California Sunshine Could be Key to Combating Drought

Some ideas are so satisfying that you wonder how they haven’t been done before. This is how solar canals fit into the U.S. mold. They will be piloted in California later this year. The western states are covered by irrigation canals that run thousands of miles, some up to 150 feet wide and others only 10 feet in length. Research suggests that we can produce renewable energy by covering these canals with solar panels. In addition, this shade will prevent water loss from evaporation by blocking billions of gallons.

“I’ve received several emails from people saying, ‘Hey, that was my idea ten years ago! But nobody wanted to do it,’” Roger Bales, the engineer leading the pilot, says with a laugh. Since 2014, India has been developing solar canals. The idea was also explored in Costa Rica. The U.S. has long held plans to build solar canals, but there is not enough information to justify the higher initial costs.

This was changed in the last year. Bales and co-workers at University of California, Merced released a study that found California could cut its water consumption by 65 billion gallons per year if they replaced all 4,000 miles of their canals with solar panel. That’s enough to irrigate 50,000 acres of farmland or provide water for the homes of more than two million people. They estimate the solar aqueducts would generate around 13 gigawatts of energy—roughly half of the new renewable capacity that the state needs to meet its goal of generating 60% of its electricity from clean sources by 2030.

“If California can’t save the world, I’m not sure who can”

In February, California’s Department of Water Resources awarded a $20 million grant for Bales’ team to build a prototype, which will cover 8,500 feet of canals in the San Joaquin valley’s Turlock Irrigation District. Bales’ team is currently designing the system, and its first stretches—likely generating roughly 5 megawatts altogether—should be up and running by early 2023.

The Turlock district, which provides water to 4,700 farmers across 150,000 acres, reached out to Bales’ team to volunteer for the pilot: the town is hoping to shut down two nearby gas-fired power plants soon, and is keen to scale up its renewable supply. Local officials were also interested in the project’s plan to build energy storage into the panel coverings, Bales says, which will allow the district to release energy into the electric grid at times when the sun isn’t shining and supply is lower.

Bales has worked on climate issues since the 1980s, spending the first half of his career in research at the University of Arizona, and he’s used to the slow pace of progress. But he says he’s finally seeing momentum around climate solutions in California, where he moved in 2003. “I thought this was probably the best place to advance solutions: We have the technology, we have the funding. We also have the economy. We have the political will, in most cases,” he says. “If California can’t save the world, I’m not sure who can.”

You can scale up solar power without consuming U.S. soil

Bales has spent the last two decades leading the Sierra Nevada Research Institute, trying to improve understanding on how climate change is affecting the water system in that region, and how the mountains’ forests drought resistance would change as California’s climate shifts. The institute where Bales is still co-director aims to link scientists and financiers to fund urgent forest restoration.

This new phase of his career is dedicated to solutions rather than research. The solar canals project forms part of that. The key to climate action, he’s found, is an area not often associated with scientists: communication. “To deliver projects that meet multiple needs, you have to get lots of different agencies—state and local—working together,” he says. “So here I am, an engineer at this point in my career, trying to get people to talk to each other.”

It appears to be working. After the 2021 study’s release, Bales was “overwhelmed” with calls from media, local officials, and even U.S. Senate staff expressing interest in building solar canals. The enthusiasm makes sense: to meet the Biden Administrations’ ambitious targets, solar needs to scale up rapidly, from 2.8% of U.S. electricity today to as much as 45% by 2050—requiring an area of land twice the size of Massachusetts, per official estimates. The expansion, however, may conflict with the government’s plan to conserve 30% of the nation’s lands and waters by 2030. Already, it is causing problems with activists and local governments. They have opposed the expansion from Texas to Maine because of concerns about loss of wildlife habitats and farmland. Covering aqueducts could avoid such impacts while contributing to the nation’s solar needs, along with conserving precious water as droughts continue to worsen across the western U.S.

Cost problem

But there’s a long way to go before solar canals reach the kind of scale that the 2021 paper imagined—and not all stretches of California’s canals will be suitable for solar installations, Bales says. The Turlock pilot will be monitored by his team for two years. His team then attempts to launch additional projects in that time frame, until the state makes a decision on how to proceed.

There is a potential issue with making sure utilities have access to the canals in order to perform maintenance. Bales states that the team has been exploring modular design options to temporarily remove parts of the system. He also said that the panel cover should make maintenance easier: keeping the sun off the canal will reduce algae and weed growth and reduce the need to treat water for drinking. (Bales’ team does not foresee a significant impact on water birds, who have been known to drink from irrigation canals, but a representative of bird-conservation non-profit The National Audubon Society will help them monitor this during the pilot, he says.)

As with other climate solutions, the greater challenge lies in proving that solar canals can be economically viable. The process of installing panels over canals—using either a steel truss or tension cables—will be more expensive than mounting panels on the ground, increasing the cost of generating energy. The 2021 study estimated that panels placed over canals with a steel beam would cost around $2.02 per Watt, while panels using tensioned cables would run $1.82 per W. It is slightly less than $1.66/watt for ground-mounted conventional panels that are located next to canals.

Bales pointed out, however that ground-mounted estimates do not take into account the cost of land. When cost savings from not having to use up agricultural land, avoiding water loss, and maintenance are taken into account, he says canal-mounted panels would be “very competitive.” “There are still some unknowns. What if it costs 5% more than we anticipated? 10% more? Are our costs too high? We will find out.”

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