It’s like Tesla versus Edison all over again. Alternating current (AC) is king today, but when it comes to finding ways to improve data center energy efficiency, some industry experts say direct current (DC) deserves a second look.
Electric power is delivered to businesses, residences, and yes, data centers, in the form of AC. IT infrastructure (servers, networking and storage equipment) all consume power in the form of DC, requiring a conversion. In addition, uninterrupted power supply (UPS) systems take AC power, convert it to DC, and then back to AC before sending it out to compute equipment where each device’s power supply converts it back to DC again. All of these conversions result in energy loss of 10 to 20%, depending on the efficiency of the power systems along the way. “People look at this power loss and say ‘Gee, wouldn’t it be great if we just used DC power instead?’” said John Stanley, a research analyst focused on eco-efficient IT for The 451 Group. For large data centers, those power losses translate into considerable operating expenses.
Delivering DC power with fewer intervening conversions wouldn’t just reduce power loss, it would also result in less waste being given off as heat. In turn, that would translate to less power used to cool IT equipment and drive denser environments.
The DC-powered data center comes alive
People have been talking about DC-powered data centers for years, but some industry observers say the spike in demand for compute services will force data center operators to reconsider DC power.
“It’s not a matter of if, but when, DC becomes relevant in the data center,” said George Slessman, CEO at IO, a provider of modular data centers and colocation facilities. “Everyone that manages a data center should be aware of [DC power] and starting to understand it.”
Indeed, the Web 2.0 data centers of the world are already starting to make the switch to DC power. Facebook OpenCompute server designs, for example, call for DC power supplies. Google, too, advocates minimizing power conversions to improve data center energy efficiency.
For its part, Slessman’s IO is working to make DC power an option for smaller data centers. Working with power infrastructure provider The ABB Group, IO plans to deliver a DC-powered version of its IO Anywhere data center module by the end of the year.
The DC-powered IO modules could be filled with equipment from Hewlett-Packard Co., Dell Inc., Cisco Systems Inc. and others – “a limited but relevant” list of IT equipment providers, Slessman said.
Slessman acknowledged that moving to DC power does require a change in outlook. “There are no deficiencies with DC, but it is different from AC from an operational perspective.” Cabling, for one, is different, as are troubleshooting and break/fix processes, he said.
A 1% solution?
Not everyone in the data center industry is sold on the inevitability – or desirability – of DC power in the data center.
“People complain about triple conversion [of AC], but DC is complex to deploy and is not standardized,” said Hervé Tardy, a vice president and general manager at Eaton Corp., whose data center products include backup UPS and power distribution systems. “Is AC inefficient? Yes. Does it work? Yes. Is it easy to deploy? Yes.”
Tardy said Eaton would monitor data center demand for DC power, likely from energy-conscious “mega” data centers. But overall, he predicted they will be “a niche, limited to a few high-profile cases.”
The 451 Group’s Stanley concurred. “Where DC power makes sense is if you’re building a new data center and it is going to be a homogenized build, with lots and lots of identical servers; it hardly ever makes sense to retrofit,” he said. “When it comes to your everyday, run-of-the-mill data center, with lots of different kinds of equipment, I don’t see a massive switch to DC power.”