The Power of Solar Panels Above Water Canals in California
11th July 2021
California has around 4,000 miles of canals that shuttle clean water to 35 million Californians and 5.7 million acres of farmland across the state. Covering these canals with solar panels, might be a way to save water, generate solar power while also saving money.
The story begins in the Indian state of Gujarat in 2014, when the country has invented solar panels, which are being suspended above 750 meters of irrigation canals to cut down on the evaporation of precious water droplets by providing shade from the sun’s evaporating heat.
It is also a clever way to cut down on habitat loss. By concentrating solar installations on land that is already being used, instead of building them on undeveloped land.
Photo by Sam Panthaky on GettyIgamges
Now, California is eyeing the benefits of the successful canal installations in India. UC Santa Cruz has investigated this method for use in California and estimates that. With the world’s largest irrigation canal network, and 290 days of average sunshine, California is uniquely positioned to erase its own severe water shortages with this emerging innovation of canal-covering solar farms.
On top of generating green energy it would save 63.5 billion gallons of water from evaporation annually, a massive windfall for a state which regularly suffers from droughts.
Environmental engineer Brandi McKuin of the University of California, Merced, and the University of California, Santa Cruz is the lead author of the paper that says,
“By covering canals with solar panels, we can reduce evaporation and avoid disturbing natural and working lands, while providing renewable energy and other co-benefits.”
At the same time, California has ambitious conservation goals. The state has a mandate to reduce groundwater pumping while maintaining reliable supplies to farms, cities, wildlife and ecosystems.
As part of a broad climate change initiative, in October 2020 Gov. Gavin Newsom directed the California Natural Resources Agency to spearhead efforts to conserve 30% of land and coastal waters by 2030.
Most of California’s rain and snow falls north of Sacramento during the winter, while 80% of its water use occurs in Southern California, mostly in summer. That’s why canals snake across the state – it’s the largest such system in the world. We estimate that about 1%-2% of the water they carry is lost to evaporation.
“We could save upwards of 63 billion gallons of water annually by reducing evaporation.” says Brandi McKuin, a postdoctoral researcher at UC Santa Cruz and lead author of the study and continue “That would be comparable to the amount needed to irrigate 50,000 acres of farmland, or meet the residential water needs of over 2 million people.”
This power is climate-, environment-, and budget-friendly solution.
Shading California’s canals with solar panels would generate substantial amounts of electricity. Through McKuin calculations it would be about 13 gigawatts, or “half the projected new capacity needed by 2030 to meet the state’s decarbonization goals.”
Installing solar panels over the canals makes both systems more efficient. The solar panels would reduce evaporation from the canals, and because water heats up more slowly than land, the canal water flowing beneath the panels could cool them by 10 F, boosting production of electricity by up to 3%.
Solar canal installations will also protect wildlife, ecosystems and culturally important land. Large-scale solar developments can result in habitat loss, degradation and fragmentation, which can harm threatened species such as the Mojave Desert tortoise.
With that kind of electricity, there is a possibility that diesel powered irrigation pumps, which do a number on air quality, could be replaced.
Yet another benefit would be curbing aquatic weeds that choke canals. In India, where developers have been building solar canals since 2014, shade from the panels limits growth of weeds that block drains and restrict water flow. McKuin says preventing weed growth would also lighten the load for sometimes costly mechanical and chemical waterway maintenance.
According estimates the cost to span canals with solar panels is higher than building ground-mounted systems, but when we added in some of the co-benefits, such as avoided land costs, water savings, aquatic weed mitigation and enhanced PV efficiency, we found that solar canals were a better investment and provided electricity that cost less over the life of the solar installations.
Bales and McKuin calculated by incorporating a variety of models. For instance, evaporation rates came from hydrological models. They reckoned climate models as well, to predict how the state will warm over the coming years. They also calculated how the cooling effect of the canal water would improve the panels’ generating efficiency.
Illustration by Solar AquaGrid
“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 engineer Roger Bales of the University of California, Merced. “But I think the amount of electricity could be significant, both statewide and locally.”
More information, details and photos about The Canal Top Solar Plant Project - Gujrat, India: