There is a wide variety of energy storage devices, which are used for different purposes. A distinction is made between thermal energy storage, mechanical and thermomechanical energy storage, electrical energy storage, electrochemical energy storage, chemical energy storage and thermochemical storage.
Thermal energy storage systems are used primarily in industry and commercial enterprises to put waste heat to further use and, for example, to feed it into a district heating network. Thermal energy storage systems can be divided into:
- Low-temperature energy storage: in a temperature range up to about 100 °C, water is most commonly used. This storage technology is used for domestic water heating and building heating as well as in power plants.
- High-temperature storage: by heating and cooling inorganic materials such as refractory ceramics or fills made of ceramic fillers, heat can be stored in solids at temperatures exceeding 1,000 °C. The temperature when storing out is almost the same as the temperature when storing in. This technology offers a long service life and unlimited cycle stability. Kraftblock is a high-temperature thermal energy storage device and can store up to a maximum of 1300°C.
Mechanical and thermomechanical energy storage systems are used for long-term storage of electrical energy by converting it into another form of energy. This form of energy storage includes, for example, pumped storage power plants, flywheel mass storage, compressed air storage, liquid air energy storage, and thermal potential storage.
Electrical energy storage systems store electrical energy without prior conversion. Electrical energy storage systems include double-layer capacitors, which are mainly used in high-power and short-term storage systems superconducting magnetic energy storage systems, which store energy magnetic fields of coils.
Electrochemical storage systems are rechargeable electrochemical cells that use a redox reaction to store electrical energy.
Chemical energy storage systems. For example, water electrolysis. In this process, hydrogen serves as the energy carrier. In power-to-gas energy storage, the electricity and gas grids are connected. Hydrogen and optionally methane are generated from electricity. Metal hydrides can store energy in the form of heat or the energy carrier hydrogen. Lithium-ion batteries are among the best-known chemical energy storage systems.
Thermochemical storage systems use physical bonds, the absorption or dissolution of a substance, and reversible chemical reactions to store energy. So-called latent heat storage systems use the energy changes occurring during a solid-liquid, solid-solid, liquid-gas or solid-gas phase change to store and retrieve heat. This storage technology is used in systems that use steam as the working medium.