How to adjust the temperature of solar greenhouse?

1. The ground temperature of solar greenhouse in northern China, after winter, the soil temperature drops rapidly, and a frozen layer appears on the surface. The higher the latitude, the deeper the frozen layer and the earlier the freezing. The lighting design and thermal insulation design of solar greenhouse are reasonable. In the area where the outdoor frozen soil layer is as deep as 1 m, warm crops can be produced without heating in winter, and the ground temperature can be kept above 12℃. The ground temperature from the surface to 50 cm depth has obvious warming effect, especially in the shallow layer above 10cm. There is permafrost outside the greenhouse, which can maintain a high ground temperature. This is the so-called "heat island effect".

The ground temperature in different parts of solar greenhouse is also different. Because the rise of ground temperature is the result of receiving sunlight, the distribution of light is different, the intensity and time of receiving sunlight are different, and the ground temperature in different parts is different due to the influence of the external frozen soil layer. Judging from the ground temperature of 5 cm, the central area is the highest, decreasing from south to north. The ground temperature under the rear roof is slightly lower than that in the middle and higher than that in the front area. There is little difference between east and west, the temperature near the door changes greatly, and the ground temperature in the east-west gable is the lowest.

The surface temperature changes obviously in the north-south direction, but the performance is different between sunny days and cloudy days, and the day and night are also inconsistent. On sunny days, it is the highest in front of the column and decreases from south to north. It is the highest under the roof at night and decreases southward; The change gradient of ground temperature is small on cloudy days and at night.

The vertical distribution of soil temperature is obviously different from the outside. The outdoor ground temperature of 0 ~ 50 cm increases with the depth, and the deeper the temperature, the higher the temperature, which is consistent whether it is sunny or cloudy. In the solar greenhouse, the ground temperature in the upper layer is high and the ground temperature in the lower layer is low on sunny days, and it is high on cloudy days, especially on cloudy days.

The vertical distribution of ground temperature is different between day and night. The surface temperature is the highest at 0 cm on sunny days, which decreases with the increase of depth, and is the highest at 13. At night, the depth of 10 cm is the highest, and it decreases from top to bottom. At a depth of 20 cm, there is little difference between day and night. The temperature is the highest at a depth of 20 cm on cloudy days. The effective measures to improve the soil temperature in solar greenhouse are deep ploughing, increasing the application of organic fertilizer and improving the heat absorption and storage capacity of 20 cm deep soil layer.

2. The temperature of sunlight in the solar greenhouse shines on the ground, wall, back roof, air, components and crops through the solar greenhouse, and the light energy is converted into heat energy, which makes the temperature rise. The stronger the solar radiation, the faster the temperature rises and the higher the temperature. Scattered light on cloudy days can also raise the temperature to some extent. At night or after putting down the grass, the solar radiation has been cut off. When the grass was first covered, the temperature rose slightly for a short time, generally rising by 2 ~ 3℃, and then it has been falling. Thermal insulation measures are effective and the descending speed is relatively slow.

The temperature in the solar greenhouse is related to the outside temperature, but it is not completely consistent with the outside temperature. When there is enough sunshine on a sunny day, the outdoor temperature is higher, the indoor temperature rises faster and the temperature is higher; The outdoor temperature is not low on cloudy days, and the indoor temperature is not high; On sunny days, the outdoor temperature is very low and the indoor temperature is not high. The temperature of solar greenhouse depends entirely on the light intensity. As long as there is enough light, it is not a problem to produce thermophilic crops in cold winter.

In a solar greenhouse with reasonable lighting design and thermal insulation design, the temperature difference between indoor and outdoor can exceed 25℃ at the lowest outdoor temperature in the early morning, that is, the lowest outdoor temperature can be reduced to -20℃, and the indoor temperature can still be kept above 5℃. Under different weather conditions, the correlation between the temperature inside and outside the solar greenhouse is shown in >. Table 2 1-2.

Table 2 1-2 Temperature in Solar Greenhouse under Different Weather Conditions

On sunny days, the temperature changes in the solar greenhouse are very significant. In winter, the indoor temperature often drops slightly in a short time when the grass is uncovered, and then the temperature begins to rise. Before 1 1, the temperature rose fastest, rising by 6 ~ 10℃ per hour. It often rises slowly at 12, reaches the highest at 13, and then begins to decline. After covering, it rises to 1 ~ 3℃, then slowly drops, and reaches the lowest after uncovering.

3. Temperature regulation in solar greenhouse Use plastic film in solar greenhouse as early as possible in autumn to increase soil heat storage and raise ground temperature. The adjustment of temperature mainly depends on uncovering grass to dry. According to the temperature requirements of cultivated crops, master the deflation time and adjust the size of the deflation hole. In winter, the temperature outside is very low, and the temperature difference between indoor and outdoor is large, so it is necessary to let the air out from above. In early spring, the whole film above is rolled up from the apron below, that is, rolled down and pushed up. If it is rolled up, it will automatically come back when it is blown by the wind, but it cannot be returned when it is rolled down.

If the outdoor temperature rises further, all aprons can be rolled up and tied with plastic ropes for outdoor exercise day and night.