There has been much to do of late about direct current (DC) data centers. I find this debate very interesting because it is almost reaching the fervor of the discussions that occurred between Thomas Edison and George Westinghouse in the late 1800s. Additionally, if nothing else, this proves that history does indeed come full circle, or at least comes in repeatable waves. Instead of deciding whether or not to place an Edison power station on every street corner or to have one large alternating current (AC) distribution system, today's AC vs. DC colloquies center on whether to leave the AC to DC power conversion in the hands of a server's power supply unit (PSU) or move that function to the rack or even a dedicated transformer room.
The discussions seem to focus on the following points. I have not organized them into pros and cons because what is a pro for one decision may be a con for another. These talking points are simply what people bring up when they find themselves in the midst of a AC vs. DC debate:
- Removing the PSU from servers and doing a single conversion at the rack or in a dedicated transformer room would reduce the server room's heat output and in turn reducing the amount of cooling needed.
- Reducing the AC to DC conversion points reduces the heat loss in conversion, increasing the overall power efficiency of a data center.
- The TelCo industry has been using DC for years.
- The TelCo industry is looking at moving away from DC power.
- High efficiency AC is almost as efficient as DC.
- It may be hard to find electricians qualified for or who want to work with the amount of DC voltage necessary for a data center server room.
- The cost of retrofitting an existing data center, or the costs associated with building a new DC data center may negate the short-term, and perhaps long-term, efficiency benefits of a DC data center.
These are just some of the topics that engineers and operations managers are considering with regards to AC vs. DC. I have not made my mind up yet on the subject, and I am not necessarily sure there is a black and white answer. Very often the best solution for one problem is not the perfect solution for another. That is why despite the success of Tesla's alternating current, one can still find evidence of Edison's direct approach in the current day. Below is a list of articles that go into further detail on the subject:
War of Currents
Power-saving technologies in the data center http://searchdatacenter.techtarget.com/originalContent/0,289142,sid80_gci1144396,00.html
Engineers: DC Power Saves Data Center Dough
DC power worries data center planner
Can DC Power Cut Data Center Costs?
What's cool about DC-powered data centers
Before I go, we would love to hear your thoughts on the subject. Please feel free to post comments or e-mail me directly. The Burton Group looks forward to hearing from you!
posted by: Andrew Kutz