As California Gets Drier, Solar Panels Could Help Farms Save Water | Solar Panels Could Help California Farms Save Water

As California Gets Drier, Solar Panels Could Help Farms Save Water

Agrivoltaics—or on-farm solar arrays—are still rare in California, but experts say the shade they provide could be a game-changer in a state where many farms are struggling to plan for a future with limited groundwater.

Sheep Grazing at the Cal Poly Gold Tree Solar Farm site. (Photo credit: Tony Tran)

Sheep grazing at the Cal Poly Gold Tree Solar Farm site. (Photo credit: Tony Tran)

Satellite imagery of Topaz Solar Farm, a massive solar installation inland from San Luis Obispo in Central California, depicts an oasis of blue panels surrounded by sun-scorched earth. The images do not capture, however, the thousands of sheep hard at work under the panels, eating the non-native grasses and reducing the threat of wildfire.

The operation benefits everyone involved: Sheep farmer Frankie Iturriria gets paid for his time, the collaborating rangeland researchers are breaking ground, and the landowner BHE Renewables can maintain the property with sheep, which have less impact and are more cost-effective than mowers or other livestock. But the farm is one of relatively few examples of agrivoltaics—or combined agriculture and photovoltaic array systems—on private land in California, where the technology has been surprisingly slow to gain visibility and traction.

“I see it as a key player for maintaining food security for the 10 billion people who will be inhabiting this planet by 2050.”

Scientists, farmers, and advocates agree that one of the biggest barriers to rolling out agrivoltaics in California—the national leader in solar energy, agricultural production, and even on-farm solar—is a need for more state-specific research. Internationally, many countries in Europe and Asia are ahead of the U.S. as far as implementation; and within the U.S., the East Coast has largely been leading the charge.

Responding to skyrocketing interest from farmers and energy companies, however, California policymakers began mobilizing this year to obtain funding to advance the technology.

Some experts say that agrivoltaics is vital to preserving food production in California, where many farmers face pressure to retire parts of their land to comply with water conservation regulations or sell it to solar companies expanding production to meet national emissions reduction targets.

In agricultural hubs such as the San Joaquin Valley, where there will likely be significant shifts in the way water and farmland are used over the next several decades, agrivoltaics may offer an alternative path to viability. The approach, which provides shade, could also help directly mitigate the impact of climate change on workers and on the land itself.

Majdi Abou Najm, who is spearheading agrivoltaics research at the University of California, Davis, is among the state’s pioneers. “I see it as a key player for maintaining food security for the 10 billion people who will be inhabiting this planet by 2050,” Abou Najm said during a recent panel discussion convened by the California Council on Science and Technology (CCST). “I see it as a key player in dealing with heat extremes, with drought, with salinity, and other challenges that significantly impact our food, water, and energy security. But also, at the farm scale, I see agrivoltaics as the technology that can maximize our farmers’ and growers’ output from their lands.”

Majdi Abou Najm stands with the red filters he used in his agrivoltaics experiment with tomatoes. (Photo credit: Majdi Abou Najm)

Majdi Abou Najm stands with the red filters he used in his agrivoltaics experiment with tomatoes. (Photo credit: Majdi Abou Najm)

Notably, there are different types of agrivoltaics. CCST’s definition is “the co-location of solar panels on agricultural lands that results in the co-production of agricultural products and electricity.” Jordan Macknick from the National Renewable Energy Laboratory—which conducts agrivoltaics research in California—includes solar combined with specialty and commodity crops, solar with livestock, solar with land providing pollinator habitat or ecosystem services, and solar-integrated greenhouses in the list of approaches.

California doesn’t have a definition yet, but other places do: Some countries use an agricultural production threshold, while other U.S. states have standards for panel height and shading.

Some advocacy groups say that establishing a state-level definition of agrivoltaics is key to ensuring the technology does not replace farms. The American Farmland Trust (AFT)—which estimates 83 percent of new solar development built in the next few decades will likely be on agricultural acreage—supports agrivoltaics as long as agricultural production is guaranteed.

“We are of the mind that we should be outcome-focused as much as possible to the benefit of the farm and the long-term viability of that farm,” said Ethan Winter, AFT’s national smart solar director.

Funding State Agrivoltaics Research

Massachusetts has been a national leader in funding agrivoltaics: The Solar Massachusetts Renewable Target (SMART) offers extra compensation to solar owners for dual-use projects, and is the first program of its kind nationwide. Other Western states are working to catch up: Washington, Colorado, and Arizona have set aside funding for research and development. And while agrivoltaics projects are underway throughout California, significant statewide research funding has yet to be approved.

