California's 'Solar Canals' Will Save Water and Produce Clean Energy

A public-private-academic partnership plans to install solar panels over water canals in California in a bid to produce clean energy and help preserve the state's dwindling water resources. 

Construction of Project Nexus, the “first-ever solar panel over canal development in the United States,” will start next fall and is scheduled to be completed by the end of 2023. The 5-megawatt project will consist of three sites along canals in central California with widths ranging from 20 feet to 100 feet. 

If the pilot project proves solar canopies are a cost-effective way to produce clean energy and save water, scores of similar installations could be built atop California’s canal network—one of the world’s largest water distribution systems.

“This is a really exciting project,” California Natural Resources Secretary Wade Crowfoot said last month. “It connects our efforts in California to improve water conservation and build drought resilience with the clean energy transition we’re driving across California.”

Project Nexus was inspired by a 2021 study by University of California researchers that was published in the journal Nature Sustainability. 

Typically, 1% to 2% of the water that circulates through California’s canals evaporates, a number that is expected to increase due to the climate crisis.

Using data from satellites, climate models, and automated weather stations, the peer-reviewed study estimated that covering all of the approximately 4,000 miles of California’s canals could drastically reduce evaporation, saving 63 billion gallons of water annually—comparable to the amount of water required to irrigate 50,000 acres of farmland or meet the water needs of more than 2 million people. 

The $20 million project was announced as California continues to face a devastating "megadrought" after recording the lowest rainfall in 100 years in January and February, and amid fears that this winter’s snowpack is not thick enough to supply the country’s most populous state with fresh water over the next few months.

Official data shows that 87% of the state is under “severe drought” conditions that are stressing plants and wildlife, drying out pastures and forested areas, which could lead to more devastating wildfires this year. Governor Gavin Newson has allocated additional funds to help local communities cope with water scarcity and encourage Californians to use less water.

“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, the company that is building the solar canopies.

The study found solar canals would be able to generate 13 gigawatts of clean power, equal to approximately one-sixth of the state’s current installed solar capacity. This additional generation could help California achieve its goal of supplying at least 60% of its electricity from renewable sources by 2030 and 100% by 2045.

This clean electricity could be used to power irrigation pumps that typically burn diesel, which could help further reduce emissions and air pollution. The solar panel canopies would be built as part of microgrids that would provide power to rural communities, hence reducing the amount of electricity that is lost when is transmitted over long distances.

But solar canals, which have also been built in India, could have many other benefits. For instance, the flow of water underneath could help cool the panels, increasing their efficiency, while the shade from the panels could help fight aquatic weeds that need to be cleared out regularly.

In addition, solar canals will have a lower environmental footprint than traditional solar farms because they will be built on land that has already been developed, instead of on unspoiled areas, the study says.

The installation could be more costly compared to traditional photovoltaic systems because solar canals would require steel cables or trusses, but the study found that the additional benefits will compensate for the extra costs.  

“What we’re seeing here is actually some surprising benefits when you bring water and energy together,” said study co-author Elliott Campbell, a professor of environmental studies at the University of California. “Sometimes it leads to a smoother landing in how we transition to better ways of making energy and saving water.”