High temperature latent heat storage with a screw heat exchanger: Design of prototype

An important option for increasing the efficiency in Concentrated Solarthermal Power (CSP) is the development of systems generating steam directly in the solar field. To produce dispatchable and affordable electrical power, the integration of an efficient and economical thermal energy storage is an attractive option. To (dis)charge a storage with steam, latent heat storages are particularly suitable for the use with two-phase heat transfer media. Due to low heat conductivities of the phase change materials, the heat exchanger design is crucial. Up to now no latent storage is commercially deployed in CSP. A new latent storage approach is being developed at Fraunhofer ISE; a Screw Heat Exchanger (SHE) is employed for heat transfer. With a SHE, material can be transported during the phase change. With this innovative concept, the size of the heat transfer area and the storage capacity can be decoupled and it seems possible to develop an economically viable latent storage.