Calcium aluminate based cement for concrete to be used as thermal energy storage in solar thermal electricity plants

• Design of an efficient thermal concrete to be used as solid thermal energy storage system in solar thermal energy plants.
• Develop and characterize concrete mixes based on high alumina cement blended with blast furnace slag and suitable aggregate grading to endure long periods at high temperature.
• Thermal fatigue resistance due to heat cycles effect, from 290 °C to 550 °C, and characterization of damage evolution at micro- and macro-level.

A concept for thermal energy storage (TES) in concrete as solid media for sensible heat storage is proposed to improve the cost and efficiency of solar thermal electricity (STE) plants. Mortar and concrete mixes were designed with calcium alumina cement (CAC) blended with blast furnace slag (BFS), using aggregates of different sources and size for stability performance after long term at high temperature. Seventy-five thermal cycles of 24 h length, within the temperature range 290 °C to 550 °C, have been used to simulate the expected operating conditions of TES. The dehydration processes at microstructural level have been evaluated and correlated with mechanical properties. Dehydration processes and consecutive heat/cool cycles induce changes in concrete at micro- and macro-level. The stabilization of damage with the charge/discharge heat cycles for thermal fatigue depends significantly on the aggregate type used. CAC is a suitable binder to use in thermal energy storage systems able to maintain its properties under repetitive heat cycles.