Laboratory of Complex Dynamics Simulation, Department of Instrument Science and Engineering, School of Electronic, Information and Electrical Engineering, Shanghai Jiao Tong University1
Institute of Crop Science, Chinese Academy of Agricultural Sciences2
Shanghai Key Laboratory of Protected Horticultural Technology, Sunqiao Modern Agriculture Development Zone3
In this work, the effects of shade combination, shade height and wind regime on greenhouse climate were quantified. A two-dimensional (2-D) computational fluid dynamics (CFD) model was developed based on an 11-span plastic greenhouse in eastern China for wind almost normal to the greenhouse orientation. The model was first validated with air temperature profiles measured in a compartmentalized greenhouse cultivated with mature lettuce (Lactuca sativa L., ‘Yang Shan’). Next, the model was employed to investigate the effect of shade combinations on greenhouse microclimate patterns. Simulations showed similar airflow patterns in the greenhouse under different shade combinations. The temperature pattern was a consequence of convection and radiation transfer and was not significantly influenced by shade combination. The use of shade screens reduced air velocity by 0.02-0.20 m･s-1, lowered air temperature by 0.2-0.8°C and raised the humidity level by 0.9-2.0% in the greenhouse. Moreover, it improved the interior climate homogeneity. The assessment of shade performance revealed that the external shade had good cooling and homogeneity performance and thus can be recommended. Furthermore, the effects of external shade height and wind regime on greenhouse climate parameters showed that external shade screens are suitable for installation within 1 m above roof level. They also demonstrated that, under external shade conditions, greenhouse temperature was reduced relative to unshaded conditions by 1.3°C under a wind speed of 0.5 m･s-1, whereas it was reduced by merely 0.5°C under a wind speed of 2.0 m･s-1. Therefore, external shading is more useful during periods of low wind speed.
1. Al-Arifi, A. 1999. The influence of shading and evapotranspiration on a ventilated greenhouse environment. PhD Thesis, Ohio State University, Ohio, USA.
2. Al-helal, I.M. 1998. A computational fluid dynamics study of natural ventilation in arid region greenhouses. PhD Thesis, Ohio State University, Ohio, USA.
3. Baxevanou, C.A., D.K. Fidaros, T. Bartzanas, and C. Kittas. 2010. Numerical simulation of solar radiation, air flow and temperature distribution in a natural ventilated tunnel greenhouse. CIGR J. 12:48-67.
4. Boulard, T. and S. Wang. 2002. Experimental and numerical studies on the heterogeneity of crop transpiration in a plastic tunnel. Comput. Electron. Agric. 34:173-190.
5. Boulard, T., S. Wang, and R. Haxaire. 2000. Mean and turbulent air flows and microclimatic patterns in an empty greenhouse tunnel. Agr. Forest. Meteorol. 100:169-181.
6. Cohen, S. and M. Fuchs. 1999. Measuring and predicting radiometric properties of reflective shade nets and thermal screens. J. Agric. Eng. Res. 73:245-255.
7. Fidaros, D.K., C.A. Baxevanou, T. Bartzanas, and C. Kittas. 2010. Numerical simulation of thermal behavior of a ventilated arc greenhouse during a solar day. Renew. Energ. 35:1380-1386.
8. Katsoulas, N., A. Baille, and C. Kittas. 2001. Effect of misting on transpiration and conductances of greenhouse rose canopy. Agr. Forest. Meteorol. 106:233-247.
9. Kichah, A., P.E. Bournet, C. Migeon, and T. Boulard. 2012. Measurement and CFD simulation of microclimate characteristics and transpiration of an impatiens pot plant in a greenhouse. Biosyst. Eng. 112:22-34.
10. Kitta, E., N. Katsoulas, and D. Savvas. 2012. Shading effects on greenhouse microclimate and crop transpiration in a cucumber crop grown under Mediterranean condition. Appl. Eng. Agric. 28:129-140.
