Are Dual-Use Solar Farms a Solution for California?

Written by Meaghan Boehm
 · August 9, 2022

What if I told you that you can have both farming and renewable energy on the same plot of land? Agrivoltaics do just that. A clever combination of “agriculture” and “photovoltaic” — a method converting energy from the sun to electricity — agrivoltaics are one of four main kinds of dual-use solar that puts regenerative farming techniques and solar panels in the same location to allow both electricity generation and food production. In a recent article these dual-use solar panels were described as having wide ranging positive impacts on water, soil, and energy efficiency by providing cleaner energy, more food, and healthier soil with greater water retention and carbon sequestration abilities. 

What are the Benefits?

The Department of Energy lists several benefits of agrivoltaic installations, including three overarching categories: efficiency of land use and power generation, soil regeneration and ecological preservation, and increased revenue. Let’s review all three.

Dual use solar panels over crops

Photo credit: National Renewable Energy Laboratory

Dual-use solar panels enable both electricity and food production to happen on the same plot of land. This advantage could be key in working to solve the looming global issues of limited farmland and increasing global population. In a 2017 pilot study on agrivoltaics in Germany, land efficiency increased by 60-84%. This higher productivity can be seen in the graphic below comparing two types of cropland usage. Imagine that 100% of the plot on the left can be used to produce wheat, while 100% of the plot on the right is set up to produce solar electricity. But when both plots each hold 80% wheat and 80% solar, the efficiency of the land increases to 160% for each product. (Image source: Fraunhofer ISE)


Image source: Fraunhofer ISE


Made in the Shade

Increased productivity with agrivoltaics has a lot to do with the microclimate beneath the solar panels. Because of the combination of solar panels and plants, a more localized climate is created that can benefit both solar panel productivity and crop yield. Transpiration from the plants below cools down the solar panels above, increasing panel efficiency, while the solar panels shade the plants and conserve moisture within the region. An Arizona study found that adding solar panels to growing crops helps to moderate the severe climate variability farmers experience today. The shading and water retention provides protection from drought, but also maintains warmth for frost prevention in the winter. The result is a cooler, water-efficient, and protective microclimate for the panels, plants, and laboring farmers. Growing seasons could also start earlier and end later, resulting in increased production of crops. This overall efficiency is crucial in places like the SF Bay Area, where increasingly urban communities could benefit from more sustainable uses of agricultural space.  

Crucial to the findings of the German study are that certain crops (especially leafy vegetables, various fruits, and field forage), benefited from the additional shade, especially during periods of drought. In recent years California’s heat and drought conditions have reached record-breaking severity for everyone, including farmworkers. Limited water availability for irrigation is severely impacting crop production. In a time where people are struggling to conserve water, innovative efforts like agrivoltaics are necessary to answer this desperation. Several studies have proven agrivoltaics reduce water use when farming, but researchers at the University of Arizona found that beneath the solar panels in agrivoltaic systems, evaporation slowed by 50% as a result of the cooler temperatures. The newly structured, nutrient-filled soil could retain more water, and as a result the crops required less frequent watering than if they were directly in the sun. If Bay Area soils could have greater water retention, more water may be conserved. And any water conserved is a win for Californians.

In addition, agrivoltaics can provide a source of consistent revenue for farmers. Especially in poor growing years, revenue from solar energy will provide economic resiliency for farmers in conjunction with opportunities for nutrient and land recharge of degraded lands. The Arizona taste and preferential study also demonstrated that it would be in farmers’ best interest to grow vegetables that are indistinguishable by taste from those grown in full sunlight.

Photo of Jack’s solar GARDEN, colorado. Source: NREL

The Future Looks Bright

When it comes to best practices for agrivoltaics, much more remains to be seen. Recent U.S. studies show mixed results that can depend on weather, soil type, crop type, and geographic location. Additionally, increased costs of materials and installation of dual-use solar systems have been a cause for concern, for which research is underway. However, current success stories such as Jack’s Solar Garden in Colorado and governmental support (InSPIRE project’s Solar Development Strategies Guidebook, Southern California’s Solar Site Pollinator Scorecard, and Massachusetts’ SMART Program) have proven there is wide ranging support for dual-use solar implementation that could be expanded to California. In fact, the USDA’s Rural Energy for America Program provides grant opportunities to encourage the installation of renewable technologies serving agricultural operations to reduce greenhouse gas emissions. 

Scott Weeks, Senior Environmental Scientist for the California Department of Food and Agriculture, stated that their SWEEP program “does fund solar panels if it is offsetting the use of electricity used for irrigation”. While there are minimal projects in the state involving dual-use solar panels, this does not mean opportunities are unavailable. Through programs like these, the state of California provides room for the Bay Area to improve sustainable agriculture and energy practices.

Does dual-use solar make sense for California? Signs point toward yes. The state has already led the nation in implementing environmentally sustainable policies such as SB 1383’s zero waste initiatives and SB 100’s renewable energy requirements. Agrivoltaics would expand this proactive effort by supporting both clean energy generation and sustainable agriculture. In addition to farms, urban counties and cities within the Bay Area might consider implementing dual-use solar for gardens or even rooftop farming. And dual-use solar may work best for Californians on a smaller scale, as suggested by Kern County’s top planner, Lorelei Oviatt in The Delano Record.

I first became interested in learning more about dual use solar because it combines beneficial electrification and sustainable agriculture, two areas that align closely with Acterra’s priorities for fighting climate change. Even though more research on dual-use solar systems is needed to understand their use and success in the Bay Area specifically, the evidence we have from the U.S. federal government, state universities, and international organizations suggests undeniable benefits for farmers, citizens, and the environment. By promoting crop yields, renewable energy, water conservation, and soil regeneration, dual-use solar farms may not be the single solution to combat climate change, but could very well be an additional method to push forward California’s climate goals.

Meaghan Boehm

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