DC Power Poised To Bring Savings To Datacenters

snydeq writes "InfoWorld's Logan Harbaugh follows up his '10 IT Power-Saving Myths Debunked' to argue in favor of using DC power in the datacenter. The practice — viewed as a somewhat crackpot means for reducing wasteful conversions in the datacenter just a few short years ago — has gained traction to the point where server vendors such as HP, IBM, and Sun are making DC power supplies available in their server wares. Meanwhile, Panduit and other companies are working to bring down another barrier for DC to the datacenter: a standardized 400-VDC connector and cabling solution. And with GE working to list 600-VDC circuit breakers with the Underwriters Labs, DC's promise of reduced conversion waste could soon be commonly realized."

Comments

The arguments of olde

[cosm]

Tesla smiles in his grave as Franklin catches on fire from Nikolai's coil-arcs-of-doom.

Re:The arguments of olde

[Smidge204]

Ere... not sure why "Insightful" since Tesla was the one who invented the AC polyphase distribution system, and would probably not approve of using Edison's (not Franklin's?) DC distribution method.

That said, AC power made a lot more sense before the event of solid state power electronics. You can't reasonably convert DC to DC efficiently without using an AC phase via transformer, which was a major hurdle in using DC power. High frequency power supplies can do the job just fine, though.
=Smidge=

Re:The arguments of olde

[amn108]

Tesla was not discriminating against DC power in general, he was merely certain that it was AC electricity that was the winner for transporting electricity over long distances, to which Edison objected in favour of DC, but Tesla turned out to be right. To my knowledge, Tes;a never objected scientifically to DC being used in wherever else it was due - such as medium and shorter path interconnects and fine electronics where precise voltages were needed.

GE working with DC.

[jellomizer]

Who would have thought the GE would be a big supporter of DC.

Re:GE working with DC.

[bughunter]

GE is what became of the Edison General Electric Company, the losing proponent of DC Municipal Power a century ago.

Battle of the Currents

[Wonko the Sane]

I felt a great disturbance in the Force, as if millions of Tesla fanboys suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened.

What about a _home_ standard for DC power?

[mrchaotica]

I don't run a datacenter, but I sure would like to get rid of the power bricks that all small electronic appliances seem to come with these days!

WTF?

[Shadow Wrought]

I thought the power in D.C. caused waste and ineffeciency.

Re:WTF?

[ivan256]

The article can basically be summed up as follows:

Though there are more transmission losses with DC than with AC, if your DC->AC conversion can be done with an outdoor-rated supply, you save more in cooling by doing the conversion outdoors than you'd lose in transmission losses.

Old hat in the telco world

[Anonymous Coward]

Telco gear tends to be 48VDC all over the place. It just works. Speaking as a guy working at a telco in the IT department, I'm hugely in favor of moving to 48VDC servers.

Re:And Nikola Tesla....

[Farmer Tim]

rolls over in his grave.

If that's because of DC, does it mean he's fitted with a brushless commutator?

48VDC pros/cons (IMHO)

[mlts]

Pros:

No power supply needed for each machine. This removes a major point of failure. Instead, one would need to just step down voltages to the 5 and 12 volt rails. This also helps with cooling because the room AC/DC converter can be cooled with a dedicated system, either liquid, or part of the HVAC system.

Cons:

48 VDC needs a dedicated connector with a high plug/unplug cycle rating that people know is 48 volts and 48 volts only. It sucks when you have to manually wire it up, because this takes time and there is always the risk of getting zapped if you don't throw the right circuit breaker (or pull the right fuse) on a telco rack where 48V is in use.

Because there is only one 48VDC power supply for a room, it has to be held up to a lot more rigorous standards than average mains current. It has to not just provide 48VDC, but provide it under extremely heavy load without the voltage dropping by much.

Maybe 48 volts would be a new computer standard. The key is not having to wire it up manually like some stereo speakers, but giving it a dedicated, foolproof, power connector that Joe Twelvepack who is slurping down his seventh can of Bud Light can easily and reliably plug and unplug while staggering around in the back of the server room until his shift ends.

Re:48VDC pros/cons (IMHO)

[harmic]

As someone else here has already noted - 48VDC power supply distribution has been standard in Telco exchanges since.... forever as far as I know. When I first started working in Telecoms (early 90's) the exchange would have a separate power room with rectifiers and huge battery banks. The resulting 48VDC was distributed through the equipment room using large busbars. In latter years this approach has mostly been replaced with smaller power supplies installed in each suite of racks, but the principle is still the same. It has always seemed somewhat ridiculous to me that one powers one's server by passing 240 or 110 VAC into a UPS, convert it to DC, charge a battery with it, invert it back up to 110/240, feed it into the server, which then converts it back to DC.

The arguments of olde - don't carry much weight

[trolltalk.com]

Alternate view: http://cim.pennnet.com/display_article/347089/27/ARTCL/none/none/1/A-powerful-debate:-AC-vs-DC-distribution/

Or, to summarize - if you take a high-efficiency AC system and convert it to 480 volts, downstep to only 240 volts (and all todays' boxes can run either 110 or 220-240), you can get to within 1% of the DC system.

Add to that the savings in materials (1.5" copper wiring? Booster cables for diesels aren't anywhere near that thickness) and there's no real reason to change.

In fact, the biggest saving would probably be if we went from 120v to 240v for everything. One less down-conversion, etc.

Re:Why not 12V, 6v or 3.3v, etc?

[autocracy]

Power loss over distance. 12 volts loses four times as much energy in one foot of travel as 24 volt transmission does. Telecom gear, for example, runs on 48 volt DC. For the few feet of travel in your laptop, 12 volts is fine. Crossing a room at 12 volts, you'd get too much voltage drop.

See http://en.wikipedia.org/wiki/Electric_power_transmission#Bulk_power_transmission

Transmission efficiency is improved by increasing the voltage using a step-up transformer, which reduces the current in the conductors, while keeping the power transmitted nearly equal to the power input. The reduced current flowing through the conductor reduces the losses in the conductor and since, according to Joule's Law, the losses are proportional to the square of the current, halving the current makes the transmission loss one quarter the original value.

Already on board

[Waffle Iron]

a standardized 400-VDC connector and cabling solution

I set this kind of system up myself and it works great, assuming you need a lot of cores. I strung together 296 Intel Core 2 Duo chips in series accross the 400VDC supply, so each one gets the specified 1.35 volts. If I want to overclock, I just take a set of alligator clips and shunt across a few dozen of the chips, and it boosts the voltage to the remaining CPUs.

The only problem is that with so many chips, I get occasional failures, just like I do with my old Christmas lights. Then I have to try shunting around each of the CPUs by trial and error until I isolate the burnt out one before I can get my cluster running again. Oh yeah, I also have to be really careful to keep any peripherals I plug in away from each other and/or grounded objects.