Economizer Modes of Data Center Cooling Systems

In certain climates, some cooling systems can save over 70% in annual cooling energy costs by operating in economizer mode, corresponding to over 15% reduction in annualized PUE. However, there are at least 17 different types of economizer modes with imprecise industry definitions making it difficult to compare, select, or specify them. This paper provides terminology and definitions for the various types of economizer modes and compares their performance against key data center attributes.