Simplified dynamic modelling of the greenhouse climate | Modelisation dynamique simplifiee du climat d'une serre
1998
Bekkaoui, A.
A dynamic model of the climate of a greenhouse is developed to characterize the various phenomena of water vapour and heat transfer, to establish the thermohydric balance and to predict the evolution of the state variables. The model is described by 8 differential equations relating to the energy balance of the 7 layers of the "greenhouse system" (vegetation, cover, dry air and four soil layers) and of the water vapour balance in the air (humid air). The system of the differential equations established is then solved numerically by the method of Range-Kutta (order 4). A study of sensitivity of the model makes it possible, thereafter, to determine the parameters having a great influence on the thermohydric behaviour of the greenhouse. They are the ventilation rate, the stomata resistance and the leaf area index for the vegetation, the coefficient of transmission to the direct solar radiation and of the emissivity of the external face to the long infra-red radiation for the cover and of thermal conductivity and the coefficients of absorption and reflexion to the solar radiation for the soil. The model is validated for "Tunnel" and "Richel" greenhouses located respectively in the areas of Rabat and Agadir (Morocco). The differences resulting from confrontation between the measure and simulated state variables are very small. This shows that the developed model suitably describes the thermal and hydrous behaviour of the climate of the greenhouse. The model also makes it possible to calculate the requirements in heating and ventilation for the greenhouse and can contribute to the total management of its microclimate.
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