What is the air temperature in the solar greenhouse?

(1) Daily variation of indoor temperature

The daily change of indoor temperature depends on the change of outdoor temperature. Fig. 9 is the result measured on a sunny day, indicating that the indoor and outdoor temperature changes are consistent. At the same time, we can see that under the condition of closed greenhouse, the effect of daytime warming is obvious; At night, the indoor temperature drops slowly due to the action of the grass curtain.

Fig. 9 Daily variation of indoor and outdoor air temperature

The temperature change of solar greenhouse depends on the weather conditions. Even if the outdoor temperature is low on sunny days, the indoor temperature can still be kept high, and the heating effect is obvious; On cloudy and snowy days, even if the outdoor temperature is not low, the indoor temperature will not be very high during the day, because there is little heat accumulated indoors during the day and the indoor temperature is low at night. For example, in winter in Beijing, the highest indoor temperature can reach 30.0 ~ 35.0℃ on sunny days, and the lowest can reach 10.0 ~ 13.0℃. Cloudy days are about 16.0℃ and 7.0 ~ 8.0℃ respectively; On the day of snowfall, the highest temperature is only11.0 ~13.0℃, and the lowest temperature is 6.0 ~ 7.0℃. The greenhouse with poor performance even drops below 5.0℃, and some will be frozen.

The temperature change in greenhouse is also related to greenhouse management. As shown in figure 10, after the curtains were opened in the morning, the indoor temperature dropped slightly for a short time, and then rose rapidly. Open the skylight for ventilation around noon, and the temperature drops wave by wave. This trend continued until the skylight was closed, and the curtains were closed at night, and the indoor temperature slowly dropped. It can be inferred that if temporary indoor heating measures are taken in severe cold season, the temperature will also change due to the change of heating quantity.

Figure 10 Daily variation of indoor temperature and management measures

(2) There is basically no winter in sunlight greenhouse.

The seasonal change of indoor temperature is mainly restricted by the change of external temperature. It can be clearly seen from the figure 1 1 that the seasonal variation of indoor temperature is basically consistent with the external temperature. As can also be seen from the figure, there was an obvious cooling process in early February and early March, but the indoor cooling was far more stable than the outdoor greenhouse with stable and good performance.

Figure 1 1 Seasonal variation of temperature in solar greenhouse

According to the indoor temperature measurement of several solar greenhouses in Beijing, the average indoor temperature can be kept above 15.0℃ in general years, 17.0 ~ 17.5℃ in October, and 18.0℃ in February, except for a few ten days. Except for a few days, the lowest temperature is generally above 10.0℃. The average temperature difference between indoor and outdoor is 20.0 ~ 25.0℃.

Tables 4 ~ 7 list the data of average indoor temperature in winter and ten days in two greenhouses in Beijing. According to the standard of dividing the four seasons in greenhouse, we can know that there is no winter in energy-saving solar greenhouse in Beijing.

Table 4 Average winter temperature of energy-saving solar greenhouse with short back slope14 (℃) (1990—1991,Shaling)

Table 5 Temperature Status of Energy-saving Solar Greenhouse with Short Back Slope in 70 Days in Winter (℃) (1990—1991,Shaling)

Table 6 Temperature Status (℃) in Long Back Slope Energy-saving Solar Greenhouse 10 and February (Daxinzhuang11991-1992)

Table 7 Average monthly temperature (℃)11-February (Daxinzhuang1991-kloc-0/992)

According to the data of Yinchuan area, the energy-saving solar greenhouse is winter from the first ten days of February to the first ten days of February. 65438+ 10 Mid-October to late February is the spring and autumn season; It will be summer after the end of March. Simple solar greenhouse 12 is winter from late February to mid-October; 65438+1late October to mid-March is the spring and autumn season; Enter summer after late March. The information provided by Gansu Vegetable Research Institute also shows that there is basically no winter in the energy-saving solar greenhouse.

(3) The duration above a certain limit temperature in the greenhouse in winter is different.

Around noon on a sunny day, the indoor temperature can generally exceed 25.0℃, but the duration is different. In the last ten days of 1 1, the indoor temperature rose by 25.0℃ for 5-6 hours (10: 00-16: 00); 65438+5 hours at the beginning of February (10: 00—15: 00); It lasted more than 6 hours in early February. Duration of indoor temperature exceeding 20.0℃,1late October 165438+ to mid-February 16: 00, lasting 7 hours; From the end of February, 65438 to the end of October, 65438/kloc-0, which lasted for 5 hours (10: 00-15: 00). Before 65438+early February, the indoor temperature was higher than 28.0℃ for more than 3 to 4 hours, which appeared around noon; From late February of 65438 to 10 of 65438, it was only 1 ~ 2 hours.

(4) Daily accumulated temperature

The final yield of any crop growth and development needs certain light and heat indicators. Table 8 is based on the measured data of Beijing solar greenhouse. As can be seen from Table 8, the daily average positive accumulated temperature of solar greenhouse in Beijing during the month of 65438+ 10 was above 320.0℃ and above 200.0℃. The average accumulated temperature during the day is ≥ 20.0℃; February 135.0℃, 10/010.0℃; The average accumulated temperature at night in 65438+February ≥ 10.0℃ is above 70.0℃; 1 month is above 20.0 ~ 30.0℃.

Table 8 Temperature Index of Solar Greenhouse (℃) (Beijing, 1989— 1990)

(5) The horizontal distribution of indoor air temperature is uneven.

The observation data of Ningxia Academy of Agricultural Sciences in Yinchuan showed that the temperature in the middle of energy-saving solar greenhouse was the highest, followed by that in the north and the lowest in the south, with an average temperature difference of 65,438 0.7℃ between north and south, and higher in the west than in the east, with an average temperature difference of 65,438 0.4℃. Simple solar greenhouse also has the highest temperature in the middle, but the temperature in the south is higher than that in the north during the heating stage, with an average temperature difference of 65438 0.4℃. In the cooling stage, the temperature in the northern part of the greenhouse is higher than that in the southern part, with an average temperature difference of 0.5℃; The temperature difference between the east and the west of the greenhouse is still higher than that in the east, and the average temperature difference is 1. 1 ~ 1.6℃. The temperature difference between the east and the west is caused by the greenhouse door opened on the Dongshan wall. The back wall and roof of the energy-saving greenhouse are thicker, and the thermal insulation performance is better than that of the simple solar greenhouse, so the temperature is higher than that of the south day and night. The back wall of the simple greenhouse is thin, and the heat preservation is poor. The light here is not as good as that in the south, and it is not easy to heat up during the day.