Because the offer and the demand for the use of electricity, heating, cooling, or mechanical power differs many times, energy has to be stored,especially in the case of decentralized energy systems based on renewable energy. There are many technologies available, from the simple storage of fire wood, over many kinds of batteries for specific purposes, to differing sizes of tanks and other possibilities. For more information and facts please visit, e.g.: https://www.smart-energy.com/storage/the-different-types-of-energy-storage-and-their-opportunities/ or https://www.greentechmedia.com/articles/read/most-promising-long-duration-storage-technologies-left-standing or https://www.sciencedirect.com/topics/engineering/energy-storage-technology or https://en.wikipedia.org/wiki/Energy_storage or https://energystorage.org/why-energy-storage/technologies/ , last visit: 05. June 2022.