The San Diego County Water Authority and the city of San Diego on Jan. 5 said they were considering a new pumped storage opportunity at an existing reservoir site.
The potential project would create a new, up to 500-megawatt source of renewable energy that could provide electric grid stability to the region during peak times for energy use or other days when demand for electricity is high and renewable energy supplies are scarce, the water authority said in a news release.
Through the release of a joint request for letters of interest in the proposed San Vicente Energy Storage Facility, the water authority and the city of San Diego are reaching out to electric utilities, developers, investors and energy off-takers to help determine who may be interested in participating in the potential project.
The request will also help determine what possible next steps are in the best interests of regional ratepayers and stakeholders, the water authority noted.
"With the capability to provide the region with up to eight hours of storage capacity daily, the project could support electrical grid operations that are essential to integrating large new supplies of renewable electricity into the California and Western power grids - notably solar, but also wind," the news release said.
The backbone of the project would consist of an interconnection and pumping system between the existing San Vicente Reservoir and a new, smaller reservoir located uphill.
The pumping system would be used during off-peak energy-use periods to pump water from the existing San Vicente Reservoir to the new upper reservoir. This pumping would create a bank of stored hydroelectric energy in the upper reservoir that would be released to the lower reservoir by gravity at times when other renewable energy supplies, such as solar, are unavailable and when energy demand and electricity costs are higher.
According to the news release, pumped storage offers benefits to electrical grid operators such as the California Independent System Operator as well, including helping to maintain certain voltage levels on the grid and the capacity to quickly ramp up or down energy generation as needed.
Compared to other storage technologies such as batteries, pumped storage offers the benefits of large size and a long duration of storage services, which could be important factors in California's push for added renewable electricity, the water authority said.
California's renewable portfolio standard is slated to reach 50 percent by 2030.
The water authority currently operates a pumped storage facility at Lake Hodges, California, which began its operations of pumping water to Olivenhain Reservoir and generating up to 40 megawatts of electricity on demand for the region through downhill releases in 2011.
Water authority, San Diego joint permittees on preliminary FERC permit
As partners, the water authority and San Diego are joint permittees on a preliminary permit issued by the Federal Energy Regulatory Commission, which allows for the development of a pumped storage facility near San Vicente Reservoir.
This preliminary permit is an early step in determining if and how the project could be developed over the next decade.
In addition to the existing San Vicente Dam and reservoir, the potential project would make use of the nearby 500-kilovolt Sunrise Powerlink transmission line and the 230-kilovolt Sycamore substation, both of which are primarily owned by San Diego Gas & Electric, a subsidiary of investor-owned utility Sempra Energy.
Additional information about the San Vicente Energy Storage Project study is available here.
Public power and pumped storage projects
Public power entities are also taking a closer look at pumped storage projects.
Missouri River Energy Services on Dec. 7 said that it has applied for a new permit to study the potential for a 1,200-megawatt pumped storage hydroelectric facility, known as the Gregory County Pumped Storage Project, on the Missouri River in south central South Dakota.
Other public power entities are already utilizing pumped storage. For example, the New York Power Authority operates the Blenheim-Gilboa Pumped Storage Power Plant.
The Tennessee Valley Authority's Raccoon Mountain Pumped-Storage Plant is TVA's largest hydroelectric facility.