11. Kittas, C. and A. Baille. 1998. Determination of the spectral properties of several greenhouse cover materials and evaluation of specific parameters related to plant response. J. Agric. Eng. Res. 71:193-202.
12. Kittas, C., A. Baille, and P. Giaglaras. 1999. Influence of covering material and shading on the spectral distribution of light in greenhouses. J. Agric. Eng. Res. 73:341-351.
13. Kittas, C., T. Bartzanas, and A. Jaffrin. 2003. Temperature gradients in a partially shaded large greenhouse equipped with evaporative cooling pads. Biosyst. Eng. 85:87-94.
14. Launder, B.E. and D.B. Spalding. 1974. The numerical computation of turbulent flows. Comput. Method. Appl. M. 3:269-289.
15. Lee, I.B. and T.H. Short. 1998. Predicted effects of internal horizontal screens on natural ventilation of a multi-span green-house. In: 91st Annual International Meeting of ASAE, Paper No. 987014, Orlando, FL, USA, July 12-16.
16. Miguel, A.F., N.J. van de Braak, and G.P.A. Bot. 1997. Analysis of the airflow characteristics of greenhouse screening materials. J. Agric. Eng. Res. 67:105-112.
17. Mohammadi, B. and O. Pironneau. 1994. Analysis of the k-epsilon turbulence model. Wiley, New York, Masson, Paris.
18. Montero, J.I., P. Muñoz, M.C.Sánchez-Guerrero, E. Medrano, D. Piscia, and P. Lorenzo. 2013. Shading screens for the improvement of the night-time climate of unheated greenhouses. Spain. J. Agr. Res. 11:32-46.
19. Muñoz, P., J.I. Montero, A. Anton, and N. Iglesias. 2004. Com-putational fluid dynamic modelling of night-time energy fluxes in unheated greenhouse. Acta Hort. 691:403-410.
20. Nebbali, R., J.C. Roy, and T. Boulard. 2012. Dynamic simulation of the distributed radiative and convective climate within a cropped greenhouse. Renew. Energ 43:111-129.
21. Piscia, D., J.I. Montero, E.J. Baeza, and B.J. Bailey. 2012a. A CFD greenhouse night-time condensation model. Biosyst. Eng. 111:141-154.
22. Piscia, D., J.I. Montero, M. Melé, J. Flores, J. Perez-Parra, and E.J. Baeza. 2012b. A CFD model to study above roof shade and on roof shade of greenhouses. Acta Hort. 952:133-139.
23. Richards, P.J. and R.P. Hoxey. 1993. Appropriate boundary conditions for computational wind engineering models using the k-ε turbulence model. J. Wind. Eng. Ind. Aerod. 46-47:145-153.
24. Sapounas, A.A., S. Hemming, H.F. De Zwart, and J.B. Campen. 2010. Influence of insect nets and thermal screens on climate conditions of commercial scale greenhouses: A CFD approach, p. 1-11. In: XVII World Congr. Intl. Commission Agricultural Biosystems Eng. (CIGR). Québec, Canada, 13-17 June, 2010.
25. Tong, G., D.M. Christopher, and B. Li. 2009. Numerical modelling of temperature variations in a Chinese solar greenhouse. Comput. Electron. Agric. 68:129-139.
26. Vlamdimirova, S.V., R.A. Bucklin, and D.B. McConnel. 1996. Influence of shade level, wind velocity, and wind direction on interior air temperatures of model shade structure. Trans. ASAE 39:1825-1830.
27. Willits, D.H. 2000. Intermittent application of water to an externally mounted, greenhouse shade cloth to modify cooling performance. Trans. ASAE 43:1247-1252.
28. Willits, D.H. 2001. The effect of cloth characteristics on the cooling performance of external shade cloths for greenhouses. J. Agric. Eng. Res. 79:331-340.
29. Willits, D.H. 2003. The effect of cloth temperature on the cooling efficiency of shade clothes in greenhouses. Trans. ASABE 46:1215-1221.