| Sunlight greenhouse plays an important role in winter vegetable production in north of China. But, there are many problems in present greenhouse production which include less feasible structure, low solar radiation utiliaztion rate, bad performance of heat preservation and lackness of temperature forecast software inside sunlight greenhouse.The sunlight greenhouse environment factors which include solar radiation, air and surface temperature, relatively air humidity, wind speed and direction, soil water content and heat flux were measured continuously in two testing sunlight greenhouses in Beijing from December to next March in 2001 and 2003, respectively. And the characteristics of solar radiation and temperature and heat flux were analyzed from the above measured data.Based on the balance of energy and mass of air, north wall, east wall, west wall, back roof, cover of sunlight greenhouse, a dynamic thermal environment model was built. The input parameters of the model included geographical factors, structural factors, thermal properties of greenhouse materials and initialization meteorologic conditions inside and outside the sunlight greenhouse. The heat gain of solar radiation for each surface was calculated by Cloud Cover Coefficient Method. And the shades on the ground, north wall, back roof from the east and the west wall were computed and the effect on their heat gain were also analyzed. The heat exchange of wall and back roof was calculated by the method of heat response. The output parameters of the model were temperature and relatively air humidity. The model was realized by software VB 6.0. By the software, the simulated value and measured valu over 10 continuous different weather days were compared and the result showed that the curve of simulated data was good and the absolute error was no more than ± 1.0°C and the relatively error was less than 10%.Performance of heat preservation of sunlight greenhouse for different materials, different thickness, and different arrange were also compared by the above mathematics model. Some results were found that the performance of heat preservation could be strengthened by adding heat insulation material to solid material, and with the increasing of thickness of heat insulation material and solid material, the velocity of increasing temperature decreased. And in theory validation, the thickness of larger than 36cm for red brick could ensure the steady of air temperature and the thickness of 10cm of polypropylene was the better. For the optimization of structure of back roof, adding the, thickness of solid material to increse temperature was not good and wasteful for the material. However, when three kinds of heat insulation materials were placed on the outer surface of back roof, the performance of heat preservation could be enhanced. And the polypropylene of heat preservation was best in three heat insulation materials.Based on the mathematics model, temperature forecast software was explored. It included input module, solar radiation computation module, temperature simulation and forecast module, structureoptimization module, data manage module and output module. Solar radiation computation module included solar radiation computation of each surface inside the greenhouse, solar radiation computation of visual point and its shade, solar radiation computation of different shapes for front roof, distance of greenhouses and evaluation of light and thermal of greenhouse. When the parameters which included geograpical and structure facors, thermal properties of greenhouse materials, initialization meteorologic conditions inside and outside the sunlight greenhouse were inputs to the temperature forecast module, the air temperature, humidity and the temperature of each surface inside the sunlight greenhouse could be forecasted. And the module could be used as reference to low temperature defense and energy expend of greenhouse in winter. The software was used in varous styles of input and output. And it could resolve the repeated inputs of the same parameters such as the g...
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