Unconventional energy storage systems

Energy storage systems consist of matching devices for charging and discharging and the energy carrier. In principle all energy carriers (mechanical, electric, thermal, chemical) can be recycled, but the process differ greatly in complexity and efficiency. Storage cycles with high energy density materials show low efficiencies and vice versa. Grid-connected PV systems can use the storage capacity of the utility network and there is no need for additional energy storage in the near future. Stand-alone PV systems require energy storage systems but up to now there is no system available for long-term storage. It may be expected, that hydrogen systems will be on the market within the next few years. (ISE)