A new study published in the journal Nature Sustainability reports that covering California’s approximately 4,000 miles of public water delivery infrastructure with solar panels can result in significant water, energy, and cost savings for the state. The study illustrates a savings of some 63 billion gallons of water annually – enough to irrigate 50,000 acres of farmland or meet the residential water needs of more than 2 million people. Based on data from the published study, the researchers estimated that covering the state’s canals with solar would generate 13 gigawatts of power, which is more than half the projected new solar capacity needed by 2030 to meet the state’s decarbonization goals.

The study, conducted by researchers from the University of California, Merced and UC Santa Cruz, explored the interconnected nature and costs of moving water across the state – the water/energy nexus. It revealed that there are numerous compounding advantages to be gained by mounting solar panels over open water canals when compared to conventional ground-mounted solar systems, including added efficiency resulting from a shading/ cooling effect.

“We were surprised by the significant evaporation savings, which we project to be as much as 82%,” said Dr. Brandi McKuin, report lead author. “That amount of water can make a significant difference in water-short regions.” Because the solar panels shade the canals from direct sunlight, McKuin added, they can not only mitigate evaporation but also curtail the growth of aquatic weeds and reduce maintenance costs, while the evaporation that does occur actually cools the panels, thereby increasing their efficiency in converting sunlight to electricity.

The study estimates that, for California, the resulting annual savings in maintenance costs could be as much as $40,000 per mile of canal. In addition, the retirement of old diesel pumps and generators in favor of solar arrays would contribute to cleaner air in California’s Central Valley, which suffers from among the worst air quality in the nation. Report co-author Roger Bales, Distinguished Professor of Engineering at UC Merced, comments “What is most compelling about this study is when you tally up the multiple benefits. 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.” The analysis shows that adding solar coverings above canals that run across ‘already disturbed land’ means developers can avoid protracted environmental permitting and right-of-way issues so systems can be deployed more quickly and cost effectively.

The UC Solar AquaGrid study comes at a time when there is growing urgency for shifting from fossil fuels to renewable energy. We are rethinking how aging water and energy infrastructure can adapt to the challenges of sustainable water management, catastrophic wildfires, and multi-day power outages, as well as growing acceptance of climate change and the fact that the American West is currently experiencing a historic "megadrought” — an ongoing stretch of extended dry conditions worse than any experienced since 1603 according to a recent report in the journal Science. The Biden administration has called for rapid modernization of our water, transportation, and energy infrastructure to withstand the impacts of extreme climate. Federal agencies have been directed to identify new opportunities to spur innovation, commercialization, and deployment of clean-energy technologies and infrastructure.

“Aqueducts are the arteries of our economic and social development, and have captured the public’s imagination for centuries,” notes former State Water Board Chair Felicia Marcus. “A significant amount of our state’s electricity bill comes from moving, treating, and heating water, so water efficiency is also energy efficiency. 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.”

California is calling for 50% of California’s electricity to come from renewable sources by 2030 and starting five years later, will prohibit the sale of new gas-powered cars. The New York Times recently reported that, according to analysts, if every American switched over to an electric vehicle, the U.S. could end up using roughly 25 percent more electricity than it does today.

The Solar AquaGrid research study was conducted by University of California researchers with underwriting from NRG Energy, and development support from Bay Area agency, Citizen Group. The project tested the thesis that, by erecting a modular system of solar shading panels over California’s exposed aqueducts, the state can reduce evaporative water loss and provide a variety of benefits that yield more ‘bang for the buck’ than current land-based solar PV installations. As the project moves towards a creation of well-situated demonstration model, the development team is also contemplating integration of battery storage features in order to deliver distributed clean energy and smart metering to local communities.

“The SolarAqua Grid model provides a combined, integrated response to addressing our water/ energy nexus,” continued Bales. “It can help address California’s underlying vulnerabilities while meeting both state and federal level commitments to produce renewable energy, lower greenhouse gas emissions, and mitigate climate change. Solutions such as these are not only viable but more urgently needed than ever before, particularly as the region returns to what many researchers refer to as a paleo-drought – a worst-case scenario for water managers.”