A public-private-academic partnership among Turlock Irrigation District (TID), the Department of Water Resources (DWR), Solar AquaGrid, and the University of California could contribute to a more water resilient future for California, positioning the US state to meet its ambitious clean energy goals. 

TID will pilot Project Nexus which involves building solar panel canopies over a portion of the publicly owned irrigation district’s existing canals. It will serve as a proof of concept to pilot and further study the solar over canal design, deployment, and co-benefits on behalf of the state of California using TID infrastructure and electrical grid access. The project is set to break ground later this year with completion expected in 2024 at multiple locations throughout the TID service territory in California’s Central Valley. The US$20 million project is being funded by the state of California.  DWR will oversee administration of the project and provide technical assistance, as well as serve as a research partner. 

“In our 135-year history, we’ve always pursued innovative projects that benefit TID water and power customers,” said TID Board President Michael Frantz. “There will always be reasons to say ‘no’ to projects like this, but as the first public irrigation district in California, we aren’t afraid to chart a new path with pilot projects that have potential to meet our water and energy sustainability goals.” 

Inspiration for Project Nexus

The inspiration for Project Nexus comes from a recent University of California study, published in March 2021 in the journal Nature Sustainability. The study illustrated that covering California’s 6437km of canals with solar panels could save 286Mm3 of water annually, comparable to the amount needed to irrigate more than 200km2 of farmland or meet the residential water needs of more than two million people. According to the study, the 13GW of solar power the panels would generate each year would equal about one sixth of the state’s current installed capacity. 

“We are excited to explore new efforts to advance the integration of renewable energy into our water supply delivery system,” says Karla Nemeth, Director of DWR. “The project offers great potential, and we look forward to collaborating with our local and academic partners to advance these type of multi-benefit projects.” 

Turlock Irrigation District has retained Solar AquaGrid as project developers and programme managers for TID and Project Nexus. The two agencies have been collaborating since the project’s inception. Solar AquaGrid originated the project after commissioning the University of California Study in 2015 and has facilitated collaboration among the various parties to bring Project Nexus to fruition. 

The name Project Nexus is a nod to the water-energy nexus paradigm gaining attention among public utilities across the US. They are increasingly recognising the symbiotic relationship between water management and energy management and are finding ways to design projects and actions that benefit the management of both resources beyond what has been done historically.

Project Nexus goes beyond recognising the linkage that water is used for energy production and energy is used for water treatment and conveyance. With Project Nexus, existing water conveyance infrastructure will serve as the foundation for solar canopies to produce renewable energy. 

Project benefits

The water in the conveyance infrastructure has the potential to cool the solar panels, increasing their efficiency. Solar cells become less efficient as they heat up and so the water’s cooling effect can increase their conversion ability. In addition, shading exposed waterways can not only reduce evaporation but curtail the growth of aquatic weeds, improving water quality and reducing canal maintenance costs.

Putting solar panels over canals rather than on land elsewhere can also save money, save permitting time, and gives already disturbed land a double use rather than building on undisturbed land. The project partners also anticipate adding energy storage capabilities that can support the local electric grid when solar generation is suboptimal.

An estimated 2590m of solar panels are expected to be built over three sections of Turlock Irrigation District’s canals which will be of various orientations and canal widths, ranging from 6-30m wide. It is expected that several types of solar panels may ultimately be selected for implementation so that variations in performance can be studied.

An overall analysis of water, land use and maintenance cost savings, renewable electricity generation, and corresponding reductions in greenhouse gas emissions will provide Project Nexus partners a holistic look at the compounding advantages resulting from solar over canal deployments.

While Project Nexus, especially if expanded beyond a demonstration project, offers benefits to TID, the project is seen as a template with potential to be replicated elsewhere in the state to help California achieve its water and energy goals. 

“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. “We are excited to partner with Turlock Irrigation District, DWR, and UC Merced to develop this first-in-the-nation pilot project and bring needed innovation to the Central Valley. 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.” 

All information provided courtesy of Turlock Irrigation District.

The study, Energy and Water Co-Benefits From Covering Canals With Solar Panels by McKuinet al, was published in Nature Sustainability in 2021.