Modelling the thermal performance of a naturally ventilated greenhouse in Zimbabwe using a dynamic greenhouse climate model
University of Zimbabwe, Department of Physics, Faculty of Science, P.O. Box MP167, Mount Pleasant, Harare, Zimbabwe; Ghent University, Department of Biosystems Engineering, Faculty of Bioscience Engineering, Coupure Links 653, 9000 Gent, Belgium
The Gembloux Dynamic Greenhouse Climate Model (GDGCM), previously validated for a tomato crop in European greenhouses, was adapted to simulate the microclimate in a naturally ventilated Zimbabwean greenhouse containing a rose crop. The GDGCM consists of a system of differential equations based on the heat and mass balances of the layers of a greenhouse, and were worked out within the Transient System Simulation (TRNSYS) program. Modified sub-models to calculate the greenhouse air renewal rates and crop canopy resistance to water vapour transfer were introduced. Numerical results obtained using the model were compared to experimental measurements carried out in a full-scale commercial naturally ventilated Azrom type greenhouse with a rose crop. The simulated results showed good agreement with the observed values of all parameters for most parts of the day. For the period of observation (the whole year from May 2007 to April 2008) the mean standard errors between the predicted and experimental greenhouse air temperature and relative humidity, canopy temperature and crop transpiration were 1.8°C, 14.8%, 1.9°C and 14.2Wm-2, respectively, in winter and 1.3°C, 8.6%, 1.6°C and 21.8Wm-2, respectively, in summer. The model adequately simulated the internal greenhouse microclimate using outside climate data including incident solar radiation, cover transmittances and greenhouse configuration as inputs and can thus be used to predict the inside greenhouse climate and as a design tool to evaluate and optimise the effects on the inside greenhouse climate of ventilation, cover properties, the settings of the control system and other climate management practices. © 2012 Elsevier Ltd.
Climate management; Crop transpirations; Experimental measurements; Greenhouse climates; Greenhouse microclimate; Natural ventilation; System of differential equations; Thermal Performance; Computer simulation; Crops; Differential equations; Greenhouse effect; Greenhouses; Solar collectors; Ventilation; Water supply; Climate models; air temperature; canopy; climate modeling; evapotranspiration; experimental study; fruit; greenhouse ecosystem; heat balance; management practice; microclimate; model validation; relative humidity; ventilation; water vapor; Zimbabwe; Lycopersicon esculentum