Validation of a dynamic model for predicting energy use in greenhouses

This paper describes the measurements made in a polyethylene-covered unventilated greenhouse containing a growing crop and their use to validate a previously reported predictive mode of transient energy use. Over a 40 h period of intensive measurement and a 5-day period in winter, the measured and predicted energy use differed by no more than 10%. Prediction of maximum day-time temperature was satisfactory, the greatest error being 2·2° at 27·6°C. The following parameters are examined in relation to the sensitivity of the model to variations in their magnitude: sky temperature, air infiltration, ground sink temperature, thermostat setting, internal and external heat transfer coefficients, incident solar radiation, cover transmittance and plant transpiration. Some areas where further work is necessary are suggested.