Modeling and parametric studies for thermal performance of an earth to air heat exchanger integrated with a greenhouse M.K. Ghosal, G.N. Tiwari * Centre for Energy Studies, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016, India Received 28 August 2004; received in revised form 15 March 2005; accepted 2 October 2005 Available online 15 November 2005 Abstract A thermal model has been developed to investigate the potential of using the stored thermal energy of the ground for greenhouse heating and cooling with the help of an earth to air heat exchanger (EAHE) system integrated with the green- house located in the premises of IIT, Delhi, India. Experiments were conducted extensively throughout the year 2003, but the developed model was validated against typical clear and sunny days experiments. Parametric studies performed for the EAHE coupled with the greenhouse illustrate the effects of buried pipe length, pipe diameter, mass flow rate of air, depth of ground and types of soil on the greenhouse air temperatures. The temperatures of the greenhouse air, with the experimen- tal parameters of the EAHE, were found to be, on average 7–8 °C higher in the winter and 5–6 °C lower in the summer than those of the same greenhouse without the EAHE. The greenhouse air temperatures increase in the winter and decrease in the summer with increasing pipe length, decreasing pipe diameter, decreasing mass flow rate of flowing air inside buried pipe and increasing depth of ground up to 4 m. The predicted and measured values of the greenhouse air temperatures that were verified, in terms of root mean square percent deviation and correlation coefficient, exhibited fair agreement. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Greenhouse; Solar energy; Earth air heat exchanger; Thermal modeling 1. Introduction Heating and cooling of a greenhouse is one of the most energy consuming operations among the various activ- ities performed for protected cultivation. In Northern India, the temperature of the ambient air, as well as the enclosed air of a greenhouse rises to an undesirable level both during the summer period and even during clear days of the winter. Temperatures exceeding 45 °C in summer and dropping to 6 °C in winter are common inside the greenhouse for the climatic conditions of Northern India [1]. A large variation of temperatures between the day and night hours, both in the summer and winter periods, produces adverse effects on the quality and growth of crop in the greenhouse. For heating, as well as for cooling of the greenhouse, it is of primary importance to 0196-8904/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.enconman.2005.10.001 * Corresponding author. Tel.: +91 011 2659 1258; fax: +91 011 2658 1121/2686 2037. E-mail address: gntiwari@ces.iitd.ernet.in (G.N. Tiwari). Energy Conversion and Management 47 (2006) 1779–1798 www.elsevier.com/locate/enconman