A Request for Proposals (RFP) has been issued for a 500MW pumped hydro energy storage project at a reservoir in California by the San Diego County Water Authority.
The authority supports water supplies for more than three million people, supplying wholesale to 24 retail water providers. It has decided to put its San Vicente Reservoir into dual use by turning it into an on-demand clean energy facility while it also supplies water.
A smaller upper reservoir would be constructed above the main San Vicente body, with tunnels and an underground powerhouse built between the two. At times of abundant local renewable generation from solar and wind, when power is cheap, water will be driven upwards from the lower reservoir.
When demand then peaks, water is dropped from the upper reservoir and passed through four reversible pump turbines to generate power. San Diego County Water Authority (SDCWA) said that water will not be lost during the exchange from one reservoir to the other. The project is expected to be used to store energy for about five to eight hours.
Also, due to the closed loop design which will mostly hold imported water, the project will be “largely immune” to conventional hydroelectric power’s main challenges that — as has been the case with some of California’s hydro facilities this year — can see electricity production hampered by fluctuating water levels.
As well as assisting California to meet its long-term clean energy goals and shorter-term energy security issues, the authority believes the project, which it wants built by 2030, can earn revenues that will help lower the cost of water for ratepayers.
The San Vicente Energy Storage Facility is being jointly planned with the City of San Diego and the RFP issued this week calls for a full-service private partner with a multidisciplinary team that can develop, deliver and operate the project. Proposals must be submitted by 3 November.
‘Exciting project meets multiple goals’
Energy-Storage.news first reported on the project as the idea was put forward by the two city groups at the beginning of 2017, with engineering firm Black & Veatch hired in 2018 to evaluate early design proposals.
The project then received US$18 million from the California state budget in July this year, which is enough to advance the initial design, conduct environmental reviews at state and federal level and get federal licensing from FERC.
Governor Gavin Newsom’s administration issued its Electricity System of the Future roadmap for California to achieve 100% carbon-free electricity by 2045 in line with its state policies in late July. It identified long-duration energy storage as a key enabler of this goal, while ensuring stability and reliability of the system.
Pumped hydro is one of the long-duration storage options along with a range newer technologies like flow batteries and green hydrogen — many have said it will be necessary to combine the different options.
Statistical modelling and forecasting analysis by Strategen Consulting and the California Energy Storage Alliance has shown that to meet the 2045 target and a 60% renewable energy by 2030 interim goal, from 2025 onwards, the majority of energy storage deployed in the state needs to be long-duration.
The San Vicente project is among a number of pumped storage projects proposed in California. Earlier this year, environmental consultant Jeff Harvey wrote a Guest Blog for this site about another, Eagle Mountain, which would repurpose infrastructure at an abandoned mining site.
“This is an exciting project that meets multiple goals for the San Diego region, including protection from blackouts and supporting climate-friendly energy sources. We are committed to finding a private partner who can help move this from concept to completion,” San Diego County Water Authority director of engineering Gary Bousquet said.
