Predicting the Microclimate in a Naturally Ventilated Plastic House in a Mediterranean Climate

The microclimate of a naturally ventilated plastic house was simulated for 23 days using the Gembloux Greenhouse Dynamic Model (GGDM). Improved calculations of natural ventilation flux and stomatal resistance of vegetation were introduced, based on experimental equations from previous research. A linear non-dimensional ventilation function was developed and compared with those obtained by other authors. Experimental microclimate parameters were used to validate the dynamic performance of the model. Good agreement was obtained between prediction and measurement. For the period from 7 April to 18 April 1992, the standard deviations between the predicted and experimental soil temperature, interior air temperature, relative humidity and crop transpiration were 0·5°C, 0·8°C, 4·3% and 17·8 W/m2, respectively. Sensitivity analysis showed that the external wind speed and the opening angle of the vents were the most important factors influencing the ventilation flux, and that the influence of internal global solar radiation on crop transpiration was much more important than inside air saturation deficit.