11
Ways to Save Energy in a Data Center
Gartner suggests enterprises can save 1 million kilowatt hours by
implementing 11 best practices in the data center. While cooling
consumes a major chunk of electrical energy in a traditional data
center, “green” ones can save it substantially.
In a
conventional data center, 35% to 50% of the electrical energy consumed
is for cooling versus 15% in best-practice "green" data centers,
according to research firm Gartner.
“Virtually all data centers waste enormous amounts of electricity using
inefficient cooling designs and systems,” said Paul McGuckin, research
vice president at Gartner. “Even in a small data center, this wasted
electricity amounts to more than 1 million kilowatt hours annually that
could be saved with the implementation of some best practices.”
The
overriding reason for the waste in conventional data center cooling is
the unconstrained mixing of cold supply air with hot exhaust air. “This
mixing increases the load on the cooling system and energy used to
provide that cooling, and reduces the efficiency of the cooling system
by reducing the delta-T (the difference between the hot return
temperatures and the cold supply temperature). A high delta-T is a
principle in cooling,” McGuckin said.
Here
are those 11 best practices that Gartner suggests to save millions of
kilowatt hours annually.
Plug
Holes in the Raised Floor —- Most raised-floor environments exhibit
cable holes, conduit holes and other breaches that allow cold air to
escape and mix with hot air. This single low-tech retrofit can save as
much as 10% of the energy used for data center cooling.
Install Blanking Panels — Any unused position in a rack needs to be
covered with a blanking panel to manage airflow in a rack by preventing
the hot air leaving one piece of equipment from entering the cold-air
intake of other equipment in the same rack. When the panels are used
effectively, supply air temperatures are lowered by as much as 22
degrees Fahrenheit, reducing the electricity consumed by fans in the IT
equipment, and potentially alleviating hot spots in the data center.
Coordinate CRAC Units — Older computer room air-conditioning units (CRACs)
operate independently with respect to cooling and dehumidifying the air.
These units should be tied together with newer technologies so that
their efforts are coordinated, or remove humidification responsibilities
from them altogether and place those responsibilities with a newer piece
of technology.
Improve Underfloor Airflow — Older data centers typically have
constrained space underneath the raised floor that is not only used for
the distribution of cold air, but also has served as a place for data
cables and power cables. Many old data centers have accumulated such a
tangle of these cables that airflow is restricted, so the underfloor
should be cleaned out to improve airflow.
Implement Hot Aisles and Cold Aisles — In traditional data centers,
racks were set up in what is sometimes referred to as a "classroom
style," where all the intakes face in a single direction. This
arrangement causes the hot air exhausted from one row to mix with the
cold air being drawn into the adjacent row, thereby increasing the
cold-air-supply temperature in uneven and sometimes unpredictable ways.
Newer rack layout practices instituted in the past 10 years demonstrate
that organizing rows into hot aisles and cold aisles is better at
controlling the flow of air in the data center.
Install Sensors — A small number of individual sensors can be placed
in areas where temperature problems are suspected. Simple sensors store
temperature data that can be manually collected and transferred into a
spreadsheet, where it can be further analyzed. Even this minimal
investment in instrumentation can provide great insight into the
dynamics of possible data center temperature problems, and can provide a
method for analyzing the results of improvements made to data center
cooling.
Implement Cold-Aisle or Hot-Aisle Containment — Once a data center
has been organized around hot aisles and cold aisles, dramatically
improved separation of cold supply air and hot exhaust air through
containment becomes an option. For most users, hot-aisle containment or
cold-aisle containment will have the single largest payback of any of
these energy efficiency best practices.
Raise the Temperature in the Data Center — Many data centers are run
colder than an efficient standard. The American Society of Heating,
Refrigerating, and Air-Conditioning Engineers (ASHRAE) has increased the
top end of allowable supply-side air temperatures from 77 to 80 degrees
Fahrenheit. Not all data centers should be run at the top end of this
temperature range, but a step-by-step increase, even to the 75 to 76
degrees Fahrenheit range, would have a beneficial effect on data center
electrical use.
Install Variable Speed Fans and Pumps — Traditional CRAC and CRAH
units contain fans that run at a single speed. Emerging best practice
suggests that variable speed fans be used whenever possible. A reduction
of 10% in fan speed yields a reduction in the fan's electrical use of
approximately 27%, and a 20% speed reduction yields electrical savings
of approximately 49%.
Exploit “Free Cooling” — "Free cooling" is the general name given to
any technique that cools air without the use of chillers or
refrigeration units. The two most common forms of free cooling are
air-side economization and water-side economization. The amount of free
cooling available depends on the local climate, and ranges from
approximately 100 hours per year to more than 8,000 hours per year.
Design New Data Centers Using Modular Cooling — Traditional
raised-floor-perimeter air distribution systems have long been the
method used to cool data centers. However, the use of modular cooling
(in-row or in-rack) is considered as a more-energy-efficient data center
cooling strategy.
“Although most users will not be able to immediately implement all 11
best practices, all users will find at least three or four that can be
immediately implemented in their current data centers,” said McGuckin.
“Savings in electrical costs of 10-to-30% are achievable through these
most-available techniques.”
