Abstract:

This study compares the photothermal performance of the newly introduced solar greenhouse with the current thick wall chamber, so as to provide a reference basis for the construction of solar greenhouse in Hohhot. According to the microclimate monitoring data of four types of solar greenhouses, the variation laws of meteorological elements such as daily average temperature inside and outside the greenhouse, daily minimum temperature inside and outside the greenhouse, daily maximum temperature inside and outside the greenhouse and illumination in the greenhouse were analyzed. The results show that the double-film double-cover water tank heat storage solar greenhouse is the solar greenhouse with the highest indoor temperature level, during the overwintering period (January 12^th-February 21^st), the daily average temperature is 20℃, the daily average maximum temperature and minimum temperature are 35.7℃ and 13.6℃, respectively. The thick wall chamber is the solar greenhouse with the lowest temperature among the four types of greenhouses, the daily average temperature is 15.1℃ and the daily average minimum temperature is 6.1℃. Under sunny condition, the peak temperature of different types of solar greenhouses could reach 35-40℃, and under cloudy weather, the peak temperature of various types of greenhouses is slightly lower, up to about 30℃. Under overcast condition, the indoor temperature of various types of greenhouses decreased significantly and that of all types of greenhouses is below 20℃, and the heating effect of straw solar greenhouses is more significant, which is better than that of other types of greenhouses, however, its thermal insulation effect is poor, and the heating and thermal insulation effect of thick wall chamber are neither ideal. According to the statistics of the number of days with the daily minimum temperature in the greenhouse lower than 8℃, the thick wall chamber has 34 days with the minimum temperature lower than 8℃, more than 4/5 of the total statistical days; the straw greenhouse has 18 days, more than 2/5 of the total statistical days; the solar greenhouse with double-film single-cover water tank heat storage has 8 days, about 1/5 of the total statistical days; and the solar greenhouse with double-film double-cover water tank heat storage has only 2 days. The temperature in the greenhouse increases with the increase of light intensity, under sunny condition, the rising time of temperature lags behind that of light intensity by 2~4 hours and the peak value of light intensity can reach more than 20000 lx; under cloudy condition, the rising time of temperature lags behind that of light intensity by about 1 hour, and the peak value of light intensity can reach 5500-8000 lx. Considering the factors such as temperature, light and weather condition, the indoor and outdoor temperature difference of double-film double-cover water tank heat storage solar greenhouse in winter is the largest, and its thermal insulation effect is the best, the double-film single-cover water tank heat storage solar greenhouse comes the second, followed by the straw solar greenhouse, and the thermal insulation performance of thick wall chamber is the worst among the four types of greenhouses.

Key words: Hohhot, solar greenhouse, photothermal performance, daily average temperature, daily maximum temperature, daily minimum temperature, different weather conditions