UC Researchers Identify ‘Land-Sparing’ Solar Sites

There can sometimes be a trade-off when sprawling solar farms pop up on agricultural land: farmland disappears, perhaps forever, in return for growth in the promising renewable energy sector, according to researchers from the University of California (UC) system. But what if large solar installations could be built away from agricultural land, helping eliminate potential competition between two important industries?

In a new study, researchers at UC Riverside and UC Davis say they explored the possibility of developing solar installations on a variety of unconventional sites in California’s Central Valley. They say they focused on this region, which comprises 15% of California’s landmass, because it is an area where food production, urban development and conservation collide.

Michael Allen, a distinguished professor emeritus of plant pathology and biology at UC Riverside and director of the university’s Center for Conservation Biology, says many existing solar farms are built in unsuitable areas, where they may encroach on natural or agricultural lands already under threat from urban sprawl.

“When a piece of land is developed for a solar installation, it is very unlikely to be reverted into agricultural land, even when the lease to the solar company eventually runs out. That’s because flattening and compacting the land, as well as the long-term application of herbicides to keep the site clear of weeds, spoils the land for future farming,” says Allen. “For this reason, it is important that we explore alternative sites for new developments as the industry continues to grow.”

The researchers evaluated four unconventional areas: (1) developed areas within agricultural landscapes, such as rooftops, transportation corridors, and parking lots; (2) land that is too salty for crops to grow, either because of naturally occurring salts or buildup from human activities; (3) reclaimed areas that were previously contaminated with hazardous chemicals; and (4) reservoirs and irrigation channels that can accommodate floating solar panels.

UC Researchers Identify 'Land-Sparing' Solar SitesCombining all these potential sites, the team identified more than 8,400 square kilometers (equal to 183,000 football fields) of the Central Valley’s 55,800 square-kilometer footprint as nonagricultural, developed land suitable for large solar installations. The researchers say these areas have the potential to generate enough solar energy to exceed California’s 2015 projected demands by 13 times for solar photovoltaic (PV) power and two times for concentrating solar power (CSP), which are plants that convert sunlight into thermal energy.

“The study highlights the wealth of sites for solar energy generation that don’t conflict with farmland or protected areas,” says Rebecca R. Hernandez, assistant professor of earth system science and ecology at UC Davis. “Since farming is an incredibly energy-intensive industry, the land-sparing sites we identified could provide a win-win situation for both farmers who need more energy and the energy providers that wish to serve them.”

The research paper, “Land-Sparing Opportunities for Solar Energy Development in Agricultural Landscapes: A Case Study of the Great Central Valley, CA, USA,” was published in Environmental Science and Technology. Madison Hoffacker, a graduate student in the Energy Graduate Group at UC Davis, was first author on the paper.

Photo courtesy of Far Niente Winery/UC Davis: A “floatovoltaic” installation at Far Niente Winery in Oakville, Calif., comprises nearly 1,000 solar panels floating on pontoons on the vineyard irrigation pond. 



  1. The assumption solar sites will not return to agriculture seems unfounded. They represent medium term improvements with minimal impact to soils. In many climates, pollinator friendly vegetation can give soils a chance to revitalize for the next generation, with little to no need for herbicides.

  2. I agree with Derek. I’ve never heard of the application of herbicides on solar farms here in Vermont. However, I am all for the kinds of solar development mentioned in this article. These less natural sites, however, are more costly to develop. So, to make this viable, there would need to be a small extra bonus for developing sites like these.

  3. I remember the saying ‘If there’s a will, there’s a way.’ Both are important and glad that solution has been indicated included in the article. Let’s all move forward continue in going green for I know as a consumer can really benefit from these renewable energies (got mine installed with Reboot Solar) and is keeping, loving Mother Earth. This continues until the next generation.


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