Two-stage direct expansion solar-assisted heat pump for high temperature applications

Direct expansion solar-assisted heat pump (DX-SAHP) systems have been proposed as viable alternatives to conventional solar-assisted heat pump systems. This study proposes the use of two-stage DX-SAHP systems for high temperature applications in the range of 60–90 °C. The study investigates the capability of these systems of meeting loads with high temperature requirements. The thermal performance of the systems is analyzed for refrigerant R-134a, using a one-cover solar collector. Comparisons between the two-stage DX-SAHP and the single-stage DX-SAHP systems are performed and presented. A graphical procedure is illustrated and used for sizing the solar collector area and the heat pump compressor displacement capacity for the two DX-SAHP systems.