Smart Grid: Pumped Hydro Energy Storage at San Luis Reservoir

On a recent sunny Saturday, I hopped in a car with my wife and drove to San Luis Reservoir, which is about 30 miles east of Gilroy, CA (Garlic Capital of the U.S.). Romero Overlook Visitors Center is on Route 152 and is a good place to visit the reservoir. ::continue::

Map for San Luis Reservoir

My plan was to see the reservoir that is used for pumped hydro energy storage. A bigger reservoir?(for pumped hydro energy storage ) is in Oroville, CA, which is probably two hours away from us, too far for a nice Saturday outing.  I had read about the subject of energy storage, and covered it in a previous blog. It was about time for me to go there and take a look at real storage.

San Luis Reservoir

There were many wind power generation gears on the hill surrounding the reservoir, but they are for research purposes and are not used for production.

Wind power generation gears on the surrounding hills

Demand and supply of power are not uniform throughout the year or even on the same day. For example, demand is higher during the day and lower at night. Pumped hydro energy storage uses two reservoirs with different elevations. Hydroelectric power generators generate power by releasing water from a height and moving turbines with it. When demand is high, water in the reservoir at the higher elevation falls to another reservoir at the lower elevation to generate power. When demand is low (and, therefore, power is less costly), the water at the lower elevation is pumped back to the reservoir at the higher elevation so that the power equivalent of water is stored.

At the reservoir we visited, San Luis Reservoir is at the higher elevation, while O’Neill Forebay is at the lower. The picture below shows four shafts at the edge of San Luis Reservoir that release water (and pump it back up). Behind the shafts, you can see a bank. There is a power plant at the other side of the bank. The elevation difference is about 320 feet and the generated power for a year is about 348 MKWh.

Four shafts at the edge of San Luis Reservoir release water

At the other side of the bank, you can see a hydropower generation plant.

The other side of San Luis Reservoir and the hydro power plant

You can also see a large substation close to the power plant.

Substation near the power plant

Overall, it was a nice outing to actually see energy storage in action.

Zen KishimotoBy Zen Kishimoto, PhD, Principal Analyst, Green IT, AltaTerra Research

You can also find this blog post and more on under Zen and the Art of Data Center Greening.


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AltaTerra Research is a research consultancy specializing in sustainable business and the commercial marketplace for clean technology solutions. Through research reports, executive events and advisory services, AltaTerra helps forward-looking organizations improve resource-efficiency in their operations and capitalize on new 'green' market opportunities. From our headquarters in Silicon Valley, we have been serving a global base of corporate, institutional, and government clients since 2007.

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