California Completes Solar Canopy Over Irrigation Canal

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People to tend to get overwrought when the conversation turns to solar panels. They don’t want to see them on farmland, or the side of buildings, along highways, or on rooftops in their neighborhoods. In fact, they don’t want to see them at all if they can help it. That antipathy has led many solar developers to consider other locations that are less offensive to the eyes of such discerning people, places like the roofs of big box stores, sports arenas, or parking garages.

In the western part of the US, hundreds of miles of irrigation canals bring vital fresh water to farmers, but those canals have a problem. A significant amount of the water they carry evaporates into the atmosphere before it can be put to use irrigating crops or slaking the thirst of farm animals. What if we put solar panels over those canals? Might that reduce evaporation losses while producing some lovely zero-emissions electricity?

Indeed, it might. To find out if the idea works in the real world, Project Nexus, a 1.6 megawatt solar array that covers a portion of the irrigation canals in the Turlock Irrigation District, is now operational. Tyurlock is part of California’s Central Valley, where much of America’s produce is grown.

Funded by a $20 million investment from the state of California, Project Nexus is only the second canal-based solar array operating in the United States. There are a few other similar projects in other countries. The first solar canal project started producing power in October 2024 for the Pima and Maricopa tribes, known together as the Gila River Indian Community, on their reservation near Phoenix, Arizona. Two more canal-top arrays are already in the works nearby.

Solar Panels In The Central Valley

According to Grist, Project Nexus was built in two phases. A 20-foot-wide stretch was completed in March of this year, while another 110-foot-wide section was completed at the end of August. Researchers will now study the project’s performance over time, while a new initiative led by California universities and the company Solar Aquagrid will push to fast-track the deployment of solar canals across the state.

Supporters claim putting solar arrays above irrigation canals can provide multiple benefits. The water beneath the panels helps to keep them cool, which boosts their efficiency in hot weather. Shade from the panels can also prevent water loss through evaporation in drought-prone regions and can limit algae growth in waterways.

In addition, solar canals can provide a faster path to clean energy development than utility-scale solar farms, especially in rural parts of the US where big renewable projects increasingly face community opposition, Grist says. Placing solar panels atop existing infrastructure doesn’t require altering the landscape, and the relatively small installations can be plugged into nearby distribution lines, avoiding the cumbersome process of connecting to the higher-voltage wires required for bigger undertakings.

“Why disturb land that has sacred value when we could just put the solar panels over a canal and generate more efficient power?” asks David DeJong, director of the Pima-Maricopa Irrigation Project, which is developing a water delivery system for the Gila River Indian Community.

The purpose of these early arrays is primarily to power onsite canal equipment like pumps and gates, but they can also supply clean energy to the broader electrical grid. A coalition of environmental groups in the US has estimated that putting panels over 8,000 miles of federally owned canals and aqueducts could generate over 25 gigawatts of renewable energy and reduce water evaporation by tens of billions of gallons.

Water is becoming a more precious commodity by the day, as the demand for water from the Colorado River increases even as the amount of water available decreases due to a reduction in snow packs, more severe drought conditions, and population growth in the American Southwest.

Drawbacks

Covering canals with solar panels does have some drawbacks. First, it costs more to cantilever them over the canals than simply attach them to conventional ground-mount systems and can require using more concrete and steel. Wider canals may also require support structures for panels within the waterway, which can disrupt the flow of water.

Earlier this year, a senior engineer at Arizona’s Salt River Project recommended that the power and water utility not pursue a solar-canal pilot ​“based on cost estimates and project concerns,” after comparing the unique design to both rooftop and utility-scale solar alternatives.

Ben Lepley, the founder of engineering firm Tectonicus, which designed the Gila River Indian Community’s 1.3-megawatt system south of Phoenix, told Grist that putting solar over canals is still a wise choice for irrigation districts faced with high electricity costs and limited options for generating their own solar power. While acknowledging that the initial costs are ​“definitely higher,” Lepley pointed out that such systems can be installed quickly. ​“By the next year, you can have really cheap electricity, and that gives [irrigation districts] stability over the 30 year life of the project.”

The Gila River Indian Community is building solar over canal installations as part of its broader mission to ​“generate enough renewable energy to completely offset the electrical use by the irrigation district,” said DeJong. He noted the district pays about $3 million a year for the 27 million kilowatt-hours of electricity it needs to pump, move, and store water.

An End To Subsidies

The community built its first solar-over-canal project above the Casa Blanca Canal thanks to a $5.7 million grant provided by the Inflation Reduction Act. That grant was part of a $25 million provision that supplied funding for the US Bureau of Reclamation to design, study, and deploy projects that put panels over waterways. Irrigation districts in California, Oregon, and Utah received the remaining funds to develop their own installations.

Indigenous communities are always the last in/first out when it comes to federal funding, and with the failed US administration now ripping up the IRA because it was too even-handed and did not guarantee priority to white males descended from northern European ancestors, support for future clean energy is likely to disappear. Nevertheless, a handful of projects are already moving forward without reliance on federal government grants.

DeJong said that construction is 90 percent complete on the tribal community’s second solar-canal project, a nearly 0.9-megawatt array built in partnership with the Army Corps of Engineers. That project is expected to come online before the end of this year. The community is self-funding a similar-sized project over the Santan Canal and is developing a floating solar array on one of its reservoirs, with both systems scheduled to be completed by early next year. In all, the installations will provide 4 megawatts of local clean power capacity.

“We have become really familiar with the economics of building these [canal] projects,” said Lepley, whose firm also worked on the Gila River Indian Community’s second and third solar-canal systems. ​“We have a pretty good playbook of how to continue these projects going forward, even without any grant funding from the federal government.”