Influence of Selected Factors on Heat Exchange with the Ground in a Greenhouse

Abstract

<abstract> The objective of this study was to determine the impact of interior temperature range, according to the cultivated crop, height of the floor relative to ground level, and thermal insulation of the foundation, on heat exchange with the ground in a greenhouse. Two ranges of required interior air temperature were adopted: 8°C to 24°C for year-round cultivation of carnations, and 17°C to 27°C for cultivation of tomatoes. For economic reasons, the interior climate in greenhouses is usually poorly controlled. Only heating to a minimal air temperature in winter, increased mechanical ventilation at night, and shade curtains in summer to avoid overheating were assumed. At a time with no heating, the interior temperature is free-floating. The analysis was performed for an entire year, which allowed including both diurnal and seasonal heat buffering in the ground. Altogether, 12 variants of a free-standing greenhouse located in a moderate climate zone in the south of Poland were analyzed. WUFI Plus software was adopted for simulating the thermal performance of the greenhouse, including the ground. The software was first validated with long-term measurement results of thermal conditions in the ground beneath a greenhouse. The results show the impact of particular factors on transient heat exchange with the ground, and thus on energy demand for heating in winter and overheating in summer.