Publication: Life cycle of analysis of three different air conditioning system
Date
2002-03-01
Authors
Ling, Chen En
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
At present, there is more than one technically acceptable air conditioning system for a
particular building. The current practice in system selection is based on the first cost
criteria. The purpose of this project is to investigate the use of Life cycle cost analysis
as opposed to the first cost criteria in choosing a system. Life cycle cost not only
considers the first cost but it also includes the operating cost over the useful life of the
equipment in its selection criteria. This may prove to be more comprehensive and may
result in a more prudent choice of system. In this project three types of technically
feasible design were analyzed namely the air cooled chilled water system, water cooled
chilled water system and the direct expansion system.
It was found that when first cost is used as criteria of selection then the direct expansion
type of system is the most affordable system. However if life cycle cost analysis is the
benchmark criteria for selection then the air cooled chilled water system fits the criteria
most comfortably and the direct expansion type of system was found to be the most
expensive to own over a life period of 10 years. It was found that at a discount rate
ranging from 2% to 10%, the life cycle cost of direct expansion system starts to exceed
that of the air cooled chilled water system and water cooled chilled water system for the
period after 3 to 4 years of operation. It was found that at 4% discount rate, after 5
years of operation, the direct expansion system is 12.68% more expensive to own
compared to the air cooled chilled water system despite the fact that the initial cost of
the air cooled chilled water system was 66.67% more expensive then the direct
expansion system.
The major contributing factor to the higher cost of owning the direct expansion system
is the fact that its annual electrical energy consumption cost is 33.45% higher than that
of the air cooled chilled water system and 34.79% higher then that of water cooled
chilled water system.
The study confirms that a life cycle cost analysis is desirable for selecting the type of
system for a particular air conditioning project.