DC Versus AC Power Debate Continues

The debate over which form of electrical power, DC or AC, is best suited for industrial distribution and use looks set to continue for the foreseeable future.

People who like their utilities with a side of history know that Thomas Edison always thought DC power was safer, more reliable, and easier to manage. But he lost out to Nikola Tesla and George Westinghouse, who pushed the idea – based on the technology and the economies of the day – that AC power could be stepped up and transmitted long distances over relatively thin, inexpensive wires, only to be stepped back down again before use.

Such has been the state of industrial power since the late 1870s. There’s growing interest of late, however, in putting DC power back to work as a primary main source, especially in data and telecommunications centres, where nearly all power is already being converted to DC at the equipment level.

The justification for turning back the clock and revisiting the DC debate is fairly simple. In a current data centre power configuration, you have AC power being transformed, rectified and converted as many as five times before it serves any real purpose. All of those conversions reduce efficiency, generate heat and require expensive equipment that takes up valuable floor space. Up to 30 percent of the power feeding into a typical data centre is wasted as a result of the AC conversion process.

DC systems work by eliminating all of the conversions within the data centre by simply converting the AC main power to 575 VDC or 400 VDC and distributing it throughout the data centre. That power can be delivered directly to some DC-specific IT equipment. For the rest, the DC data centre system steps down the power to 48 VDC, which can be applied to the servers. Proponents claim you get a cleaner, simpler power infrastructure that takes up less space, generates less heat and gives back the 30 percent efficiency hit you take converting and reconverting AC.

The whole concept got a credibility boost last week when GE’s Consumer & Industrial’s electrical division said it would partner with Validus DC Systems, a Brookfield, Connecticut maker of integrated DC power and cooling infrastructure for data centres and telecommunications facilities.

The “strategic alliance agreement” will have the pair developing and marketing a new enterprise-class DC solution that combines protection technologies from GE with the Validus end-to-end power and cooling system.
Validus has put together an interesting little video on the subject.

Here’s what Validus officials say you can get by switching a 2.5 MW data centre with a 2N system, from typical AC to a straight DC system.

• A reduction of 25 percent in overall energy consumption. At .14 per kWh, that equals $3.3 million (£20.2 million) per year in annual savings.
• Use of about 50 percent less real estate in the data centre for power gear.
• Improved reliability (99.9998 percent, they claim) with fewer single points of failure, and markedly less heat.

For customers building new data centres, Validus and GE folks say starting out DC makes even more sense. Initial cost of the electrical distribution equipment is reduced some 50 percent and installation costs are 20 to 40 percent lower depending on site conditions and power density.

It’s a compelling case. But as in the days of Edison and Tesla, the debate rages unabated. Earlier this month, Forbes Magazine asked Schneider Electric’s executive vice president in charge of strategy and innovation, Phillipe DeLorme, if it mattered whether the power coming into a data centre was AC or DC.

“So far there is no solid proof of concept for DC distribution for data centres,” DeLorme said. “We are still a long way from that. The next disruption in the market will not come from that. It will be from the players who are most agile in bringing together expertise in power, white space management, cooling systems, security and so on.”

What do you think? Are you ready to tell clients that it’s a good time to think about a DC power system? Will you consider a DC-only infrastructure for your next new data centre project? And more importantly, was Thomas Edison right all along?

Chris Gonsalves blogs for Channel Insider.