Comprehensive energy, economic, and environmental analysis of a hybrid photovoltaic–thermal (PVT) heat pump system

This study investigates a parallel indirect-expansion solar-assisted heat pump (SAHP) system integrating photovoltaic–thermal (PVT) collectors to meet domestic space heating, hot water, and appliance electricity demands for a typical household in Germany. A transient mathematical model captures the interdependencies between heat and electricity flows, enabling evaluation of thermodynamic, economic, and environmental performance across 54 heat pump designs with 3 refrigerants. The SAHP is compared to standalone heat pumps and natural gas boilers under varying electricity and natural gas prices. Results indicate that the SAHP system can cover over one-third of annual heating demand and half of appliance electricity demand using solar energy, with Munich achieving the highest solar coverage (39 %). HFC-32 (R32) outperforms propane, which in turn outperforms R410A, with levelized costs of energy, in electricity equivalents, of 0.272, 0.276 and 0.283 Euro/kWh, respectively. The SAHP system proves more cost-effective than standalone heat pumps or natural gas boilers unless energy prices are exceptionally low. Optimizing water tank designs for lower-temperature operation could further enhance SAHP competitiveness against PV-driven heat pumps.