Analysis of centrifugal chillers with oil-free magnetic bearings for enhancing building energy performance

Fu Wing Yu, Kwok Tai Chan, Rachel Kam Yung Sit

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


This article examines the actual operating performance of centrifugal chillers with oil-free magnetic bearings (hereafter oil-free chillers) to analyze energy saving potentials for commercial buildings. A chiller system retrofit for a shopping arcade involved replacing three existing constant speed water-cooled centrifugal chillers by three oil-free centrifugal chillers of the same capacity. The coefficient of performance was calculated based on operating data logged at 1-h intervals for over 1 year before and after replacement. Oil-free chillers with variable speed control operated at a higher coefficient of performance under part load conditions, reducing the total electricity consumption of the shopping arcade by 9.6%. If the average technical efficiency in data envelopment analysis was improved to 1 from 0.6 in the existing case, the average system coefficient of performance could increase from 6.2 to 10.3. The improvement involved controlling the temperature of supply chilled water at a lower boundary curve and operating an equal percentage of capacity among chillers. It is economically viable to design an all-variable speed chiller system with oil-free chillers instead of the conventional constant speed system for a reference office building in a subtropical climate.

Original languageEnglish
Pages (from-to)334-344
Number of pages11
JournalScience and Technology for the Built Environment
Issue number2
Publication statusPublished - 17 Feb 2017


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