Are Data Centers Finally Ready For DC Power?

1sockchuck writes "It's been five years since a landmark study outlined the potential benefits of DC power distribution in data centers. But adoption of DC in data centers remains limited, even as the industry aggressively pursues a wide array of other energy savings strategies. Advocates of DC distribution are hoping a new study will jump start the conversation about DC distribution, which can save energy by eliminating several wasteful AC-to-DC conversions within a data center. Meanwhile, an industry association for DC power adoption, the EMerge Alliance, has formed a new technical standards committee for data centers, and is advancing a 380-volt DC power standard. Will DC distribution ever gain momentum in data centers?"

Comments

Edison reaching out from beyond the grave

[ravenspear]

I told you bitches I would prevail one day!

Re:Edison reaching out from beyond the grave

[Wonko the Sane]

AC was the answer to how to transport electricity long distances

AC was used because using transformers to convert between voltage levels was more efficient than motor-generators and solid state electronics hadn't been invented yet. All other things being equal, DC is always more efficient than AC for long distance transmission.

Re:Edison reaching out from beyond the grave

[Elder Entropist]

Very high voltage was the answer to how to transport electricity long distances. AC was the answer to how to convert that high voltage to safer/useful low voltages cheaply. Very high voltage DC can lose less power over distance than AC. On smaller/cheaper wires too due to the AC skin effect.

Re:Edison reaching out from beyond the grave

[Mr Z]

The problem with DC back in Edison's day was that you couldn't easily step it up or down. DC doesn't have higher losses than AC at the same voltage. In fact, DC radiates less energy away than AC does, and is therefore more efficient.

Ohmic losses all come down to I^2 * R. R is the resistance of the cable, and I is current. To deliver a given amount of power, you have to have a certain V*I. To reduce Ohmic losses, then, you have to reduce the amount of current, which means going up in voltage.

Incidentally, that's also what's driving automobile manufacturers toward 48v instead of 12v, since it would cut the current from the battery by a factor of 4, thereby reducing the amount of loss in the wiring by a factor of 16. That means you can use smaller wires to deliver the same amount of power, safely.

Re:Edison reaching out from beyond the grave

[Anonymous Coward]

Way to take a completely normal, productive conversation and shit all over it.

Try being less of an asshole for a day or two. You might find that people hate you less.

Re:Edison reaching out from beyond the grave

[EETech1]

That's why they use 380 volts! One big splice goes to all the 12 volt stuff, then another splice comes off of that splice to do the 5 volt stuff. It is not run through regulators, it just happens automatically due to the superior characteristics of DC power! They also tap into the ground wire at various places to get the -5 and -12. Magic I tell ya!

It sees it's best efficiencies running near 100% utilization through so you want to plan your workloads accordingly, or you risk watching your $#!+ let out it's magic smoke! So all in all it should drive down the price of "the cloud" by forcing competition!

Win, Win!

Re:Edison reaching out from beyond the grave

[Anonymous Coward]

At 60 Hz, the skin effect is virtually nonexistent.

Monster Cable begs to differ!

Re:Edison reaching out from beyond the grave

[ktbaia]

I beg to differ. The Electronic Power Steering in my 1995 NSX decidedly does NOT feel like crap. When EPS systems were first put on production cars (the NSX was the first), it was on sports cars, where good steering feel is very important. See this link for information on how a decent EPS system should work. Just because Toyota can't figure out how to do a decent EPS doesn't mean that it hasn't been done. http://www.nsxprime.com/FAQ/Technical/eps.htm

Re:Telecom's been doing this for many, many years.

[Shatrat]

I work with DC power in Telecom and it has 3 huge advantages I can think of off the top of my head:

1) You centralize your rectification. Instead of having hundreds of power supplies running at 80% efficiency, you can have a large rectifier system running at up to 96%.
2) Lead Acid batteries are hugely more reliable and less expensive than equivalent UPS systems, and provide more holdover time. They're still expensive and finicky, but many times less so than a UPS.
3) Any old technician with a brain in their head can run DC power feeds to equipment relatively safely due to the low voltages involved. AC power work of any kind should have a qualified electrician involved.

Re:Why 380v?

[RichMan]

440 * sin(120) = 381.05 ....

3 phase has 2 ways of looking at the voltages, Y or delta.
The 3 phase delta is 440v when you measure between any pair of the 3 wires. The center point is ground. You don't see that in delta, but you do when measuring it in Y form. The same signals that are 440v when measured as a pair are 3 x 380v when looked at in the Y configuration.

So 3 phase 440v gives you 3x 380v to ground.

As to the 12v/5v/1.5v/ whatever you are going to have to do DC to DC all over the place. Better to have as high a voltage as possible for less current and less losses.

Re:And in related news...

[DickBreath]

Would an AC current be generated by Tesla spinning in his grave?

Re:Telecom's been doing this for many, many years.

[vlm]

4) Done right with a positive ground system, leads to less corrosion problems with outside plant. Admittedly "inside" the data center, if you're got corrosion, you're doin it wrong.

5) Less AC hum. We had some microwave site to site short hop gear back in ye olde NTSC days that could only be run off battery without 60 hz interference bars on the screen. Not technologically relevant anymore, but the point remains that DC is always going to be cleaner than AC.

6) Better lightning protection. I'm sure its happened, but I've never heard of losing a telco DC bus. Big conductors, giant batteries across them, lightning is just not an issue anymore at the power level (still need to ground feedlines / waveguide / whatever you've got at home like that)

7) dump most of the power conversion heat in the battery room where its all built to handle high temp and no one visits (other than occasional battery maint). Cheaper cooling in the data center, data center is somewhat more habitable, etc.

Re:Google 12VDC proposal better.

[Wonko the Sane]

what about salt water filled copper pipes for the conductors?

Excellent idea! Hydrogen gas, oxygen gas, chlorine and an ignition source all in the same package. What could possibly go wrong?