Photovoltaic-thermal solar-assisted heat pump systems for building applications: A technical review on direct expansion systems

Buildings have a crucial role in global energy consumption and the release of greenhouse gases, especially due to their heating, cooling, and hot water systems. This study examines the incorporation of photovoltaic thermal (PV/T) and heat pump (HP) technologies, with a specific emphasis on their joint utilization in solar-assisted heat pump (SAHP) systems for enhancing building energy efficiency. The study conducts a thorough examination of contemporary literature to evaluate the effectiveness, feasibility, and performance metrics of PV/T-SAHP systems. Notable progress has been made by incorporating hybrid PV/T collectors, which can produce both electricity and thermal energy at the same time. This has led to enhanced system efficiency and increased reliability in operation. SAHP systems can be classified into numerous configurations, including direct expansion (DX) and indirect expansion (IDX) systems. Their performance under various climatic situations is thoroughly assessed. Concerning the direct expansion systems, the key numerical findings from the papers available in the scientific literature are summarized and discussed. The review highlights the capacity of PV/T-SAHP systems to improve energy efficiency, diminish carbon footprints, and promote sustainability in building applications. Identify future research directions to enhance system design, integration, and performance for wider implementation in low-carbon building initiatives.