8. Conclusion

The massive development of renewable energies on the power grid requires a significant amount of storage, primarily to provide reserves and flexibilize demand. With wind and solar power the fastest-growing forms of electricity generation worldwide, it is only logical that installed stationary storage capacity should increase rapidly.

Depending on requirements, storage may be located "behind the meter", in renewable energy production plants (mainly wind and solar), or at nodes in the distribution or transmission grid. In almost all cases, a storage system is only profitable if it provides several services that can be sold or valorized.

The most widely used technology, apart from a few sites equipped with STEPs, is lithium-ion batteries. But this situation may change, as many storage technologies (including lithium-ion) are still under development....