1. Context

Most of the world's electrical energy storage is currently provided by 350 water pumping stations between 2 reservoirs; these stations are known as STEP (Stations de Transfert d'Énergie par Pompage). Their overall power is close to 150 GW, enabling the average electrical power consumed to be modulated by ± 6% (22,000 TWh divided by 8,760 h equals 2,500 GW). They generally run on fresh water.

STEPs are used, above all at present, to ensure peak consumption and the quality and security of the power grid. In the future, they may have an even more important role to play in the storage of intermittent energies, particularly wind and solar. Hence the need to assess the scale of future storage requirements, the potential of STEPs (to meet them in various forms), and the corresponding costs and impacts.

This paper analyses this problem in 4 chapters:...