Synergies between high temperature heat pumps and salt hydrate thermochemical systems for waste heat recovery

Kurzfassung

Efficient utilization of waste heat is crucial for global energy needs and carbon neutrality. High-temperature mechanical heat pumps (HTHPs) are key in this effort but are limited by their evaporator temperatures. This study aims to upgrade and reintegrate the waste heat of an HTHP in the range of 105-140 ℃ by cascading with a dual-reactor salt hydrate-based thermochemical energy storage system. The proposed system uses the waste heat of an HTHP to generate water vapor in an evaporator, driving hydration in one reactor and charging in another. A thermodynamic analysis of the system evaluates its performance using K2CO3/H2O as the working pair, with the evaporator temperature varied from 100 ℃ to 90 ℃. Lowering the evaporator temperature increases thermal output, but is constrained by the HTHP’s temperature requirements. The system delivers 55.36 kW per unit mass flow rate of air at a heat upgrade efficiency of 45.68%, with a heat source at 140 ℃ and evaporator at 100 ℃. This study attempts to establish a framework for designing efficient thermally driven cascaded heat pumps.