A Comprehensive Research on the Meteorological Environment in Sun-light Greenhouse (Ⅲ)——A Comparative Research on the Total Amount of Direct Radiation in the Greenhouse with Different Arc Lighting Surfaces

In this paper, we calculated and compared the mean daily amount of direct solar radiation of each month from October to April in four types of greenhouse in Beijing region. Each type of these greenhouses has its specific arc lighting surface. The results showed that the total amount of direct radiation in composed type greenhouse with circular-parabolic was the most, and that in the type with elliptic surface was the least in the period from October to April. In winter (November-February) ,the greenhouse with circular surfaces was better than that with parabolic surface. But in spring (March-April) ,the result was contray to that in winter.