Two industry giants appear ready to square off on the merits of direct current in the data center. Schneider Electric recently published two white papers analyzing both the benefits of direct current and comparing those results with papers published by The Green.Ch Grid, Lawrence Berkeley, and the Electric Power Research Institute. These papers reported energy efficiency savings ranging from less than 1 percent to more than 28 percent, with Schneider and the Green Grid supporting the lower values.
Schneider Electric vice president, Data Center Global Offer, Kevin Brown 

Schneider’s vice president, Data Center Global Offer, Kevin Brown used LinkedIn as a vehicle to challenge direct current adherents to a debate on the merits, with few responses. Both Schneider white papers can be found on their website and also on the Mission Critical website.

Although official agnostic, ABB’s purchase of Validus makes it the most prominent vendor of direct current technology for data centers. At a March 30, 2012, tour of Switzerland’s Green.Ch data center in Lufpig, a number of ABB executives guessed that the facility could realize as much as 10 percent energy savings compared to conventional alternating current operation. Exact figures are not available; however, Frantz Grüter, Green.Ch’s CEO, publicly stated that he expected energy savings of greater than 20 percent.

The Green.Ch Data Center should make a good test facility for a side-by-side comparison. Grüter, ABB, HP, and the Green.Ch design team developed the colo facility in such a way that it accommodates both ac and dc customers. While Grüter supports the use of dc in data centers, he does not want to alienate potential customers who might be tied to ac or who find dc arguments unpersuasive.

The Green.Ch data center is Grüter’s fourth and largest facility, with the 3300-square meter (sq m) phase one already fully operational. Phases two and three will bring the facility to approximately 10,000 sq m of white space.

The Green.Ch facility’s PUE is 1.4, which is good for a colo, but not overly impressive, as several comparable U.S. developers expect to see PUEs as low as about 1.2. This PUE, combined with the ability to support power densities reaching 20 kilowatt/rack mean that ABB should be able to derive meaningful data by studying the facility.

It is less than clear, though, whether ABB will be able to obtain publishable and verifiable data, though. Grüter is a businessman at heart, and Green.Ch a business. Early customers have been drawn to Green.Ch’s promise of data security and privacy, which Grüter calls the equivalent of the famously secretive Swiss banking industry.

Neil Rasmussen
Neil Rasmussen, Schneider Electric’s senior VP of Innovation

The Schneider white papers make interesting reading, and they are especially effective at rebutting the high end of the energy savings range, with both Brown and Neil Rasmussen, Schneider Electric’s senior VP of Innovation,describing the 28 percent high end as the media misreading a poorly written part of the Lawrence Berkeley report. Much of the purported energy savings in this report can be attributed to poor information about server efficiency and Berkeley’s use of an obsolete UPS in its testing, according to both men.

Schneider’s white paper comparison is interesting and compelling, and its white paper comparing dc to ac operation remains one of the few side-by-side comparisons, especially considering that so few professionals have taken Brown’s challenge.

Brown and Rasmussen are also willing to dispute other benefits claimed by dc adherents, with Rasmussen being especially willing to dispute reliability and safety claims, as he notes that most industry experience with direct current has been in applications where access to electrified equipment is much less and standards much different.

In time, the market will decide this debate, and ABB’s long experience in direct power applications make it a logical developer of dc in data centers. Rasmussen allowed that Schneider would develop a direct current solution if the market demanded it, but the company remains skeptical that direct current will become more than a niche solution.