DC-power Sparks Interest among Data Center Designers

Rising data center power and cooling costs have renewed industry interest in DC-power, but is DC really a cure-all or just more snake oil?

Up until this point, DC-power hasn’t been very attractive for a number of reasons. The large amount of copper wiring required for DC-power distribution is expensive and takes up valuable space in the data center. DC-engineered facilities are also more complicated to install and maintain, creating headaches that most data center professionals don’t want or need.

However, tech industry leaders, such as Sun Microsystems and Intel, are paying attention to DC-power. They know data centers are desperate to cut power and cooling costs and are banking that many larger data centers can afford the upfront investment in DC-engineered facilities.

This summer, more than 20 tech companies teamed up with the Department of Energy’s Lawrence Berkeley National Laboratory to run a side-by-side demonstration of a conventional AC-powered rack of servers next to a DC-powered rack. The hope was that DC might prove to be the cheaper, cooler-running, and more reliable data center power option.

AC vs. DC

Could DC-power have finally come of age? According to a whitepaper by American Power Conversion Corp., one of our trusted data center vendors, AC-power and DC-power should be compared based on efficiency, cost, compatibility and reliability. Let’s use this as our guide for comparison.

Efficiency:
DC-power is often touted as being more efficient than AC-power because it requires fewer power conversions that can result in power losses. On the surface this makes sense, but it doesn’t take into consideration that DC cabling must be greatly oversized to deliver the same power. You end up trading increased infrastructure costs and a loss of space for a relatively minor gain in data center efficiency.

Cost:
There isn’t a real cost advantage to making the switch to DC, even though DC-power might lower your overall energy costs. As I mentioned earlier, DC-power requires more extensive infrastructure and engineering. There’s a higher upfront cost which offsets most long-term savings.

Compatibility:
This one is a toss-up as well. Compatibility with AC- or DC-power supplies is determined largely by the type of equipment your facility uses. Keep in mind, though, that it is difficult to obtain DC versions of many pieces of equipment. If your data center uses a mix of AC and DC products, it’s probably a wise decision to go with AC-power.

Reliability:
For the most part, reliability is controlled by battery system rather than the type of power used. When compared with an equivalent DC-powered system, AC-power is just as reliable for data center use.

PTS’ Perspective

The use of DC-power in the data center isn’t common – and with good reason. There is no clear benefit to switching from AC- to DC-power, but there are quite a few drawbacks. Rising energy costs are enough to make companies reevaluate the concept, but AC will remain the dominant choice for data center power in the foreseeable future.