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Air Conditioning Equipment & Systems
Economizer Cooling Solutions
Economizer Cooling Solutions for Data Centers, Computer Rooms, and Server Rooms
The data center cooling system is a primary
target for energy efficiency improvements. Emerson Network Power
analyzed data center energy usage and found that cooling systems —
comprised of cooling and air movement equipment — account for 38
percent of energy consumption within this mission critical facility.
Fortunately, cooling system technologies, such as Economizers, exist
that can substantially slash costs from the data center electricity
bill.
Economizer systems can have a significant impact
on energy usage. In many locations, economizers can be used to allow
outside cool air to complement data center cooling systems and
provide “free cooling” during colder months. A study on building
control systems conducted by Battelle Laboratories and reported by
the National Building Controls Information Program, found that on
average the normalized heating and cooling Energy Use Intensity
(EUI) of buildings with economizers was approximately 13 percent
lower than those without economizers1.
When an economizer system is operating, the use
of an air conditioning system’s compressor(s) and related
electro-mechanical components is reduced or eliminated. This reduces
energy consumption.
This data center cooling system incorporates economizers in modular
mixing boxes mounted on top of the computer room handling units.
The two basic types of economizer systems are air economizers and fluid
economizers. While both have the ultimate goal of free cooling, they
possess fundamental differences that impact the environments in
which each is most appropriately used. The air economizer serves as
a control mechanism to regulate the use of outside air for cooling
in a room or building. It admits into the room the appropriate
volume of outside air to satisfy cooling demands. Sensors on the air
economizer measure the outside and inside air conditions. If outside
conditions are suitable for the use of outside air for cooling, the
economizer introduces the outside air for complete or partial
cooling of the space. During the time these conditions exist, the
need for the air conditioning system’s chiller(s)/compressor(s) is
reduced or eliminated, which results in significant energy savings.
Liebert Economizer Solutions
Air economizers are available in two types: a “dry air” system and
an “evaporatively conditioned” air system. The former is the most
common, but its use is restricted to a few geographic locations
because of contamination issues and the high cost of energy required
to add moisture to the room when the outside humidity is too low or
too high. The evaporatively conditioned system is an economical
method for conditioning the air before it comes into the data
center, but reliability issues (mildew concerns and high maintenance
requirements) have generally made this approach unattractive to most
data center operators.
As its name would suggest, a fluid economizer
system is typically incorporated into a chilled water or
glycol-based cooling system. This type of economizer works in
conjunction with a heat rejection loop consisting of a cooling tower
or drycooler to satisfy cooling requirements. With the economizer
operating, the fluid used in the cooling system passes through an
additional heat exchanger/coil, minimizing the need for
chiller/compressor operation.
During colder months, the glycol solution
returning from the outdoor drycoolers or cooling tower feeding the
CRAC units is routed to the second coil, which becomes the primary
source of cooling for the room. As long as the “free cooling” fluid
is 8 degrees Fahrenheit below the air temperature returning to the
CRAC unit, there is some benefit for having the free cooling
running, because it minimizes the load on the primary cooling
method. Similarly in CRAH units, a secondary heat exchanger between
the cooling tower fluid and the chilled water loop takes away part
of the heat from the return water loop and reduces the load on the
chiller.
To learn more about PTS recommended Economizer Cooling Solutions,
contact us or visit (in alphabetical order):
To learn more about PTS consulting services to support Air Conditioning Equipment & Systems deployments and support,
contact us
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1. Battelle Pacific Northwest National Laboratory, 2003. Characterization of Building Controls and Energy Efficiency Options Using Commercial Building Energy Consumption Survey.
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