Making Your Data Center Energy Efficient, One PUE at a Time

After all, if your company doesn't know what data center components waste energy, how can you change it?

By Lex Coors, Vice President Data Center Technology and Engineering Group, Interxion

The statistics say it all: data center greenhouse gas emissions are set to overtake the airline industry in the next five to 10 years, quadrupling by 2020, and data centers can be more than 40 times as energy intensive as conventional office buildings.

As you can imagine, most companies undertaking data center projects are thinking in terms of how to cut costs versus how to help the environment, but they may want to adjust their focus. The Environmental Protection Agency (EPA) has estimated that improving the energy efficiency of America's data centers by only 10 percent would save more than 6 billion kilowatt-hours each year, totaling more than $450 million annually.

Large, centralized, efficient data centers have always been seen as energy hogs, but the problem has accelerated in recent years. Data centers account for about 1.5 percent of total U.S. energy use, currently at a cost of $4.5 billion annually -- an amount that is expected to almost double over the next five years, according to the EPA. Data center designs like Yahoo's chicken coop and Google's chiller-less are some of the more recent groundbreaking developments in efficient data center design for specific use.

Unfortunately, the design does not match all data centers from an availability viewpoint, and because most companies do not have the ability to apply R&D resources, they will need to focus on greening their current data centers rather than building from the ground up.

Understanding PUE -- The First Step to Green

Obtaining a green data center ultimately boils down to design, equipment selection, and operation, all of which measurement is an important part. The first step in this process is to improve a data center's Power Usage Effectiveness (PUE) ratio -- the de facto data center energy efficiency metric. Developed by The Green Grid, PUE is designed to show how much energy is used driving IT and compute components, such as the servers and switches, versus secondary components, such as cooling and lighting. The actual ratio is determined by the relationship between the "Total Facility Energy usage" (TFE) and "IT Equipment Energy usage" (IEE). Although the guidelines provide a compelling framework for achieving a low PUE, companies also need to have an attainable ratio in mind to set as their ultimate goal for data center sustainability.

PUE by the Numbers

According to industry standards, the average PUE is still around 2.5, and an optimal PUE would be the theoretical 1, meaning that the energy usage from the infrastructure is equal to that of the IT usage. Unfortunately, this is not always physically possible, as some infrastructure services, such as cooling, almost always have energy losses -- at least for the time being.

As a rule of thumb, data centers with a PUE of 1.5 can be typically still be considered green or energy efficient as they continue to drive toward the Nirvana of 1. Most new European data centers are deemed efficient, with PUEs between 1.2 and 1.4. (If they are not designed to deliver within this band, most local government agencies will not grant a construction permit.) Achieving these specific PUEs is where data center design and equipment and operational efficiency play a critical role.

Design Efficiency

There are many different data center designs that can lead to better efficiency and green credentials. Modular design, hot/cold aisle separation, and computational fluid-dynamics (CFD) modeling are some of the more well-known. For example, modular design is unique in that it allows for future data center expansion without interruption of services to customers.

Equipment Selection

Research by McKinsey and the Uptime Institute has identified five key steps to achieving operational efficiency gains:

  • Eliminate decommissioned servers, which can lead to an overall gain of 10 - 25 percent
  • Virtualize, which can lead to gains of 25 - 30 percent
  • Upgrade older equipment leading to a 10 - 20 percent gain
  • Reduce demand for new servers, which can also increase efficiency by 10 - 20 percent
  • Introduce greener and more power efficient servers and enable power saving features; this also equates to a 10 - 20 percent gain

By following the above steps, an organization can look to achieve an overall efficiency gain of 65 percent, thereby significantly improving its PUE ratio.

Operational Efficiency

The third and final piece of the efficiency puzzle is in operations. An efficient data center should have hands-on expert support in energy efficiency implementation efforts, as well as best-practice customer installation check lists.

Data center staff needs to know how to safely increase IT equipment inlet temperatures and energy usage though such things as innovative hot and cold aisle designs. To do this, they need to have the tools in place to measure and analyze efficiency, implement the latest efficiency ratings, develop and implement first phase actions, and integrate figures and ratings with corporate social responsibility. Without such expertise in place, companies will find it hard to reach desired efficiency gains.

What's Next?

Energy-efficient data centers are real and achievable, but organizations must work together. Vendors should be providing standard meters on all equipment to measure energy usage versus productivity. After all, if a company doesn't know what data center components waste energy, how can they change it?

It's not just component manufacturers who are responsible. Data center providers should provide leadership for industry standards and ratings that work, data center design and operational efficiency steps, and support for all customer IT efficiency improvements. What is apparent is that the whole industry, from the power suppliers to the rack makers, all need to work together to improve efficiencies and ensure that today's companies are at the forefront of efficient, green data center design.

Lex Coors is vice president for the data center technology and engineering group at Interxion, a company focused on data center colocation and associated managed services with 28 data centers in 11 countries across Europe. You can contact the author at

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