Air Economizers

An air economizer brings in outside air directly into the data center to provide cooling. It is used mostly when the outside air is cooler than the inside air, essentially it means "opening up the windows" for almost free cooling. According to GreenerComputing.com, the widespread use of air-side economizers has the potential to reduce annual cooling energy consumption costs by more than 60 percent. Figure 11-6 shows how such a system works.

A data center can also benefit from cooler daytime and nighttime temperatures, as a data center requires cooling around the clock. It works by opening an outside air damper and blowing outside air into the data center when the outside air is cool enough to lower the temperature inside. A return air damper closes as the outside air damper opens. A third damper connected to the return duct helps avoid overpressurization of the room. Filters are used on the outside air before entering the space to remove contaminants in the air.

The first thing a data center manager is likely to worry about with an airside economizer is that contaminants, such as pollution from the outside, will cause problems with delicate electronic circuits. Particulate particles

Figure 11-6

AIR ECONOMIZER COOLING. HOT AIR IS FLUSHED OUTSIDE, AND OUTSIDE AIR IS DRAWN IN

Figure 11-6

AIR ECONOMIZER COOLING. HOT AIR IS FLUSHED OUTSIDE, AND OUTSIDE AIR IS DRAWN IN

in the air could cause conductor bridging and damage to the circuits. Humidity is also a concern as too much moisture in the air could also play havoc with sensitive equipment. But studies performed by the Lawrence Berkley National Laboratory, Intel, Microsoft, IBM, HP, and others have demonstrated that servers are not nearly as fragile as once thought. Servers running with no humidity control and in temperatures up to 90 °F have functioned fine with little or no increase in failure rates. Savings of 60% to 70% in cooling costs were reported in these studies.

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