Pumped Hydroelectric Storage

Pumped hydroelectric storage (PHES) is similar in many aspects to conventional hydropower; however, the primary difference is that it has pumping capability through a dedicated pump or through a pump-turbine unit. A number of existing PHES plants use variable speed pump-turbine units. The advantage of variable speed units is that the plants use asynchronous motor generators that allow the pump-turbine rotation speed to be adjusted. PHES allows regulation of the amount of energy absorbed in pumping mode. It provides management tasks for such power systems as balancing, frequency stability, and black starts. Current trends for new PHES development generally show that developers operating in liberalized markets are tending to repower, enhance projects, or build pump-back PHES rather than traditional pure pumped storage. Seawater PHES technology has yet to develop a commercial track record however, with only one completed plant worldwide.