Sacramento Eyes Giant Water Battery

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The City of Sacramento, California is forging ahead with plans to construct a 400 megawatt battery made entirely out of water. That almost sounds like some kind of high tech miracle but it’s not. Water batteries, aka pumped hydroelectric facilities, use established technology and old fashioned gravity.

Pumped hydro is currently the only utility-scale energy storage devices in common use globally, including in California and the US. Another new pumped hydro project is already in the works for California, so you’re going to hear a lot more about pumped hydro in the future.

Why Pumped Hydro?

Given the drought in California the timing might seem a bit odd for water-intensive energy projects. However, the idea behind pumped hydro is to circulate the same water, rather than letting it run through as in a conventional hydroelectric dam.

In a pumped hydro system, water is shunted from a lower reservoir to a higher reservoir at night, during off-peak hours when electricity rates are lower, so the basic idea is to save money.

You also get bonus points for using renewable energy to do the pumping. Given their potential for enormous capacity, pumped hydro systems are ideal for storing energy from intermittent sources, namely wind and solar (check out this pumped hydro system in Wales for the wind angle).

Even without renewable energy, the carbon footprint reduction and financial savings both kick in because pumped hydro can reduce or eliminate the need to build new fossil fuel power plants to handle peak use periods.

Another sustainability aspect of pumped hydro is the potential for using existing reservoirs, as illustrated by a proposed pumped hydro system in New York.

Our sister site PlanetSave also notes that a company called Gravity Power, LLC has been developing a modular pumped hydro system that could help reduce the need for new reservoir construction.

The Iowa Hill Pumped Hydro Project

Sacramento’s planned pumped hydro system is called the Iowa Hill project. It is going to use Sacramento’s existing Slab Creek reservoir on the American River for the lower reservoir. The upper reservoir, which will not dam the river, will be new construction with a capacity of 6,400 acre-feet.

The project will also piggyback on transmission lines from Sacramento’s existing hydroelectric facility.

In the latest developments, recently the Sacramento Municipal Utility District engaged Jacobs Associates for preliminary design and yesterday the global engineering firm GEI Consultants, Inc. announced that it is leading the design team for the upper reservoir.

As for renewable energy, the Iowa Hill project already gets bonus points for reclaiming and re-using Sacramento’s existing hydro resources. Wind and solar also come into play, as explained in the Utility District’s FAQ:

It would play a crucial role in allowing us to add larger supplies of intermittent wind and solar power, because power generated at Iowa Hill could fill in supply “gaps” when the sun doesn’t shine or the wind doesn’t blow. In addition, it would allow us to use excess wind or solar power to pump the water uphill when demand for electricity is low.

The project is still undergoing feasibility studies, primarily to determine if the geology of Iowa Hill can support the new reservoir and related underground tunnels.

A final decision on moving forward is expected in 2017.

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