Dynamic characteristics and performance enhancement of a novel hybrid system integrating transcritical CO2 heat pump and absorption thermal energy storage

With efforts to mitigate the greenhouse effect, the proportion of nonlinear renewable energy in the power grid is rapidly increasing. The harmonization of supply and demand side poses a significant challenge that urgently needs to be addressed. The current energy storage technologies for peak load shifting still face obstacles such as high cost, low performance, and geographical limitations. A novel hybrid system (CHP-ATES) integrating transcritical CO2 air source heat pump (ASHP) and absorption thermochemical energy storage (ATES) for domestic hot water and space heating is proposed. Its high heat storage density, long-term heat storage capacity, adjustable generation temperature, and excellent heat transfer performance have shown significant value in providing demand response. The reasonable combination is adopted to realize cascade utilization of the heat energy of transcritical CO2 ASHP, which maximizes energy efficiency and reduces heat loss. The periodic performance coefficient of CHP-ATES is 64 %–81 % higher than that of sensible thermal energy storage (WTES), with a 25 %–37 % reduction in heat loss rate, showing excellent energy-saving potential. The dynamic operation characteristics of CHP-ATES were analyzed as a function of operating conditions and charging/discharging process. The long-term heat storage capacity of ATES was evaluated. The 72-h heat storage capacity of ATES was 140 % higher than WTES. The weekly electricity cost decreased by 31.5 %–47.6 % compared to direct heating heat pump. The levelized costs of heat and electrical energy storage are 0.0537 $/kWh and 0.1531 $/kWh, respectively, with a payback period of 7.93 years as an alternative to gas boilers. This work provides a solution to promote the goal of carbon neutrality through efficient thermal energy storage combined with demand response.