Comparison of solar assisted heat pump systems for heating residences: A review.

[Display omitted] • Performance, complexity and cost determines the preferability of SAHP. • Each SAHP has a range of ambient conditions in which it excels in performance. • The increase in performance with the complex structure brings along the cost problem. • It is possible to use PV/T with low cost add-ons in IDX-SAHPS. • Finned collectors can increase heat gain from air in DX-SAHPS. Solar assisted heat pump (SAHP) systems have been a popular research topic in last decades because of their proven improved performance by integrating solar energy to system. Filling the literature gap in SAHP systems comparison in terms of performance and structure, contributes to the determination of the appropriate type. For this purpose, in order to compare the systems, 77 recent studies are reviewed. Systems are classified according to their configurations to provide an infrastructure for comparison. Considering the collector structure, the effect of solar radiation and ambient temperature on SAHP systems performance are examined, and the ambient condition ranges preferable for each system are identified. The complexity of systems is expressed with the type and number of components used, and the costs of the systems are compared taking into account the payback period. Reviewed studies reveal that, direct expansion systems should be preferred because of their utilization of solar and air simultaneously as heat source, below solar irradiation of 400 W/m2. Indirect expansion systems are more complex than direct expansion systems and this limits their preferability. However, replacing the solar-side evaporator with a solar air preheater, thereby integrating the existing solar system and air source heat pump system, can simplify the indirect expansion systems. The temperature rise problem that prevents the use of photovoltaic thermal panels in indirect systems can be eliminated with low-cost external cooling devices. [ABSTRACT FROM AUTHOR]