REI found another opportunity to improve cooling under the raised floor. Excess cabling had accumulated in the underfloor space, restricting airflow, but tidying the coils of cable addressed that issue, Myers says.
Data centres such as REI's also maximise cooling efficiency by matching the airflow characteristics of perforated floor tiles to the server racks they cool. The tiles, placed in the cold aisles of a data center, allow air circulating below the raised floor to reach computing equipment. A high-flow tile would be used for a rack with 30 pieces of gear, while a tile with a lower flow rating would be used for a rack with just one device operating. "Only put enough there to meet the load," Stachowiak says. "Nothing else."
The REI retrofit project also considered its power distribution units (PDUs) and uninterruptible power supply (UPS) units. CLEAResult found that the company's PDUs were redundant since the UPSs were equipped with distribution panels. The PDUs were removed. The two remaining UPS units were given a firmware and software upgrade to boost efficiency.
Myers says the multifaceted approach to the data center refit saves REI 2.2 million kilowatt-hours annually. The cooling work, which includes the evaporating cooling tower and other measures such as a hot-aisle/cold-aisle containment curtain, conserves 1.8 million kilowatt-hours, while the PDU/UPS project saves 400,000 kilowatt-hours.
Partnerships Provide Data Center Efficiency Assist
Some data centres are getting an efficiency assist from outside parties. At Dupont Fabros' ACC7 data centre, clients will play a role in the company's improved cooling system. The data center operator will mandate that ACC7 customers use chimney racks or row-based hot aisle containment, Rosenberger notes. (Chimney rack systems vent hot air to the above ceiling plenum. With row containment, server racks are oriented so they direct exhaust into a hot aisle and then into the above ceiling plenum.)
The combination of cooling methods will lead to a low PUE value, according to Rosenberger. He says engineering data suggests an annualized PUE for the facility of 1.13 or lower.
Dupont Fabros, meanwhile, is taking steps to make its cooling greener. Evaporative cooling plants at four data centers on its Northern Virginia campus have been converted to use reclaimed, as opposed to potable, water. The ACC7 facility, scheduled to open in June, will use reclaimed water from the onset, Rosenberger says.
The use of reclaimed water in combination with improved PUE will reduce costs as well as conserve resources. The reclaimed water conversion will reduce the cost of water consumption by 50 to 65 percent. This savings is passed through to the customers, according to DuPont Fabros. "That's an option if reclaimed water exists," Rosenberger says. "It can save the customer money and is also environmentally friendly."
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