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

Chiller VFD Retrofit

Project Cost: $139k ROI: 3.8 yearsPG&E Rebate: $31k Annual Savings: $29k

Project Cost: $110kROI: 3 yearsPG&E Rebate: $15k Annual Savings: $32k

Project Cost: $78k ROI: 1.1 yearsPG&E Rebate: $36k Annual Savings: $39k

After Hours Cooling Project

VFD CDA Compressor Retrofit

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?• 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.