A financial feasibility evaluation of using evaporative cooling with air-conditioning (in hybrid mode) in commercial buildings in India Varun Jain, S.C. Mullick, Tara C. Kandpal ⁎ Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi — 110016, India abstract article info Article history: Received 22 March 2012 Revised 2 November 2012 Accepted 4 November 2012 Available online 19 December 2012 Keywords: Hybrid system Direct evaporative cooling Payback period Life cycle cost Net present value Results of a preliminary analysis to study the financial feasibility of a hybrid mode operation of a direct evaporative cooler (DEC) with an air conditioning (AC) unit to reduce the annual expenditure on electricity usage (as against a standalone AC unit to provide almost similar level of comfort) are presented. Four different building applications located in four different cities of India have been considered in the study. The hybrid mode operation is found financially attractive for movie theater and waiting hall building applications for all the climatic conditions consid- ered in the present study. © 2012 International Energy Initiative. Published by Elsevier Inc. All rights reserved. Introduction The need and use of air-conditioning are rapidly increasing in urban India and normally vapor compression systems are being used for this purpose. As a consequence the electrical consumption for air-conditioning is also increasing at a rapid rate. It is therefore imperative to develop and implement practically feasible alternative options that can provide acceptable levels of comfort with relatively lower electricity consumption. For commercial buildings, use of direct evaporative cooling based systems in a hybrid mode with conven- tional vapor compression based air-conditioning systems during hot and dry months of the year is one such possibility. Besides the opera- tional issues of a hybrid system, the primary consideration in making a choice for the hybrid system as against a standard vapor compres- sion based air-conditioning system would concern the financial viability of increased capital investment (higher cost of a hybrid sys- tem consisting of both the vapor compression air-conditioning (AC) system as well the direct evaporative cooler (DEC) as against its lower overall cost of operation due to lower electricity consumption of the hybrid system as against that of a standalone AC unit for satisfaction of the same demand). The approach and the results of an attempt to study the financial feasibility of an investment in a hybrid (AC + DEC) system as compared to a standalone AC system are presented in this paper for four Indian cities. Four cities in India namely Akola (hot and dry climate), Bangalore 1 (temperate climate), Delhi (composite climate) and Indore (composite climate) were considered for the study. Though the sites of Delhi and Indore are in the same climatic zone, but being in different regions their ambient conditions differ considerably and hence also the room conditions (Hindoliya, 2005). Building application configurations con- sidered include (i) high density office (with high internal loads due to occupancy, lights, computers etc.), (ii) low density office, (iii) movie theater and (iv) waiting hall. The external and internal input parame- ters to TRNSYS (2005) for these buildings are presented in Table A1 of the Appendix (Jain, 2010). In the case of the standalone AC unit the room temperature is set at 26 °C and RH ≤70%. Since with the use of a direct evaporative cooler (DEC) the attained room conditions change with ambient conditions, a range of room temperatures and relative humidity values are considered as set points (27.1 °C, 70%; 27.6 °C, 60%; and 28.1 °C, 50%) (Jain, 2010). A systematic procedure (Fig. 1) was followed for estimating the electricity requirement for maintaining the desired comfort level in the chosen building configurations at the four selected locations. TRNSYS (2005) was used to simulate the rooms/buildings. The fractions of time during the year when cooling is needed and a DEC can provide the acceptable comfort were estimated. The results obtained are summarized in Table 1. Analysis The hybrid system considered in the system consists of a DEC unit along with the AC unit arranged in a manner that whenever the required comfort is not achieved with the DEC unit, the AC unit is switched on and DEC unit is switched off. The AC unit considered in the study is a split air cooled system with indoor and outdoor units interconnected with refrigerant piping and its cost includes the cost of refrigerant piping, cost of air distribution system and standard control Energy for Sustainable Development 17 (2013) 47–53 ⁎ Corresponding author. Tel.: +91 11 26591262. E-mail address: tarak@ces.iitd.ac.in (T.C. Kandpal). 1 New name for city of Bangalore is Bengaluru. 0973-0826/$ – see front matter © 2012 International Energy Initiative. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.esd.2012.11.002 Contents lists available at SciVerse ScienceDirect Energy for Sustainable Development