ISHS Acta Horticulturae 719: International Symposium on Greenhouse Cooling
THE COOLING PERFORMANCE OF NATURALLY VENTILATED GREENHOUSES IN THE SOUTHEASTERN U.S. |
| Authors: | D.H. Willits, S. Li, C.A. Yunker |
| Keywords: | Greenhouses, fan ventilation, natural ventilation, greenhouse cooling, sweet bell pepper (Capsicum annuum) |
| Abstract:
The cooling performance of two naturally ventilated (nv) greenhouses was compared to that of two fan ventilated (fv) greenhouses in Raleigh, North Carolina, in the summer of 2005. The fv houses, 6.7 m x 12.1 m, were cooled using a fan and pad system with air exchange rates of 0.087 m3/m2 s. The nv houses were 6.4 m x 11 m Low pressure fog (400 kPa) supplemented the cooling in both nv houses except when top vent only cooling was used. All four houses were planted in early June with three cultivars, Waki, Walter and Zamboni, of sweet bell pepper (Capsicum annuum) at a density of 2.6 plants/m2. Air and canopy temperatures were always higher in the nv houses than in the fv houses; however, daytime transpirations were not different. Differences in internal conditions between the two nv houses were small when fogging took place in both houses. When one nv house operated with top vent only and no fog, air and canopy temperatures were significantly higher than in the other nv house. Total yields in the fv houses were approximately double those in the naturally ventilated houses. Defects were higher in the fv houses, but not enough to offset the increase. Walter was least affected by the differences in house type while Waki was the most affected. | |
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