Introduction An ever increasing amount of data is being created, stored and served every day. Social networking, online videos, IoT devices, and automobile advanced driver-assistance systems (ADASs) are among the major contributors of this data onslaught. Referring to ADASs, for…

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U.S. data centers consume about 100 billion kilowatt-hours of electricity, representing more than 2% of all U.S. electricity use according to U.S. Department of Energy (DOE) estimates. With the data explosion apparent in cloud computing, the Internet of Things, digital recordkeeping and the like expected to continue to increase for the foreseeable future, we need a revolutionary change in how data centers consume energy and achieve greater efficiencies.

Clearly there is a need for the DOE’s Better Buildings initiative in which data centers partner with the agency to commit to reducing their energy consumption. The agency’s two programs include the Better Buildings Challenge, which requires a commitment from organizations to reduce their total data center energy consumption by 20% within 10 years, and the Better Buildings Data Center Efficiency Accelerator, in which an organization commits to reduce the energy consumption of one or more data centers by 25% within five years.

Central to this program is improving the efficiency of data center infrastructure, which uses at least as much power as the data processing, networking and storage equipment. Of the energy required for the infrastructure, cooling the building accounts for a vast majority. According the DOE, data center infrastructure energy efficiency can be improved 20% to 40% by applying “best management” energy-efficiency measures and strategies, typically with short returns on investment payback. Common upgrades include managing cool airflow to the servers, optimizing cooling systems and supplying air to the servers within the ranges recommended by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).

Power Usage Effectiveness in Data Centers

With nearly three million data centers in the United States, the DOE is encouraging these facilities to monitor and measure power usage effectiveness (PUE), which is calculated by dividing the energy consumption of the data center by the energy consumption of the IT equipment. Currently, the average PUE is roughly 2.0 for most data centers in the U.S.

But saving energy is about more than just “being green.” Making data centers more energy efficient will go a long way in meeting the ever-growing demand for increased computing and data-storage capacity. In the fight for scarce dollars, investing in valuable computing capacity will have a greater impact than throwing money at wasted energy consumption.

Conflicting Priorities

Often, conflict exists between IT, facilities and the financial decision-makers in an organization—simply because of the inherent conflicts in their job-related objectives as well as divergent opinions about the data center decision process.

“If your data center strategy is not aligned with your company goals, we send in a business consultant first to help get IT out from the closet and into the boardroom,” said Per Brashers, founder of Yttibrium, a consultancy focused on big-data infrastructure solutions. “IT is an asset that needs a business champion to get the most value from your infrastructure investment.”

Obviously, risk aversion is a big factor in operating a data center. Even though the server manufacturer might warrant its equipment at server-inlet temperatures exceeding 100°F, it would be difficult to convince a data center operator to raise cold-aisle temperatures even as high as 80°F.

Innovations in Data Center Cooling Systems

ASHRAE has proposed that data centers operate at elevated server-inlet temperatures, with a goal of encouraging the use of outside air and evaporative cooling as the most efficient means of air-based cooling.

Direct evaporative cooling consumes 70% less energy than traditional air conditioning, but that level of energy savings does come with the drawback of higher relative humidity. Reports indicate that some of the biggest data center operators, including Facebook, use direct evaporative cooling.

The alternative, indirect evaporative cooling, will reduce the temperature without adding moisture. Used by Google and Amazon, the indirect method is slightly less efficient than the direct method, but it still consumes a fraction of the energy of a typical compressor-bearing cooling system.

coolingFigure 1: In indirect and indirect/direct evaporative cooling systems, heat is absorbed from warmer air by water, lowering air temperature and increasing its relative humidity.

An even more advanced system uses a mixture of direct and indirect evaporative cooling, combined with advanced monitoring and controls. For example, an indirect/direct evaporative cooling system such as Aztec, manufactured by Dallas-based Mestex, will use about a third of the energy of a similar-size air-cooled rooftop unit or chiller system. Going a step further to employ outside air for cooling can reduce the energy use to less than a quarter of what conventional systems require.

Progressive companies that have already deployed these technologies can regularly and justifiably claim PUEs of under 1.1—a sharp contrast to the average performance measure (2.0) of U.S. data centers. “A watt costs about $1.90 per year including taxes,” said Brashers. “For example a 1 megawatt facility with a PUE of 1.90 spends more than $1 million on waste energy, whereas a facility with a PUE of 1.07 spends $148,000 on waste energy.”

Flexible, Scalable, Energy-Saving Options

“Modular data centers are emerging as an alternative to the traditional brick and mortar data center,” according to a June 2015 report from the research agency Markets and Markets. According to the report, the market for modular data centers—a set of various pre-engineered custom modules including IT, power, cooling and generators—is expected to triple (to $35 billion) by 2020.

HVAC units designed to be “plug and play,” provide an economical way for data centers add cooling capacity as they add computing capacity. The scalability of this type of HVAC system helps eliminate overprovisioning and wasted energy costs associated with having more cooling capacity than is needed.

The Bottom Line

Indirect/direct evaporative cooling systems, which can harness cooler outside air to support indoor cooling, are proven to reduce power consumption compared with traditional air conditioning (including last-generation computer room air conditioning units, or CRACs). The system’s digital controls, when integrated with other building automation systems, can extend the savings even further.

“For the foreseeable future, HVAC purchasing decisions will be based on the ability to reduce energy consumption and costs,” said Per Brashers. Current best practices for energy efficiency in data centers include energy-saving HVAC technologies (for new or retrofitting cooling equipment) that provide the following:

  • High-performance air-handling efficiencies using direct-drive plenum fans with variable-frequency-drive (VFD) controls that reduce energy consumption when equipment is operating at part load, which is typically more than 95% of the time.
  • Refrigerant-free evaporative cooling technology, which is proven to reduce power usage by up to 70% compared with traditional air conditioning.
  • Direct digital controls that help monitor and adjust HVAC systems for comfort, costs and energy efficiency (including PUE). These controls should be accessible remotely 24/7 through a web interface, as well as locally via a new equipment- or wall-mounted digital dashboards

By employing best practices, such as those described here, a growing number of highly efficient data centers—particularly those of the bigger players, such as Amazon, Facebook and Google—that have taken energy-saving measures. But with three million data centers in the U.S., there is even greater opportunity to achieve energy efficiency and save on operating costs at the small- and midsize level—where scalable, plug-and-play HVAC can provide an affordable option for indirect/direct evaporative cooling—for retrofits, “build as you grow” modular data centers and new construction.

Leading article image courtesy of Paul Hartzog under a Creative Commons license

About the Author

data centerMichael Kaler is president of Mestex. Mestex, a division of Mestek, Inc., is a group of HVAC manufacturers with a focus on air handling and a passion for innovation. Mestex is the only HVAC manufacturer offering industry-standard direct digital controls on virtually all of its products, including Aztec evaporative cooling systems—which are especially suited for data center use—as well as Applied Air, Alton, Koldwave, Temprite and LJ Wing HVAC systems. The company is a pioneer in evaporative cooling and has led industry innovation in evaporative cooling technology for more than 40 years.


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