A Specific Feature of CSP – Increasing Dispatchability and Efficiency with Thermal Energy Storage

The option to integrate cost effective storage systems directly into the plant environment represents a significant advantage of solar thermal power plants against other renewable energy technologies like PV or wind. Thermal energy storage systems store excess thermal heat collected by the solar field. Storage systems, alone or in combination with some fossil fuel backup, keep the plant running under full-load conditions. Improvements on operational flexibility and energy dispatchability by thermal storage and hybridisation are identified as key technology objectives for R&D development. The capability of storing high-temperature thermal energy leads to economically competitive design options, since only the solar part of the plant has to be oversized. This solar thermal power plant feature is tremendously relevant, since penetration of solar energy into the bulk electricity market is possible only when substitution of intermediate-load power plants of about 4,000-5,000 hours/year is achieved. The presentation covers the commercially available two-tank molten salt storage concept as well as alternative approaches for various plant architectures e.g. direct steam generation and air cooled receivers. Most of these approaches are still in the pilot or demonstration phase and need to be validated and proven for up-scaling to commercial scale. Finally current research topics are addressed covering heat transfer fluids and storage materials with superior thermo-physical properties as well as new concepts for improved heat transfer and storage design