ISHS Acta Horticulturae 614: VI International Symposium on Protected Cultivation in Mild Winter Climate: Product and Process Innovation
GREENHOUSE CHARACTERISTICS AND MICROCLIMATIC CONDITIONS |
| Authors: | J.I. Montero, A. Antón |
| Keywords: | ventilation, light transmission, cooling |
| Abstract:
In spite of the trend of the last years towards increaseing technology, most greenhouses in mild winter climates are still of the low cost type. Currently, efforts are being made to improve the internal climate of simple greenhouses by incorporating simple technology. As a result, greenhouses which are midway between plain shelters and advanced structures are being developed. This paper discusses some of the recent research studies aimed at improving the greenhouse structures of mild winter climates. - Improving greenhouse light transmission. Simulation models are being used to enhance the light transmission of low roof slope conventional greenhouses. The most relevant results of these studies have indicated that for Southern European latitudes, increasing the roof slope of the southern side in east-west oriented asymmetrical greenhouses increased the radiation transmission in autumn and winter. Agronomical tests showed a clear rise in production and quality associated to the increase in winter light. Some other studies have shown that highly transmissive films gave an increase in yield for a summer tomato crop, provided that greenhouse temperature and humidity are well controlled. - Improving natural ventilation. The understanding of the airflow in and around the most popular greenhouses is increasing. For this purpose, wind tunnel tests conducted on scale-models are being done together with full-scale measurements in real greenhouses. Computational Fluid Dynamics (CFD) is another useful technique being used to study the air exchange process. Information on the relative resistance to airflow of different types of openings has been developed. Also, the important effect of insect-proof screens on ventilation is better understood now. All this body of knowledge is expected to be incorporated in future greenhouse designs, in which the type, size and arrangement of ventilators, roof slope and geometry will be considered to mitigate the excessive heat load of most current greenhouses. - Improving greenhouse cooling. Evaporative cooling is a well-known technique for reducing temperature. Although no important breakthrough has been made lately on this matter, better efficiency is expected to be achieved in the future by a more accurate control of ventilation and evaporative cooling. It is worthy of mention that reducing the vapour pressure deficit by shading, ventilating and or evaporative cooling can alleviate the effect of low quality or saline water in many horticultural crops, a major problem (low water quality) in many greenhouse areas. Finally, the recent efforts to make greenhouse production “greener” should be mentioned: analysing the greenhouse environmental impact by identifying the most contaminating processes in the production chain, reducing contamination and waste from greenhouse production and conducting research to develop techniques which are environmentally friendly with the are ways to pursue the goal of zero-waste greenhouse production. | |
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