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ISHS Acta Horticulturae 456: II Modelling Plant Growth, Environmental Control and Farm Management in Protected Cultivation

MEDITERRANEAN GREENHOUSE ENERGY BALANCE

Authors:   G. P.A. Pita, M. Pontes, A. Vargues
Keywords:   Greenhouse model, Energy fluxes
DOI:   10.17660/ActaHortic.1998.456.45
Abstract:
The energy balance of a Mediterranean greenhouse has been evaluated, measuring the different energy fluxes between the greenhouse and the surroundings.

The experiments were conducted in a chapel type greenhouse, with wooden structure, 17m wide and 30 m long, 5.5 m height in the center and 2.2 m height laterally. The greenhouse was cladded with a single layer of a 200 μm polyethylene film. The greenhouse was oriented North-South and located in Fataca, Odemira, Portugal (Lat. 37° 35' N, Long. 8° 40' W). Two sets of instruments were mounted, one outside and another inside the greenhouse.

The greenhouse boundary considered establishing the energy balance was the plastic cover and the upper soil layer. Two different types of days were selected, the clear sky days and the clouded days.

For the clear sky days the evaluation of the different energy fluxes shows that during the day time the incoming solar radiation was equally distributed between the soil heat flux, the lateral and roof convective exchange, the thermal radiation flux and the ventilation (leaks). At night the incoming soil heat flux was lost mainly by thermal radiation. A model to predict the greenhouse climate was developed and validated with the measurements.

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