How installing solar canopies over canals can help California fight drought

Joseph Guzman
·5 min read
17

Story at a glance

  • The $20 million experiment, dubbed “Project Nexus,” is funded by the state of California and will assess whether solar panel canopies erected over exposed irrigation canal systems can significantly reduce water evaporation while simultaneously generating renewable power.

  • Researchers from the University of California, Merced determined that covering the 4,000 miles of California’s open canals with solar panels could save upward of 63 billion gallons of water each year.

  • The study found the solar canopies could generate about 13 gigawatts of renewable power annually, the equivalent to about one-sixth of California’s installed capacity.

A first-in-the-nation project to determine whether covering sections of canals with solar panels can help California reach its renewable energy goals is gearing up to break ground early next year.

The $20 million experiment, dubbed Project Nexus, is funded by the state of California and will assess whether solar panel canopies erected over exposed irrigation canal systems can significantly reduce water evaporation while simultaneously generating renewable power. The project in California’s San Joaquin Valley is a partnership between utility company Turlock Irrigation District (TID), California’s Department of Water Resources (DWR), solar energy company Solar AquaGrid and the University of California, Merced.

The pilot project materialized following results published in a 2021 study outlining the potential benefits of the concept. While the idea is novel in the U.S., researchers looked at a large-scale, solar-canal system in Gujarat, India, and considered what the concept could do for California.

Researchers from the University of California, Merced determined that covering the 4,000 miles of California’s open canals with solar panels could save upward of 63 billion gallons of water each year, the residential water needs of about 2 million people, or enough to irrigate about 50,000 acres of farmland. In terms of power generation, the study found the solar canopies could generate about 13 gigawatts of renewable power annually, the equivalent to about one-sixth of California’s installed capacity. That’s about half the projected new capacity needed by 2030 to meet the state’s decarbonization goals.

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“Another benefit is that it would avoid land use. Solar canopies over canals avoid the development of large tracts of land that would be required for ground-mounted systems. If we use canal infrastructure, that’s already disturbed land,” Brandi McKuin, lead author of the study and project scientist with UC Merced, said in an interview.

“There’s a benefit to ecosystems and perhaps even it could avoid some of the protracted disputes over land use that other large utility scale solar projects have had to deal with, for example, tribal sovereignty,” McKuin added.

Another benefit is the microclimate of the canals can cool the solar panels and increase their efficiency. McKuin said field studies show solar canals in India cooled panels by as much as 10 degrees and had on average 3 percent higher output than ground mounted systems with the same configuration.

The shade from the panels could also limit light to aquatic weeds and reduce algae growth, which could result in big maintenance savings for entities that manage the canal systems.

For Project Nexus, less than 2 miles of irrigation canal operated by utility Turlock Irrigation District in California’s San Joaquin Valley will be covered with solar canopies.

One location in the town of Ceres involves covering about a mile straightaway of relatively narrow, 20 to 25 feet wide, canals and testing multiple different mounting technologies and solar panel designs.

“At this site it’s going to be 8,000 linear feet of solar panels. So you’re going to have the ability to A-B test different hypotheses,” Josh Weimer, external affairs department manager for Turlock Irrigation District, said in an interview.

“So testing panels a little bit closer to the canal, some a little bit taller, and seeing if there is an efficiency difference. We’re also looking at potentially using two types of solar panels, mono-facial and bi-facial. With bi-facial you have the ability to potentially generate energy from the underside of the solar panel, and that might be a potential benefit if there’s some reflection from the water underneath the panel,” Weimer added.

At the second location in the town of Hickman, just east of Modesto, a 500-foot stretch of canal that is 110 feet wide will also be covered using cable suspension.

Weimer says the biggest hurdle is devising a viable and cost effective way to engineer the mounting techniques. There are also concerns about the canopies obstructing access to canals for maintenance.

The concept, if successful and scaled up, could potentially help California reach its climate goals and provide water and energy solutions to a state that has long suffered from severe drought. Weimer says using land the electric utility already owns for solar infrastructure could significantly cut costs.

“We have renewable energy requirements. We are going to need more and more renewables to meet our 2030 and 2045 goals. And so this could potentially be an option for us to scale up. We have 250 miles of canals. So we’re interested in studying this in a very small section,” Weimer said.

Groundbreaking on the project is anticipated for early 2023, and the project is expected to be completed in 2024.

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