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10: Green IT Case Studies for Universities and a Large Company 179

location. The team took a look at this problem and recommended what tiles
needed to be moved and which perforated tiles needed to be replaced with
solid tiles. Medium flow tiles were installed in areas where additional air flow
was needed.
As we moved to longer-range improvements, the team recommended
turning off some of the redundant CRAC units. Extra CRAC units had been
installed initially to ensure sufficient cooling and compensate for mainte-
nance and unplanned failures. It is not uncommon to have 20 percent more
units installed than are needed to handle the cooling capacity. Turning off
extra CRAC units would save electricity and extend the life of those units not
in use. To ensure that no problems were introduced by turning off particular
CRAC units, a three-step process was used. A total of 11 units were turned
off, five in the first step and three in each of the subsequent steps. At $0.04
per kilowatt hour, this results in an estimated annual savings of $19,250.
More important, the 481,250 kilowatts saved can be applied to run other
equipment as a result of this best practice.
Other changes such as increasing the chilled water temperature and
increasing the supply air temperatures from the CRAC units were imple-
ptg
mented, providing additional savings.
Recent analysis of DCiE metrics has shown that data centers that leverage
free cooling technologies have a variability of up to 20 percent improvement
for the same IT load depending on the time of day and time of year. Free
cooling leverages the outside temperature when it is colder than the inside
temperature (for example, nights and winter). Unfortunately, this data center
did not leverage free cooling.
Other options such as free cooling continue to be investigated. It is esti-
mated that the outside temperature at this specific location is colder than the
inside data center temperature approximately 40 percent of the year.

Future Plans and Government Involvement

Because water conducts heat 3,700 times better than air, several equip-
ment manufacturers are making liquid cooling devices that move the liquid
cooling closer to the IT equipment than the CRAC units, which are liquid-
cooled. Options now exist for in-row cooling, overhead cooling, rear-door
cooling, and aisle-based heat containment systems. These techniques have
the added benefit of having the cooling closer to the equipment being cooled,
further increasing cooling efficiency. The trade-off is that chilled water pipes
now need to be installed closer to the IT equipment aisles, decreasing the
amount of flexibility in IT aisle changes.