A COMPARATIVE STUDY OF THE TRADITIONAL AIR CONDITIONING SYSTEM AND THE COGENERATION DISTRICT COOLING SYSTEM IN SINGAPORE

Abstract

Cogeneration (Cogen) District Cooling System (DCS) is an alternative solution for centralized air conditioning system in building. The result in this dissertation shows that Cogeneration DCS system can provide quantitative saving to building owners in terms of lower initial building cost, less investment in air-conditioning system, more space for commercial usage, reduced or outsourcing of operation and maintenance (O&M). The other benefits which are not estimated includes the elimination of constraints for building design and architecturally aesthetic. The Cogen DCS also helps the economy to save energy. Samples of Building are selected for the study of its air conditioning system. The building characteristic is used to determine the air conditioning system equipment cost. The air conditioning system cooling capacity, load and usage pattern are also calculated. With this data, the cooling capacity unit rate in $/RT-hr are calculated and compared. The building cooling loads are used to size the Cogen DCS plant. Cogen DCS is sized according to the power generation and the waste heat recovery used in electrical and absorption chillers. In turns, Cogen DCS produces chilled water for sale to buildings to meet its cooling needs. The Cogen DCS operation is also tailored to building's cooling load over a one-year period. The result shows that the quantity of energy produced by Cogen DCS plant is more efficient than electrical power supplied by generating companies. In terms of unit cost, the $/RT-hr rate of Cogen DCS is cheaper than the stand-alone air condition system in building during peak hour, at 65.2cent/RT-hr. The net present value method is used to analyse the Cogen DCS plant investment based on its expenses and revenue. Internal rate of return method is used to counter check the NPV and determine its yearly return. Sensitivity analysis is used to justify forecast of expenses and revenues. The Cogen DCS is a capital-intensive investment that needs ready buyer to the produced chilled water. It will not be justified to build if not enough buyers to the produced chilled water. In this study, a Cogen DCS plant of 2 x 5.2MW with 11,000RT cooling capacity can be viably set up at the condition of60 percent sign up to buy the chilled water, even ifinvestment and O&M costs is increase by 50 percent.