Thermal Model of a Passive Solar Greenhouse

High tunnel horticulture can improve yield, quality, prevent disease and reduce pest control issues. Growing in high tunnels the available growing season of a crop can be extended as higher temperatures can be maintained inside a high tunnel than in open fields. High resolution measurements for air and soil temperatures, solar insolation, relative humidity and wind speeds have been recorded inside Quonset style passive solar high tunnels, and adjacent open fields, for two growing seasons (2015 and 2016) at Guelph, Ontario. Lower than expected frost resistance was observed inside the high tunnels. An Artificial Neural Network was used to predict air and soil temperatures as a function of weather and high tunnel properties. The model was validated by comparing model predictions of air and soil temperatures to the measurements. The data was tested using different combinations of parameter values to observe the effects of parameter choice on predicted high tunnel microclimate. Temperatures recorded inside high tunnel or greenhouse environments were found to be sensitive to choices of model parameters, such as soil, glazing and thermal properties. The model and data collection was part of a longer study intended to benefit Canadian growers. An ability to accurately predict high tunnel microclimate will help growers choose crops best suited for high tunnels at their location. The data and models resulting from this study will also be useful for identifying methods of reducing energy costs in new high tunnel installations through structural changes and by modifying operating methods.