PG&E and Altera
Data Center
Energy Efficiency Project
PG&E and Altera:
A History of Energy Efficiency
• After hours cooling project
• Chiller VFD retrofit
• CDA compressor replaced with
VFD CDA compressor
• Data Center Efficiency Project
PG&E and Altera:
A History of Energy Efficiency
VFD CDA
Compressor Retrofit
Project Cost: $110k
ROI: 3 years
PG&E Rebate: $15k
Annual Savings: $32k
After Hours
Cooling Project
Project Cost: $78k
ROI: 1.1 years
PG&E Rebate: $36k
Annual Savings: $39k
Chiller VFD Retrofit
Project Cost: $139k
ROI: 3.8 years
PG&E Rebate: $31k
Annual Savings: $29k
Altera Data Center Energy
Efficiency Project Objectives
• Keep servers between
68° and 77° F (ASHRAE)
• Reduce energy use
• Accommodate server growth
• Increase server and data center
reliability
Data Center Layout
Data Center Before Improvements
Portable AC unit
Two Interests Meet
• Altera had a temporary cooling unit in
place to serve a ‘hot spot’ and was
looking at ways to handle planned
load increases.
• In PG&E’s territory, improving data
center energy efficiency by 15%
would save 100 GWh of electricity –
the equivalent of powering 15,000
homes for a year or taking almost
8,000 cars off the road.
Why is Airflow a
Problem in Data Centers?
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Wasted energy
Wasted money
Less capacity
Less reliability
Why Do These Problems Exist?
In a typical data center…
• Only 40% of AC air is used to cool servers
Robert 'Dr. Bob' Sullivan, Ph.D. Uptime Institute
• HVAC systems are 2.6 times what is actually
needed
Robert 'Dr. Bob' Sullivan, Ph.D. Uptime Institute
• Not a big concern when power density was
low but it continues to grow (about 150w/sqft)
• The culprit: allowing hot and cold air
to mix
First Step:
Assess Current Situation
• Data loggers placed in the inlet
and discharge air streams of each
cooling unit.
• Four loggers placed in each cold aisle.
• Current transformers installed on the
electrical distribution circuits feeding the
two roof-top condensing units.
• Total rack kW load was recorded to
establish baseline.
Findings
• Temperature across cooling units
ranged from 12° to 18°F.
• Temperature variance of up to
14° degrees from one server to
another.
• Approximately 45 kW could be saved
in theory if air flow was ideal
Second Step: Implement
Ideas from Meeting with PG&E
• ALL servers must be in hot/cold
aisles (HACA)
• Blanking plates between servers
• Strip curtains at ends of aisles
• Remove perforated tiles from
hot aisles
• Partitions above racks
Third Step:
Altera Adopts Changes
• APC in-row coolers installed
• Temporary cooling unit removed
• Blanking plates added
• Installed strip curtains to separate the
computing racks from the telecom area
• Shutting off CRAC unit
Addition of APC IRCs’
Simple changes, big benefits
Simple Changes, big benefit
Final Measurement and Review
• Even after Altera made all of these
changes, excess cooling capacity
still existed.
• PG&E recommended shutting down a
second CRAC unit, thus putting all
primary cooling on chilled water units.
Altera’s New and
Improved Data Center
• Temporary mobile cooling unit gone
• Two CRAC units shut off
• Server temperature variance a
mere 2° F
• Net electricity reduction of 44.9 kW
• Annual energy savings of 392.9 MWh
• Overall energy savings: 25%
Moral of the Story?
• Improving airflow is a safe and
sensible strategy to simultaneously
make data centers greener, more
reliable, higher capacity, and more
economical to operate.
• To achieve results such as Altera’s, it
takes teamwork between IT, Facilities,
HVAC experts, and PG&E.