Editor's Note: This feature is part of a special section on new power paradigms. For more, see the related articles at bottom or go to Power Management DesignLine.
Cars and heavy industry get the headlines, but the pristine IT data center hides an enormous consumer of energy that is rapidly increasing its carbon footprint. Consuming enough energy to power as much as 25,000 to 35,000 homes, these centers are alarming accounting departments and raising the hackles of green activists worldwide.
At the heart of the problem is inefficient power delivery, specifically power conversion, memory leakage, cooling and distribution losses. In recognition of this, the world's top engineers have scrutinized everything from power distribution to server and point-of-load power supplies to minimize power waste. Their work has led to architectural breakthroughs that look to fundamentally change the face of power delivery for decades to come.
Commenting on the problem of efficiency, Stephen Oliver, vice president of marketing and sales at Vicor (Andover, MA), said "For every watt of power used usefully you have to put 2.3W into the building just to get there." Oliver was essentially referring to a metric called power usage effectiveness, or PUE. PUE was defined by an organization of IT professionals called The Green Grid that was formed to promote energy efficiency in data centers. PUE is the ratio of total power used by a data center divided by the IT equipment power.
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The power chain in a typical U.S. data center has two primary obstacles to efficiency: the number of power conversions in the chain and the
The aggregate inefficiency comes as a result of all of the power conversions in a data center and the efficiency of components such as processors, memory and disk drives. For example, a server power supply might offer 90 percent efficiency. That 10 percent of energy that is not used effectively adds to the PUE. Moreover that 10 percent of wasted energy is dissipated as heat. The power required to cool the equipment is also captured in PUE.
Dallas Thornton, division director at the San Diego Supercomputer Center (SDSC) located at the University of California San Diego (UCSD), believes data centers can hit a PUE goal in the 1.3 to 1.4 range. Thornton is currently working on an addition to the SDSC. He states, "Typical data centers today are in the 1.8 range. Inefficient data centers can be over 2."