We propose a TES system that combines a thermochemical storage (TCS) section with a sensible-heat storage (SHS) section (see Fig. 1). The TCS section is comprised of a tube bundle that houses gaseous and solid reactants undergoing a reversible chemical reaction. Since the tubes separate the reactants from the HTF, the gas-reactant pressure is decoupled from the HTF pressure and can therefore be controlled independently. During charging a “hot” HTF enters the TES system from the top and the gasreactant pressure in the TCS section is reduced to perform the endothermic reaction at “medium” temperatures.
During the subsequent discharging a “cold” HTF enters the TES system from the bottom and is preheated in the SHS section before entering the TCS section. By increasing the gas-reactant pressure, the equilibrium reaction temperature increases, and therefore the exothermic reaction can be performed at temperatures exceeding those of the preceding endothermic reaction. As a result, the HTF can be heated to an outflow temperature during discharging that is equal to or higher than the HTF inflow temperature during charging. To optimize the performance of the TES system for a given application, alternative storage materials and/or combinations of TCS, SHS, and latent-heat storage sections may be considered.
- Control over heat-transfer fluid outflow temperature
- Outflow temperature during discharging can be higher than inflow temperature during charging
- Potential for high energy-storage density
- Operating temperature range can be adapted through the selection of a suitable TCS reaction system and adjustment of the gas reactant pressure
- Thermal-energy storage for CSP plants or for advanced adiabatic compressed air energy storage (AA-CAES)
- Chemical or thermal processes requiring thermal energy supplied at constant power and/or temperature
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