How to use the solar greenhouse correctly
Sunlight is the indispensable energy for green plants to carry out photosynthesis, and it is also the main heat source of solar greenhouse. Therefore, when designing a solar greenhouse, we must first solve the problem of lighting in the greenhouse and limit the transmission of sunlight to the interior of the greenhouse.
Solar greenhouses in northern China are mainly used in winter, spring and autumn. In winter, the sun has a low altitude Angle, with sunrise in the southeast and sunset in the southwest. Therefore, in order to maximize the use of sunlight in winter. Solar greenhouses mostly use a north-south, east-west extension of the orientation.
Practice has proved that the outside temperature is very low in winter mornings. After the eastern greenhouse lifts the curtain in the morning, the indoor temperature often drops significantly. The orientation of the solar greenhouse is as far as possible to the west, which is conducive to extending the afternoon light time and night insulation. 5 degrees to the west is appropriate, should not exceed 10 degrees.
When the Angle of light increases from 0 degrees to 40 degrees. It has little effect on the transmittance of transparent materials. The reflection loss rate of light volume is only a few percent; When the incidence Angle varies from 40 degrees to 60 degrees, the transmittance decreases significantly with the increase of the incidence Angle. When the incidence Angle is greater than 60 degrees, the transmittance decreases sharply. Therefore, the incidence Angle of 40 degrees or the projection Angle of 50 degrees is the critical point that affects the light transmittance of the transparent material. In the early stage of the development of the solar greenhouse, the lighting Angle of the sun on the winter solstice reached 50 degrees was set as a reasonable lighting roof Angle.
Keep warm
The thermal insulation of solar greenhouse consists of two parts: thermal insulation envelope and active thermal insulation. The insulation material on the front slope should use flexible materials to easily put away after sunrise and put down at sunset.
The research and development of new front roof insulation materials mainly focus on the requirements of easy mechanization, cheap price, light weight, aging resistance, waterproof and other indicators.
The solar greenhouse is mainly composed of three parts of the enclosure wall, the rear roof and the front roof, referred to as the "three elements" of the solar greenhouse, of which the front roof is all the lighting surface of the greenhouse, the front roof is only covered with plastic film lighting during the daytime lighting, when the outdoor light is weakened, the active thermal insulation is covered with plastic film in time to strengthen the thermal insulation of the greenhouse.
Due to the development of the plastic industry and the easy damage of glass, most rural solar greenhouses use plastic film as roofing material. In particular, the plastic solar greenhouse in the north of China on the basis of soil greenhouse, with obvious efficiency, energy saving, low cost characteristics, welcomed by farmers and consumers, is one of the effective measures to develop high-yield agriculture, will be faster development. Practice has proved that where the outdoor temperature is not lower than -25 ° C, the special structural properties of plastic solar greenhouse can make the indoor temperature above 5 ° C, satisfactory results can be obtained.
Sunlight is the indispensable energy for green plants to carry out photosynthesis, and it is also the main heat source of solar greenhouse. Therefore, when designing a solar greenhouse, we must first solve the problem of lighting in the greenhouse and limit the transmission of sunlight to the interior of the greenhouse.
Solar greenhouses in northern China are mainly used in winter, spring and autumn. In winter, the sun has a low altitude Angle, with sunrise in the southeast and sunset in the southwest. Therefore, in order to maximize the use of sunlight in winter. Solar greenhouses mostly use a north-south, east-west extension of the orientation.
Practice has proved that the outside temperature is very low in winter mornings. After the eastern greenhouse lifts the curtain in the morning, the indoor temperature often drops significantly. The orientation of the solar greenhouse is as far as possible to the west, which is conducive to extending the afternoon light time and night insulation. 5 degrees to the west is appropriate, should not exceed 10 degrees.
When the Angle of light increases from 0 degrees to 40 degrees. It has little effect on the transmittance of transparent materials. The reflection loss rate of light volume is only a few percent; When the incidence Angle varies from 40 degrees to 60 degrees, the transmittance decreases significantly with the increase of the incidence Angle. When the incidence Angle is greater than 60 degrees, the transmittance decreases sharply. Therefore, the incidence Angle of 40 degrees or the projection Angle of 50 degrees is the critical point that affects the light transmittance of the transparent material. In the early stage of the development of the solar greenhouse, the lighting Angle of the sun on the winter solstice reached 50 degrees was set as a reasonable lighting roof Angle.
Keep warm
The thermal insulation of solar greenhouse consists of two parts: thermal insulation envelope and active thermal insulation. The insulation material on the front slope should use flexible materials to easily put away after sunrise and put down at sunset.
The research and development of new front roof insulation materials mainly focus on the requirements of easy mechanization, cheap price, light weight, aging resistance, waterproof and other indicators.
The solar greenhouse is mainly composed of three parts of the enclosure wall, the rear roof and the front roof, referred to as the "three elements" of the solar greenhouse, of which the front roof is all the lighting surface of the greenhouse, the front roof is only covered with plastic film lighting during the daytime lighting, when the outdoor light is weakened, the active thermal insulation is covered with plastic film in time to strengthen the thermal insulation of the greenhouse.
Due to the development of the plastic industry and the easy damage of glass, most rural solar greenhouses use plastic film as roofing material. In particular, the plastic solar greenhouse in the north of China on the basis of soil greenhouse, with obvious efficiency, energy saving, low cost characteristics, welcomed by farmers and consumers, is one of the effective measures to develop high-yield agriculture, will be faster development. Practice has proved that where the outdoor temperature is not lower than -25 ° C, the special structural properties of plastic solar greenhouse can make the indoor temperature above 5 ° C, satisfactory results can be obtained.
