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.

Nondestructive Measurement Method of Leaf Area Index Using Near-infrared Radiation and Photosynthetically Active Radiation Transmitted through a Leafy Vegetable Canopy

“…Calculating rPPFD requires the calibration between two sensors to measure PPFD at two points under the same light conditions, which is difficult in a greenhouse because a spatial difference of the light environment fluctuates temporally due to the film and structural materials (Llorenc et al 2016;Matsuda et al 2020). In addition, if sensors are installed for LAI measurement over a long period, periodic sensor inspections are necessary because of the possibility of dirt on sensors.…”

Estimation of Photosynthesis Loss Due to Greenhouse Superstructures and Shade Nets: A Case Study with Paprika and Tomato Canopies

“…This reduction in I in was partly due to the reflection and absorption of the incoming PAR by the cover material. In addition, I in was reduced because of interceptions by the greenhouse structural elements (e.g., the ridges, trusses, and folded shade nets), which prevented some of the PAR transmitted by the cover from reaching the PPFD sensor (Matsuda et al, 2020). Because the cover material has a diffusing property that scatters photon flux in various directions, any greenhouse structures above the PPFD sensor could have reduced I in , even if these structures did not occur along the straight line between the sun and the PPFD sensor.…”

Spatiotemporally variable incident light, leaf photosynthesis, and yield across a greenhouse: fine-scale hemispherical photography and a photosynthesis model

“…Multipoint measurement using many photon sensors is costly, whereas mobile measurement using a single sensor is time-consuming and ignores fine-scale temporal changes in PPFD. As an alternative, numerical models of the effects of greenhouse architecture and solar trajectory on PPFD have been developed (e.g., Castellano et al, 2016;Cossu et al, 2017;Kozai & Kimura, 1977;Matsuda et al, 2020). Such models can accurately describe sunlight distribution in a greenhouse, but the simulated greenhouse geometry must be revised when applied to other greenhouses.…”