floatovoltaic installation Credit: Far Niente Winery
A floatovoltaic installation at Far Niente Winery in Oakville, Cal., comprises nearly 1,000 solar panels floating on pontoons on the vineyard irrigation pond.

Non-traditional sites identified for future solar farms

Equivalent of 183,000 football fields of non-agricultural land identified in study aiming to ease competition among farmers, conservationists and energy companies.

There's 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. However, what if large solar installations could be built away from agricultural land, eliminating the competition between two important industries?

In a study published in Environmental Science & Technology, researchers at the University of California's Riverside and Davis campuses explored the possibility of developing solar installations on a variety of unconventional sites in California's Central Valley. 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.

"In the era of looming land scarcity, we need to look at underused spaces," said corresponding author Rebecca R. Hernandez, an assistant professor in the department of land, air and water resources at the University of California-Davis. "This paper provides a menu of sorts for farmers, agricultural stakeholders and energy developers to think about energy projects on spaces that don't require us to lose prime agricultural and natural lands, which are becoming increasingly limited."

Previous studies have shown that solar installations are often built on natural areas or croplands, which takes that land away from conservation efforts or agriculture. For example, one study based in Leece, Italy, reported that 51% of the area's solar devices were located on untouched and agricultural land, including century-old olive groves.

Michael Allen, a distinguished professor emeritus of plant pathology and biology at the University of California-Riverside and director of the university's Center for Conservation Biology, said many existing solar farms are built in unsuitable areas, where they 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," Allen said. "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.

Combining all of these potential sites, the team identified more than 8,400 sq. km (equal to 183,000 football fields) of the Central Valley's 55,800 sq. km footprint as non-agricultural, developed land suitable for large solar installations. These areas have the potential to generate enough solar energy to exceed California's 2015 projected demands for photovoltaic (PV) power — plants that use solar cells to directly convert sunlight into electricity — and for concentrating solar power (CSP) — plants that convert sunlight into thermal energy — by 13 times and two times, respectively.

"The study highlights the wealth of sites for solar energy generation that don't conflict with farmland or protected areas," Hernandez added. "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 title of the paper is "Land Sparing Opportunities for Solar Energy Development in Agricultural Landscapes: A Case Study of the Great Central Valley, CA, USA."

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