This is a rendering of solar panels installed over a canal in California’s Central Valley. Researchers at University of California Merced campus studied the concept. These solar panels will not only generate electricity — they will also save water. Image by Solar AquaGrid LLC
It’s not often that an engineering innovation solves multiple problems at the same time, but “solar canals” seem to do exactly that! The idea has been discussed for years, but has recently been implemented in a few pilot projects. For example, see:
https://azmirror.com/2024/07/08/the-us-is-about-to-get-its-first-solar-covered-canal/
Solar canals were first deployed in India about a decade ago. It inspired Ben Lepley, the founder of engineering firm Tectonicus, to create designs for applications in the U.S. That has resulted in the soon-to-be-commissioned Casa Blanca project — a 1.3 megawatt, half-mile-long installation located on the Casa Blanca Canal, part of the canal network owned and operated by the Gila River Indian Community. The project received funding from a $25 million provision of the Inflation Reduction Act that allocated through the U.S. Bureau of Reclamation.
The graphic below shows how covering a canal with solar panels mitigates several issues:
First and most obvious, a lot of electrical energy can be generated without having to clear existing land and secure rights of way or special zoning. Lepley’s analysis estimates a generating capacity of around 3 MW per mile of canal. To simply the hardware required, the solar panels would be mounter horizontally and not tilted for best exposure to the Sun. Since canals often change direction, the optimum tilt angle would change along the route and mechanically complicate installation.
Also, reducing direct sunlight on the canal inhibits the growth of algae in the water, and that lowers the cost of end-use water treatment.
Further, the solar panels will operate with about 2% greater efficiency due to cooler air temperatures above the water and reduced reflection from the ground. Solar panels always work better when cooler.
But the biggest gains may be from the reduced evaporation of precious water from the now-shaded canal. Here’s some real numbers: The Central Arizona Project (CAP) is the state’s major canal system, and delivers water from both the Colorado River and Lake Pleasant (which is fed by the Agua Fria River). The CAP stretches for 336 miles, and suffers a water loss of around 4.5% to evaporation. That amounts to 25,000 acre-feet of water (8.2 billion gallons) — enough water to supply 80,000 average homes for a year!
If these pilot projects pan out, and they are projected to perform well, solar canals could be scaled up nationwide. If the entire 8,000 miles of canals and waterways managed by the Bureau of Reclamation were covered with solar panels, they would generate over 25 GW of renewable energy and reduce water evaporation by tens of billions of gallons. This data comes from 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.
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