One
of the most exciting and talked about best practices for data center efficiency
is often labeled “free cooling”-the use of Air-side Economizers to dramatically
reduce energy consumption and costs. Air-Side economizers
have become a talking point, it seems, in any current data center cooling
discussion.
What are Air-Side
Economizers?
Mechanical cooling, depending on the source, is estimated to consume anywhere from 33% to 40% of a facility’s incoming electricity. Designed to accompany or circumvent this process, Air-Side economizers can bring nature into the data center whenever the ambient conditions are favorable.
Mechanical cooling, depending on the source, is estimated to consume anywhere from 33% to 40% of a facility’s incoming electricity. Designed to accompany or circumvent this process, Air-Side economizers can bring nature into the data center whenever the ambient conditions are favorable.
The outside air
is brought into building and distributed via a series of dampers and fans. The
servers ingest the cool air, transfer heat, and expel hot air to the room.
Instead of being recirculated and cooled, the exhaust is simply directed
outside. If the outside air is particularly cold, the economizer may mix the
inlet and exhaust air, ensuring that the resulting air temperature falls within
the desired range for the equipment.
The economizer
design is typically integrated into a central air handling system with ducting
for both intake and exhaust. The equipment includes filters to reduce the
amount of particulate matter or contaminants that are brought into the data
center space.
However, air
side economization is possible when the data center is located at a cold place
where cold air are easily available for most of the year. That's the reason
Facebook constructed its data center in Prineville, Oregon where the
company pioneered a design that relies 100 percent on using outside air
to cool its servers. However recently, Facebook constructed data center in
North Carolina where the temperature is not as same as Prineville. But despite
this Facebook has been able
to cool its servers through the North Carolina summer using only fresh air and
no mechanical refrigeration, even on days when the
temperature reached 102 degrees.
But to
how to achieve this was a major question for Facebook.The key to the cooling
breakthrough was raising the temperature inside the Facebook data center,
allowing servers to run at an inlet temperature of 85 degrees F. That’s
about five degrees warmer than Facebook’s data center in Prineville, Oregon,
where the company pioneered a design that relies 100 percent on using
outside air to cool its servers.
July
2012 was the second hottest month on record in North Carolina, with the
temperature hitting 102 degrees on July 1. Surprisingly, the Power Usage
Effectiveness (PUE) for Forest City clocked in at 1.07 versus 1.09
in Prineville during roughly the same period. Despite the record-breaking
heat, they didn’t run the DX coils at all (in North Carolina) in summer.
According to Facebook mechanical engineer Dan Lee, it shows that when the
record hot days occurred, relative humidity was low, allowing the misting
system to provide all the needed cooling.”
