Raising questions on pumped hydro storage technology

Jack Geisler /

Published Aug 29, 2013 at 05:00AM

In a July 31 front-page, feature article (“Hydropower project floated near Bowman”), The Bulletin describes and illustrates the workings of a technology used at many sites around the globe and referred to in the article as “Pumped Hydro Storage” (PHS).

The idea is pumping water from a main reservoir (in this instance, the Prineville Reservoir) to a smaller reservoir situated nearby at a higher level. The water, thus stored, can be released at any time to drive a hydroelectric power generator.

The article also reports that a federal energy commission has granted a preliminary permit to Prineville Energy Storage, LLC, an affiliate of Boise, Idaho-based Gridflex Energy, to gauge the feasibility of building a 40-foot dam and reservoir immediately west of the Prineville Reservoir. Presumably, this will become the new PHS device.

As I understand it, a PHS device or its equivalent is an essential adjunct of primary power-generating facilities such as wind farms and solar-panel arrays that need output stored for later distribution. But this article, confined such as it is to the consideration of an entity (the Bowman Dam at the Prineville Reservoir) that has no primary power-generating capability at all, seems to stand in advocacy of PHS technology as a means of operating a stand-alone power plant. What is the primary generating facility that pumps the water to the upper reservoir? One can only assume from this article that, in the case of the PHS device proposed for installation at the Bowman Dam, it will come off the regional power grid.

If that is the case, the article fails to address an important point: You do not get out of a PHS device the power that you put into it. What are the numbers here? To cite a source reputable in business circles, The Economist put the typical efficiency at 70 to 75 percent in an online article (“Packing Some Power,” March 3, 2012, www.economist.com/node/21548495). In other words, the primary generating facility must provide a surplus of 25 to 30 percent of the power distributed to the consumer in order to run the PHS storage device.

If the primary generating facility is a “clean” one (wind, solar power), then no carbon dioxide gets emitted into the global atmosphere. The consumer (or some government incentive) must still pick up the 25 to 30 percent overhead, but that’s the cost of “going green.” However, if the PHS is storing power whose primary generation is from the burning of fossil fuels, then we have a 25 to 30 percent increase of emitted carbon dioxide per unit of power distributed, which is quite the antithesis of the “green” technology sought today.

The question is: Who would want to use a PHS device as a stand-alone power plant, anyway? I can think of one reason: Buy power off the grid to top up the reservoir in off-peak hours, and then release that water during peak hours to produce power through the hydroelectric generator of the PHS device.

Such a buy-low, sell-high scheme could generate profit for the operating company. The consumer, who presumably gets passed the bill for the 25 to 30 percent efficiency loss of generating power in this way, doesn’t benefit. Neither does the global atmosphere that receives the extra 25 to 30 percent carbon dioxide from the coal or oil-fired plants that generate the primary power on the grid that will run this proposed stand-alone PHS device.

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