It is known that the higher the evaporation temperature, the higher the coefficient of performance of a heat pump for hot water supply. Flat-plate solar collectors which were insulated on the back and bonded with flexible polycrystalline silicon-type photovoltaic modules on the upper surfaces were used in a heat pump system as the evaporator in order to increase the coefficient of performance and to generate electric power. The total area of the collectors was 3.24 m2 and the photovoltaic modules covered 76 percent of the area. The characteristics of the photovoltaic array and the thermal performance of the heat pump were studied experimentally. The results indicated that a coefficient of performance (COP) of the heat pump as high as six could be obtained at 40°C of the water temperature at the inlet of the condenser in the daytime in winter. The peak electric power generated was 120 W. It was found that the photovoltaic modules on the collectors did not influence the performance of the heat pump appreciably. When there was little solar radiation, the COP of the heat pump became two which was very low. This defect was improved by using an evaporator, which had a high convective heat transfer coefficient, arranged in parallel with the fiat-plate collectors.

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