Articles
A comparison of two greenhouse structures under sub-humid conditions in terms of changes in temperature and relative humidity
Article number
1271_2
Pages
9 – 16
Language
English
Abstract
The microclimate in a fan-pad evaporative cooled tunnel (FPVT) and an open-ended, naturally-ventilated tunnel (NVT) was investigated.
The experiment consisted of two greenhouse ventilation systems, the FPVT and the NVT. Two microclimate variables, air temperature and relative humidity, were measured inside the tunnels.
There were significant differences in the daytime air temperatures and relative humidity levels between the FVT, NVT and the outside.
The temperature in the NVT was 4 to 5°C higher than in the FPVT at midday, when solar radiation was at its peak.
The relative humidity was higher in the FPVT than the NVT. At night, there was no significant difference in temperature.
The relative humidity differed significantly between the FPVT, NVT and the outside.
The microclimate in both tunnels was not uniform.
During the daytime, the air temperatures were lower in the crop canopy than close to the cover, however at night, air temperatures were lower close to the cover than within the crop canopy in both tunnels.
The total yield and total marketable yield from the FPVT were not significantly different from the total yield and total marketable yield from the NVT. The total unmarketable yield was significantly (P<0.001) higher in the NVT than in the FPVT. A cost benefit analysis for FPVT and NVT needs to be conducted for these two tunnels.
Whitewashing and near infrared reflective screens could be investigated as tools to reduce the extreme solar heat gain of the greenhouses.
The experiment consisted of two greenhouse ventilation systems, the FPVT and the NVT. Two microclimate variables, air temperature and relative humidity, were measured inside the tunnels.
There were significant differences in the daytime air temperatures and relative humidity levels between the FVT, NVT and the outside.
The temperature in the NVT was 4 to 5°C higher than in the FPVT at midday, when solar radiation was at its peak.
The relative humidity was higher in the FPVT than the NVT. At night, there was no significant difference in temperature.
The relative humidity differed significantly between the FPVT, NVT and the outside.
The microclimate in both tunnels was not uniform.
During the daytime, the air temperatures were lower in the crop canopy than close to the cover, however at night, air temperatures were lower close to the cover than within the crop canopy in both tunnels.
The total yield and total marketable yield from the FPVT were not significantly different from the total yield and total marketable yield from the NVT. The total unmarketable yield was significantly (P<0.001) higher in the NVT than in the FPVT. A cost benefit analysis for FPVT and NVT needs to be conducted for these two tunnels.
Whitewashing and near infrared reflective screens could be investigated as tools to reduce the extreme solar heat gain of the greenhouses.
Authors
E.L. Thipe, T.S. Workneh, A.O. Odindo, M.D. Laing
Keywords
greenhouse, ventilation, microclimate, temperature, relative humidity, Africa
Groups involved
- Division Greenhouse and Indoor Production Horticulture
- Division Precision Horticulture and Engineering
- Division Plant-Environment Interactions in Field Systems
- Working Group Nettings in Horticulture (subgroup of Protected Cultivation in Mild Winter Climates)
- Working Group Light in Horticulture
- Working Group Organic Greenhouse Horticulture
- Working Group Modelling Plant Growth, Environmental Control, Greenhouse Environment
- Working Group Protected Cultivation, Nettings and Screens for Mild Climates
- Working Group Vegetable Grafting
- Working Group Computational Fluid Dynamics in Agriculture
- Working Group Design and Automation in Integrated Indoor Production Systems
- Working Group Mechanization, Digitization, Sensing and Robotics
- Working Group Greenhouse Environment and Climate Control
- Commission Agroecology and Organic Farming Systems
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