal, copper wiring and glass or plastic fiber glazing in photovoltaic panels is burdened with considerable “embedded energy” within it, so each panel provides small but very expensive growing space (except when compared to high-tech, computerized greenhouses with air conditioning and movable benches.)  It is unlikely that growing grains or dry beans under photovoltaic arrays will ever be cost-effective. 

So, what is different and distinctive about the shaded growing spaces under photovoltaic panels? For one thing, these areas have solid or slotted covers, rather than being diffused and porous like most leafy canopies. Secondly, all constructed spaces in a photovoltaic array are of similar height and size, whereas the height and size(s) are highly variable in natural or semi-managed forests.  

In natural settings, “nurse trees” also offer much more than shade and temperature buffering to understory plants; they also offer mycorrhizal connections and soil fertility renewal. Some deep-rooted legume trees also pump and leak water and nutrients to other plants in their nurse plant guild that are too young to do this on their own 

The crops discussed here that are most suitable for agrivoltaics conditions are high-value cash crops or nutritionally dense fruits and vegetables for home or community consumption. These crops are more suitable for agrivoltaics conditions compared to grain or bean crops, for example. Medicinals and pharmafood crops would likely be a better fit for growing conditions that are produced from dual-use land environments. 

Agrivoltaic pepper plants in Arizona. Photo: AgriSolar Clearinghouse 

Considerations for Crop Selection 

It is important to consider what shape, size, and habit of crop plants might be most appropriate for agrivoltaics production over an extended period of time. When considering crops that will be well-suited for the conditions of an agrivoltaics site, it is important to consider the following points. 

Crop Characteristics: 

  • Vining or “bush” growth forms 
  • Sun-loving or shade-loving  
  • Height and width of fully grown plant 
  • Multiple harvests or single harvests required? 
  • Root depth 

If we were to design an “ideotype” best suited to the photovoltaic micro-environment, it would need to meet at least five of the following plant characteristics: 

  • Vertically-vining or “indeterminate” growth forms that make maximum use of the space under solar panels by being trellised or “stiffer” scandent plants that lean upon a trellis (such as dragon fruit and capers). Vining plants that spread out beyond the perimeters of the panels may have a cooling effect that increases photovoltaic energy production efficiency (his strategy assumes that the interspaces between panels are not being utilized in another way). 
  • Tolerate moderate (especially mid-day) shade, with interception or screening of photosynthetically active radiation (PAR) in the range from 35 to 50% of total daylight,  
  • Growth habit that will allow for harvesting of seed, fruit, flowers, floral buds, or leaves from waist high (1 meter or 3.28 feet) to shoulder-high (1.4 to 1.8 meters or 4.59 to 5.9 feet) above the ground to allow work by hand or mechanical harvesters. 
  • Can be harvested or “cut” multiple times per season, pruning them to stimulate subsequent regrowth and recutting within three to four weeks of the previous harvest. 
  • Be either deep-rooted or shallow-rhizomatous perennials with runners, or longer-lived seasonal annuals that can be uprooted after the last harvest to allow new transplants to go into the same space. 

Now that we’ve established the ideal architectural and behavioral criteria for selecting crop plants, here is a list of crops that meet three or more of these criteria. These lists emphasize high-value crop plants that have other adaptations to hot, dry conditions but may require partial shade or frequent cutting and harvesting. 

Berry vines and bushes with long, arching shoots that can be both vertically and horizontally trellised: currants, dewberries, gooseberries (Ribes spp.); brambleberries, blackberries, dewberries, and loganberries (Ribes spp.), grapes, including muscadines, musquats, scuppernongs, etc. (Vitis spp.) 

Arborescent and scandent cacti with high-value fruit: cochineal nopal (Opuntia cochiillifera) dragonfruit cacti, including  white-fleshed pitahaya (Selinicereus undulatus), red-fleshed pitahaya (Selenicereus costaricensis), and  yellow pitahaya (Selenicereus megalanthus); pitahaya agrias (Stenocereus gummosus, S. quereteroensis, and S. griseus), longer-lived seasonal annuals that can be pulled up after the last harvest to allow new transplants to go into the same space.      

