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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."
Tesla smiles in his grave as Franklin catches on fire from Nikolai's coil-arcs-of-doom.
'We are trying to prove ourselves wrong as quickly as possible, because only in that way can we find progress.' RPF
Who would have thought the GE would be a big supporter of DC.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
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.
Suggestion for the DC power supply designers: have a heart and build GFCI into the spec.
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!
"[Regarding the 'cloud,'] ownership was what made America different than Russia." -- Woz
In the 80's we built custom interfaces for large computers using wire-wrap Standard Logic Inc. wiring modules. The planes of wiring were assembled into rackmount chassis which were fed DC power via a vertical bus-bar system in the rack. The busbars were about .5 X 1 inch solid copper, insulated by shrink tubing with holes cut for the threaded holes in the busbar. The power supplies were rackmount 100 or 200 A Lambda supplies providing either 5 volts or 12 Volts. It was occasionally a pain to be called into the computer center in the middle of the night to replace one of those heavy power supplies - at least they were at the bottom of the rack.
OZ
enough is too much
Switching power supplies have gotten much more efficient in the past few years. Now it makes sense for a standard DC bus to run everything. The telecoms have been doing this for ages.
Only the State obtains its revenue by coercion. - Murray Rothbard
I thought the power in D.C. caused waste and ineffeciency.
If brevity is the soul of wit, then how does one explain Twitter?
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.
rolls over in his grave.
If that's because of DC, does it mean he's fitted with a brushless commutator?
Blank until
Well, if you put a magnet on him and wound wire around the coffin that could be a clean source of electricity...
I'm the Devil the Windows users warned you about.
Assuming that you don't modulate the phase variance of the deflector dish, of course.
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?
Think Deeply.
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.
One can't help but reflect upon these two and their stubborn support of DC and AC respectively. Edison created a circus atmosphere demonstrating the dangers of AC. He electrocuted dogs & other animals and even participated in the design of the electric chair to prove his point.
Edison's financial ambition was part of the problem, and his inability to understand AC, but mostly it seems to have been an emotional attachment to DC.
Let's hope that in our time emotion and personal gain have no part in such decisions.
...omphaloskepsis often...
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.
Kevin Smith on Prince
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.
Just a side note, this has already been growing in the field of UPS units for at least 5 years, and it's not terribly hard to find UPS units and PSU units with DC connectors.
(Since to use a UPS without DC means converting battery's DC, sending it to the PSU in AC where it's converted back again.)
In Soviet Russia jokes are formulaic and decidedly non-humorous.
I call not true!
The body is exceptionally good at accomidating a stable force acting on the system. What causes most electricution deaths are the sudden change in voltages throwing the heart out of rhythm or scrambling the brain log enough for the person to die.
The actual physical damage of electricution is usually very minor (first or second degree burns through the path of the current). The alternating nature of AC makes it much more likley to mess up the heart and brain. 120 chances a second. DC only has one chance.
Now DC will cause greater BURNS because the constant voltage at the same power can generate more heat, but the burns are not what kill you.
Neither article you cited mentioned DC vs AC. Almost every mention of current related it to HOUSEHOLD current which suggests AC.
Finally, the blood cannot be "charged." It is a fluid with some conducting ability since it is full of various ions. Any charge it does accumulate would almost immediatly ground out to the rest of the body and from there to the earth.
If you want to make dramatic claims please provide plenty of citations
However, in these links there was no reference to this at all.
I don't think there is any truth to this.
Maybe, but it it has nothing to do with "blood polarization". There is more than one way to measure AC: peak, or RMS
1 amp DC carries more energy than 1 amp AC (peak) and thus is more harmful.
1 amp DC is exactly equivalent to 1 amp AC (RMS) in terms of energy and harm*.
*One possible exception is if the AC is very high frequency and the load is not purely resistive. Then you get wacky tesla coil effects.
> I don't run a datacenter, but I sure would like to get rid of the power bricks...
DC vs AC wouldn't help you rid yourself of power bricks. No more than it can help a datacenter get rid of power supplies in each server. Telco equipment runs on 48 volts not to save electricity but because of the way telephone exchanges are built. Telephones don't go down, period. So how do they accomplish this miracle? Huge battery banks. Back in the day a DC-AC conversion system large enough to run a whole switch plus drive every telephone would have been all but impossible. So they just ran everything directly from the batteries and used the mains to charge the batteries.
This DC in the datacenter thing is just a green craze that will pass. It is pure unadulterated snake oil. Go reread the summary. They ain't even doing the smart thing and adopting the telco 48V standard. Does anything in a server run on 48V? No. Does anything in a server run on the 400V they are proposing? No. So a DC-DC conversion will be needed, i.e. a switch mode power supply. Guess what is in a current server? A switch mode power supply. Current PC power supplies are available with efficiencies over 90% without buying too far off the mainstream. I seriously doubt these DC powered supplies will be much better and in the end that is the ONLY number that matters. Except these DC installations have to factor in the power loss from the big AC-DC conversion and worry about redundency, backup power, etc.
Democrat delenda est
Re: Title
Why don't you do it yourself? It's not like there's anything stopping you.
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
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.
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
Yes,
AC has better voltage drop and in most cases voltage conversions.
DC is more effecient in closed loops.
So you want distance ac is king. However your car will never be AC. DC is far safer in such situations.
I have always been under the thought. Electric companies should deliver AC to the home. Where it gets converted to DC.
i thought once I was found, but it was only a dream.
