Numerical Simulation and Experimental Analysis of a Modular Storage System for Direct Steam Generation

Thermal energy storage is a key technology for the commercialization of solar thermal power plants. This paper gives an overview of a coupled system comprised of concrete regenerators and latent heat storages for direct steam generation, as developed by the German Aerospace Center. Methodologies for an effective transient numerical description of the heat conduction processes inside the single modules and in the whole storage system are presented and their validity is proven by experiments. The presented process has a nominal system pressure of 105.6/80.0 bar for charging/discharging; the corresponding boiling temperatures are 315/295 degrees C. As storage material of the latent heat storage, sodium nitrate with a melting point of 305 degrees C is applied. With the presented models, a prediction of the storage system's temperatures, capacities, and effectiveness is possible. As a result, the design of a 1000-MWh(th) storage system is presented.