Viewpoint: Pumped Storage: An Idea Whose Time Has Come … Again

Pumped-storage facilities are a special class of hydroelectric facilities, the value of which increasingly is being recognized. Worldwide, many pumped-storage projects are now under way, including the 13 examined in this issue of HRW (see article on page 14). Additional pumped storage is being pursued elsewhere, and new projects can be expected to add more than 20,000 mw to worldwide generating capabilities.*

This new activity represents resurgence in the development of pumped storage. Many such facilities were built in the 1970s and 1980s, although relatively few have been built in recent years. Today’s circumstances are ripe for this type of facilities.

Pumped-storage plants are the “race cars” among power generating facilities. Their dynamic, rapid response capabilities make them highly valuable for keeping electrical grids stable and reliable.

Traditionally, one way of keeping grids safe was by maintaining levels of “spinning reserve” adequate to accommodate unforeseen occurrences. For example, a grid would maintain enough spinning reserve to replace the capacity of the largest generating unit on the system in the event of that unit’s forced outage. If the largest unit was a 500-mw base load coal-fueled unit, then other units on the system would be operated at reduced output to ensure that at least 500 mw was available in the event of the unforeseen loss of this large unit. In years past, a similar type of reasoning led to grids having reserve margins of, typically, 20% or more.

In response to economic pressures, reserve margins have eroded in many regions to 10% or less (and, in too many instances, sufficient capacity is not available to meet total annual peak loads). In addition, the complexity and diversity of systems has increased the challenges of sustaining reliability.

Storage of electricity is not a new concept. It is often proposed as a means of bolstering system reliability. Some storage proponents advocate technologies that are exotic, expensive, and immature for storing the large amounts of electricity that are meaningful for grid operation — e.g., batteries, flywheels, compressed air, etc. Pumped-storage technology is well-proven and cost-effective, and up-to-date technology improvements have made new facilities even better than their predecessors.

The rush to wind power in some regions has added to needs for pumped storage … how better to accommodate an intermittent power source like wind than with pumped storage (and it’s ability to ramp up, or down, hundreds of megawatts in seconds)?

In most world regions, pumped storage is a good thing that there is not yet enough of.

Carl Vansant

*In the United States, the Hydro Review article, “Hydro Development: A New Day” (Volume 27, No. 2, April 2008), identified 15 pumped-storage projects totaling nearly 10,000 MW.

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