ISHS Acta Horticulturae 115: Symposium on More Profitable Use of Energy in Protected Cultivation
COOLING GREENHOUSE CROPS IN A MEDITERRANEAN SUMMER CLIMATE |
| Authors: | C.H.M. van Bavel, E.J. Sadler, J. Damagnez |
| Abstract:
In a sunny and warm climate, evaporative cooling can be used to limit the temperature of the air in the greenhouse to a value slightly higher than that of the outside wet bulb. Model calculations made for summer conditions in Avignon, France, show, however, that this method can not result in an appreciable reduction of plant temperature, soil temperature, or daytime water stress below the values found in a normally vented greenhouse. The fluid-roof solar greenhouse approach, which represents a wavelength-selective method of shading, can accomplish reduction of Plant and soil temperature, and of water stress. If groundwater is available as the sink for the intercepted solar energy, the method is even more effective. In either case, the need for ventilation is limited to that needed to prevent very high humidity and internal condensation. The best control of plant temperatures should be obtained by combining the fluid-roof system with evaporative cooling, at the cost of a large amount of forced ventilation. The main conclusions of our analysis agree with existing data on actual leaf temperatures in glasshouses as related to ventilation. | |
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