A new greenhouse energy model for predicting the year-round interior microclimate of a commercial greenhouse in Ontario, Canada

Modelling the energy use and microclimate of a greenhouse can be a valuable tool for commercial growers, making it possible to predict the impact of making changes to greenhouse systems and operation. This allows energy saving scenarios to be identified and can reduce energy use costs. In this study, a lumped capacitance thermal model is developed to simulate the greenhouse interior microclimate based on exterior conditions and operating settings. The current study incorporated many aspects of a complex commercial greenhouse not commonly seen in literature, such as evaporative cooling pads, dehumidification technology, gas burners, energy curtains, supplementary heating and lighting, and forced ventilation. The model was successfully validated at multiple greenhouse sections of a commercial greenhouse during spring, summer, and fall conditions in the southern Ontario climate. Data was collected from the greenhouse from March to November of 2019 at 15-minute intervals. The measured interior temperature and relative humidity data were used to evaluate the accuracy of the model simulations, while other measurements, such as solar radiation, were used as model inputs. The study greenhouse was unique, as potted rose crops were cycled between sections during the growth stage. This made variation in plant properties relatively small during the different seasons. Detailed information on the model methodology was included to improve reader’s understanding. Overall, the model accuracy is comparable or even better when compared to similar models in the literature, proving it is versatile and can be used as a design tool moving forward. In the future, the current model will be used to conduct comparative analyses of a range of different energy-use reduction technologies and operating procedures (including year-round production) to quantify the most economically and practically feasible options specifically for Ontario greenhouse growers.