Cities rely on proven technology to meet climate goals

SAN DIEGO, California – When you think of renewable energy, solar and wind naturally come to mind. But have you ever thought about how you can generate energy when the sun is down and the wind is still? Neena Kuzmich of the San Diego Water Authority explains that with big climate goals on the horizon, cities like San Diego are tapping into the world of pumped storage hydropower.

“The problem right now is that these renewables are intermittent,” Kuzmich said.

Here’s how it works: A city builds a new retention basin over its current reservoir. Newly built underground tunnels will be connected to an underground power plant that uses surplus renewable energy to pump water from the lower reservoir to the upper basin during the day. At night, the water will flow back down through this pipeline and flow through the turbine pump station. This electricity will then generate clean energy to power the city’s grid.

“The beauty of pumped storage is that it’s a proven technology that will last 100 years,” Kuzmich said.

Already in operation at more than 40 locations across the United States, pumped storage hydropower has worked beautifully for decades, but now bigger goals call for bigger solutions.

“The renewed interest comes as we begin to move more and more towards renewable energy. They need longer-term storage,” said Greg Stark, the technical director for hydropower at the National Renewable Energy Laboratory.

Many cities like San Diego already have dams and reservoirs. This new project would allow them to serve a dual purpose.

“You hear the stories about drought. This is truly a drought-proof supply because it’s our emergency water,” Kuzmich said. “This type of installation would allow us to store the excess energy generated by these solar panels during the day and use it in the evening hours from 4pm to 9pm, which is really the high energy time by the homeowners and the Company.

“And it’s just like when the sun goes down, and so all the solar energy goes away, and that’s where pumped storage fits in really well,” Stark said.

Stark explains that cities can rely on this technology for their ability to shift energy in time.

“When the wind and sun didn’t show up and they were forecast to show up and they’ve gotten a lot better at the predictions but there are still times when it’s not quite there and historically what they would do , they would fire up a gas turbine to fill that gap. Imagine a world where all that stuff has to go. What’s left that you can turn on and off at the same time? Storage is one thing and hydropower is another,” said Stark.

If all goes according to plan, the San Vicente reservoir will do just that in about eight to 10 years.

“You need something to essentially look at replacing these natural gas plants that we have, because if we’re really going to be 100% clean energy, we need some type of plant that can replace these stable base-load plants, and an energy storage plant does that,” said Kuzmich.

The next 10 to 25 years are packed with climate change goals, and these experts say it’s part of the puzzle to get there.

“The versatility of water is really amazing to the average person, who might not even realize that we can generate energy with water,” Kuzmich said.



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