What are the characteristics of the temperature change in the greenhouse?

The greenhouse is a closed space, and the temperature change in the greenhouse is essentially different from the temperature change under the external natural conditions. On sunny days, high temperatures often appear in greenhouses. If cooling measures such as ventilation are not taken, the temperature is often higher than 30℃ at 9:00- 15, and the highest temperature can reach above 40℃. In cold season, the temperature difference between indoor and outdoor can reach above 40 ~ 50℃. The temperature at night is also about 30℃ higher than that outside, and the temperature difference between day and night is large (Figure 8).

Fig. 8 Temperature change curve of sunlight greenhouse

Indoor temperature is also influenced by the outside world, with obvious daily and seasonal changes. The daily variation of temperature depends on the time of the sun, weather conditions and the time of rolling grass. After sunrise, when the lid is lifted, the sunlight enters the room, and the temperature rises rapidly, reaching the highest temperature around 14, and then decreases with the weakening of light, and then cools rapidly after 16. In production, ventilation and other cooling measures must be taken during high temperature during the day to control the temperature below 30℃. On cloudy days, the light is weak, the temperature in the greenhouse is low, and the temperature difference between inside and outside the greenhouse is small. The seasonal variation trend of temperature in greenhouse is basically the same as that in outdoor, but the seasonal variation range of temperature in greenhouse is smaller than that in outdoor. From June to April, the temperature difference between inside and outside the greenhouse is large, and the greenhouse effect is obvious. After May, the temperature difference between inside and outside the greenhouse gradually decreased (Figure 9).

Fig. 9 Variation curve of ten-day average temperature in solar greenhouse