Story image

Schneider Electric: Whatcha got under the (data center cooling) hood?

07 Sep 17

Not a typical question you ask in a data center but maybe you should ask that question the next time you’re in the market for a chiller or computer room air conditioner (CRAC). 


Because the compressor is like the engine of the cooling system. It’s kind of like going into a car dealership to buy a car, and not asking what kind of engine it has. 

You may be hauling a heavy trailer, or driving lots of city miles, or not driving much at all. All of these situations call for different engines. 

Like cars, cooling systems use different compressors for different situations. Paul Lin and I recently released a new white paper  titled, The Different Types of Cooling Compressors that discusses these different compressor types.

The paper doesn’t get into the theory of refrigeration or the fine details of how each compressor works. 

But it does provide an overview of each of the main types of compressors you typically see in a data center and a brief explanation of how the compressor works. 

Then for every compressor type, we list their main benefits and limitations, along with the typical applications they best suited for.

If you don’t have time to read the paper, I’ll leave you with some high-level facts about compressor types:

  • There are generally 10 types of compressors, 5 of which are commonly found in data centers.
  • Centrifugal compressors have very high efficiencies, but are best suited for applications over 700 kW.
  • Reciprocating single-acting compressors have the lowest cost / kW but also have the lowest efficiency and most vibration.
  • Variable load compressors, like some digital scroll compressors, don’t vary the speed of the motor, they vary the load while the motor spins at constant speed. Variable speed compressors vary the speed of the motor and are more efficient.
  • Centrifugal compressors can use different energy sources for driving the compression, i.e. electrical motor, steam turbine, or gas turbine.
  • Rotary-scroll, Rotary-vane, and Reciprocating compressors (welded hermetic) provide the smallest capacities. But, some lower-capacity compressors like rotary-scroll can also be used in larger equipment when paralleled to achieve larger capacities, and may only be cost effective up to certain capacity limitations.

I’m in the middle of writing a paper that focuses on the fourth bullet.  This issue, in particular, causes much confusion in the marketplace. 

Simply put, variable loading does not equal variable speed.

Article by Victor Avelar, Schneider Electric Data Center Blog

MulteFire announces industrial IoT network specification
The specification aims to deliver robust wireless network capabilities for Industrial IoT and enterprises.
Google Cloud, Palo Alto Networks extend partnership
Google Cloud and Palo Alto Networks have extended their partnership to include more security features and customer support for all major public clouds.
DigiCert conquers Google's distrust of Symantec certs
“This could have been an extremely disruptive event to online commerce," comments DigiCert CEO John Merrill. 
Schneider Electric's bets for the 2019 data centre industry
From IT and telco merging to the renaissance of liquid cooling, here are the company's top predictions for the year ahead.
China to usurp Europe in becoming AI research world leader
A new study has found China is outpacing Europe and the US in terms of AI research output and growth.
Google says ‘circular economy’ needed for data centres
Google's Sustainability Officer believes major changes are critical in data centres to emulate the cyclical life of nature.
52mil users affected by Google+’s second data breach
Google+ APIs will be shut down within the next 90 days, and the consumer platform will be disabled in April 2019 instead of August 2019 as originally planned.
Ramping up security with next-gen firewalls
The classic firewall lacked the ability to distinguish between different kinds of web traffic.