Abou Najm’s research, which focuses on the productivity of a wide range of crops grown underneath solar panels, is seen as a California success story. He will soon begin a five-year, 10-acre agrivoltaics research project in collaboration with the Sacramento Municipal Utility District, which is currently installing a new 344-megawatt, 1,700-acre solar farm in Placer County. In November, U.C. Davis will host the first agrivoltaics conference in California with industry partners from Germany.

“Agrivoltaics is an exciting application of technology that California must embrace as we look to the future.”

Ruth Dahlquist-Willard, the interim director of U.C. Sustainable Agriculture Research and Education Program (SAREP) who works with small farms in the Fresno area of the Central Valley, is watching the research. She supports exploring agrivoltaics on farms of all sizes in her region, but emphasized that pilots are needed so farmers can plan for altered crop yields under shade and obvious on-the-ground challenges, including that the panels can affect tractor access and irrigation systems and need regular maintenance.

Research will not only help landowners and solar developers implement agrivoltaics but also understand the implications for their bottom lines. Based on her interviews with California landowners, Stanford University researcher Ranjitha Shivaram said there is uncertainty about the financial impact of solar installation: The state’s utility regulator recently made significant cuts to the amount of money Californians get paid for the solar energy they send back to the grid. Shivaram also flagged new costs for solar developers, such as increased maintenance to address dust during harvest and damage caused by livestock.

Funding for California agrivoltaics research also suffered a recent blow. A state bill dedicated to awarding grants for agrivoltaics research and development died in early September, in part due to lack of funding. S.B. 688 aimed to address the impacts of agrivoltaics on farms, on the state’s agricultural economy, on electricity generated from solar panels—and the potential of agrivoltaics systems to reduce the impact of extreme heat on crops, livestock, and agricultural workers.

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“Agrivoltaics is an exciting application of technology that California must embrace as we look to the future,” Senator Alex Padilla (D-CA), who introduced S.B. 688, told Civil Eats. “I will continue to explore how to best promote innovation that benefits farmers and agricultural workers alike. I am confident California can capitalize on the potential here as we modernize our industries.”

Kara Heckert, AFT’s resilient agriculture western advisor, who advocated for S.B. 688, remains hopeful. “Frankly, I was disappointed, but I’m also pleasantly surprised to see the bill got as far as it did,” she said. “There are a lot of unanswered questions and things we need to learn about scaling up agrivoltaics in California—but there’s also a lot of openness. I didn’t talk to a single stakeholder who didn’t think it was ever going to work.”

There are several other potential funding sources for agrivoltaics research in California that advocacy groups are tracking. A.B. 408, which includes $20 million for agrivoltaics installation projects, was co-authored by Senator Padilla and will be considered next year. Additionally, the California Energy Commission (CEC) has launched several programs with funding opportunities for farmers.

The Community Alliance with Family Farmers (CAFF), which also supported S.B. 688, is particularly interested in ensuring agrivoltaics research includes California’s small-scale, diversified farms.

“The industry is moving much faster than policy. We’re ready, and we’re pushing the industry through policy changes, which is what is really needed next.”

“On the whole, family-scale farmers are certainly never the priority when it comes to technological innovation,” Jamie Fanous, CAFF’s policy director, told Civil Eats. “If there is a state program in the future to encourage agrivoltaics, I hope small and underserved farmers—who have historically been left out—have just as much access to those resources as larger operations.”

Lucy Bullock-Sieger, the vice president of strategy for Lightstar Renewables—which collaborates with groups like AFT on policy and helps lead the Coalition for Community Solar Access—said there’s significant enthusiasm for agrivoltaics in her industry, both from utility-scale and smaller-scale solar developers.

Lightstar, which uses a model where landowners receive lease payments, has agrivoltaics projects under construction throughout the country; in California, the company is waiting for the state to release its new community solar program, which will offer better solar energy rates for residents with low and moderate incomes.

“The industry is moving much faster than policy,” she said. “We’re ready, and we’re pushing the industry through policy changes, which is what is really needed next. The industry and developers are really turning to [agrivoltaics], and that has shifted a lot even in the last year.”

Agrivoltaics Benefits

The No. 1 motivating factor for farmers to adopt agrivoltaics in California is declining water availability, said Stanford researcher Shivaram.

