Calculation of the irradiance of solar radiation in a greenhouse with a complex structure using a diagram for sky view factor

Abstract

The irradiance of solar radiation in a greenhouse with a complex structure was calculated using a diagram for sky view factor (DSVF) and compared with observed values. Structural materials (such as side pillars and rafters) and non-structural materials (such as lock channels, door frames, and ventilation fans) were treated as sunshine obstacles, including lower rafters and equal leg angles in the inner spaces of the greenhouse. Radiation directions simulated using a DSVF were used for calculating the irradiance of diffuse solar radiation. With respect to the irradiance of total solar radiation on a sunny day, the calculated values were found to be higher than the observed values early in the morning. However, the overall fluctuation due to diurnal change of the solar elevation and in the sharp drops due to the sunshine obstacles were reproduced. Furthermore, the diurnal changes of the irradiance of non-direct solar radiation on a sunny day and the irradiance of total and non-direct solar radiations on a cloudy day could also be reproduced. The relative error of the calculated irradiance of daytime (from 04 :00 to 20 :00) total and non-direct solar radiations to the measured value was 4.3% for the total radiation on the sunny day, 5.5% for the non-direct radiation on the sunny day, -1.1% for the total radiation on the cloudy day, and 0.3% for the non-direct radiation on the cloudy day. The results of this study indicated that the DSVF can be useful for calculating diffuse solar radiation.