A photovoltaic and thermal hybrid panel which was made of an aluminum roll -bond panel with a photovoltaic module on the surface was developed recently for use as an evaporator of a heat pump for residential hot water supply and room heating.1) Pressure loss of the refrigerant at the evaporator was large. Therefore, in the present study, shapes of the inlet and the outlet of the panel were modified to reduce pressure loss; also, thermal performance of the heat pump which adopted three evaporator panels connected in series was examined. Total area of the panels was about 1.9 m2 and the rated capacity of the compressor was 250 W. These modifications reduced pressure loss and improved thermal performance. The effect of the location of the feeler bulb on performance of the heat pump was also examined. It was inferred that the feeler bulb fixed on the tube at the outlet of the evaporator should be as close as possible to the evaporator outlet.

The thermal performance of an uncovered radiator and a radiative cooling system was investigated experimentally and theoretically. The net radiative power of a black painted surface at ambient air temperature was measured by heat flux plates at night in order to use the results for predicting temperatures of the radiator surface and the fluid in the cooling system on the same night. The net radiative power obtained by the measurements was 40–60 W/m2 on clear nights in the summer and 60–80 W/m2 in the fall and winter. The average temperature of the energy storage tank on clear nights became 2–5°C below the ambient temperature. The experimental and analytical results agreed well with each other.

An aluminum roll-bond panel with a photovoltaic module on the surface was developed recently for use as an evaporator of a heat pump for residential hot water supply and room heating [Proceedings of the JSES/JWEA Joint Conference, Okinawa, pp. 305–308 (in Japanese)]. In the present study, the panel was modified to reduce the large pressure loss of the refrigerant flow at the evaporator. Total area of the panels was 1.9m2 and the rated capacity of the compressor was 250 W. A collector efficiency factor of 0.9 was obtained for the evaporator. The effect of the location of the feeler bulb on performance of the heat pump was also examined.

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