Cooling and Heating a Greenhouse in Baghdad by a Solar Assisted Desiccant System
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Abstract
Modeling the microclimate of a greenhouse located in Baghdad under its weather conditions to calculate the heating and cooling loads by computer simulation. Solar collectors with a V-corrugated absorber plate and an auxiliary heat source were used as a heating system. A rotary silica gel desiccant dehumidifier, a sensible heat exchanger, and an evaporative cooler were added to the collectors to form an open-cycle solar assisted desiccant cooling system. A dynamic model was adopted to predict the inside air and the soil surface temperatures of the greenhouse. These temperatures are used to predict the greenhouse heating and cooling loads through an energy balance method which takes into account the soil heat gain. This is not included in conventional methods. The results showed satisfactory agreement with published papers. Also, the results of heating and cooling loads obtained revealed good agreement with those obtained from conventional methods when the soil heat gain is included. Two identical collectors in series of total area of 5.4m2 were employed as a heating system which provides an outlet air temperature of 30 o C at air mass flux of 0.06 kg/s.m2 at midday in January. While, a 65 oC outlet air temperature was achieved for the same mass flux at midday in August. The desiccant cooling system
was operated in five operating modes; the ventilation mode and four recirculation modes with 20%, 50%, 70%,and 90% recirculation. The simulation results showed that a regeneration temperature of 60-70 o C is satisfactory for a cool supply air temperature of about 19.5 o C. Also, it was noted that 20-30 % recirculation of return air would result in suitable indoor greenhouse conditions for most periods of system operation. In addition, the coefficient of performance COP of the system was high compared with the conventional vapor compression systems.
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Abdel-Ghany A.M. Solar energy conversions in the greenhouses. Sustainable Cities and Society 2011; 1: 219– 26.
Abdel-Ghany A.M., Al-Helal I.M. Solar energy utilization by a greenhouse: General relations. Renewable Energy 2011; 36:189-96.
Abdel-Ghany A.M., Kozai T. Cooling Efficiency of Fogging Systems for Greenhouses. Biosystems Engineering 2006; 94 (1): 97–109
Aldrich R.A., Bartok J.W. Greenhouse Engineering.New York: Ithaca, 1994.
Amri-Alm A.M.S. Solar energy utilization in greenhouse tomato production. Journal of King Saud University, Agricultural Sciences 1997; 9: 21–38.
ASHRAE Handbook of Fundamental, American society for Heating, Refrigeration and Air Conditioning Engineers, Inc., New York,(1997).
Businger J.A. The glasshouse (greenhouse) climate. In Physical of Plant Environment 1963 (ed. By W.A. van Wijk).
Davies P.A. A solar cooling system for greenhouse food production in hot climates. Solar Energy 2005; 79 (6): 661–8.
Duffie J.A. and Beckman W.A., Solar Engineering and Thermal Process, John Wiley and Sons, New York, (2006).
Fong K.F., Chow T.T., Lin Z., Chan L.S. Simulation–optimization of solar-assisted desiccant cooling system for subtropical Hong Kong. Applied Thermal Engineering 2010; 30: 220–8.
Ganguly A., Ghosh S. Model development and experimental validation of a floriculture greenhouse under natural ventilation. Energy and Buildings 2009; 41: 521-7.
Hepbasli A. A comparative investigation of various greenhouse heating options using exergy analysis method. Applied Energy 2011; 88: 4411–23.
Jain D., Tiwari G.N. Modeling and optimal design of evaporative cooling system in controlled environment greenhouse, Energy Conversion and Management 2002; 43 (1):2235–50.
Joudi K.A., Dhaidan N.S. Application of solar assisted heating and desiccant cooling systems for a domestic building. Journal of Energy Conversion and Management 2001; 42:995-1022.
Joudi K.A., Madhi S.M. AN EXPERIMENTAL INVESTIGATION INTO A SOLAR ASSISTED DESICCANT EVAPORATIVE AIR CONDITIONING SYSTEM. Solar Energy 1987; 39 (2): 97-107.
Kano A., Sadler E.J. Survey of Greenhouse Models. J. Agr. Met. 1985; 41 (1): 75-81.
Kittas C., Karamanis M., Katsoulas N. Air temperature regime in a forced ventilated greenhouse with rose crop. Energy and Buildings 2005; 37 (8): 807–12.
Kothari S., Panwar N.L. Steady state thermal model for predicting micro-climate inside the greenhouse. Inst. Eng. (India) J. Agric. Eng. 2007; 88:52–5.
Kurklu A., Bilgin S., Ozkan B. A study on the solar energy storing rock-bed to heat a polyethylene tunnel type greenhouse. Renewable Energy 2003; 28 (5): 683–97.
Mastalerz J.W. The Greenhouse Environment. John Wiley and Sons, New York, 1977
Mesmoudi K., Soudani A., Zitouni B., Bournet P.E., Serir L. Experimental study of the energy balance of unheated greenhouse under hot and arid climates: Study for the night period of winter season. Journal of the Association of Arab Universities for Basic and Applied Sciences 2010; 9: 27–37.
Moneer A.K. A preliminary computer simulation of an open solar assisted desiccant cooling system, M.Sc. Thesis, university of Baghdad, Baghdad, (1997) flow heat exchanger system. Solar Energy 2007; 81:723–41.
Shukla A., Tiwari G.N., Sodha MS. Experimental study of effect of an inner thermal curtain in evaporative cooling system of cascade greenhouse. Solar Energy 2008; 82 (1):61–72.
Singh G., Singh P.P., Lubana P.P.S., Singh K.G. Formulation and validation of a mathematical model of the microclimate of a greenhouse. Renewable Energy 2006; 31: 1541–60.
White J.W., Aldrich R.A. Progress report on energy conservation for greenhouses research. Floriculture Review 1975; 156: 63-5.