High Temperature Solid Media Thermal Energy Storage for Solar Thermal Power Plants

Solid sensible heat storage is an attractive option for high temperature storage applications regarding investment and maintenance costs. Using concrete as solid storage material is most suitable, as it is easy to handle, the major aggregates are available all over the world and there are no environmentally critical components. Long term stability of concrete has been proven in oven experiments and through strength measurements up to 500 °C. Material parameters and storage performance have been validated in a 20 m³ test module with more than 23 months of operation between 200 and 400 °C and more than 370 thermal cycles. For an up-scaled concrete storage design with 1100 MWh capacity in a modular set-up for a 50 MWel parabolic trough power plant of the ANDASOL-type, about 50,000 m³ of concrete is required and the investment costs are approximately 38 million Euro. The simulation of the annual electricity generation of a 50 MWel parabolic trough power plant with a 1100 MWh concrete storage shows that such plants could operate for about annually, delivering ca. 3,500 full load hours in southern Europe, about 30 % of this electricity is generated by the storage system. This number will further increase, when improved operation strategies are applied. Approaches for further cost reduction using heat transfer structures with high thermal conductivity inside the concrete are analyzed, leading to a 60 % reduction in the number of heat exchanger pipes required. For implementation of the structures, the storage is build up of precast concrete blocks