What is Pumped Storage Hydro

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Project Cross Section

Pumped storage hydro is a simple energy generation and storage concept that involves pumping water from a lower to an upper impoundment thus creating stored energy. When energy is needed, the water flow is reversed, run through hydroelectric turbines, and released back in the lower impoundment. This traditional application of pumped storage hydro often uses inexpensive power generated at night, when energy demand is the lowest, to pump, and when electrical demand is highest, reverse the operation and generate energy.

In the past decade, however, as greater renewable generation has been interconnected into the grid, new pumped storage equipment has been designed and installed that allows very quick mode change from pumping to generating.  This new capability allows utility and grid operators to use pumped storage hydro as a “shock absorber” — allowing for the quick generation of power when there is not enough or to soak up and store excess power when there is too much.  This fast acting equipment is being planned for the Coffin Butte development.

Another aspect of the Coffin Butte project relates to the ability to utilize a closed-loop system to minimize environmental impacts.  A closed-loop facility is built off-stream, away from sensitive riparian habitat. During operations the water is reused by cycling it back and forth between the upper and lower water impoundments, thus creating an efficient use of water resources. After a single fill of the lower impoundment, a closed-loop facility only requires an annual recharge to make-up for minimal losses due to evaporation and seepage.

The Coffin Butte Closed Loop Pumped Storage Hydro Project will be a versatile tool with all the attributes needed to quickly and reliably service the modern energy and transmission needs of the Northern Plains and Pacific Northwest.