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Dual-use solar: An exploration of potential in the San Joaquin Valley

April 25, 2024

Dual-use solar — the co-location of solar with one or more other land use — has the potential to provide added environmental, social, and economic benefits compared to traditional solar development. Previous blog posts provided a primer on the range of uses, benefits, and applicability of three forms of dual-use solar — agrivoltaics, ecosystem services-based solar, and floatovoltaics — and an overview of policy considerations. We concluded that, while dual-use solar is not a silver-bullet solution to barriers facing utility-scale solar deployment, it can complement traditional projects and provide opportunities to increase local benefits of solar development.  

This blog investigates the potential of dual-use solar in a particular region — California’s San Joaquin Valley (“the Valley”) — informed by expert insights and background interviews with local stakeholders, including county-level officials, advocacy organizations, developers, and experts on dual-use configurations. The Valley is one of the most productive agricultural regions in the country, with abundant sunshine, a growing number of utility-scale solar sites, and increasing groundwater constraints. At first glance, the region seems ripe for agrivoltaics. However, our findings suggest that dual-use configurations that provide ecosystem services could be most suitable for the Valley today while agrivoltaics and floatovoltaics configurations continue to scale and advance technologically. All configurations face implementation challenges and require additional policy support and developer uptake.  

Background on the San Joaquin Valley  

The San Joaquin Valley is an agricultural powerhouse for California and the United States, producing more than half of the state’s agricultural output. However, overuse of water resources and climate change-induced droughts have led to significant water scarcity challenges. In 2014, the state passed the Sustainable Groundwater Management Act (SGMA) requiring groundwater users to bring their water basins into balance over the next two decades. To achieve these water reductions, the San Joaquin Valley will likely need to fallow at least 500,000 acres of agricultural land by 2040.  

At the same time, California is pursuing ambitious climate and clean energy goals. In 2018, the state passed SB 100 which requires 100% of the state’s retail electricity needs to be met with zero-carbon and renewable resources by 2045. A thoughtful approach to the clean energy transition, which includes a mix of clean energy resources, will be crucial for an affordable, reliable, and land-smart clean energy future. In 2022, the San Joaquin Valley produced nearly 15 GWh of solar electricity, accounting for 45% of the state’s 33 GWh. With even more projects planned or in progress, it is evident that utility-scale solar development in the Valley will continue to be a critical piece of California’s climate solution. Nonetheless, solar deployed in the Valley today is still just a fraction of the region’s resource potential.  

The ongoing and continued loss of agricultural land, coupled with the clean energy transition, will result in significant changes to the region’s landscape, economy, and industries. The Valley faces various socio-economic and environmental challenges; years of intensive agricultural production and heavy industry result in poor air quality, polluted water, and degraded ecosystems. Industrial facilities have often been sited near marginalized populations, perpetuating inequities and environmental burdens. Over half of the Valley’s population lives in census tracts classified as disadvantaged, accounting for 27% of the state’s disadvantaged populations despite making up only 11% of the state’s total population.  

The land use and industrial transitions in the Valley present opportunities to develop clean energy industries that contribute to the region’s long-term goals, including expanding the economic base, creating new jobs and economic opportunities for individuals, improving environmental conditions, and ensuring equitable distribution of benefits and burdens.  

Understanding the potential of dual-use solar in the Valley 

The Valley’s land use shifts and clean energy deployment make dual-use solar an ideal potential fit — building solar will help California achieve its clean energy needs and bring new economic activity to the region. Placing solar on transitioning farmland can provide new revenue streams for owners of fallowed agricultural land. Dual-use solar systems also offer multiple co-benefits, including improved community support, land-use efficiency, agricultural production, water savings, and ecosystem benefits.  

We spoke with six regional stakeholders to understand the potential of dual-use solar technologies in the Valley, and how the perceived benefits of these systems could play out in the specific context of the region. We asked them about the promise of three forms of dual-use solar — agrivoltaics, floatovoltaics, and ecosystem-services based solar, — community sentiments around infrastructure deployment, and other key concerns like solar’s interaction with groundwater management. Their inputs informed our discussion below of community concerns and the feasibility of dual-use solar, both today and in the future. This work was also informed by regional conversations held through a larger clean energy exploration and planning effort in the Valley led by CATF, as well as background research and conversations with dual-use experts.  

