Practical strategies to manage cooling during power outages

New data centre design trends such as increasing power density, warmer supply temperatures, right-sizing of cooling equipment, and the use of containment, can cause data centre temperatures to rise very quickly during a cooling outage. A new whitepaper from Schneider Electric #179, “Data Center Temperature Rise During a Cooling System Outage”, provides practical strategies to manage cooling during power outages.

While much attention is devoted to data centre cooling system design, most of that effort is aimed at improving the efficiency and reliability of its normal operation under utility power. The lack of attention paid to emergency operating conditions is due partly to a lack of simple tools for data centre designers to predict cooling performance under these conditions. However CFD modeling can make it easy to estimate data centre temperatures following the loss of cooling for various facility architectures, back-up power connectivity choices, and, when applicable, chilled-water (thermal) storage volumes.

IT equipment is typically backed up by UPS’s, uninterruptible power supplies, which supply power until generators come on-line following the loss of utility power to the facility. However, cooling system components such as CRAC or CRAH fans, chilled water pumps, and chillers are typically not connected to UPS’s and may not even be connected to backup generators. Consequently, the data centre supply air temperature may rise quickly following a power failure.

By placing critical cooling equipment on backup power, choosing equipment with shorter restart times, maintaining adequate reserve cooling capacity, and employing thermal storage, power outages can be managed in a predictable manner.