Establishment of estimation model of solar radiation within solar greenhouse.

The solar radiation at different points within a solar greenhouse is not only an important parameter for the simulation of crop photosynthesis and transpiration, but also an essential factor for wall energy balance in a solar greenhouse. In this paper, the shadowing effect of a solar greenhouse enclosure structure on solar radiation was analyzed, and the preventing-view's angle of any points within a solar greenhouse was calculated by using the main parameters of a solar greenhouse and the solar azimuth. Any point could be obtained by direct solar radiation if the preventing-view's angle was smaller than the solar altitude. A hypothesis is that any point obtains isotropic diffuse solar radiation form the sky, diffuse solar radiation was calculated by accumulating the non-preventing- view's angle .Based on these analyses, the direct solar radiation, diffuse radiation, and the total solar radiation at any points within a solar greenhouse on sunny days were estimated. The estimated values at certain points within a solar greenhouse were compared with measured values at that point, which were measured within a Liaoshen II type solar greenhouse. The estimated values were higher than the measured values by 6.4% and 8.8% respectively for scatter radiation and total radiation, and the possible reasons that caused estimated errors were discussed. Results showed that the daily variation of estimated direct solar radiation, diffuse solar radiation, and total solar radiation tended to agree with that of the measured values, and the estimated values overestimated the measured values. The estimated errors maybe resulted from an error of the atmospheric transparency coefficient, transmittance of solar greenhouse plastic film, shadowing of load-bearing framework, and artificial observation errors. Using software surfer 8.0, a total radiation distribution map at 2 m was provided on 2011-12-24 at 10:00 within the greenhouse. At this height, the width was 7.05 m, and the length was 60 m. Total radiation had a decreasing trend from north to south. The shadow parts meant no direct radiation. The research results can supply theoretical solar radiation at different points within a solar greenhouse for the simulation of crop and transpiration, distribution of light within crop canopy, and energy balance of an enclosure structure in a solar greenhouse. [ABSTRACT FROM AUTHOR]