Ceramic particles about one millimetre across are directly irradiated in the receiver – they act as both heat exchangers and a storage medium.
DLR (CC-BY 3.0).
In a "heat storage" infotower, a wide range of heat storage techniques using solids and liquids and both latent heat storage and thermochemical systems are explained..
Thermochemical heat storage systems take in heat using an endothermic reaction and release it again through an exothermic reaction. They have a very high energy density and are ideal for long-term storage. In the CWS (Chemische Wärmespeicherung mittels reversibler Gas- und Feststoffreaktionen – chemical heat storage by means of reversible gas-and solid-state reactions) test facility in CeraStorE at DLR Cologne, such a storage system is being tested on a larger scale for the first time.
Researchers at the DLR Institute of Technical Thermodynamics are testing ceramic materials (pictured here), molten salts, concrete and natural stone for use as thermal storage media.
By incorporating thermal energy storage, solar thermal power plants are able to provide electricity as required, even at night-time and during periods of low sunlight. DLR researchers use the 10-kilowatt test facility to examine heat storage at temperatures ranging up to 400 degrees Celsius. The storage container can be operated with different storage mediums based on salt to develop latent heat storage, and molten salt storage.
High-temperature storage could accelerate the deployment of renewable energy and also provide for more flexibility and greater efficiency in industrial processes as well as conventional power plant applications. The core of the 'HOTREG' experimental plant at the DLR Institute of Technical Thermodynamics is a five-metre-high storage unit. With the reconfigurable test unit for investigation of thermal storage, researchers can test various storage concepts, operating methods and materials.
Reconfigurable thermal storage test unit with removable inner container.
The salt-based latent heat storage system works using a phase transition. At 305 degrees Celsius, the salt absorbs energy by transitioning from a solid to a liquid state. Latent heat is 'hidden' energy. Energy is accumulated as the storage medium changes phase from solid to liquid.