Target “expects more and pays less” for its data centers.
By Steve Ryan, Robert Huang & Allison Bard
Data centers use 2% of the nation’s electricity. For a number of years, EPA ENERGY STAR has focused on providing companies with tools to gain a better understanding of the efficiency of their data center. For example, EPA’s building energy efficiency tool, Portfolio Manager, allows a company to compare its data center’s efficiency with hundreds of other data centers from across the country. Data centers that fall within the top 25% earn ENERGY STAR certification. Target, one of the largest retailers in the United States, was kind enough to share information on:
• The specific retrofit measures undertaken that led to ENERGY STAR certification; and
• The importance of Target’s commitment to sustainability to its data center efficiency efforts.
Target’s Commitment to Energy Efficiency
Target’s data centers are a critical part of the company’s business and infrastructure. As with many mission-critical data centers, improving its energy efficiency is not always the highest priority. Ted Hight, Target’s lead engineering consultant, said Target’s early efficiency efforts included “basic blocking and tackling, which involved creating hot and cold aisles, blanking plates in racks, and blocking holes in tiles under the racks.”
As a part of its commitment to sustainability, Target set a goal of increasing its percentage of ENERGY STAR-certified buildings from 9% in 2009 to 75% in 2016.1 To help meet its environmental goals and improve data center operations, Target’s technology center engineering team conducted a series of cost-effective energy-efficiency upgrades on two 45,000-square-foot2 data centers in Minnesota: Target’s Brooklyn Park facility, which was built in 2001, and its Elk River facility, which was built in 2007.
Scott Hovet, data center engineer, described the shift in attitude: “Our team developed a passion for managing our cooling technologies as mission-critical delivery, not settling for simple cooling of our IT infrastructure. Therefore, energy efficiency became a byproduct of precise technology management, which led us to perform an efficiency audit on the entire data center.”
As a result of the efficiency upgrades, Target was the first company to have two data centers earn the ENERGY STAR building certification and was named an EPA ENERGY STAR Low Carbon IT Champion in 2012. (Please visit www.energystar.gov/lowcarbonit to learn more.)
Data Center Efficiency Measures
The Brooklyn Park and Elk River data centers house 3.4 MW of IT load (enough power for 3,400 homes) to power more than 6,900 computing devices. Target’s efficiency audit determined which retrofits provided the best return on investment. With the assistance of its trade allies, a mechanical engineering firm, and incentives from Xcel Energy, Target took the following actions:
• Installed variable frequency drives (VFDs) on computer room air handlers (CRAHs), air handling units (AHUs) and exhaust fans: VFDs allow fans to run at lower speeds by controlling the frequency of the electrical power supplied to the fan motor. Fan power consumption is proportional to the cube of fan speed, so a decrease in fan speed can lead to extraordinary reductions in fan energy use.
• Reduced temperatures on generator heaters: Standby generators are typically specified with jacket and oil warmers that use electricity to maintain the system in standby mode at all times. The temperature of the generator heaters could be lowered from 140 to 110 degrees Fahrenheit because each was located within conditioned space.
• Installed timers and efficient lighting: Timers were installed to turn lights on at 6:00 a.m. and off at 4:30 p.m. Inefficient lighting was replaced with efficient lighting throughout the building (e.g., conversion of T-12s to T-8s, high-beam metal halides to high-output T-8s).
• Turned off unloaded transformers: Two unloaded power distribution units (PDUs) were taken offline at the Elk River data facility, where the computing load was not yet completely built out.
Results
Target’s data center retrofits led to more than 5.8 million kWh annually (over $500,000 in savings) and, on average, paid back in 1.4 years, including utility rebates.3 The installation of VFDs accounted for 79% of the savings realized by the efficiency upgrades. The annual carbon emission reduction achieved through these efforts is the equivalent of taking 800 cars off the road.
These measures led to 25% overall power savings on the mechanical loads. The ENERGY STAR rating system scored the Brooklyn Park data center with a 91 in 2012. This means the data center was more efficient than 91% of the data centers in the United States. The Elk River data center received the same upgrades but was not completely built out at the time of the scoring. It received a 77 in 2012.
Lessons Learned
• Top-down commitment is needed. A key to this effort’s success was that Target’s leadership was open to new ideas and concepts. Senior executives understood that data center energy-efficiency improvements aligned with Target’s sustainability and energy-saving goals and, therefore, encouraged integration of these initiatives and options throughout Target’s business model (e.g. Target’s goal of having 75% of its buildings ENERGY STAR qualified by 2016).
• Data center efficiency does not necessitate large expenditures on new equipment. Target was able to realize significant savings by retiring two unloaded transformers and lowering the jacket heater temperature settings on generators. These two efforts did not require any up-front costs.
• With a redundant system, VFD savings can be huge. Target was able to take advantage of the savings potential of VFDs due to its redundant systems. In the past, single-speed, redundant exhaust fans and AHUs were rotated on a weekly basis. By using the two redundant, variable-speed fans simultaneously — at significantly lower speeds — to accomplish the same job, enormous savings were realized. RFB
1 Learn more about Target’s sustainability commitment: http://hereforgood.target.com/learn-more/goals-and-progress
2 The data center has 45,000 square feet of white space. Other areas of the buildings are devoted to electrical/mechanical plant, storage and office space.
3 Also, since this analysis was completed, Target has installed chimneys on the cooling units, and all new CRAHs installed will be controlled by supply-side air monitoring.
— Steve Ryan is a program manager with EPA ENERGY STAR; he has managed the promotion of ENERGY STAR green IT efforts for over a decade. Robert Huang is a senior associate for The Cadmus Group, Inc., technical contractor to EPA ENERGY STAR. Allison Bard is an associate with The Cadmus Group, which is responsible for managing the EPA ENERGY STAR® Low Carbon IT campaign, which promotes energy efficiency in the green IT space.