Conspiracy Theories and Facts: AC versus DC update

I thought it might be worthwhile to give an update regarding the ongoing debate of AC versus DC in data centers since I posted my last blog on January 30th. (recap video embedded below)

Apparently, my pithy analogies and sarcastic comments aren’t appreciated by everyone.  My blog seemed to have created a buzz, and some interesting ‘hate’ mail followed.

Some of the hate mail seemed to border on conspiracy theory – that I had some ability to ‘keep DC down’ in order to prop up our AC business.  Wow… if I have that kind of power I definitely deserve a raise – I’m calling my boss right after this blog posts.

However, I still have yet to see anyone seriously challenge the analysis we put forward regarding the potential efficiency differences between AC and DC.  And by “seriously challenge” I mean a well thought out analysis that points to flaws in our paper.

Our position is that these other studies that purport anywhere from 8%-28% increase in efficiency by utilizing DC are flawed.  We have documented in white paper #151 why we think they are flawed.  If you want to read that white paper it is freely available on our web site.

Since January 30th we also updated our white paper #127 (also freely available) with some new data.   Here’s one of the conclusions of the paper:

“Use of DC instead of AC causes a reduction in total energy consumption of less than 1%. If the UPS uses eco-mode, use of DC actually increases total energy consumption.”  (I added the emphasis).

Our argument is that AC technology has evolved and become much more efficient, such that the difference between DC and AC is now negligible.  Any analysis should compare the current and best AC architecture against the best DC architecture.  This approach seems to make to sense.

What’s interesting to me is that subsequent to my January 30th blog I read an article in January/February 2012 edition Mission Critical, “The Time has Come for 380Vdc”.  This article states that there is “…improvement between 8 and 15 percent….” when using 380Vdc, but I’m not sure how or where the author drew that conclusion.

He then goes on to discuss his use of Kaizen to continuously improve and that DC is one of the technologies they are using as a result of that process.

If he is believer in Kaizen, and if our analysis is correct, maybe he should consider an AC architecture at higher voltages as we outline in our white paper.  Maybe he should consider utilizing AC with a UPS running in eco-mode.  Or, better yet, can he provide some documentation if he believes our analysis to be flawed?

I ask the DC proponents to challenge our analysis and tell me where it’s flawed.  I will restate what I have stated in the past – I am sure there will be DC architected data centers in the future, but they shouldn’t be done in the belief of achieving huge efficiency gains.

Bring on the challenges to our analysis – I think we have the facts.

If you missed the first blog I wrote about AC vs. DC take a moment to watch this video, it will get you up to speed.

About Kevin Brown:

Kevin Brown is Senior Vice President of Innovation and Chief Technology Officer for the €3.7 billion IT Division at Schneider Electric. In this role, he is responsible for driving innovation and managing the R&D portfolio for the IT Division as well as driving the overall Schneider Electric portfolio strategy for the Data Center market. Prior to this position Kevin served as Vice President, Data Center Global Strategy and Technology. Kevin has also held numerous senior management roles in product development, engineering, and software development in the power electronics and HVAC industries. He holds a Bachelor’s of Science in Mechanical Engineering from Cornell University.


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