Hybrid solar–exhaust heat recovery heat pump system: A combined experimental and numerical study for high-efficiency sustainable heating

A significant portion of building energy consumption is attributed to space heating, while a significant amount of power generator waste heat is left unused. At the same time, solar energy's sporadic nature restricts its use as a stand-alone heating source. The objective of this research is to design and evaluate a hybrid heat pump system that combines solar air heating with power generator exhaust gas recovery in order to minimize greenhouse gas emissions, improve energy efficiency, and consume less fuel in cold-climate operations. In contrast to traditional exhaust-recovery or solar-assisted systems, the suggested setup integrates waste-heat and dual renewable sources in various configurations to find the best thermodynamic performance. Through experimental validation and computational modelling, the unique hybrid design for sustainable heating is established by integrating solar and exhaust heat recovery with a heat pump cycle. Six system configurations were examined covering all possible integration sequences of the heat pump, exhaust gas recovery, and solar air heating components. Field data from a 45 kVA generator and 12 m-long solar air tubes were integrated with thermodynamic modelling in a combined simulation experimental framework. At −5 °C ambient conditions, the configuration combining the heat pump, solar air heater, and exhaust gas recovery produced the highest coefficient of performance, with a boost of up to 4770%. The system achieved significant monthly energy and cost savings, as well as up to 98% reductions in carbon dioxide emissions. While the integration of these distinct dynamic heat sources present control challenges, the modular nature of the system affirms feasible application across different scales of buildings. For next-generation building heating systems, this hybrid heat recovery technology provides an extremely effective and environmentally friendly option. This study illustrates the capabilities of hybrid renewable–waste heat recovery systems for the sustainable heating of buildings, paving the road for future experimental work and thermal energy storage integration.