Short-stature shrubs with copious production of fruits, buds, or berries over a long season: capers (Capparis spinosa); capulín sand cherries (Prunus salicifolia); chiltepín, chile del arbol, shishito, etc. (Capsicum annuum); Mexican hawthorn or tejocote (Crataegus mexicana); elderberry (Sambucus nigra); goji or wolfberry (Lycium barbarum, L. chinense, L. fremontii, and L. pallidum); Persian lime (Citrus x latifolia); key lime (Citrus aurantifolia); kumquat (Fortunella margarita and hybrids); jujube (Zizyphus jujba); guava (Psidium guajava); hibiscus or Jamaican sorrel (Hibiscus sabdardiff); or maypops and passion fruit (Passiflora spp.). 

Perennial culinary herbs that can tolerate (or increase production with) frequent, severe cuttings: Mexican oregano (Lippia berlandieri, L. graveolens), saffron (Crocus sativus), Mexican tarragon (Tagetes lucida), papaloquelite (Porophyllum ruderale) Sierra Madre oregano (Poliomentha madrensis), lavandin (Lavendula intermedia), Greek oregano (Origanum vulgare),  thyme (Thymus vulgaris), and lemongrass  (Cymbopogon citratus). 

Dwarf or drastically pruned trees with high-value fruit: dwarf varieties of figs (Ficus spp.), pomegranates (Punica granatum), cherries, including the Mahaleb cherry (Prunus mahaleb), olive (Olea europea), Sechuan peppers (Zanthoxylum armatum, Z. bungeanum, and Z. simulans), and Mediterranean sumac (Rhus coriaria). 

Long-season annual herbs or perennial pharmafoods (nutriceuticals) that can tolerate frequent cuttings: sweetleaf stevia (Stevia rebaudiana), holy basil or tulsi (Ocimum tenuiflorum), damiana (Turnera diffusa), saffron (Crocus sativus), wild Lebanese cucumber-melon (Cucumis melo, a parent of the popular beit-alpha greenhouse cucumber); and chia (Salvia hispanica). 

It is important to consider what horticultural design and density qualifies as having the optimal features required to grow in agrivoltaics conditions, for none of these proposed crops need to be grown in evenly spaced monoculture. For instance, the least sun-sensitive crop varieties can go on the periphery of the solar panels, preserving the core area for the most shade-tolerant varieties or species. 

A Speaker Discusses Agrivoltaics in Arizona. Photo: AgriSolar Clearinghouse 

Alternatively, taller woody perennials can be placed under the highest levels of the panels, with the shorter varieties or species reserved for the shortest area toward the “front” of the angled panel. However, new designs of photovoltaics have computerized solar trackers for mobile or reclinable units, so that may become an irrelevant consideration in the future. Another option is to grow indeterminate vine crops such as cucumbers or grapes on the periphery of the solar panel shadow. This might allow those crops to “crawl out,” and provide greenery that reduces ambient temperatures on the panel surface. This may increase daily energy production efficiency and extend the lifetime of the panel(s). 

A final consideration is that for extremely high-value crops like pharmafoods and pharmaceuticals, screening the sides of the growing space may reduce or halt predation by insects or vertebrate herbivores. The overall cost of construction and production in an agrivoltaic system would remain far less than that for most commercial greenhouses, but the agrivoltaic micro-climate and growing space would then be considered a “controlled environment.” 

When selecting crops that are uniquely suited to be grown in agrivoltaic settings, consider the guidance provided above. Ask questions related to the features of the solar panel design, including height, width, and other design features, as well as measurements. Then, consider the plant characteristics that are being considered for that site: height, width, water consumption, root depth, harvesting schedule, etc. Next, form a strategy from the characteristics you have identified for both the panels and the plants and make an informed decision about what will work best for that specific agrivoltaic site, as agrivoltaics conditions can vary from one site to another.

By Rob Davis, Connexus Energy 

Growing Farmers, Growing Foods is the mission at Minnesota-based Big River Farms, a program of 501(c)3 nonprofit The Food Group. They recently won the North American Agrivoltaics Award for Best Solar Farm in 2024. Big River Farms teaches farmers to farm organically, sustainably, and regeneratively while also enhancing the level of understanding of the environmental impact that can result from properly implementing these types of farming practices. Specialty crop farmers are the backbone of our food system and are major contributors to local economies. However, land access is a major barrier for many emerging farmers, including farmers of color, in both rural and urban communities.  

Big River Farms Program Manager KaZoua Berry. Photo: AgriSolar Clearinghouse 

In 2022, the Minnesota Department of Agriculture established the nation’s first Emerging Farmers Office, with the intention of helping to remove barriers that emerging farmers face when getting started in farming. This includes new Americans and first-generation farmers who lack access to land or capital. Farmland access has been identified by the Emerging Farmers Office as the most common challenge for these farmers. 

