Together with a private company, the city and the Water Authority want to build what amounts to a water battery using the San Vicente Reservoir and a new reservoir to be built nearby. / Image courtesy San Diego County Water Authority

Last year, California raised the stakes in the fight against climate change, instituting a goal of reaching 100 percent carbon-free electricity by 2045, with at least 60 percent of that power coming from renewable sources such as wind and solar.

And more than a year before the state did so, the city of San Diego made a pioneering commitment to achieving its own goal of 100 percent renewable energy by 2035, as outlined in the city’s Climate Action Plan.

Voice of San Diego Commentary

Setting these lofty energy goals is the easy part. Building the infrastructure needed to integrate these clean energy sources onto the electric grid will be much harder, and the key actions are starting now.

At first blush, it might seem that building more solar and wind power capacity is all we need to do, but it’s not that simple. Renewable energy is intermittent by nature; when the sun goes down and on cloudy days, production from solar panels tapers off.

Fixing this problem requires investment on many fronts. Energy storage, in particular, is key.

Energy storage comes in many forms. Batteries are in the news often, and they have an important role to play. But battery systems are best for short-term storage, offering only a few hours of power. A true shift to renewables requires much longer-duration, bulk energy storage technology — with overnight capacities of eight hours — able to capture vast amounts of electricity when it is available and release it to the grid when more power is needed.

Currently, California’s electrical grid has little storage infrastructure built into it. Instead, it relies on natural gas-fired plants to switch on and off as needed. Making deep cuts in greenhouse gas emissions requires new kinds of renewable gas, not to mention a much smaller role for these plants and heavier emphasis on storage to keep California’s grid reliable as we shift to renewables. In the last month alone, two major studies — one a white paper on the value of energy storage and the other an independent look at California’s global warming goals — have both underscored the need for much more investment in storage to meet our ambitious renewable energy goals.

To this end, the city of San Diego and the San Diego County Water Authority are assessing pumped-water energy storage as a way to integrate more renewable power, stabilize the power grid, reduce greenhouse gas emissions and foster economic growth. Their proposed San Vicente Energy Storage Facility would take water from the existing San Vicente Reservoir and use electricity to pump it to a smaller, higher elevation reservoir. When the grid needs more electricity, water would be released from the upper reservoir through a hydropower generator, producing renewable energy for consumers. As a way to achieve bulk energy storage over many hours, pumped-water storage is by far the least expensive option. Moreover, these assets live a long time, and once they are paid off, they are even cheaper.

The San Vicente project could provide up to 500 megawatts of electricity — enough to power roughly over 300,000 homes for more than eight hours.

The San Vicente project and other major energy storage projects throughout the state create economic opportunities through workforce training, energy efficiency projects and development projects that are important elements of climate action plans. The positive ripple effects could be profound.

Fortunately, San Diego has proven time and again that it is all in when it comes to cutting greenhouse gases and creating clean energy jobs. In order to meet our goals, we need to invest in a variety of technologies — and energy storage is key.

Jason Anderson is president and CEO of Cleantech San Diego, a regional trade association. 

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