Analyses For Solar Radiation Model In Clear Day In Nanning And Optimal Tube Spacing Of All-Glass Evacuated Solar Collecter

Based on a comprehensive review of the characteristics and development trend of solar energy utilization and an introduction to formation, characteristic and development trend of solar collector in common use, this paper analyzes the effect of the position of solar collector on the solar irradiation of tilted absorber surface, and establishes Nanning clear-sky solar radiation model. With the theoretical analysis and model calculating, it succeeds acquiring the optimum collector's azimuth angle and tilt angle to obtain maximum solar radiation. The research is highly deemed as to the engineering practice of heat utilization of solar energy.The paper is organized in five chapters. In Chapter one and Chapter two, it first explores the significance in establishing clear-sky solar radiation model and the necessity of analyzing the optimum collector's azimuth angle and tilt angle, introduces the related concepts of solar radiation and solar angle, and analyzes the weakening effect of atmosphere on solar radiation. Then the paper proposes in Chapter three a method to determine atmospheric transparency and on the basis of the meteorological data over the years in the area of Nanning, a clean-sky solar radiation model is built and a program written by Matlab 7.0 is used to calculate the total solar radiation on tilted surface in any sunshine duration or the whole daylight of any clear day, which can be used to supervise the solar energy projects. With this model the paper discusses in Chapter four the effect of the position of solar collector on the solar irradiation of tilted absorber surface, analyzes at the level of theory that the optimum tilt angle of solar collector should be the local latitude, and ascertains the optimum azimuth angle and tilt angle of the evacuated solar collector in Nanning area. Finally in Chapter five, on the basis of theoretical analysis and model calculating, it explores the variations happened to the instantaneous solar radiation and day solar direct-radiation absorbed by solar collector with the variation of tube spacing (B/D), acquiring that the optimum tube spacing (B/D) of evacuated solar collector is 2.5～3.0, which can simultaneously control the economic cost and improve the efficiency of heat collection.The originality of this paper lies as the following: first, build the clear-sky solar radiation model through determining atmospheric transparency of the area; second, find out the optimum tube spacing of all-glass evacuated solar collector through analyzing the day solar direct-radiation absorbed by heat receiver of vacuum tube.