Land not needed! Solar canals generate energy, save water

A decade ago, the western Indian state of Gujarat experimented with something nobody had ever done before – putting solar panels over top of an irrigation canal. It solved the problem of finding land for solar panels, land in India being expensive and ownership often controversial, and it provided electricity for people in rural areas that utilities had found hard to serve. 

But it also turned out that those panels did a whole lot more. Less of the water evaporated in the hot climate. The water in the canals cooled the panels so they were more efficient. And there were far fewer weeds to clog up the canals. (Similar results have been found from floating solar panels placed on hydro dams.)

By Hitesh vip – Own work, CC BY-SA 3.0, Wikimedia Commons

Since that first solar canal was completed in 2012, other larger-scale solar canals now wind through India’s countryside, simultaneously solving the two key problems of energy production and water conservation while avoiding controversy over land use. “These innovative projects can provide cheap and consistent electricity to millions of farmers and improve their profits,” says Manik Jolly, who was involved in the Gujarat pilot project when he worked at SunEdison and is now CEO of Grassroots and Rural Innovative Development, a startup in New Delhi.

Now California’s oldest irrigation district has started work on a pilot solar canal project, which they are calling Project Nexus, because it looks at a range of key concerns together that are too often addressed in isolation – water, agriculture, energy, and land use. And given that California grows food for a global population and produces more than 50% of the fruits, nuts and vegetables that US consumers eat, this pilot project could eventually have impacts far beyond the state. 

California has 4,000 miles of canals, which bring water to some 35 million Californians and 5.7 million acres of farmland. It is the world’s largest water conveyance system, and the state’s single largest user of electricity. If all the canals were covered with solar panels, a study estimated, it could save more than 65 billion gallons of water from evaporation annually. That could irrigate 50,000 acres of farmland, or meet the residential water needs of more than two million people. And it could provide approximately 13 giga watts of renewable power, equivalent to about one sixth of the state’s current installed capacity or roughly half the projected new capacity needed by 2030 to meet the state’s decarbonization goals. They could protect prime farmland from being used for renewable energy projects as the state works to decarbonize.

 “Our paper is not a detailed engineering design or conceptual design — it’s a feasibility study, a proof of concept for taking it to the next phase of investing in a demonstration project,” says engineering professor Roger Bales of the University of California, Merced. “But I think the amount of electricity could be significant, both statewide and locally.”

On Feb. 8, 2022, the Turlock Irrigation District got state funding for the pilot demonstration project, which is a public-private-academic partnership among the District, Department of Water Resources, Solar AquaGrid, and the University of California, Merced. The district, formed in 1887, provides irrigation water to 4,700 growers who farm about 150,000 acres in the San Joaquin Valley, as well as power to homes, businesses, and farms.

Concept visualization by Solar AquaGrid

“In our 135-year history, we’ve always pursued innovative projects that benefit TID water and power customers,” said TID Board President Michael Frantz. “Research and common sense tell us that in an age of intensifying drought, it’s time to put a lid on evaporation,” said Jordan Harris, CEO of Solar AquaGrid. “Our initial study revealed mounting solar panels over open canals can result in significant water, energy, and cost savings when compared to ground-mounted solar systems, including added efficiency resulting from an exponential shading/cooling effect. Now is the chance to put that learning to the test.”

The study had estimated that the annual savings in maintenance costs could be as much as $40,000 per mile of canal, while retiring old diesel pumps and generators in favor of solar arrays would contribute to cleaner air in California’s Central Valley.

 “What is most compelling about this study is when you tally up the multiple benefits,” says Bales. “Solar over canals represents the sort of shift in thinking that California and the world need as we transition our economy and infrastructure to a fossil-free, sustainable future.” And because canals were already disturbed land, systems could be deployed more quickly.

“A significant amount of our state’s electricity bill comes from moving, treating, and heating water, so water efficiency is also energy efficiency,” noted former State Water Board Chair Felicia Marcus. “We need to find every way we can to use water more efficiently, including stemming evaporative loss, as we also scale up clean energy to meet the needs of the challenging century ahead under climate change.”

Floating Solar

While solar canals put the panels over top of the canal, floating solar puts the panels on top of hydro dams or other bodies of water. While there are many such projects in Asia, floating solar has just been getting started in North America. Some California municipalities have found it could help them meet their climate action goals. 

In Sonoma County, just north of San Francisco, the town of Windsor didn’t have enough room to install solar panels on land to power its wastewater operations – but it did have a 17-acre recycled water pond. So in partnership with a solar energy equipment supplier that specializes in floating solar worldwide, it deployed a floating 1.8-megawatt array of solar panels on its biggest pond. Ciel et Terre USA leased the pond for 25 years in exchange for producing the discounted clean energy.

After the floating solar array went online in October 2020, the town estimated it would save an estimated $175,000 a year on its public works department’s electrical costs or $4 million over the next 20 years and make a significant step in achieving its emission reduction goals. 

“Floating solar is becoming an attractive energy alternative for municipalities seeking to reduce operating costs and preserve valuable land for other developments,” says Ciel et Terre representative director Eva Pauly-Bowles.

Far Niente Winery in Napa Valley, California; a floating solar system erected on the winery’s irrigation pond. By SPG Solar, CC BY-SA 3.0, Wikimedia Commons

Just north of Windsor, the town of Healdsburg also turned to floating solar. Its focus was on shade for its recycled wastewater in order to cut algae bloom, as Healdsburg provided the recycled water to agricultural users as well as vineyards.

When it added 11,600 solar panels to about half of the 15 acres of the wastewater ponds, it provided 8% of the city’s annual electrical needs. The nearly 4.8 megawatt solar installation brought Healdsburg a significant step closer to its goal of securing 60% of its energy from renewable sources by 2025.

Noria Energy installed the array, which was then the largest floating system in the US, a bit larger than one in Sayreville, New Jersey. CEO Jon Wank noted that it was often cheaper to float panels than build ground installations. “When we started these two years ago 500 kilowatts would’ve been large,” he said. 

Then, in May 2022, work began on an even larger floating solar project at the New Jersey American Water Canoe Brook water treatment plan, with 16,510 solar panels that would produce 8.9 MW of power, meeting almost all the facility’s power needs.

“I think that the intersection of energy and water is going to be extremely important in the future, especially with the challenges we are seeing with water scarcity and water quality,’ says Wank. “Our vision is to make floating solar more affordable while also preserving and improving water quality.”


Project Nexus website.

Study Shows Covering California’s Canals with Solar Panels Can Result in Significant Water, Energy, and Cost Savings. SolarAquaGrid. 

First solar canal project is a win for water, energy, air and climate in California. The Conversation, Feb. 22, 2022

Solar panels on California’s canals could save water and help fight climate change. Los Angeles Times, Apr. 22, 2021

Study looks at covering California’s canals with solar panels. High Country News, Mar. 23, 2021

New analysis shows potential for ‘solar canals’ in California. University of California Santa Cruz, Mar. 18, 2021

Windsor plans to use floating solar panel system to power town’s public water facilities. The Press Democrat, Jun. 7, 2019

Windsor builds one of the nation’s biggest floating solar arrays. Western Cities, Apr. 1, 2022

Healdsburg debuts biggest floating solar farm in nation. North Bay Business Journal, Mar. 11, 2021

The ‘solar canals’ making smart use of India’s space. BBC Future Planet, Aug. 4, 2020

India’s Solar Canals. Lateral thinking at its finest! Just Have A Think, Jan. 24, 2021.