An FAQ About Green Data Centers

Are there changes I can make to my power distribution system that will increase efficiency and save money?

Data centers use many uninterruptible power supplies. In fact, when it comes to energy consumption, UPSs are second only to air conditioning systems among components of the data center infrastructure, and they represent one of the biggest areas for potential savings, says Sams. While servers tend to be refreshed every three or four years, data center UPS equipment tends to be much older. The units are often oversized for the load and were never designed to operate efficiently when running at low utilization rates. While older units might run at 70% efficiency at low utilization levels, newer UPSs run at 93% to 97% efficiency even at low utilization levels, Sams says.

Rather than buying traditional UPSs, Terremark Worldwide went with greener technology. It replaced all of its battery-backed UPSs in its Miami data center with rotary UPSs. These use a spinning flywheel to deliver transitional power during the time interval between when power is lost and when generators come online. Stewart says flywheels aren't necessarily more energy-efficient than modern battery-backed UPSs, and the units can be heavy. But they take up less floor space and are greener because there are no lead-acid batteries to dispose of. Today, Terremark's Miami data center fits 6 megawatts of generators and UPS equipment into a 2,000-square-foot room. "To do that with a static UPS, you'd need three to five times the space just for the batteries," Stewart says.

Efficiencies can also be gained in the power distribution system. Most data centers step voltage down several times, from 480 to 208 volts and then to 120 volts. Kelley says you can reduce conversion losses by bringing 480 volts directly to the racks and stepping it down from there. Stewart says he is considering moving Terremark's system to higher European-standard voltage for the same reason. Most IT equipment already supports a 240-volt feed. He expects to see a 4% efficiency gain. "Our power bill is US$400,000 a month, so that adds up pretty quickly," Stewart says.

The best green options will vary with the configuration of each data center. The key to success is to focus on the big picture when assessing overall power and cooling needs, says Gross. "Know what you have, benchmark it, figure out where the low-hanging fruit is, and start one element at a time," he says.