Experimental and numerical study of a CO2 heat pump working simultaneously with solar and air as thermal sources

This thesis investigates the performance of dual-source heat pumps, focusing on a solar-assisted heat pump (SAHP) system tested at the University of Padova. This system, which utilizes both air and solar energy as low-temperature thermal energy sources features a 5 kW heating capacity to heat water and store it in two 200-liter storage tanks. Data from the fifth experimental campaign, spanning December 2023 to February 2024, along with earlier campaigns, were analyzed to evaluate the impact of diverse water temperature differences at the gas cooler and various air temperatures on system performance in simultaneous operation mode. A simulation model updated from a previous thesis was used to assess system behavior under steady-state and dynamic conditions and to extend the validation of the experimental data. The study further simulates the performance of the dual-source heat pump configuration over an entire heating season in Rome, catering to both domestic heating and hot water needs. Comparisons were made between three heat pump configurations: an air-source heat pump with R290 (R290-AHP), an air-source with R744 (R744-AHP), and the dual-source solar-air heat pump with R744 (R744-SAHP), to highlight the advantages of dual-source systems in this climate.