Looking ahead 20 years, many farmers will have to take land out of agriculture to comply with the Sustainable Groundwater Management Act (SGMA), 2014 legislation that has required counties to implement groundwater management plans throughout California. As a result of SGMA, AFT estimates 4 percent, or 212,000 acres, of cropland in the San Joaquin Valley alone could be permanently retired and 27 percent intermittently fallow. Conservation groups hope to see some of that land become part of corridors for native plants, waterways, and wildlife, but farmers are also looking to agrivoltaics opportunities.

This year, Majdi Abou Najm is testing his red filter with a solar cells prototype in the field. (Photo credit: Majdi Abou Najm)

This year, Majdi Abou Najm is testing his red filter with a solar cells prototype in the field. (Photo credit: Majdi Abou Najm)

Agrivoltaics may also help conserve water. “The shade that is created by the solar panels, in areas that receive more sun than plants need for their photosynthesis, reduces the heat stress on those crops, makes them healthier, and makes them require less water,” Abou Najm said. “Agrivoltaics is more than just a dual production of food and energy on the same plot of land—it maximizes the synergy between the two.”

Agrivoltaics stand to assist Central Valley farms in myriad ways, said Dahlquist-Willard. Larger farms that adopt agrivoltaics could potentially benefit smaller ones by alleviating pressure ­on regional groundwater. At the same time, farmers with less land are more likely to consider agrivoltaics than converting entirely to solar. “For a small farm—say 10, 20, 30 acres—if you convert your whole farm to solar, you’re quitting farming. Nobody does that when farming is their only source of income,” she said.

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Abou Najm published a theoretical study looking at how to grow crops—including lettuce, basil, and strawberries—under solar panels in a way that maximized productivity. He found that the blue part of the light spectrum is best filtered out to produce solar energy, while the red spectrum can be optimized to grow food; this requires a specific type of panel that’s less common but available. His follow-up research involves expanding the types of crops and conducting field trials.

U.C. Davis is filling a necessary gap in California research, though many other studies have been conducted nationally and internationally documenting crop yields under panels. Scientists have found agrivoltaics can improve the efficiency of the panels, and increase water-use efficiency, soil moisture content, and crop yields. In one cherry tomato study, production doubled under the panels and water-use efficiency was 65 percent greater.

Researchers from California Polytechnic State University in San Luis Obispo are also documenting the benefits of grazing under solar panels in California, supporting research worldwide. They are studying the benefits of sheep grazing on two solar installations, Gold Tree Farm and Topaz Solar Farm. There, they’ve found that the solar arrays can offer synergistic benefits for the sheep and the grasslands. Compared with pastures outside the solar panels, the shaded grasses have higher water content, greater nitrogen content, and lower non-digestible fiber.

Topaz Solar Farm, which was one of the largest solar installations worldwide when it was built in 2014, now pales in comparison with other projects in the U.S. Southwest, China, and elsewhere. Nevertheless, it remains a shining example of agrivoltaics on a utility-scale solar farm. According to Katie Brown, the site’s rangeland consultant, matching sheep grazers with the right solar installations—which groups like American Solar Grazing Association (ASGA) are doing—is the key to success.

Frankie Iturriria inherited his company, I & M Sheep, from his father, who started it in 1958. His shepherds, who live on-site from April through October, rotate the herds every two to three days; they move groups of 2,000 sheep onto 30-acre pastures, which are divided across the 3,500 acres housing the panels. The sheep prefer the annual, naturalized grasses—oats, brome, fescue—early in the season, which makes more space available for natives like purple needlegrass and pine bluegrass.

The solar farm, which was formerly used for grazing and hay production, is near the Carrizo Plain National Monument and rich with biodiversity, including endangered species like the San Joaquin kit fox. Unlike a mower, the sheep can cut down the grass in less time and without threatening the survival of the foxes. Sheep navigate the arrays better than cattle and are less prone to cause damage than goats.

While keeping up with the demands of the site is intensive, Iturriria recommends the model to other sheep farmers. “It allows us to continue grazing, even if a solar farm comes in,” he said. “In the past five years, a lot of solar sites have gone up in California. I know a lot of producers getting into this, and I think it’s working out for both sides.”

Anna Guth is a freelance editor and reporter based in Marin County, California. Previously a staff writer for the Point Reyes Light, she has a degree in English and environmental studies from Wesleyan University. Read more >

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