Design And Optimization Analysis Of Solar Greenhouse Daylighting Curve In Northern Cold Region

Cold weather in winter in northern China,solar greenhouse in winter production is faced with many difficulties,although the greenhouse adopted some insulation and heating measures can improve its internal temperature condition,but the sun is insufficient,the high cost of artificial light supplement problems still exist,therefore before by optimizing the greenhouse roof structure,improve the performance of greenhouse lighting is the key to solve the problem of wintering greenhouse production.Based on the design of three kinds of daylighting skeleton curves,greenhouse testing,model calculation and software simulation analysis were adopted in this study.Compared with traditional skeleton curves,solar radiation model and Ecotect software were used to optimize and analyze the daylighting performance of solar greenhouses with four kinds of daylighting curve skeleton forms.The main research contents are as follows:1.Compared with the traditional greenhouse skeleton curve,three kinds of improved lighting skeleton curves were designed by optimizing the lighting Angle and increasing the lighting area:six-node control point spline skeleton curve,1/5power function skeleton curve and 1/7 power function skeleton curve.Among the four lighting skeleton curves,1/7 power function curve has the longest arc length and the largest overall lighting Angle,while the traditional curve has the shortest arc length and the smallest overall lighting Angle.2.According to the spread of the sun’s rays in solar greenhouse,solar greenhouse roof shape parameters,shape parameters before building lighting materials optical transmission characteristics,interior space solar radiation transmission model,in terms of geographical location,time,weather conditions,greenhouse azimuth,structure parameters,the material optical properties as input parameters,construction of solar greenhouse solar radiation model is established.The maximum root mean square error(RMSE)of the measured and calculated values is 79.84 W/m2,the maximum mean absolute error is 62.72W/m2,and the maximum mean deviation is49.72W/m2.R~2 is within the range of 0.94～0.98.The high degree of coincidence indicates that the solar radiation model established in solar greenhouse has high accuracy.3.The solar radiation model of solar greenhouse was used to analyze the light environment of four kinds of greenhouse with lighting skeleton curve.It was found that the light environment of three kinds of greenhouse with lighting skeleton curve was better than that of traditional greenhouse,and 1/7 power function skeleton curve greenhouse was the best.The average solar radiation of 1/7 power function skeleton curve of greenhouse is 9.6%～17.4%higher than that of traditional greenhouse curve.Compared with the traditional greenhouse curve,the average lighting rate increased19.12%-23.78%.The spatial distribution of solar radiation in greenhouses with 1/7power function curve is better than that in traditional greenhouses.The cumulative amount of solar radiation interception is 19.5%-27.8%higher than that of traditional greenhouse curve.4.Using Ecotect software to simulate the solar irradiance of solar greenhouse surface at different orientation angles,it is concluded that the optimal orientation Angle of solar greenhouse in Changchun area is 10°w from south;It is found that the order of lighting illumination and lighting coefficient from large to small is 1/7 power function>1/5 power function>6-node control point spline>traditional curve greenhouse.