MODELLING GREENHOUSE TEMPERATURE AND HUMIDITY DYNAMICS IN ORDER TO DEVELOP AN ENERGY SAVING MODEL-BASED CONTROL STRATEGY

The greenhouse industry, especially in Northern Europe is confronted with economical, political and social pressure to reduce energy consumption. One of the most important optimization problems in optimal greenhouse production systems is the energy costs and use. The primary purpose of greenhouse ventilation is to prevent excessive rise of temperature and humidity. This is achieved by replacing the hot and humid air of the greenhouse with ambient cooler and dryer air. However, in naturally ventilated greenhouses it is difficult to achieve this target without spoiling energy. The main objective of this paper is to investigate and compare the dynamic responses of both temperature and humidity inside greenhouses to a step input in windows opening (0-100%) and in order to develop a control strategy for efficient natural ventilation for greenhouses. To quantify these dynamic responses, two models were identified based on data obtained from a set of step experiments conducted in greenhouse of the Venlo type in Beitem (Belgium). The models were validated using different data obtained from experiments were conducted in different greenhouse of the same type in Leuven (Belgium).