Solar assisted heat pump systems for low temperature water heating applications: A systematic review

Combination of solar thermal collectors and heat pumps in a single solar assisted heat pump (SAHP) system has been widely used for various purposes including water heating. International Energy Agency, Task 44 of the Solar Heating and Cooling (SHC) Programme, has been working on methods towards most effective use of solar heat pump systems for residential use. The current work aims at reviewing the past and present work conducted on the SAHP systems for low temperature water heating applications. The review approach is based on a visualisation scheme to systematically represent and classify concepts of SAHP systems. Specifically, the key performance data from a number of studies are highlighted and various configurations are compared in order to gain accurate and deep intuitive understanding of SAHP systems. The review faithfully states that having a variety of configurations, parameters and performance criteria may lead to a major inconsistency that increase the degree of complexity to compare and analyse the studies of different systems.