Solar Energy Vol. 71, No. 6, pp. 353–364, 2001 2001 Elsevier Science Ltd  Pergamon PII: S0038–092X(01)00072–X All rights reserved. Printed in Great Britain 0038-092X / 01 / $ - see front matter www.elsevier.com / locate / solener AN EXPERIMENTAL STUDY OF THE THERMAL PERFORMANCE OF AN EARTH-AIR-PIPE SYSTEM IN SINGLE PASS MODE ² N. M. THANU, R. L. SAWHNEY , R. N. KHARE and D. BUDDHI School of Energy and Environmental Studies, Devi Ahilya University, Khandwa Road, Indore 452 017, India Received 23 December 1999; revised version accepted 26 June 2001 Communicated by ERICH HAHNE Abstract—The thermal performance of an earth-air-pipe system constructed at Gulmohar farm house, Gurgaon, India has been studied. It has been used in a single pass mode to condition three bedrooms, a living room, a dining room, and a kitchen of a farmhouse. The performance of the earth-air-pipe system was first evaluated prior to the construction of the farmhouse. Accordingly, the temperature and relative humidity at suction and delivery points of the earth-air-pipe system were monitored in three seasons i.e., summer, monsoon and winter. After the construction of the farmhouse was completed, the performance of the earth-air-pipe system in question, along with performance of one of the living rooms of the farmhouse, was evaluated. The temperature and relative humidity of a conditioned room (living room of the farm house), delivery point of the earth-air-pipe system (located in the living room), suction point of the earth-air-pipe system (the hut in which blower of the earth air-pipe system is placed) and ambient air were measured. The cooling and heating potential of the earth-air-pipe system is estimated. The coefficient of performance of the installed system during summer, monsoon, and winter was found to be 7.9, 1.9 and 2.1, respectively. It is concluded that good thermal comfort conditions can be created reasonably in the building with such a system.  2001 Elsevier Science Ltd. All rights reserved. 1. INTRODUCTION the building. The simplest earth-air-pipe system would be a pipe of appropriate dimensions buried The temperature of the ground is governed by the at a depth of about 4 m in the ground and through ambient temperature and absorbed solar radiation. which air is blown with the help of a blower. If It is a well-known fact that at the depth of about the pipe is of adequate length, the ambient air 4–6 m, the earth provides a very stable thermal passing through it in summer and in winter will environment. The temperature at such depth is acquire the temperature of the surrounding earth around 268C in Delhi type climate. If for a given at that depth. In summer, when ambient air is climate (like Leh, India or the Thar desert, India) forced through the underground earth-air-pipe this temperature is not within the desired range, it system, the heat from the air is transferred to the can be modified to the desired range by a suitable pipe walls by convection, dissipated later to the treatment at the earth’s surface (Gold, 1967). For soil by conduction. The cool delivery air from the increasing subsurface earth temperature, the earth-air-pipe system can be passed through build- earth’s surface can be blackened or glazed while ing spaces to create required thermal conditions. for decreasing the subsurface earth temperature; In winter, when cold ambient air is passed the earth’s surface can be shaded, painted white or through the same earth-air-pipe system, the heat is wetted with sprayed water. For the large thermal transferred from the surrounding earth to the pipe capacity of the earth, the effect of the withdrawal by conduction and then to the air by convection, of heat or pumping in of heat on the earth heating the passing air in the process. The hot air temperature at the depth will not be significant. from the system can now be used to heat the This very stable thermal environment can be building spaces. As a result, building spaces can coupled to buildings by an earth-air-pipe system be cooled during summer and heated during to create human thermal comfort conditions inside winter by the same system. Thus, using an earth- air-pipe system, the energy and peak load require- ments for space conditioning can be significantly ² reduced, offering large energy conservation op- Author to whom correspondence should be addressed. portunities. Tel.: 191-731-460-309; fax: 191-731-470-372; e-mail: rlsawhney@hotmail.com A number of theoretical and a few experimental 353