Investigation of performance of a solar and expander-compressor enhanced dual-source heat pump for different climate zones of Turkey

Heat pumps are widely used in residential heating, and a dual-source heat pump utilizing different sources such as the solar energy to increase the performance of this system providing the evaporation of the working fluid at two different pressures. Better coefficient of performance (COP) values can be obtained by increasing the compressor inlet pressure by using high pressure refrigerant in the ejector or expander-compressor between these two evaporation temperatures. This study presents a renewable energy source and high effectiveness heat pump system for renewable heating system that can be easily integrated into buildings. The system uses two heat sources, one air and the other solar energy, in order to maximize the use of ambient energy for the heat pump to operate at high efficiency. With the advantage of relatively low operating temperature in the solar collector, the thermal efficiency of the collector will be sufficient in winter. With the electricity produced by the PV/T (Photovoltaic Thermal) cell photovoltaics in the collector, the energy demand from the grid will be further reduced. In the study, the effects of radiation, ambient and collector temperatures on system performance were investigated. COP increment potentials and optimum collector evaporation temperatures were also determined for different conditions. For 5 kW heating, 400 W/ m2 solar irradiance and 10 ℃ environment temperature, the COP of the system can be improved 25%. For the same conditions, by including the electricity produced from PV (Photovoltaic), 87% reduction in electricity demand from the grid can be achieved. In the future, using PV/T collector in in this cycle will result in carbon-free using bigger collector areas.