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When it comes to energy effi- ciency, data centers are in a league of their own. Power
density in these mission critical facilities doubles nearly every 18 months and
uptime reliability is a higher priority than
energy efficiency, says Mukul Anand,
Manager of Application Engineering,
Chiller Solutions, Building Technologies
and Solutions for Johnson Controls, Inc.
“From an energy reduction viewpoint, data centers are a unique moving
target,” Anand explains. “There is no
well-defined method to improve energy
efficiency.” These three savings strategies
can be a good start, however.
1) Equipment Optimization
About 60% of the energy consumption in a typical data center is used for
computer-related components, such as
processors, fans and data storage, Anand
explains. Another 30% goes to cooling
equipment, with 10% dedicated to electrical equipment and the remaining 2% for
lighting, monitors and other components
for data center infrastructure management. That means that tackling just the
first category, computing equipment,
could result in considerable savings.
The U.S. Department of Energy recommends starting by turning off any unused
servers, often referred to as “comatose”
or “zombie” servers, as 20-30% of servers in a typical data center are consuming
power, cooling and space without doing
any useful work. Take a regular inventory
of hardware and applications so you can
keep track of consolidation opportunities,
then build on the savings with virtualiza-tion software and more efficient servers.
“State-of-the-art servers provide the
most benefit because they have an energy multiplier effect,” Anand says. “Every
k W saved at the server translates into a
proportional reduction in BTUs because
less heat needs to be removed.”
2) Building System Savings
After ensuring your computing equip-
ment is as efficient as possible, look at
possible savings in building systems,
especially cooling. Using advanced data
center infrastructure management (DCIM)
and building management software can
assist with efficient cooling by enhanc-
ing equipment operation and providing
monitoring to help you make informed
decisions, Anand says.
“Right-sizing infrastructure equipment
to handle design and off-design condi-
tions also contributes to energy savings,”
Anand adds. “For example, a variable
speed drive chiller can run more effi-
ciently during 99% of operating hours
in low-load conditions than a chiller
designed for full-speed operation for the
hottest days of the year. For a variety of
reasons, it pays to right-size air handling
units, UPS and transformer equipment.”
The DOE also recommends variable
speed drives on cooling system fans, not-
ing that a 20% reduction in flow results in
roughly 50% savings in fan power.
“Hot aisle containment is generally the
most efficient way to arrange the racks
within data centers because it ensures
that in the working space, the temperature falls within the ASHRAE guidelines,”
Anand says. Hot air is exhausted into the
hot aisle, where it circulates back to the
CRAH unit for cooling. This allows the
CRAH unit to operate at the capacity it
was designed for and also lets you right-size the number of units. Use blanking
plates, floor tiles and other devices to
make sure air doesn’t leak between cold
and hot aisles, Anand recommends.
For persistent hot spots, the DOE recommends providing spot cooling via in-rack or in-row cooling devices. Rear door
heat exchangers are another innovative
option that involves installing a coil on the
server rack’s exhaust section to absorb
the heat and provide cooling. Air-side
economizers that draw in outside air are a
great option in the right climate zones.
Janelle Penny janelle.penny@buildings.
com is Senior Editor of BUILDINGS.
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