A relatively new approach to data center cooling known
as a “heat wheel” is gaining momentum, and likely to
gain a higher profile from an upcoming demonstration of the
technology. The heat wheel - also known as a rotary heat exchanger
or Kyoto Cooling - is a refinement of existing approaches that
take advantage of outside air to improve cooling efficiency and
reduce data center power bills.
Proponents of the heat wheel say it improves upon air-side
economization (free cooling), the use of outside air to
cool servers in the data center. Rather than introducing exterior
air directly into the server room, the heat wheel briefly mixes
the outside air and exhaust air to creates an
“air-to-air” heat exchanger.
“The inside heat from the IT room is still removed via the
heat wheel, but there is minimal air transfer between the ambient and
the computer room,” explains Uptime Technology BV of the
Netherlands. “This system has all the benefits of Airside
Economizing, without the exposures of airside economizing like
contamination and humidity control.”
Heat wheels have been used for many years in industrial air
conditioning, but never in data centers. Like air-side
economization, heat wheels could produce significant energy
savings by reducting the need to use power-hungry chillers for air
conditioning.
Uptime Technology has filed a patent application with the European Patent Office on the technology. In 2007 it partnered with Chatsworth Products Inc., joining the heat wheel with Chatsworth’s hot-air containment to produce Kyoto Cooling. The
technology has been implemented by European telecom firm KPN
in one of its CyberCenter data centers in Amersfoort, The Netherlands.
KPN uses the system at outside temperatures of up to 72 degrees
(22 C), and it effectively cools exhaust air of up to 98 degrees.
“In the Netherlands it is possible to cool the CyberCenter for
354 days a year with KyotoCooling, without needing any additional
air-conditioning,” said Max Alias, program manager CyberCenter
Services at KPN. “That provides enormous energy savings. Overall
power consumption in the CyberCenter is reduced by 20 to 30 percent.
The power consumption for cooling is reduced by more than 70 percent.
So it’s not only green, it’s also saving money.”
The Amersfoort CyberCenter will be the site of a series of
seminars December 1-4 in which Kyoto Cooling will be demonstrated.
Representatives of UpTime Technology, Chatsworth and KPN will present,
along with Bob Sullivan of the Uptime Institute in the US.
Sullivan is known for originating the hot aisle-cold
aisle configuration used in most modern data
centers. The Uptime Institute has examined the potential of
the the heat wheel in its discussions of data center
energy efficiency at several of its events, most notably its design
charette in 2007.
While Kyoto Cooling has its proponents, its use is limited to
climates with temperature profiles that would allow the heat
wheel to be used for a substantial part of the year. The
geographic range for heat wheel usage is likely to closely
resemble regions favorable for air-side economization.
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