古在, 豊樹

中村, 潤

渡部, 一郎

KOZAI, Toyoki

NAKAMURA, Jun

WATANABE, Ichiro

[SUMMARY]A solar heating system of the greenhouse, using a heat pump, was developed and its thermal performances were tested. The whole system consists of a water-to-air heat pump, air-to-water heat exchanger, a heat storage water tank, and a plastic greenhouse with the double layer movable thermal screen (Fig. 1). In this system the surplus solar heat in the greenhouse, when inside air temperature was above 22-25°C, was collected by the air-to-water heat exchanger and was stored in the heat storage water tank. The heat stored was used for heating with the water-to-air heat pump when the inside air temperature was below 11-13°C. Measurements were carried out during the period from January 13 to February 28 in 1982.Results are as follows:1) Collection efficiency, defined as in equation (3), of the greenhouse with a clear polyethylene thermal screen open was 0.07 on the average, with a minimum of 0.0 under overcast conditions and a maximum of 0.19 under clear sky conditions. Collection efficiency of the greenhouse with the thermal screen closed was 0.12 on the average, with a minimum of 0.07 and a maximum of 0.17. 2) The heat released from the storage tank accounted for about 45% of the total nighttime heating load. 3) The C.O.P. of the heat pump was increased from 2 to 5 with increasing the water temperature in the storage tank from 5 to 20°C (Fig. 3) .4) The C.O.P. of the system was as low as 1.9 on the average (Table 2). It would be improved as high as 2.5 if the system was operated at a water temperature of around 15°C of the heat storage water tank.