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

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.

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

[olddotter]

I'm not an EE. But back during the dotboom I thought it would make sense to have a big ups in the data center that output voltages that mother boards expected as input. I almost thought of rigging my own experiment using laptops as servers and feeding them all 12vdc directly from the UPS battery pack.

Ok rip it apart guys, why is wrong with that plan?

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.

Re:What about a _home_ standard for DC power?

[bughunter]

Agreed. My PC and media installations are plagued by a plethora of these heat-generating devices, as I add on printers, ethernet devices, networked disks, extra storage, converters, encoders, decoders, and the like. I had to learn to include plans for a well-ventilated place for these things.

Also, it's an inherently good idea for power savings. Power supply efficiency can go way up when both a) total power goes up and b) the supply can be designed for a constant load (which would be the case for a large data center, for sure).

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:The arguments of olde - don't carry much weight

[wsanders]

You can achieve substantial savings just by wiring your datacenter for 240V only (in the US). The rest of the world knows this already, but every time I suggest this in the US, people look at me like I have monkeys flying out my nose. Half as many amps == half as many power strips, half as many UPS devices, half as much wire, etc. With the exception of cheap-ass wall wart powered devices, I have not encountered any equipment that was not 240V compatible in the US in years.

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:What about a _home_ standard for DC power?

[WorthlessProgrammer]

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!

probably because these 'wall-warts' are linear converters - seldom better than 40% eff.

As more stuff conforms to the ENERGY INDEPENDENCE AND SECURITY ACT OF 2007, these will become much less of an issue.

IIRC there was a UPS study on DC power recently

[petermgreen]

That concluded that using the european system of 230/400 3 phase AC for distribution splitting out to 230V single phase AC near the point of use was almost as efficiant as a 400V DC system and far cheaper and easier to deploy. Your servers existing power supplies can almost certinaly handle 230V without any problems (changing a switch may be required on crappier models)

BTW in many cases there are often huge savings to be made without changing your infrastructure just by using better PSUs, cheapasss PSUs are both inefficiant and unreliable.

Re:The arguments of olde

[hardburn]

I think Tesla would be just fine with DC power if he saw what we're using it for today. Back then, there wasn't much stuff that cared which way the current flowed. Lights and electric heaters work fine either way, and motors are more efficient on AC, as is any power source that depends on spinning a generator (almost everything besides solar cells). But once you start throwing diode junctions and electrolytic capacitors into the mix, things change.

Re:What about a _home_ standard for DC power?

[zippthorne]

There is one already: USB power. Fairly low current, but a host of consumer devices from bluetooth headsets to GPS devices to iPods use it as their standard charging source.

It's a little awkward because there are more pins than ought to be strictly necessary, but it's a relatively reasonable compromise over the former solution of no common standard at all.

Is this really new?

[Logical Zebra]

I work in the telecommunications industry. It has always been standard practice (at least where I work) to use DC power supplies for data equipment if they are co-located with voice equipment, since most voice equipment uses -48 V DC power.

This has the additional advantage of utilizing the battery backup system (required for voice) to also back up the data equipment's power.