Pumped hydropower energy storage

Pumped hydropower storage (PHS), also called pumped hydroelectricity storage, stores electricity in the fonn of water head for electricity supply/demand balancing. For pumping water to a reservoir at a higher level, low-cost off-peak electricity or renewable plants' production is used. fu response to an increase in the grid's demand, the stored water is released to drive hydraulic turbines, actuating an electric generator. Variable output power can be obtained by controlling the exit flow from the upper storage. PHS plants are among the most efficient mechanical energy storage (MES) technologies with a high round-trip efficiency. The capacity of such plants can be very high, up to several thousand megawatts. However, high capital costs, certain environmental impacts, water availability, and topography challenges are the main drawbacks of PHS systems. Anyway, with all these positive and negative aspects of the technology, PHS is the most widely implemented energy storage system in the world, and as a result, is very broadly researched, presented, and discussed in various general, academic, technical, and commercial references. A very detailed report on PHS systems can be found in a recent publication by the editor of the present book and the same publisher (see Arabkoohsar & Narni, 2021). That is why, unlike the other chapters presented in this book for all other energy storage technologies, the cur­rent chapter is not going to be extensive. What this chapter presents is an overview of the fundamentals of PHS systems, a history of the development of the technology, var­ious possible configurations of that, and an overview of the current status of these sys­tems. The chapter also presents the energy and exergy models of PHS systems to be able to use them for thermodynamic analysis and in a case study it discusses analysis results for a PHS unit from the literature. Finally, it discusses the future of PHS tech­nology, some remaining gaps in the field and potential research topics in this area.