Community concerns and land-use  

Across the nation, utility-scale solar can be a contentious development in communities with concerns arising over changing land use, aesthetics, and viewshed impacts. Dual-use solar is often discussed as a solution that could generate greater community support for solar projects compared to traditional utility-scale development, particularly where concerns focus on land use and constrained land availability. Combining land uses in dual-use solar configurations could reduce land-use competition, increase land productivity, and mitigate concerns of a binary choice between producing food or energy. In highly developed regions, this could prove a valuable tactic to build new solar resources.  

The Valley is not immune to community challenges to renewable energy development, but according to our stakeholder interviews, concerns over competing land uses are not as acute as elsewhere in the country. While urban growth and development compete with agricultural land in this area, interviews suggest agricultural landowners are most concerned with groundwater constraints and the long-term viability of their land for agriculture. Landowners who lease or sell land for solar development stand a chance to make a significant profit, a good opportunity for land that could become fallowed in the face of climate change and water use limitations.  

Regional stakeholders prefer buffers between utility-scale solar and existing residential and commercial areas. Stakeholder interviews suggest that, when it comes to utility-scale solar development, communities are more concerned with ‘doing it right’ rather than ‘doing it at all.’ According to interviewees, ‘doing it right’ means meaningful community engagement in decision-making, mitigation of environmental impacts, and creation of new economic opportunities for communities. 

Ecosystem-services: A promising option for dual-use solar in the Valley today 

Given the region’s environmental concerns and questions over how fallowed land will be transitioned and managed, ecosystem-services based solar appears to be a compatible form of dual-use solar for the Valley. This type of dual-use co-locates solar with vegetation not intended for agricultural production or other practices that promote environmental well-being. Compared to other forms of dual-use, ecosystem-services based solar is more feasible to deploy at scale and can contribute to clean energy goals while addressing environmental concerns, yet it is still not without its own challenges. 

The Valley faces environmental challenges including soil degradation, air pollution, water scarcity, and habitat loss. Idle and fallowed agricultural land also creates dust, a large concern in the region. Actions common to ecosystem-services-based solar — like cover cropping — can help manage stormwater runoff, mitigate dust, support pollinators, and improve soil quality. Planting native vegetation that creates pollinator habitat has been demonstrated successfully at scale and provides benefits in heavy agricultural areas — an important aspect for the Valley’s orchards relying on pollination. A key challenge with these configurations is that planting cover crops or native vegetation may still require irrigation for which water budgets from the basin’s Groundwater Sustainability Agencies (GSA), a management agency established by SGMA, would need to account.  

Other actions that modify site design to provide ecosystem services can also be taken to preserve wildlife corridors and create species habitat. For example, local counties can set permeable fencing requirements, vegetation standards, herbicide usage limits, setbacks, and stormwater management actions. These modifications are also easier to incorporate into state and local siting and permitting requirements compared to requirements for agrivoltaics. In the Valley, many counties have already set these requirements, demonstrating local interest in promoting best practices that mitigate environmental harm and enhance existing ecosystem services. However, solar developments would ideally take steps to not only maintain existing services but to provide additional net benefits, which are often site-specific. Some solar facilities in the Valley have already demonstrated that they can retain or create additional habitat for species that are conservation priorities, including the kit fox. For example, Topaz Solar Farm, located just outside the Valley, demonstrates site design modifications to ensure wildlife corridors for large animals are minimally, if at all, disturbed.  

Although ecosystem-services based solar is more technically well-suited to the existing conditions of the Valley than other forms of dual-use, it still faces some big hurdles to being widely deployed most impactfully. A significant hurdle is in mitigating risk for developers; as mentioned in previous blog posts in this series, solar developers are generally wary of taking actions that attract at-risk species that they would later be liable to protect. If policy solutions are not in place to reduce developer risk and potential increases in project costs, developers may be dissuaded from constructing dual-use configurations. 

