Execs to ASHRAE: Don't Favor Economizers

A proposal to establish fresh air cooling as the preferred method for cooling data centers has unified six of the leading data center operators, who today issued an unusual joint statement opposing the proposal.

Leading executives from Google, Microsoft, Amazon, Digital Realty Trust, DuPont Fabros Technology and Nokia are urging a key HVAC standards body - the Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) - to establish cooling performance-based efficiency goals for data centers, rather than favoring one economizers over methodologies.

The joint statement was published today on Google Public Policy Blog, and signed by six executives who are among the leading voices in the data center industry. They include:

The group said a proposed change to ASHRAE Standard 90.1 "requires data centers to use economizers."  

"We believe that for data centers, where the energy used to perform a function (e.g., cooling) is easily measured, efficiency standards should be performance-based, not prescriptive," the group wrote. "In other words, the standard should set the required efficiency without prescribing the specific technologies to accomplish that goal."

Using outside air economizers to cool data centers – also known as free cooling - allows data center operators to save money by using fresh air to cool server rooms, rather than relying upon chillers that use large amounts of energy. Free cooling typically requires filtering for particulates and careful monitoring of humidity in the data center.

But the ability to use economization is dependent on geography and climate, as the temperature and humidity conditions will determine how many hours a year a data center can use free cooling. That's why induistryu groups like The Green Grid have published tools illustrating the best areas for fresh air cooling.

The issue isn't just location, either. While Google is a pioneer in using economizers (see Google's Chiller-less Data Centers), it is also seeking patents on cooling systems using other approaches.

"In many cases, economizers are a great way to cool a data center (in fact, many of our companies' data centers use them extensively), but simply requiring their use doesn’t guarantee an efficient system, and they may not be the best choice," the joint statement read. "Future cooling methods may achieve the same or better results without the use of economizers altogether. An efficiency standard should not prohibit such innovation.

"Thus, we believe that an overall data center-level cooling system efficiency standard needs to replace the proposed prescriptive approach to allow data center innovation to continue," it continued ."The standard should set an aggressive target for the maximum amount of energy used by a data center for overhead functions like cooling. In fact, a similar approach is already being adopted in the industry."

That referred to a recent agreement between data center consortiums in the U.S., Europe and Japan to establish Power Usage Effectiveness (PUE) as “the industry’s preferred energy efficiency metric.” The PUE metric (PDF) compares a facility’s total power usage to the amount of power used by the IT equipment, revealing how much is lost in distribution and conversion.