COMMISIONING OF A THERMAL ENERGY STORAGE SYSTEM FOR DIRECT STEAM GENERATION

Abstract

Direct steam generation is a promising option for CSP technology, for reducing the costs of solar thermal power generation. These new solar thermal power plants require adapted storage concepts, where the two-phase heat transfer fluid poses a major challenge. A three-part storage system is proposed for the two phase fluid water/steam. Concrete storage is used for the process steps involving the transfer of sensible heat – i.e. preheating of water and superheating of steam – while for the two-phase evaporation a phase change material (PCM) storage will be employed. This technology is being developed by DLR and Ed. Züblin AG. A combined storage solution with a concrete storage for superheating of steam and a PCM-storage for evaporation of water was build in 2009 in a direct steam test loop, set up at the power plant Litoral of Endesa in Carboneras, Spain. This high temperature storage system has a total capacity of ca. 1000 kWh and is the first demonstration of such a combined storage system for the two phase heat transfer fluid water/steam. Commissioning of this storage system was successfully completed in July 2010, implying first heat-up of the concrete storage to expel the excess water in the concrete, first heat-up of the PCM storage including final filling of the storage with salt and first cycling tests. Results are presented in this paper.