Putting your data center on an energy diet

Computerworld - Sal Azzaro, director of facilities for Time Warner Cable Inc., is trying to cram additional power into prime real estate at the company's 22 facilities in New York.

"Its gone wild," says Azzaro "Where we had 20-amp circuits before, we now have 60-amp circuits." And, he says, "there is a much greater need now for a higher level of redundancy and a higher level of fail-safe than ever before."

If Time Warner Cable's network loses power, not only do televisions go black, but businesses can't operate and customers can't communicate over the company's voice-over-IP and broadband connections.

When it comes to the power crunch, Time Warner Cable is in good company. In February, Jonathan Koomey, a staff scientist at Lawrence Berkeley National Laboratory and a consulting professor at Stanford University, published a study showing that in 2005, organizations worldwide spent $7.2 billion to provide their servers and associated cooling and auxiliary equipment with 120 billion kilowatt-hours of electricity. This was double the power used in 2001.

According to Koomey, the growth is occurring among volume servers (those that cost less than $25,000 per unit), with the aggregate power consumption of midrange ($25,000 to $500,000 per unit) and high-end (over $500,000) servers remaining relatively constant.

One way Time Warner Cable is working on this problem is by installing more modular power gear that scales as its needs grow. Oversized power supplies, power distribution units (PDU) and uninterruptible power supplies (UPS) tie up capital funds, are inefficient and generate excess heat. Time Warner Cable has started using Liebert Corp.'s new NX modular UPS system, which scales in 20-kilowatt increments, to replace some of its older units.

"The question was how to go forward and rebuild your infrastructures when you have a limited amount of space," Azzaro says.

With the NX units, instead of setting up two large UPSs, he set up five modules -- three live and the other two on hot standby. That way, any two of the five modules could fail or be shut down for service and the system would still operate at 100% load.

Other approaches

Some users are trying innovative approaches. One new way of approaching the power issue is a technique called combined heat and power, or cogeneration, which combines a generator with a specialized chiller that turns the exhausted waste heat into a source of chilled water. (See related story.)

Another new approach is to build data centers that operate off DC rather than AC power. In a typical data center, the UPSs convert the AC power coming from the utility's main power supply into DC power, then back into AC again. Then the server power supplies again convert the power to DC for use within the server.