Enhancing CO2 heat pump efficiency for integrated DHW and cooling via solar assistance and thermal inertia
This article investigates an integrated architecture designed to optimize the efficiency of CO2 cooling in regions with high solar irradiance and extreme ambient temperatures. The system utilizes solar hybrid panels (PVT) as the primary endothermic source, generating electrical energy injection into the main grid and simultaneously capturing thermal energy for domestic hot water (DHW) preheating. This thermal energy is processed by a secondary R290 circuit that generates a stable energy reserve within a glycol-water Integrated Thermal Buffer (ITB). The core of the proposed innovation lies in the active transfer of 10.8 kW of cooling power from the secondary circuit directly to the primary CO2 rack via subcooling. Thermodynamic modelling, validated through Danfoss Coolselector®2, demonstrates that when the system reaches a critical ambient stress of 37 °C, the ITB intervention effectively lowers the gas cooler exit temperature to 30.65 °C. This shift allows the cycle to operate in a stabilized high efficiency trans critical regime at 77.93 bar, achieving a global COP of 2.42. The energy balance confirms a net energy profit of 2.99 kW, as the 6.51 kW power reduction in primary compressors significantly outweighs the marginal consumption of the support circuit. Furthermore, although this study focuses on a specific power configuration, the modular nature of the ITB architecture allows for various power combinations and scalable deployment across different industrial capacities. The results validate the system as a robust and water-free solution for the decarbonization of food retail, hospitality, and healthcare establishments.