ASHRAE Journal - June 2021 - 36
TECHNICAL FEATURE
Data Centers
Where and How Should
PUE Be Improved?
BY NICK CASALE, P.E., ASSOCIATE MEMBER ASHRAE
Power usage effectiveness (PUE) is the overall building power (or energy) divided by
the IT power within the building. This metric for benchmarking efficiency is regularly
used in the data center industry. However, questions persist regarding how it is calculated,
measured and communicated to peers, owners, laypeople and end users. So,
where and how should it be improved? This article proposes a standardized methodology
for how to use PUE for system and component comparisons and for infrastructure
design.
Background
In 2012 ASHRAE Technical Committee 9.9, Mission
Critical Facilities, Data Centers, Technology Spaces
and Electronic Equipment, established Special Project
Committee 90.4 to develop ANSI/ASHRAE Standard
90.4, Energy Standard for Data Centers.1 Originally published
in 2016 and updated in 2019, the standard supplements
existing energy codes with tools and requirements
better suited to data centers.
In 2013 ASHRAE Technical Committee 9.9, in conjunction
with The Green Grid Association, published PUE: A
Comprehensive Examination of the Metric,2 which is part of
the ASHRAE Datacom Series. While this book covers a lot
of information on basis and theory behind PUE and how
it is to be applied, challenges remain in applying the
metric consistently across the many sectors of the data
center industry.
Nick Casale, P.E., is principal at kW Mission Critical Engineering, Troy, N.Y.
36
ASHRAE JOURNAL ashrae.o rg
J U N E 2021
The PUE book serves primarily to benchmark new and
existing facilities, while Standard 90.4 is used to validate
that engineering designs meet baseline efficiencies.
The book focuses on existing facilities and the measurement
of PUE. While this is one application in which
PUE is used, existing facilities are not the only means by
which the metric is applied in common practice:
* Industry professionals use PUE as a means of
validating existing facilities and also as a means of
predicting the theoretical efficiency of new facility
designs.
* Equipment manufacturers often illustrate the efficiencies
of their equipment by using a term designated
by the book as partial power usage effectiveness (pPUE).
Per the definition of partial PUE as described by the
book, this application is often misapplied by the manufacturers.
https://www.ashrae.org/
ASHRAE Journal - June 2021
Table of Contents for the Digital Edition of ASHRAE Journal - June 2021
Contents
ASHRAE Journal - June 2021 - Intro
ASHRAE Journal - June 2021 - Cover1
ASHRAE Journal - June 2021 - Cover2
ASHRAE Journal - June 2021 - 1
ASHRAE Journal - June 2021 - Contents
ASHRAE Journal - June 2021 - 3
ASHRAE Journal - June 2021 - 4
ASHRAE Journal - June 2021 - 5
ASHRAE Journal - June 2021 - 6
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ASHRAE Journal - June 2021 - Cover3
ASHRAE Journal - June 2021 - Cover4
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