Thermal energy storage with flexible discharge performance based on molten-salt thermocline and thermochemical energy storage

Abstract

Thermocline sensible thermal energy storage has prospects in cost-effective thermal energy storage. In this study, we combined a molten-salt thermocline with thermochemical energy storage to improve the flexibility of thermal discharge performance. For the thermochemical energy storage material, a composite was synthesized using calcium hydroxide and silicon-impregnated silicon carbide foams with an energy capacity of 1.8 MJ (0.50 kWh) and volumetric energy density of 0.79 MJ L-material−1. The composite was loaded onto an indirect fixed-bed reactor that used molten salt as the heat transfer fluid. The temperature of the composite reached 637 °C at a hydration pressure of 812 kPa. The thermochemical energy storage reactor exhibited a variable maximum outlet temperature of the heat transfer fluid in the range 524–583 °C and maximum discharge power of up to 0.6 kW (discharge power density up to 0.25 kW L-material−1) on changing the hydration pressure and flow rate of the heat transfer fluid. The results confirm the significance of thermochemical energy storage to the system in boosting the temperature of the thermocline and variable discharge performance. The novel hybrid system has a superior discharge performance compared with that of the conventional thermocline thermal energy storage, and it is a promising option for flexible large-scale energy storage and power generation driven by renewable energy.