News and New Products

Soaring power costs pace power-supply efficiency for servers

By Margery Conner, Technical Editor -- EDN, 2/26/2007

A generation ago, aluminum producers located their smelters close to dams to take advantage of cheap hydroelectric power; now, server farms cozy up to dams for the same reason. Witness Google’s locating its newest facility in The Dalles, OR, on the banks of the Columbia River. Energy costs for datacomm- and telecom-processing centers, where servers may number in the hundreds or even thousands, have skyrocketed: Energy costs outstrip equipment costs over the life of the server. In total 59% of typical data-center power consumption is for power delivery, some of which goes to power-supply inefficiency and air-conditioning power to keep the supplies and servers cool. So, efficiency has become an important factor in selecting power supplies for servers. In addition, overall power density becomes important within server farms. Manufacturers want to cram as many servers as possible into their facilities, and, if the servers' power supplies require massive power-sucking air conditioning, then the overall power density for the facility drops.

This reality is making digital-power supplies viable for servers. Previously, the additional costs of a processor and its attendant firmware development made digital control out of the question for the cutthroat pricing of “silver-box” (closed-frame)-enclosed supplies. With the reality of lifetime power costs making the additional digital-control expenses cost-effective, digital power is also becoming cost-effective because of its ability to react in real time to load fluctuations and to intelligently transmit operating information to the host.

With those factors in mind, power-supply start-up ColdWatt has introduced a digitally controlled family of ac/dc supplies ranging from 650 to 1200W that, the company claims, have efficiencies of 88 to 91% and can reduce power for cooling by more than 40%. The 1+1, 650W, redundant-configuration subsystem fits into a 1U rack, requires 2.15-in. width, and costs $143.51. The 1200W version provides N+1 redundancy with a 90.1% efficiency and power density of 15W/in.³ and costs $265.20.