Simple greenhouse climate model as a design tool for greenhouses in tropical lowland

Six prototypes plastic greenhouses were built in the tropical lowlands of Indonesia. The geometrical dimensions were designed using computational fluid dynamics (CFD) by taking local climate parameters as static reference boundary conditions. It is necessary to evaluate the climate dynamics inside the greenhouse during varying climatological conditions. A greenhouse climate model was developed to optimise cover properties and ventilation rate as main parameters, calculating only three state variables: average greenhouse air temperature TAir, average greenhouse air water vapour pressure (expressed as air water vapour pressure deficit DAir), and average canopy temperature TCan. Solar radiation distribution, air exchange by ventilation, and crop transpiration constituted the backbones of the model. The climate outdoor and inside the test greenhouses with crops having leaf area index from 0.02 to 4.10 were measured for one growing season. Measurements and calculations of TAir and DAir agreed satisfactorily, with less than 5% errors. It is concluded that the model is robust and could be used as a design tool for the tropical lowland greenhouses.