The US is about to get its first solar-covered canal

The first canal-based solar project in the U.S. is nearing completion on tribal lands south of Phoenix, Arizona.

Native Americans have been using canals to irrigate the Gila River Valley for thousands of years, starting with the Huhugam people. Now at least a small slice of the modern-day system of canals that winds through the area will double as a location for generating solar energy for the Pima and Maricopa tribes.

Thousands of miles of federally owned canals stretch across the country, channeling water to thirsty crops, rural communities, and hydropower plants. Placing solar panels over these canals could create a gigawatt-scale source of clean energy with lower environmental impact than large-scale solar farms, but so far the idea has been slow to catch on.

A canal solar concept was deployed in India about a decade ago, and it inspired Ben Lepley, the founder of engineering firm Tectonicus, to create designs, prototypes, and techno-economic analysis for such a project in the U.S. Those plans have resulted in the soon-to-be-commissioned Casa Blanca installation — a 1.3 megawatt, half-mile-long pilot project located on the Casa Blanca Canal, part of an extensive canal network owned by the Gila River Indian Community.

The pilot received money from a $25 million provision of the Inflation Reduction Act that supplies funding for the U.S. Bureau of Reclamation to design, study, and deploy projects that put solar panels over waterways. Lepley’s firm has also won a Department of Energy Small Business Innovation Research Grant and is working with the California Energy Commission and University of California, Merced on the project.

It’s early days for this technology, but another canal installation, Project Nexus, in California’s Turlock Irrigation District, broke ground in May of this year and has already constructed foundations. Developers expect it to be completed in 2025.

The merits and messiness of solar canals

Gargantuan utility-scale solar systems are facing pushback in states ranging from Ohio to Texas, often from farm communities. Local opponents have argued that big solar installations take farmland out of production, reduce property values, and possibly harm wildlife. Federal efforts to build clean energy on public land also face opposition from advocates concerned about the potential impact on fragile ecosystems or tribal communities.

Erecting solar on top of federally owned canals could be a win-win. The approach limits the disruption to ecosystems, and some studies suggest it actually has the potential to help canals do their jobs better; an over-the-canal design can prevent water from evaporating and inhibit algae growth. The comparatively small installations can also connect clean power directly to the distribution grid, an important distinction as it has become increasingly difficult to connect large projects to the transmission grid.

But while pairing solar with canals has benefits in terms of land use and the environment, deploying solar panels over water infrastructure presents a unique set of building requirements.

Maintenance staff and machinery need unimpeded access to the canals in emergencies, according to Lepley, who is system designer for the project. Crucially, the design of the support structure must allow for easy removal of bovines, Buicks, and La-Z-Boys.

“Cows, cars, and couches somehow always end up in the canal,” said Lepley. 

These requirements — plus the added steel and concrete materials — make the systems more expensive and technically complex than conventional ground-mounted solar arrays on trackers.

Along with George Cairo Engineering, the engineer of record for the Casa Blanca Canal solar project, Tectonius has evaluated a number of designs for the over-canal hardware. ​“We looked at steel use, concrete use, solar panel costs, wind lift and weight, power production, and access,” said Lepley. The engineers ultimately arrived at a patented, modular, and prefabricated design that makes it safe to build over moving water without impeding canal flows or access.

The long, narrow solar array design would snake along the line of the canal and tap into the local electrical distribution grid every 1,000 feet, or every one megawatt.

In general, Lepley said the capital cost for canal solar is roughly double that of land-based solar due to the cost of steel and foundations needed to support the PV panels above a canal. Lepley did not disclose the per-megawatt-hour cost of the design, but said his models and lab data suggest that in hot, arid environments, canal-based solar is ​“more valuable” than land-based solar, helping chip away at the higher upfront capital cost.

“Canal solar allows for greater power production per land size, cleaner water, less power transmission losses, and significant reduction in evaporation,” he said.

Lepley’s studies detected a 1.9 percent energy boost in solar power generation, owing to a reduction in infrared radiation reflected from the ground. The boost is equivalent, on a system-wide scale, to 21 gigawatt-hours worth of electricity or $2.3 million per year, according to the engineer.

With this plan, ​“we’ve passed those savings on to the ratepayers and prevented a huge amount of CO₂ from warming our atmosphere, all without bulldozing vast tracts of the Sonoran Desert.”

While this just-imagined market is still at the pilot stage, the math suggests the potential is much bigger. Covering the entire 8,000 miles of canals and waterways managed by the Bureau of Reclamation with solar panels could generate over 25 gigawatts of renewable energy and reduce water evaporation by tens of billions of gallons, according to a letter sent to Interior Secretary Deb Haaland and Bureau Commissioner Camille Touton in 2023 by a coalition of more than 100 climate and environmental groups.

The Casa Blanca project, set to connect to the distribution grid at the end of summer, will give the U.S. its first look at this new possibility for generating clean energy.