Data-center power glossary

If you thought IT acronyms were hard to remember, wait until you sit down with your facilities team to discuss your data center's electric bill. You need to learn a whole new vocabulary when you start talking about lowering the building's energy use.

Here's a crib sheet of a dozen of the most commonly used energy terms and acronyms so you can learn the jargon for going green.

1. AC/DC

Yes, this is the name of Australia's greatest rock band, but it's also a key trend in data-center design. AC stands for alternating current, and DC stands for direct current. Leading-edge data-center designers are looking at power supplies based on DC power -- rather than today's AC power -- because DC power promises to be more energy efficient.

2. Carbon footprint

No relation to Sasquatch, although to corporate executives it can be an equally large and scary beast. A company's carbon footprint is the amount of CO₂ emissions its operations produce. In setting goals to reduce their carbon footprint, many companies target their data centers because they consume 25% or more of the electric bill.

3. CFD

It sounds like the acronym for the Chicago Fire Department, but this version stands for computational fluid dynamics. CFD high-performance-computing modeling has been used for a long time in the design of airplanes and weapon systems. Now it's being applied to air flow in data centers for optimal air-conditioning design.

4. Chiller

This isn't what you drink at the beach on a hot day. Rather, it's a machine that uses chilled water to cool and dehumidify air in a data center. Of all the components of a data center's air conditioning system, this is the one that consumes the most amount of electricity -- as much as 33% of a data center's power.

5. Close-coupled cooling

This sounds like a technique that would come in handy on Valentine's Day. In fact, it's a type of data-center air-conditioning system that brings the cooling source as close as possible to the high-density computing systems that generate the most heat. Instead of cooling down the entire room, close-coupled cooling systems located in a rack cool the hot air generated by the servers in just that rack.

6. CRAC

This is not what you sometimes see when a plumber bends over, although it's pronounced the same way. We're talking about a computer-room air-conditioning system. CRAC units monitor a data center's temperature, humidity and air flow. They consume around 10% of a data center's power.

7. DCiE

This acronym has nothing to do with the nation's capital, although its pronunciation is similar. DCiE is the Data Center Infrastructure Efficiency metric (also called DCE for Data Center Efficiency). DCiE is one of two reciprocal metrics embraced by The Green Grid industry consortium; the other is Power Usage Effectiveness (PUE, below).(See "Two ways to measure power consumption.") DCiE shows the power used by a data center's IT equipment as a percentage of the total power going into the data center. A DCiE of 50% means that 50% of the total power used by a data center goes to the IT equipment, and the other 50% goes to power and cooling overhead. The larger the DCiE, the better.