ENERGY FACT: DATA CENTERS CONSUME UP TO 50 TIMES AS MUCH ELECTRICITY
PER SQUARE FOOT AS STANDARD OFFICE SPACE, ACCORDING TO ENERGY STAR.
floor can severely restrict the flow of
ventilation, which increases the demand
for fan energy and degrades cooling
performance. Also, the cabling behind
servers is a potential obstruction for air,
which moves from the cold aisle, which
is usually in front of the server racks,
across the server to the hot aisle behind
IT personnel focus first on their
equipment and whether it is operating
correctly. They may not think about the
impact that air flow has on energy. And
they may not be responsible for the energy
bill – in fact, they may not even see it.
Younger: When servers are taken out of
a rack, it is important to put in a blanking
panel. Otherwise air from the cold aisle
can short circuit through the empty server
slot to the hot aisle without doing any
Stachowiak: Basically you want to
avoid instances where a single hot spot is
causing an entire center to be overcooled.
For example, if a fan fails inside a server
or the airflow is obstructed by cabling
behind it, you want to address the hot spot
only rather than lower the temperature
throughout the facility, which wastes a lot
of energy. We take in an infrared imager
so we can see any hot spots.
Where else can ventilation air leak
or be obstructed?
Younger: Be aware of the floor tile
itself as well as the underfloor plenum.
Perforated tiles in cold aisles should
not be obstructed by other equipment,
chair mats or desks. Also, floor grommets
should be used to maintain air flow
patterns wherever there are penetrations
for cabling coming up through the floor.
Also, be aware of covering your unused
What about server consolidation
CRAC units. Cold underfloor air can
backflow out the top of these units if they
are not covered.
and virtualization? How do they
help to increase energy efficiency?
Younger: Consolidation refers to
running different applications on the
same server. This can
be more efficient in
terms of utilization than
a one app/one server
approach. If a lot of
individual servers are
working at part loads,
they will draw more
power than a smaller
number of servers
operating at higher
space and creates virtual
servers to make it easier
to segregate and manage
are consolidated, take unused units out
of the rack. This ensures that the servers
cannot draw electricity or be powered on
accidentally. Then install blanking panels
on all empty server slots.
What do operators need to monitor
to maintain peak efficiency?
Stachowiak: Server utilization should
be monitored because a department
within an organization might discontinue
using a particular application, resulting
in an underutilized server that no one
Younger: Monitor power loads and
HVAC temperatures throughout the
space. For example, lower supply
temperatures from CRAC units may
indicate hot spots that should be
identified. When new equipment is
added, the facilities department should
work with the IT department to ensure
that air flow is adequate. This may mean
adjusting fan speeds or moving floor tiles.
Many newer servers can tolerate higher
temperatures than older units, and it is
possible that temperature setpoints can
be raised to reduce energy costs.
Stachowiak: And don’t forget air filter
replacement. The easiest way to do this
is by installing a magnehelic gauge on the
filter. These cost as little as $20 and will
notify you if dirt is causing a pressure
differential across the filter.
BUILDINGS editor Chris Olson talked
with Vice President Bill Younger of
Energy Performance Services and Michael
Stachowiak, Senior Energy Engineer
V, both with CLEAResults, an energy
efficiency consulting firm.
A data center’s first priority is its
high-tech server hardware, yet to
be efficient, operators also need to
focus on facility maintenance. What
is often overlooked?
Stachowiak: A general concern is that
IT and facilities people may be divided
into camps that do not communicate
regularly unless there are problems.
Because each focuses on its part of the
business, they may not be in touch with
each other on shared goals and possible
solutions. Sometimes they even mistrust
How do you remedy that situation?
Stachowiak: Upper management
has a role to play here. Executives
should recognize the cost savings and
performance benefits that are possible
from the two working together and
create a culture where it is expected. The
result can be fewer equipment failures,
increased uptime and capacity, and lower
IT and facility costs.
Younger: Once you solve a problem
that has a benefit to both sides, you often
start changing the culture, one solution
at a time. For example, IT people may
not know that the underfloor plenum is
a big duct. For example, if you help them
to clean up the plenum by removing
unnecessary cabling, and improved
airflow stops an overheating server from
setting off alarms, both sides are happy.
Even though newer data centers usually
have their cables trays overhead, you still
find unused cabling under the floor.
What are the factors involved in
good air flow management?
Stachowiak: Cable management is a
big part of air flow management because
cabling obstructs air flow. Unused or
unorganized cabling under a raised
Don’t Overlook Operational Efficiencies in Your Data Center