The overall objective of the TCSPower project is to realise a new, efficient, reliable and economic thermochemical energy storage (TCS) for concentrated solar power plants which has the capability to contribute significantly to further cost reduction of regenerative electricity production. This will be achieved by applying reversible gas-solid reactions. Dissociation of calcium hydroxide is used for storing thermal energy in a temperature range between 450 and 550°C in connection with trough power plants with direct steam generation. For the higher temperatures of central air receiver CSP plants the redox reaction of manganese oxide will be applied.The scientific and technological development in the proposed TCSPower project is focused on three areas: (1) chemical reaction system and storage material issues, (2) design of the TCS reactor taking heat and mass transport aspects in combination with reaction kinetics into account, (3) system integration of the TCS system into the CSP plant.The outcome of the project will include suitable, long-term stable calcium hydroxide and manganese oxide materials with improved functionality in regard to reversible reaction kinetics and heat transfer. A simulation tool for the design of TCS reactors with improved heat and mass transfer characteristics will be applied to identify suitable reactor concepts for the hydroxide and the redox reaction system. Both concepts will be experimentally evaluated in laboratory scale. Additionally, an up-scaling to 10kW will be realized for the more promising reaction system to evaluate the performance of a pilot-scale TCS reactor experimentally.Based on the obtained results, two application-oriented concepts for the integration of the respective TCS systems into CSP plants will be elaborated. Finally, strategies for up-scaling to commercial scale and a techno-economic evaluation of the thermochemical storage systems will be developed.