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水の潜熱を利用した根圏および地上部冷却による施設生産における作物生育環境の改善に関する研究
https://doi.org/10.24514/00001690
https://doi.org/10.24514/00001690898edbfb-e153-4899-89be-69c38932dbf0
| 名前 / ファイル | ライセンス | アクション |
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nivts_report_No9p211-270p.pdf (12.1 MB)
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| Item type | 紀要論文01 / Departmental Bulletin Original Article(1) | |||||||||||
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| 公開日 | 2019-03-22 | |||||||||||
| タイトル | ||||||||||||
| タイトル | 水の潜熱を利用した根圏および地上部冷却による施設生産における作物生育環境の改善に関する研究 | |||||||||||
| タイトル | ||||||||||||
| タイトル | Improving Environmental Conditions in a Greenhouse by Cooling the Air and the Root Area Using Latent Heat | |||||||||||
| 言語 | en | |||||||||||
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| 言語 | jpn | |||||||||||
| 資源タイプ | ||||||||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||||||||
| 資源タイプ | departmental bulletin paper | |||||||||||
| ID登録 | ||||||||||||
| ID登録 | 10.24514/00001690 | |||||||||||
| ID登録タイプ | JaLC | |||||||||||
| 著者 |
安場, 健一郎
× 安場, 健一郎
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| 抄録 | ||||||||||||
| 内容記述タイプ | Abstract | |||||||||||
| 内容記述 | In Japan, air temperatures in greenhouses may become too high during summer for cultivating some plants, so the greenhouses are often cooled by taking advantage of latent heat. The latent heat approach relies on the principle that when water is vaporized it draws heat out of the surrounding environment, producing a cooling effect. This approach to cooling is also useful for humidity control in greenhouses. However, an easy method of cooling the root area by means of latent heat has not yet been developed, and the threshold level of cooling that is required to promote crop growth is not clear. Misting is a useful method for cooling the air by taking advantage of latent heat, but it is difficult to control the cooling effect because the ventilation rate of the greenhouse affects the resulting cooling efficiency. To solve these problems, a method for controlling the degree of cooling of the root area and air in greenhouses was developed. Microporous film was used to cool the root area. Gas and water vapor can penetrate the microporous film, but liquid water cannot. When the hydroponic bed was created from microporous film, water in this bed was able to evaporate through the film, and oxygen from the ambient air passed through the film in the opposite direction and was dissolved in the root water. The relationship between water temperature and airflow velocity at the surface of the microporous film was investigated by connecting a duct to the bottom of the bed made of microporous film. A low airflow velocity (1.2 to 1.5m s^1) was more effective than other rates (0, 10, and 20m s^-1). The cooling efficiency with microporous film was about 60% of the theoretical cooling effect predicted by latent heat calculations. The rate of oxygen supply through the microporous film was about 0.22 μmol m^-2 sec^-1.The use of a hydroponic bed made of microporous film decreased temperatures in the root area and suppressed the decrease in the concentration of dissolved oxygen in the nutrient solution that occurs at higher temperatures, making it possible to grow spinach plants to commercial size even at high air temperatures. To confirm this result, spinach was grown in a polystyrene bed, a bed of microporous film, or a bed of microporous film combined with the abovementioned airflow treatment ; the bed of microporous film consisted of a polystyrene side wall and a bottom created from microporous film. The airflow treatment decreased the nutrient solution temperature and diminished the growth inhibition that occurs at high root temperature. To investigate the growth of spinach under a root-zone cooling treatment, a cooling tube that consisted of a duct made from microporous film and a polyethylene tube was developed. The duct was created from a nylon mesh tube covered with microporous film ; the mesh tube passed through a polyethylene tube 18cm in circumference. The cooling tube was placed in the center of the row of plants. The space between the duct and the polyethylene tube was filled with water, and the duct was connected to a blower to promote evaporation. Use of the cooling tube decreased soil temperatures just under it ; growth rates of the spinach plants grown with this system were about 25% greater than in plants exposed to a high root-zone temperature. A real-time calculation node for transmitting ventilation and evaporation rates was created by using a ubiquitous environmental controlling system, as these parameters are used to control mist cooling in greenhouses. In this system, information about the status of the environmental control devices (e.g., the amount by which the shade curtain is open) and sensor readings (e.g., for air temperature) are broadcast over a local area network. The node receives data on air temperatures inside and outside the greenhouse, on relative humidity inside and outside the greenhouse, on solar radiation outside the greenhouse, and on the degree of opening of the shade curtain. It then calculates the ventilation and evaporation rates by using the heat-balance method. In addition, it calculates the weight of misting water required to increase the relative humidity in the greenhouse to 100% and forecasts the air temperature at 100% relative humidity. It also calculates the weight of misting water required to decrease the air temperature to a preset value and forecasts the relative humidity at that temperature. The user can then monitor the ventilation rate and other useful information about the effectiveness of the mist cooling in real-time. A method of adjusting the roof window angle and misting to optimize air temperatures and relative humidity in a naturally ventilated greenhouse was also developed. The window angle was adjusted every 2 min to maintain the enthalpy in the greenhouse at 60 kJ kg^-1, which was equivalent to air-conditioning at 23℃ and 82% relative humidity. Mist was sprayed if the relative humidity decreased below the target relative humidity. This method maintained adequate air temperature and relative humidity during cool periods. In warm periods, an excessively high window angle decreased the cooling effect caused by misting, so it was necessary to adjust the window angle to avoid an unacceptable decrease in relative humidity in the greenhouse. Tomato was cultivated in a rockwool system in a greenhouse that used the abovementioned environmental control methods combined with CO_2 enrichment. This approach increased early yields for long-duration cultivation, so it appears that the approach improved environmental conditions for tomato cultivation. | |||||||||||
| 書誌情報 |
野菜茶業研究所研究報告 en : Bulletin of the National Institute of Vegetable and Tea Science 巻 9, p. 211-270, 発行日 2010-02-26 |
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| 出版者 | ||||||||||||
| 出版者 | 独立行政法人 農業・食品産業技術総合研究機構 | |||||||||||
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| 収録物識別子タイプ | ISSN | |||||||||||
| 収録物識別子 | 1346-6984 | |||||||||||
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| 関連タイプ | isIdenticalTo | |||||||||||
| 識別子タイプ | DOI | |||||||||||
| 関連識別子 | 10.24514/00001690 | |||||||||||
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| 出版タイプ | VoR | |||||||||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||||||||
