Digital Realty Saves Water with Innovative Cooling Technology

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Reducing water use in the data centers has led to a new type of free-cooling system: one that uses pumped-refrigerant economization and consumes no water.

Digital Realty, which supports the data center and colocation strategies of more than 1,000 firms around the world, has turned to this technology to save more than 300 million gallons of water annually in its data centers, compared with using chilled-water systems. Specifically, it is installing Liebert DSE free-cooling systems from Emerson Network Power.

“Digital Realty, along with certain major technology companies and other pioneers, is showing that clean energy can power even the largest and most high-performance data centers,” the company said in a recent white paper. “And as more organizations consider moving from traditional to cleaner sources of power, they are also showing that renewable energy can be cost-effective.”

California Trending

In 2012, when Emerson Network Power first proposed its Liebert DSE pumped-refrigerant economization systems to Digital Realty, only air and water coolants were approved in California for data center economization.

The California Energy Commission’s Title 24 required that air-side economization systems be capable of carrying 100 percent of the IT head load when outside temperatures were at or below 55°F. Water-side economization systems were required to carry 100 percent of the IT heat load at temperatures of 40°F or lower.

But Digital Realty and Emerson collaborated in 2015 to gain the approval of the California Energy Commission (CEC) for pumped-refrigerant economization as a prescribed option for data center cooling in California.

As described in a recent joint case study, this ruling paves the way for companies in that state to more easily deploy the energy- and water-saving data center technology.

Designed for efficiency

The Liebert DSE system has several components: a pumped refrigerant economizer, a highly efficient microchannel condenser and an indoor CRAC unit. It maximizes annual energy savings and provides superior availability without the need for separate economization coils.

When outdoor ambient temperatures are low enough, an integrated refrigerant pump circulates refrigerant in lieu of the compressor to maintain the desired supply-air temperature. The refrigerant pump uses a faction of the energy used by the compressor.

As outdoor ambient temperatures rise, the Liebert DSE system automatically switches on compressors to maintain the desired supply-air temperature. Its thermal controls work to automatically optimize the entire system to provide more free cooling throughout the year.

Changeover between compressor mode and the refrigerant economizer mode is almost instantaneous, whereas traditional economizer systems typically operate in economizer mode only when the economizer season is stable—not changing back and forth during the night, for example.

These advanced thermal controls also enhance cooling-unit operation and availability by protecting units from adverse events, with automated routines for unit protection, fast restart, unit cascading and contaminant removal.

The unit control communicates alerts; auto-tunes important operating parameters, such as fan speed, compressor utilization and economization; and prevents cooling units from exceeding critical thresholds.

In addition to the water savings, this approach offers other advantages:

  • No costly water treatment required
  • No outside-air contamination in the data center
  • No dampers or louvers to maintain
  • Instant, automatic economizer changeover to increase free-cooling hours

Read full article at: Data Center Journal

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