AS YOU DRIVE through the Central Valley, it is hard to miss the iconic California Aqueduct, which moves millions of gallons of irrigation water through a large canal in the middle of the state. The canal is visible because it’s open on top — a fact that also allows a sizable percent of the water to evaporate, as the region now faces increasingly high temperatures for much of the year.
A few years ago, scientists began asking: What if we covered the canal with solar panels?
Now, that question has prompted a pilot project. In late March, the first-ever solar canal — known as Project Nexus — was connected to the grid in Turlock.
The $20 million state-funded project, which began in 2022, consists of two canopy-shaped sections of solar panels that are just 700 feet long and 20 feet wide. Together the sections have the capacity to produce over a megawatt of electricity.
The pilot was completed as a partnership between the Turlock Irrigation District, the California Department of Water Resources, University of California at Merced and Solar AquaGrid — a Bay Area advisory firm.
The groups are still working on building another 300-foot-long and 110-foot-wide section, as well as incorporating battery storage.
“We’re demonstrating that it can be done,” project scientist Brandi McKuin said. “It’s important to have prototypes to study because that’s where innovation comes along.”
In addition, a coalition of seven research universities has launched the California Solar Canal Initiative, which intends to use research to help accelerate the widespread construction of solar canals.
Benefits for land, water and energy
Led by USC Dornsife Public Exchange — a group dedicated to bringing public and private sector partners into collaborations with academic researchers — faculty at the seven collaborating colleges and universities have begun studying the viability of a broader effort. Researchers are aiming to determine the best locations for additional solar canals, how they could compete on the market, the policy and regulatory pathways that would advance or hinder construction, and the impact of solar canals on disadvantaged communities.
McKuin and a team of researchers at UC Merced, published a 2021 study on the potential water and energy savings that might result in covering the 4,000 miles of canals in the state with solar panels.
“We can think of (solar canals) as a multi-benefit infrastructure,” McKuin said, “It’s a triple win for land, water, and clean electricity.”
The study estimates that solar canals running the entire length of the aqueduct could provide up to 13 gigawatts of clean energy, which is enough electricity to power roughly 2 million homes per year. In California, the overall energy demand can vary between about 25 gigawatts on an average spring day to over 50 gigawatts on a hot summer afternoon.
David Wooley, executive director of the Center for Environmental Public Policy at the University of California, Berkeley, said the potential increase of electric power in the system from solar canals will be important because the demand for electricity is growing as the state continues to electrify and add AI data centers.
California has some of the most ambitious climate goals in the country. One of its targets, mandated by state law, is to cut greenhouse gas emissions by 48% below 1990 levels by 2030. The state also has a goal of achieving 100% clean power by 2045.
While state officials say they are on track to achieve these goals, an analysis released last year by the nonprofit Next 10 and consulting firm Beacon Economics found that California has fallen behind. Researchers at the California Solar Canal Initiative say the project can help close the gap.
Reducing water lost to climate change
Solar canals work like pool covers. As the California Water Board estimates that the state could lose up to 10% of its water supply by 2040 due to climate change, solar canals may also offer a promising solution.
The UC Merced study found that they could save up to 63 billion gallons of water every year. That is enough to meet the needs of up to 2 million residents annually.
Some farmers in the Central Valley have added solar panels to their land, and more will likely do so in the coming years thanks in part to California’s groundwater rules, which will require a reduction in the number of acres farmed. And while agrivoltaics — the practice of integrating solar panels with agriculture — is on the rise, there’s also growing concern about the potential for solar farms to displace wildlife habitat and farmland across the state.
Covering the existing canals may help by reducing the amount of agricultural land and natural habitat needed to set up solar farms — saving 40,000-50,000 acres.
Beyond the water and energy benefits, the study determined that solar canals could help reduce pollution in Central Valley communities, which have some of the worst air quality in the country. Surrounded by mountain ranges, the valley becomes a pool for air pollutants from heavy truck traffic on Interstate 5 and Highway 99, diesel-burning generators, engines, and irrigation pumps, as well as heavy agricultural machinery like tractors.
More locally available energy from solar panels might help farmers and residents electrify more buildings and vehicles faster, said Monica Dean, director of the climate and sustainability practice at USC Dornsife Public Exchange.
“We’re starting to already see a lot more agricultural equipment that’s available in electric form, including tractors and other things. That could have a huge public health benefit by reducing the amount of pollution that’s coming off of a lot of those vehicles,” Dean said. The availability of more local power in the region would also allow for more EV charging stations along I-5.
At the same time, said Dean, more solar canal projects would increase job opportunities for the local workforce during construction, but also for building and maintaining the panels over the long term. In a region dominated by low-paying agriculture jobs, this type of community investment could be especially valuable.
These projects could help save farmers and canal owners and operators money on land and maintenance costs too. “If the Turlock Irrigation District wanted to build a solar plant nearby, the land would cost around $50,000 to $60,000 an acre,” McKuin said. “So by using their existing infrastructure, they save money there.”
Additionally, aquatic weeds tend to love the warm, wet environment in the canals, but researchers anticipate that covering them with solar panels will cut down on weed growth by lowering the amount of sunlight required for photosynthesis. In turn, this would decrease maintenance costs for canal owners and operators.
Not all canals are ideal for solar panels
With the Project Nexus canopies constructed and generating electricity, researchers plan to study the pilot’s impacts and effectiveness in order to understand how to replicate it elsewhere.
As McKuin and the other researchers see it, these canopies probably won’t cover the entire aqueduct. For instance, some portions of the aqueduct are lined with concrete and other portions are not. McKuin said that some districts with natural canal beds are less inclined to install solar panels because they lose more water to seepage than evaporation. “Not all 4,000 miles (of the aqueduct) are created equal, and so in some cases it might be super easy and an obvious choice to install this kind of technology. In other cases, it just might not be practical,” Dean said.
Dean said the biggest barrier to accelerating solar canal projects is determining where to start.
“There’s a complex kind of jigsaw puzzle of who owns the canals, who owns the water … and who supplies the electric power to end use customers. So a lot of things have to be lined up in order to do this kind of project.” David Wooley, UC Berkeley Center for Environmental Public Policy
At UC Berkeley, David Wooley is working on a team that is looking at the regulatory aspects of the project and economic opportunities to support the investment into solar canals.
“There’s a complex kind of jigsaw puzzle of who owns the canals, who owns the water … and who supplies the electric power to end use customers. So a lot of things have to be lined up in order to do this kind of project,” Wooley said.
To address this complexity, he said the California Solar Canal Initiative team is working on a toolkit for government agencies, utilities, and community members to use when deciding whether and how to implement solar canals.
In addition to the research team, the initiative is guided by an advisory council that will assist in ensuring that project outcomes can be put into practice on the ground. Chaired by Solar AquaGrid, the council includes members from universities, private companies, and several state agencies.
“Collaboration to solve really big challenges like climate change and transform our systems and how we think is key,” Dean said. “No one has all the power and ability to do this alone, and so we need more collaborations.”
This story was produced with support from the Climate Equity Reporting Project at Berkeley Journalism.
