Numerical simulation of the effect of different mulches on the heat storage capacity of a Mediterranean greenhouse soil

Abstract

In the Mediterranean greenhouse areas, a large majority of growers rely on passive techniques to improve the microclimate of the greenhouse during the winter period, rather than using more expensive systems such as active heating. Some of these techniques such as different types of mulch (sand, plastic films, etc.) are used to improve the heat storage capacity of the greenhouse soil. A proper modeling of the role of the greenhouse soil a heat store would allow the verification of which techniques have a larger positive effect on the heat store capacity of the soil (i.e. type, color and thickness of the mulch, soil moisture content, etc.) and how to optimize their management by the grower. In recent years, CFD has been successfully used to model the greenhouse microclimate under very different scenarios, but little has been done to include in the simulations the role of passive techniques in the winter period microclimate, such as the role of the soil as a heat store. In the present work, a CFD model of a Mediterranean greenhouse and its soil has been developed, and the effect on the heat storage capacity of the soil as well as in the ambient of 2 different types of mulch (black plastic film, semi-transparent plastic film) was evaluated, by comparing the temperature measured at 4 different depths and ambient temperature (at two heights), during daytime period with the values provided by the model. The evolution of the temperatures at different soil depths followed the same pattern in both the experiments and the simulations. Good quantitative agreement was found between values predicted by the model and the measurements with differences being always lower than 2°C.