Big River Farms works with farmers who are in constant need of land to farm on. Last year in Big River Farms’ incubator program, several farmers stated that they are ready to leave the incubator farm if they can buy land or access land elsewhere so that they can scale up independently. Expanding their program to solar sites will enable Big River Farms to build leadership and capacity in the immigrant community, diversify and enhance local food production, improve access for low-income households to healthy food, and build cultural bridges between emerging farmers and the larger community.   

Big River Farms, the Food Group, USDA Emerging Farmers Office, and Connexus Energy. Photo: AgriSolar Clearinghouse 

“With thoughtful planning and procurement, the community benefits of multi-acre solar projects can be numerous,” said Brian Ross, vice president of Renewable Energy for Great Plains Institute. “It’s important that we are stacking solutions to local food production and access into the clean energy transition.” 

With this project, the visibility of the dual-use solar will create new connections to the host communities for the solar arrays and build Big River Farms’ success and enhance its mission.  Association of the solar facilities with the Big River Farms’ equity goals will help resolve concerns about loss of agricultural capacity in communities hosting solar development and can contribute to accelerated deployment of solar sites on arable soils.  

“A quarter of an acre between rows can become an incredibly productive plot of land that right now isn’t necessarily in use,” said Sophia Lenarz-Coy, executive director of The Food Group. 

Abundant Crops Grown by Big River Farms Between Rows of Solar Panels. Photo: AgriSolar Clearinghouse 

The Solar Farmland Access for Emerging Farmers project seeks to increase land access to BIPOC and immigrant farmers through the utilization of spaces around solar farms, while concurrently documenting the safe and scalable practices that solar asset owners and insurers can implement as prerequisites of site utilization. Big River Farms, Great Plains Institute, US Solar, and Connexus have worked together to implement best practices from the National Renewable Energy Lab that have created replicable guidance for others seeking to collaborate and enable solar facility access for farming activities. 

Winners of the North American Agrivoltaics Award for Best Solar Farm in 2024: The Food Group, Big River Farms, US Solar, NREL, Great Plains Institute, and Connexus Energy. Photo: AgriSolar Clearinghouse 

Community opposition to multi-acre solar development is driven in part by communities misunderstanding the local benefits of agrivoltaics and thinking that farmland is being taken out of production. Developing solar does not mean farmland is being destroyed or taken out of production. LBNL’s recent research and NREL’s latest publications from the InSPIRE study show that utilities and solar developers need to maintain and improve what is known as “solar’s social license” in communities nationwide. To avoid the worst effects of climate change, more than 3 million additional acres of solar arrays need to be built by 2030.  

While incorporating agriculture into solar designs has been shown to increase public acceptance of solar, some approaches are looking at elevating solar panels 10 feet to grow commodity corn and continue status-quo farming approaches. However, hand-harvested crops commonly sold in farmers markets nationwide can readily be grown in abundance with existing solar facility designs, such as one or two panels on single-axis trackers and torque-tube height of six feet.  

Big River Farms Tomato Crop at US Solar Big Lake Array. Photo: AgriSolar Clearinghouse 

Through the Big River Farms program, farmers learn to scale up their food production while implementing sustainable and regenerative farming practices that improve water quality and usage. Having land access to get started as a specialty crop farmer fills a critical niche in helping address the larger challenges related to land ownership and sustainable, specialty farm operations. Building skills, network, and resources, especially in the agrivoltaics community, helps prepare specialty crop farmers for the next stages of their success. 

Moving Forward: Growing Farmers, Growing Crops 

Moving forward, Big River Farms and Great Plains Institute have been identifying barriers, challenges, and successes of utilizing solar spaces and gathering feedback from farmers, utilities, solar facility owners, and host communities. This project will build capacity and enhance the possibility of success for emerging farmers among immigrant and BIPOC farmers. It will also diversify local agricultural and food-production markets. Most importantly, it will help enhance the communities’ understanding of agrivoltaics systems and diminish the misunderstood concept that solar is taking over valuable agricultural lands.  

With these concepts and practices in place, it will help the organization achieve and sustain the mission of “Growing Farmers, Growing Foods. Through education, the emerging farmers will succeed and prosper, and through sustainable and regenerative agrivoltaics farming practices, the foods will grow as well.