Avraham Arbel
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Gradual Fogging System for Cooling Greenhouses
Vegetablesתחום או ענף אגרוטכנולוגיה
תאריך עדכון 18/5/2010תיאור מלא Gradual Fogging System for Cooling Greenhouses
Avraham Arbel, Mordechai Barak and Gia Lador – Institute for Agricultural Engineering, ARO
Shabtai Cohen, Dudu Elkayam, Rivka Offenbach, Avi Osherovitz, Dorit Hashmonai, Israel Tzabari and Rami Golan – Central and Northern Arava R&DEmail address of the writer: arbel@volcani.agri.gov.il
Abstract
Greenhouse crop production in Israel is based mainly on the export of agricultural products during the winter, due to the relative advantage of these products in the European market, this market is characterized by a high level of demand for quality products, that is, products that are free of pesticide residue and arrive in a regular, systematic manner. Lately, this market has been over-supplied with agricultural products, following the entrance of countries in southern Europe and North Africa, which compete for the same share of the market. As a result, the profitability of the crop has declined. The consistent supply of quality agricultural products throughout the year promises a noticeable market solution to growers and could help Israeli growers compete in the crowded marketplace. This requires growing and/or planting during the summer, when the ambient heat- is very high due to solar radiation and summer temperatures. To respond to this challenge, a fogging system was developed for cooling greenhouses. The system was used during the 2008-2009 growing season at the Yair Research Station in the Arava, in structures planted with peppers. The first year was mainly dedicated to testing the physical performance of the apparatus, which included a ventilation system, a fogging mechanism and controls. The system was programmed according to the conditions desired in the greenhouse (28°C and 80% relative humidity) during, extreme midday temperature, and installed according to the following specifications:
Fogging – In order to supply water gradually, lines of nozzles were divided into three groups (one-sixth, one-third and one-half of the nozzles). This distribution, together with the partial and alternate activation of the supply lines and changes in the pressure (within the acceptable range), allows the gradual change in the water supply necessary to respond to the initial low demand during the night-time and morning hours, as well as the increased need for water corresponding to increased heat-loads during the day and night.
Greenhouse ventilation – Roof openings allowed air to enter the greenhouse and fans were installed on the sides of the greenhouse. The fans were divided into two groups. One group of fans (the controlled group) was operated at a variable frequency. The desired air supply was obtained by installing a number of groups of fans, and also by timing the frequency in the controlled group.
Control system – The desired conditions were achieved by timing the supplies of air and water, within the range of permitted deviation. In light of the promising results that were obtained, we can point to the following main conclusions: The actual conditions in the greenhouse corresponded closely to the desired conditions and the system of controls coped well with extreme situations in which the desired conditions could not be achieved. The control system operated effectively and without frequent changes in its activity. We recommend that this work be continued, with attention paid to the following issues: additional algorithms for the system of controls, and inclusion of additional operational controls, such as heating and natural ventilation.שפה English
מחבר Avraham Arbel, Mordechai Barak, Gia Lador, Shabtai Cohen, Dudu Elkayam, Rivka Offenbach, Avi Osherovitz, Dorit Hashmonai, Israel Tzabari and Rami Golan
שנה 2009
שייכות yzvieli
תאריך יצירה 18/5/2010
תאריך עדכון 18/5/2010
