4. Conclusion and prospects

For electricity , there is a set of technologies allowing various needs to be met: massive storage, electrical grid stability, mobile systems, hybrid or electric vehicles, etc. Two major storage means dominate the electricity storage market:

• for the very large quantities of electricity that must be stored at the national level, PHES is the most efficient and cheapest storage medium. In the future, it is possible to envisage the construction of artificial PHES schemes on land or at sea to manage intermittent energies;

• for lower quantities of electricity such as those required by vehicles and mobile electronic devices, Li-ion technologies dominate the market but for other less demanding...