Potential energy project could benefit water ratepayers

An exciting concept is emerging in San Diego County that could reduce pressure on water rates across the region and expand opportunities for renewable energy.

The system under consideration is essentially an incredible “battery” that could store up to 500 megawatts of renewable energy. There’s still a lot of work to be done to determine whether this idea pencils out — but it’s important even at this early stage because it highlights how the San Diego County Water Authority and its member agencies are continually seeking ways to make the best use of the region’s water infrastructure.

At the simplest level, the project would work like this: When regional energy supply exceeds demand, water would be pumped uphill from San Vicente Reservoir near Lakeside to a new smaller reservoir, creating a bank of stored hydroelectric energy for later use. When regional energy demand and electricity prices rise, the stored water would be released to San Vicente by gravity, turning turbines and generating power.

Such a project would support electrical grid operations that are essential to integrating large new supplies of other renewable electricity into the California and western power grids — notably solar, but also wind. It also would make it easier to quickly increase or decrease energy generation as needed.

In March, the Water Authority’s board of directors authorized staff to seek detailed proposals for this project after 18 qualified parties expressed interest. During that process, we confirmed several valuable conclusions:

• The potential project would be a valuable resource. Located in an energy load center, it would help stabilize the energy transmission grid operated by the California Independent System Operator.
• The project size is appropriate. A 500-megawatt project with five to eight hours of energy storage would help investor-owned utilities meet a state mandate to procure 50 percent of their energy from renewable energy sources by 2030.
• Infrastructure exists to support the project. Existing resources the project could capitalize on include the San Vicente Dam and Reservoir and a nearby high-voltage transmission line.

In mid-July, the Water Authority issued a Request for Proposals in partnership with the city of San Diego, which owns San Vicente Reservoir. The competitive bidding process will help ensure maximum value. The Water Authority and the city expect to evaluate proposals this fall and to seek approval from the board to begin negotiations with a potential full-service team by the end of 2017.

The Water Authority already has a long history of leadership and innovation in the energy sector. For instance, it operates an energy storage facility at Lake Hodges, which generates up to 40 megawatts of electricity on demand for the region. The Water Authority also has installed more than 7,500 solar panels total at three facilities that produce an estimated total of 2.7 million kilowatt-hours of renewable energy annually, enough to reduce the agency’s energy expenses by nearly $5.6 million over 20 years.

And the agency in May received a $1 million incentive to install industrial-scale batteries at its Twin Oaks Valley Water Treatment Plant — another element of our efforts to maximize value for the region’s water ratepayers.

For more information about the San Vicente Energy Storage Project study, go to www.sdcwa.org/san- vicente-energy-storage-facility-study.

Mark Muir is chair of the board of directors of the San Diego County Water Authority.