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ISHS Acta Horticulturae 797: International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions

GREENHOUSE COOLING AND CARBON DIOXIDE FIXATION BY USING HIGH PRESSURE FOG SYSTEMS AND PHYTOCONTROL STRATEGY

Authors:   U. Schmidt, C. Huber, T. Rocksch, R. Salazar Moreno, A. Rojano Aguilar
Keywords:   ventilation, phytomonitoring, gas exchange efficiency, closed greenhouse
DOI:   10.17660/ActaHortic.2008.797.39
Abstract:
An experiment was performed to compare a new control strategy for coupled cooling and CO2 enrichment purposes. Tomatoes were grown in a hydroponic system. Sensor informationís about plant responses were integrated into the new control. The core idea for the new cooling method is a changing in the priority of the technical systems. If cooling is required first, the fog system is operating to produce latent energy. The roof ventilation is operating as a subordinated actuating element. The mean function of the ventilation is the vapour outlet. The vent is open only for a very short time with a maximum of 10% when vapour saturation deficit under the roof is too small. Only in case of high leaf temperature the ventilation will allocate for a maximum air exchange (stress protection). The descending fog is leading to cold air stream down to the bottom of the greenhouse and helps to fix the CO2 between the plants. A horizontal sensor chain was installed in the greenhouse to measure the dynamics of the temperature, humidity and CO2 profile. In the result significant lower time with vent opening in the DescFog control variant was obtained. Due to this and descending fog strategy the daily CO2 concentration inside the DescFog cabin was 700 ppm against 350 ppm in the comparison cabin. This generates higher light use efficiency but lower leaf transpiration. Nevertheless, the vegetative and fruit growth in the DescFog cabin was higher.

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