The San Diego County Water Authority, in partnership with the city of San Diego, is preparing to assess the potential for a major hydroelectric power project at San Vicente Reservoir to boost the region’s local energy supply now that the San Onofre Nuclear Generating Station is permanently offline.
The proposed pumped storage project could generate up to 500 megawatts, enough power for approximately 325,000 homes. It would require the construction of a small reservoir in the hills above San Vicente Reservoir, along with other facilities.
Power would be generated during peak-demand periods by allowing water to flow downhill in a tunnel from the upper reservoir and turn turbines before entering the San Vicente Reservoir. Water would be pumped back uphill during off-peak periods much like it is at the Water Authority’s 40-megawatt pumped storage project that connects Hodges Reservoir with Olivenhain Reservoir. That kind of arrangement allows the Water Authority to generate power when it’s needed most and generate revenues for offsetting expenses.
The Water Authority, in cooperation with the city of San Diego, has issued a request for proposals seeking firms that could evaluate the economic and financial requirements of a pumped storage facility at San Vicente. The study will include an analysis of the power market, potential sites for an upper reservoir, regional power needs, and associated construction and operating costs.
The initial assessment is expected to cost less than $150,000 and be completed next spring. Construction likely would take at least five years. It would be done in partnership with the city of San Diego, which owns San Vicente Reservoir.
“Given the closure of the San Onofre plant, it makes sense for us to determine whether we can leverage our experience with hydroelectric power to help meet the region’s need for clean energy,” said Frank Belock, a deputy general manager at the Water Authority. “The concept of pumped storage at San Vicente has been on our radar for years and is a natural next step now that the San Vicente Dam Raise project is almost complete. An independent economic review will help the Board of Directors determine whether we should make it a priority.”
Southern California Edison announced June 7 that it was permanently retiring the 2,200-megawatt San Onofre Nuclear Generating Station. Twenty percent of its output went to San Diego Gas & Electric. The shutdown prompted efforts to find replacement energy sources for ensuring regional power reliability.
The County Water Authority Act was amended by the state Legislature in 1999, enabling the agency to enter the wholesale markets for electricity and gas. It also allowed the Water Authority to sell hydroelectric power generated by the agency’s water delivery system to any retail electric provider.
The proposed project at San Vicente is expected to generate between 240 and 500 megawatts, depending on the location of the upper reservoir, projected price differences between peak power and off-peak power, operational constraints and other factors.
Previous studies have identified four potential sites for an upper reservoir, which likely would hold up to 10,000 acre-feet of water. By comparison, San Vicente Reservoir will have the capacity for 242,000 acre-feet of water when construction to raise the dam is completed late this year. The city of San Diego and the Water Authority have an agreement for joint use of the expanded reservoir.
The 40-megawatt pumped storage project at Hodges Reservoir was completed in September 2012. It includes a pump station, an electrical switchyard and an inlet-outlet structure for moving water. A 1.25-mile-long steel pipeline rises 770 feet in elevation from Hodges to Olivenhain reservoirs, allowing the Water Authority to produce power quickly in response to regional demand.