Studies on the Solar Irradiation in Glasshouses (1)

An analytical procedure is proposed for the calculation of the solar irradiation in glasshouses. The difference of transmission mechanism sbetween direct and diffuse solar radiation and the transmission characteristics of surfaces have been taken into account for various types of glasshouses. Some results of a paticular glasshouse whose dimensions are given in Figs. 1, 2, 3 and 4, are obtained as follows:(A) Mean daily integrated solar irradiation on the floor of the E-W house is 86% of that of the outside on the winter solstice under clear sky condition and 79% on the summer solstice. On the other hand, in the N-S house of the same shape, mean daily integrated solar irradiation is 76% of that of the outside on the winter solstice.(B) The difference between the maximum daily integrated solar radiation on the floor and the minimum is 5Kcal·m-2·day-1 on the winter solstice and 250Kcal·m-2·day-1 on the summer solstice. On the other hand, in the N-S house of the same shape, the difference between the maximum daily integrated solar irradiation on the floor and the minimum is 280Kcal·m-2·day-1 on the winter solstice and 700Kcal·m-2day-1 on the summer solstice.(C) When 50% of the south roof is shaded in the case of the E-W house, the mean daily integrated solar irradiation on the floor is 90% of that of non-shaded glasshouse on the winter solstice and 70% on the summer solstice under clear sky condition.(D) The diffuse solar irradiation on a horizontal plane in a glasshouse made of perfect diffusing material whose transmissivity is 100% is 83% of that of the outside at its maximum and 60% at its minimum. The maximum diffuse solar irradiation on the floor is 70% of that of the outside.Numerical calculation has been done on HITAC 5020 at the Tokyo University Computer Centre.