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 ^°C and 400 ^°C and more than 370 thermal cycles. For an up-scaled concrete storage design with 1100-MWh capacity in a modular setup for a 50 MW_el 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 MW_el parabolic trough power plant with a 1100-MWh concrete storage illustrates that such plants can operate in southern Europe delivering about 3500 full load hours annually; about 30% of this electricity would be generated by the storage system. This number will increase further, 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.