Structurally sound solar greenhouse can fully utilize solar energy for agricultural production. In the northern regions of our country, the Shouguang-style solar greenhouses we build can maintain temperatures above 15℃ during winter nights without additional heating. These are primarily used for cultivating off-season vegetables in the deep winter months.

I. Design Principles of Solar Energy-saving Greenhouses

Ensure adequate wall thickness to prevent wall heat loss.

The rear wall of the greenhouse (including both sides) should be 1.2 times the thickness of the local 80% guaranteed frost depth, ensuring that the greenhouse walls are not frozen through in over 80% of the years, thus preventing heat loss through the walls.

2. Lower the height of the rear wall, extend the rear roof, and reduce the area for heat dissipation.

Most of the solar greenhouses already built in various regions feature a short-pitched structure with a low back slope angle, resulting in poor light transmission and a large top surface area for heat dissipation, which negatively impacts deep winter crop production. Solar greenhouses primarily disperse heat energy outward through the greenhouse film. By extending the back slope, the covered area of the film can be reduced, thereby decreasing the heat dissipation surface area and enhancing insulation performance. Generally, extending the back slope from the standard 1.5 meters to 2.4 meters can reduce the heat dissipation area by approximately 10%.

3. Thicker roof structure, enhancing the thermal insulation performance of the roof.

By thickening the rear roof, adding an insulation layer to enhance its heat storage and insulation effects, and preventing heat loss through the rear roof. The construction of the rear roof in a solar greenhouse involves first laying wooden boards, then covering them with bundles of corn stalks or reed mats, followed by straw, topped with clay soil. The total thickness exceeds 70cm, making this rear slope serve the functions of both the rear wall and the roof. During winter and spring, it accumulates a large amount of solar radiation heat from the stalks, which is slowly released at night.

4. After scientific determination of the canopy inclination angle, increase the light coverage area to enhance warming effects.

The construction of a solar greenhouse requires that the rear roof angle be designed to ensure that sunlight can reach the interior surface of the rear roof during winter. This structure, although reducing the membrane surface, increases the采光 area, significantly enhancing the effective lighting and warming effects.

5. Scientifically determine the curvature of the front canopy to ensure the solar incidence angle and increase the transmittance of sunlight.

The front facade of the solar greenhouse has a curvature of 60 degrees, decreasing to 40 degrees at a distance of 1 meter from the front, 30 degrees at 2 meters, 25 degrees at 3 meters, 20 degrees at 4 meters, and 18 degrees at the top. Most of the front facade maintains a solar incidence angle of 45 degrees or less, ensuring a reflectance of no more than 10%.

6. Multi-layer coverage to reduce heat dissipation.

The film covering of the solar greenhouse accounts for about half of its surface area, making it crucial for reinforced frost and heat preservation. Covers can be made of cotton blankets; straw curtains (size 1.2m x 7.5m, weight must exceed 20kg); or double-layered coverage (an additional layer of old greenhouse film over cotton blankets or straw curtains), which not only enhances insulation but also prevents rain or snow from dampening the covers and reducing their insulation properties.

7. Lower the cultivation beds to increase ground temperature, and pile soil against the rear and side walls for frost protection.

The cultivation beds are lowered by 30-50cm. To prevent heat conduction and avoid the drop in ground temperature during winter, a frost-proof trench 40cm wide and 50cm deep is dug in front of the solar greenhouse. Outside the rear and side walls, a soil pile of about 1.5m wide and over 1m high is stacked, which not only raises the ground temperature in the solar greenhouse but also improves the thermal insulation performance of the greenhouse walls.

8. Added indoor reservoirs to enhance water temperature.

A 3m long, 2m wide, and 2m deep (12m3 volume) pond was constructed within a greenhouse. The pond is filled with water on a regular basis, covered with a greenhouse film, and preheated inside. Irrigation is then performed using the preheated water.