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Direct and Diffused Solar Radiation into Vinyl Film Greenhouse

By 智和 原口, 芳輔 中野, 正治 黒田, Tomokazu Haraguchi, Yoshisuke Nakano and Masaharu Kuroda


Solar radiation distribution on vinyl film greenhouse floor was clarified using a light analizing model. Observed shortwave radiation in outside was divided into direct and diffuse radiation components. Diffuse radiation was separated into 36 pieces of small suns in the hemisphere. Greenhouse walls were assumed to be composed of 10 pieces of flat film. Transmission, reflection and absorption rates on each walls were determined calculating the angle between wall and incoming radiation. The calculation of diurnal change of shortwave radiation showed good agreement with the observed data. Daily total radiation on floor was 10% higher than observation. The daily radiation in east-west oriented greenhouse was slightly higher than north-south oriented house. Radiation at center was higher than the surrounding spots. To improve the accuracy of the model, it is neccesary to take into account the changes of optical characterisics of vinyl film. The calculation of succesive reflective radiation on vinyl films must be taken into account, also.単棟ビニールハウス内の床面における日射量分布について実験と解析を行った. 解析手法は, まず野外の日射量を直達放射と散乱放射に分離し, 壁面に対する光線の入射角から反射・透過・吸収量を求めた. 散乱放射は天空を36等分しそれぞれに小太陽を仮定し直達光と同様の解析を行った. ハウス壁面を計10面の平面に分割した. 壁面から射出される散乱光は全方向に均等に散乱すると仮定し, 形態係数の理論を適用し床面への到達量を求めた. 管型日射計3点を用いた実験と解析を比較した結果, 正午前後に最大20%の誤差が生じたが, 日総量では10%以内の推定が得られた. 解析によれば南北棟, 東西棟共にハウス壁面より中央部分の方が, 北側より南側の方が日射量が高いことが明かとなった. また, 床面全体の日射受光量は東西棟は南北棟より正午前後に高くなることが明かとなった.モデルの精度を上げるためには, ハウス壁面の透過率におよぼす汚れ, 水滴の付着の影響, ハウス壁面における2次反射などを考慮する必要がある

Topics: ビニールハウス, 日射量, 推定手法, 農業工学, vinyle greenhouse, solar radiation, estimation method, agricultural engineering
Publisher: Faculty of Agriculture, Kyushu University
Year: 1995
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