In an energy storage facility, stored water serves as a ready energy source, generating power as it flows downhill to turn hydroelectric turbines. In San Diego County, energy storage could support electrical transmission grid operations that are essential to integrating growing renewable wind and solar power supplies.
The Water Authority and the City of San Diego are joint permittees on a preliminary permit issued by the Federal Energy Regulatory Commission which allows the agencies to pursue development of an energy storage facility near San Vicente Reservoir. The preliminary permit is an early step in the process of determining if and how the Water Authority and the City could develop the project in the next decade.
The proposed up to 500-megawatt energy storage facility would supplement the region's energy needs during peak demand periods and generate up to 8 hours of stored energy, enough to supply approximately 325,000 homes annually.
The San Vicente Energy Storage Facility would establish a small reservoir above the existing San Vicente Reservoir, and a tunnel system and underground powerhouse to connect the two reservoirs. The powerhouse would contain four 125 MW reversible pump-turbines capable of lifting water to the upper reservoir or generating power as it flows down. During peak energy demand, water would flow down to generate carbon-free power. During off-peak periods, including daytime when renewable wind and solar power supplies exceed demand, water would be pumped to the upper reservoir.
This would be a closed loop, off-stream system in an upland area with no natural water body. The exchange of water between the two reservoirs would not consume water or interfere with existing water supply, water quality, fisheries, or recreational uses of the San Vicente Reservoir.
Energy storage provides benefits to the energy grid and to water and energy consumers by:
- Producing energy on demand
- Making beneficial use of surplus zero-carbon renewable wind and solar energy that would otherwise be lost during times of low demand
- Generating additional revenue that offset Water Authority and City costs and help stabilize water rates
- Reducing overall greenhouse gas emissions by using available renewable energy to pump water up to the upper reservoir during low-demand periods, and generate zero-carbon power by releasing water downhill by gravity during high-demand periods
- Help to balance the energy grid and enhance system reliability by responding to peak energy demands
Connecting to the Grid
Power generated at the San Vicente facility would be delivered into the local grid via new transmission lines parallel to the Sunrise Power Link. The new lines would connect to an existing Sycamore Substation owned by SDG&E approximately five miles away.
Partnering with City of San Diego
The San Vicente Dam and Reservoir are owned and operated by the City of San Diego. The Water Authority completed raising the San Vicente Dam in 2014, and now owns the additional storage capacity in the expanded reservoir. The two parties prepared a joint Preliminary Application Document (PAD) and a Notice of Intent for submission to the Federal Energy Regulatory Commission (FERC), the agency responsible for approval of all energy generation projects on July 28, 2015. The PAD outlines the plan for implementing the project, identifies what environmental resource studies are needed, and is a precursor to submitting a formal FERC license application. Other activities underway include the procurement of professional services for an Owners' Advisor. The Owners' Advisor would assist the Water Authority and City and perform additional analysis and recommend a business model for delivering the project. The Water Authority and the City would develop the project as joint partners.
Future Development Milestones
|July 2015||Submit License Preliminary Application Document/Notice of Intent to FERC|
|Late 2015||Award and Owners' Advisor professional services contract|
|Mid to Late 2016||Business models identified for possible Board action|
Future milestones will be determined upon Board approval of a business model.