Several years ago NECA member company Southern Contracting in San Marcos, Ca., made a strategic decision to diversify company resources and pursue energy solutions projects. Southern’s recently completed Olivenhain/Lake Hodges Hydro Plant and Pump House projects are another testament to the company’s commitment to pursuing green energy work.
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Pumped-hydro energy storage is the most established technology for utility-scale electricity storage, but it has languished in the U.S. since the 1990s. When Southern had an opportunity to take on a PHES project that would not only add to the company’s energy solutions project experience but help lower energy costs for consumers, it jumped at the chance.
“This project is unique in many ways,” said Jim Filanc, Southern’s director of marketing. “There aren’t many places where gravity is the tool that makes energy savings possible.”
The project components consist of a pump station, power generating turbines and a 69 kV switchyard.
During the planning phase of the Lake Hodges projects’ design, the San Diego Water Authority recognized the hydroelectric generating potential of the 770-foot elevation difference between Olivenhain Reservoir and Lake Hodges. The Lake Hodges Pump Station, as originally planned, contained three vertical pumps and two pressure-control valves. By replacing the pressure-control valves, pumps and motors with reversible motor-generator/pump turbines and appropriately sizing the tunnel pipeline, all of the elements of a pumped-storage capability became available.
Under the revised design, power is generated when water flows back to the Lake Hodges reservoir during the day through two turbine generators with a combined capacity of 95 mW of electricity. This captured energy will provide revenue to pay back the cost of the pumped-storage equipment and facilities and support other Water Authority activities.
“So water is pumped uphill at night, at a cost of six cents per kilowatt hour,” Filanc said. “During the day, the water pumps downhill, taking advantage of gravity, at a cost of16 cents per kilowatt hour. Essentially, gravity is the energy storage mechanism for the project. The savings between night and day time energy pricing makes it possible.”
The Lake Hodges Pump Station’s pumpturbines will produce a maximum output of 40 megawatts during water transfers from Olivenhain Reservoir to Lake Hodges. The electricity generated is transmitted to an outdoor switchyard located adjacent to the pump station, then to a 1,400-foot-long transmission line that will connect to the existing local transmission system.
The original above-ground pump station structure was modified to be mostly below ground to accommodate the pumped storage equipment, providing the added benefit of reduced visual impact to the area. “This project will soon be generating revenue and saving energy,” Filanc said. “It’s a complete win-win solution.”
Filanc emphasized that credit for Southern’s initative into the energy solutions market belongs to company President and CEO Tim McBride. “The reason our company is positioned so well now is because Tim made a strategic decision to diversify into more sustainable energy projects several years ago,” he said. The company just awarded the contract to change out the city of San Diego’s 35,311 street lights from high-pressure sodium to induction street lights.
>>Read Southern’s fact sheet about the Olivenhain/Lake Hodges Hydro Plant and Pump House projects