PROTECTED CROPS IN HUMID TROPICAL REGIONS HOW COULD WE AVOID OR REDUCE EXCESSIVE TEMPERATURES ? HOW COULD WE SELECT THE CLADDING MATERIALS AND THE GREENHOUSE DESIGN ?
Particularly during the rainy season, it becomes absolutely necessary to use an effective technique of ventilation. Among the following methods commonly used, none is completely satisfying :
- "Shading", because of limited external natural luminosity ;
- "Evaporative systems", because of the high continuous relative humidity rate of the air ;
- "Cooling", by refrigeration or dehumidification of the atmosphere, as it requires high investment and working costs ;
- "Dynamic ventilation", due to the high and quick "greenhouse effect" in a completely closed area.
Regarding the cladding materials, glass must be excluded and the polyethylene film seems to be the only adequate plastic material. The most promising direction regarding the improvement of internal climatic surroundings is the greenhouse design and, so so far, commercially speaking, no polyvalent greenhouse has really been designed specifically for tropical humid areas.
Natural ventilation must be the first priority of the tropical shelter designer keeping in mind the continuous presence of trade winds and the rising of warm air masses.
Furthermore, a performant tropical shelter must meet the following requirements :
- A perfect compromise between ventilation and protection from the heavy rains diverted by strong winds ;
- Robustness because of the risk of intense cyclones ;
- Low cost with a view towards the development and the extension of the protected crops in the humid tropical areas.