Agrivoltaics are incompatible with existing large-scale agricultural activity in the Valley  

Although the San Joaquin Valley is an intensive agricultural region, agrivoltaic configurations today might not be compatible with existing crop production and livestock. Crop production in the Valley is dominated by tree nuts like almonds, pistachios, and walnuts, along with grapes and citrus which are currently not compatible with dual-use solar. Agrivoltaic configurations are best suited for row crops like leafy greens and tomatoes that can be hand-harvested or maintained with smaller equipment and can grow under standard panel heights. Today, compatible crops like tomatoes make up only 3% of the region’s crop production, and lettuce only 1%. Additionally, agrivoltaic configurations have not yet been demonstrated at the scale of agricultural activity in the Valley. It is possible that solar technologies will develop to fit these crop types in the future, or that crop production in the Valley could change due to shifting climactic conditions, in which case agrivoltaics could become more relevant.  

Likewise, large-scale co-location of solar with livestock grazing will likely not be a major development in the Valley. North of the Valley, Coyote Creek Agrivoltaic Ranch is a 200 MW site combining sheep grazing with solar. But sheep production in the U.S. and in California overall is declining annually. The livestock industry is dominated by cattle and dairy operations, which are far less compatible for solar grazing operations due to livestock size and behavior.   

Floatovoltaics are in pilot stage and worth watching 

Efforts to install solar over water canals have caught much attention regionally and nationally. Floatovoltaics have been demonstrated to reduce water evaporation losses, a big upside for a drought-prone region like the Valley with an extensive network of irrigation canals. Project Nexus, a first-of-its-kind project in the nation, will pilot the installation of solar panels over irrigation canals. The initiative is a collaboration between UC Merced, Turlock Irrigation District (TID), the California Department of Water Resources, and the developer Solar AquaGrid. TID, which manages the irrigation canals and provides retail electricity, is uniquely positioned to manage the panels over its canals. A UC Merced study, from which the idea initially stemmed, modeled the potential of covering all the state’s irrigation canals, estimating that they could produce a combined 13 GW of electricity, or roughly 19% of California’s anticipated solar needs by 2045. Although this configuration has been proposed for canals across the state, implementation will be more challenging where canal operation and electricity sales are managed by distinct entities. Another challenge to widespread implementation is an acute lack of transmission to move electricity from rural areas of the Valley where irrigation canals are prevalent to areas of high electricity demand.  

Policy constraints and enablers 

Several policy hurdles stand in the way of dual-use solar proliferating, and most involve existing land-use policies and regulations. Agricultural land protections, like those of the Williamson Act, make installing solar on agricultural land challenging, even if on fallowed land or co-located with crop production. Additionally, local land-use regulations may not support zoning or re-zoning for combined land uses. 

However, this is a new and evolving space with opportunities for innovative policy and planning solutions. Coordinated decision-making and alignment between SGMA implementation and state and local energy planning could identify vulnerable lands most suitable for solar. Finding such synergies could minimize disturbance to prime agricultural lands and sensitive habitats. Actions that support ecosystem-services based solar could be more widely required through various local permitting and siting regulations, like vegetation, fencing, and stormwater management requirements. Additional research, supported by the state, could identify actions best suited for the Valley’s characteristics. A statewide definition of and guidance for dual-use solar configurations could also help local jurisdictions implement effective local policies.  

The future of dual-use solar in the Valley 

Dual-use solar is an important tool in the clean energy transition toolkit, but it will not singlehandedly solve the barriers to clean energy deployment. Utility-scale solar is a reality of the clean energy transition, and dual-use configurations providing ecosystem services can be considered today to minimize impact to surrounding communities and ecosystems while helping the region meet its climate goals. Agrivoltaic and floatovoltaic configurations are in earlier stages and could be more seriously considered in the Valley if and when technologies can comport with the Valley’s crop and livestock outputs and its unique water challenges. Over time, opportunities may even exist to explore how dual-use solar could promote groundwater recharge. For example, installing raised panels on frequently flooded land could create a hybrid ecosystem services-based solar and floatovoltaics configuration.  

Further quantitative and feasibility analysis could identify which actions are best suited and develop support policy options for the most compatible forms of dual-use solar.  

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