FEASIBILITY OF EMPLOYING A HEAT INSULATION WALL AS THE NORTH WALL OF A CHINESE SOLAR GREENHOUSE IN A SEVERELY COLD AREA OF CHINA

The conventional north wall of a Chinese solar greenhouse (hereafter referred to as a "solar greenhouse") can release heat inside and help maintain a high indoor air temperature (T-in) during winter nights. However, the construction of conversational walls face problems of high cost, low construction quality, environmental damage, etc. Based on this, heat insulation walls have aroused much interest. However, this kind of wall can barely store and release heat, putting the solar greenhouse at risk of low T-in. The purpose of this study is to investigate whether the impact of the heat insulation wall could be weakened by decreasing the heat loss through the greenhouse envelope. The thermal environment of a solar greenhouse located in a severe cold area of China (Mohe County, Heilongjiang Province) was examined during sunny days, of which the north wall was constructed from polystyrene boards and plastered with 10 mm-thick mortar. During the experiment, the outdoor air temperature (T-out) was -22.8 +/- 5.6 degrees C during the night, reaching a low of -34.7 degrees C. The amount of heat released from the north wall can be neglected, as it was 5.4% of the total heat obtained by the test solar greenhouse. In comparison with conventional solar greenhouses, both heat loss through the building envelope and the heat obtained from the test solar greenhouse during the night decreased. As a result, T-in was maintained at 10.6 +/- 2.9 degrees C, with a low of 6.8 degrees C, during the night, which was within the normal range of a conventional solar house located in northern China. Thus, the impact of the heat insulation wall on T-in in the sunny days was weakened by decreasing the heat loss through the greenhouse envelope. Nevertheless, more work on the performance of test solar greenhouse on cloudy days and summer days should be conducted to fully validate the proposed hypothesis.