Great Power Debate

The DC power alternative

Data center projects usually translate into big-ticket deals. From the user’s perspective, data centers are hungry beasts that consume massive amounts of energy. One reason for this large energy consumption? Unlike other facilities, they operate 24/7.

The latest debate concerns direct current (DC) powered data centers, which are being compared with the proven alternating current (AC) powered data centers. The basic operating logistics of a data center is AC to DC to AC to DC.

AC is the primary form of electrical transmission supplied by utility company. Then distribution units change that AC flow to DC. The DC then turns back to AC to flow to the servers, which shifts to DC once again to juice up each individual server.

In a pure DC scenario, there is only one conversion from AC to DC, and that is when power flows in from the utility. After that, the data center and its components can run off DC power. One potential benefit of a DC-powered data center is that with fewer conversions, there is inherently less power loss.

According to Energy & Power Management magazine, “Computers and servers equipped with DC power supplies, instead of AC power supplies, produce 20 to 40 percent less heat, reduce power consumption by up to 30 percent, increase server reliability, offer flexibility to installations, and experience decreased maintenance requirements.”

Data centers—as a major potential storehouse of information—remain hot commodities. They are now being addressed in Congress. In July, the U.S. House of Representatives approved a bill requiring the U.S. Environmental Protection Agency (EPA) to study the use of energy-efficient servers that can reduce the power demand of equipment-packed data centers.

The government has caught on to the fact that data centers consume way more energy than originally anticipated, due mainly to faster servers. These same servers provide government agencies and entities with the speed they desperately require.

Relevance measured in gigawatts

Interest is rising in the DC-powered option, and the initiative launched in Silicon Valley in June was one of the biggest moves toward making this solution mainstream.

Pentadyne Power Corp., a commercial manufacturer of clean energy storage systems, using advanced composite flywheel technology, became a participant in a demonstration project at the Sun Microsystems’ campus in Silicon Valley. The basis of the project is to prove that data centers can conserve massive amounts of energy by opting for DC architecture as opposed to AC. This is important given the fact that data centers are notorious for consuming vast amounts of energy to support the servers.

This particular project may draw attention and eventually support from those that are actively involved at this point. The U.S. Department of Energy’s Lawrence Berkeley National Laboratory, the California Energy Commission, Sun Microsystems, Intel, Cisco, Pentadyne and others are all key players in this development initiative.

Achieving energy savings through the DC-powered option is the underlying motivation for this high profile project. The purpose is to illustrate how energy savings at data centers throughout the United States could easily translate into billions of dollars. The prediction is that DC power would, cumulatively, save thousands of gigawatt hours per year.

The findings could prove incredibly relevant. Because of such high numbers in consideration, the translation rate achieved is astounding; the group has noted that one gigawatt hour is enough energy to power more than 60,000 average homes for a year, and therefore, saving thousands of those gigawatts per year can help make a dent in the energy crisis currently affecting the United States.

Getting the gig

Many may not be ready to make the jump to a completely DC-powered data center, and there is a good reason.

In the end, it is not entirely clear who the real winner is in this great AC/DC debate. The heat alone produced by data centers leads many to look for alternate ways to power them, and perhaps the DC option is the way to go. The fact that telecommunications companies have been successfully using DC for many years adds credibility to the DC side of the debate.

Though some data center owners and operators are not quite ready to migrate to DC, many—propelled by the promise of energy savings—are starting to look into it. Rising energy costs alone may convince some to make the switch.

There is no simple answer to which solution is best suited for which situation. Contractors should study the pros and cons of both DC and AC power, so the next time a data center project rolls around, they can be best prepared in the event the DC idea is thrown out on the table.        EC 

STONG-MICHAS, a freelance writer, lives in central Pennsylvania. She can be reached via e-mail at 



About the Author

Jennifer Leah Stong-Michas

Freelance Writer
Jennifer Leah Stong-Michas is a freelance writer who lives in central Pennsylvania.

Stay Informed Join our Newsletter

Having trouble finding time to sit down with the latest issue of
ELECTRICAL CONTRACTOR? Don't worry, we'll come to you.