There are a number of companies providing commercial DC solutions for data centers. Validus DC Power is providing products for DC power distribution, while Power Loft is building a brand new data center optimized for DC power.
RichM
Data Center Knowledge
These days they are usually switching power supplies, which are quite efficient (not to mention smaller).
From TFA:
The power starts at the utility pad at 16,000 VAC (volts alternating current), then converted to 440 VAC, to 220 VAC, then to 110 VAC before it reaches the UPSes feeding each server rack.
That's just stupid. I hope it's just a case of a journalist not correctly understanding (which is a common problem). Given the usage of numbers like 220 and 110, instead of the standard 240 and 120, I do suspect it is a journalist giving wrong info. But even many computer people don't know what the standard power voltages are (and have been for decades). Lots of people in the USA still refer (incorrectly) to "two twenty" and "one ten". The standard in Europe is 230 volts.
With so many conversions taking place, there will be a lot of power loss. To begin with, the computers should have been operated directly on the 240 VAC, not 120. That 240 VAC should have been obtained from the utility power directly (though voltages like 7200, 7620, 7970, 12470, 13200, 13800, 14400, 19920, 22860, 23900, 24940, 34500, etc, are more common ... I've never heard of 16000 being used). Since power comes in as three phase, the ideal voltage conversion would have been 240 VAC line-to-neutral, which would give 416 VAC line-to-line. Neutral harmonics issues can be avoided by use of oversized neutrals or multiwire neutral.
Do AC wiring correctly, and the advantages of DC are minimal at best. Where the DC plan can have an advantage is that the conversion to 400 VDC, done on a large scale, can be done more efficiently. If that doesn't happen, then it's just one AC-to-DC conversion vs. another AC-to-DC conversion. When the 400 VDC gets to the computers, you still need a PSU to convert the 400 VDC to the various voltages provided to the components inside the computer box (e.g. 12V, 5V, 3.3V, etc).
AC voltage conversion can be more efficient than 98% when properly designed low impedance transformers are used. That can beat the DC conversions ... even DC-to-DC, in most cases. So you want to do conversion of DC only once or certainly no more than twice.
It has been reported that mainboards can be designed to efficiently convert 12 VDC to the other voltages needed. Google's original proposal was to supply computers with 12 VDC, allowing them to be manufactured without the PSU entirely, and thus in a smaller footprint as well as having the increased efficiency. The 12 VDC would come from a large PSU in the middle of the rack (to limit the length of wire carrying the higher current that is involved with a low voltage). That large PSU would be designed to accept AC at any voltage from 380 to 480, 50 or 60 Hz, and thus be usable just about everywhere in the world. The PSU may even operate more efficiently when fed with full three phase power (the full cycle nature of three phase power reduces the level of filtering needed for smooth DC).
Running DC is NOT a crackpot idea. It just needs to be studied correctly, in its various possible forms, and compared to CORRECT designs of AC wiring, in its various possible forms. The choice of 400VDC for distribution within a data center to the individual PSUs is a reasonable one, given that the existing PSU designs go through a conversion to 340VDC to 380VDC, anyway. But these same PSUs, especially in the larger form of one per rack, could just as well be designed to operate from 380 VAC, 400 VAC, 416 VAC, or 480 VAC.
Maybe DC is the right choice. Or maybe AC can still be the right choice when engineered correctly (which far too often is not done, sometimes due to ignorance, sometimes due to budget limitations which would never go for DC anyway, and sometimes just due to mental inertia).
now we need to go OSS in diesel cars
The reason Tesla/Westinghouse won the current wars with Edison because there wasn't any good way to step DC voltages up or down. You can't transmit power very far at 110 volts. AC allowed the use of inexpensive and transformers to step voltage down at the customer site and transmit at high voltage over long distance.
Today solid state converters do allow the step up / down of DC voltage, and very high voltage DC can be sent over long distances with less loss than the same AC at the same voltage. At least one power company is looking at using DC transmission lines over long distance.
AC power still makes more sense for consumer and most industrial use, but for transmission and delivery of power in bulk DC seems to be making a comeback.
Fewer. It takes fewer wires. Or it takes less wire.
This is nice, but I see it as interim until we can produce superconducting puddles at room temperature.
The highest drawing stuff in the home often works better on AC. The motors that run the compressor on refridgerators and air con are more efficient that way. Any electric heaters (potentially stoves, water heaters, and furnance, depending on the setup) are more efficient on AC (I think--it'll be about equal at worst). Incandecent bulbs don't care, and flurecents can use either one (though the ballast has to be setup specifically for AC or DC). LED lights would care, but those are really expensive, anyway.
That leaves computers and home entertainment equipment. However, they use a multitude of different voltages, so there's going to be some DC-DC conversion involved. The difference between AC-DC and DC-DC conversion efficiency isn't that big. Certainly not big enough to justify putting in extra DC-dedicated wiring.
You're better off buying high efficiency power supplies on your computer and fully shutting off entertainment stuff (which you can often only do by unplugging it).
Not a typewriter
Moving the AC->600VDC stage out of the controlled environment will be a savings even if you keep the inverter and stay AC in the datacenter.
for actually going DC in the datacenter, the top benefit is losing the inefficiency and heat of the inverter stage of the UPS.. Instead, you have the potentially smaller losses of several smaller 600VDC to 48VDC converters in the racks and potentially cheaper power supplies that don't have to care about power factor.
The con side is the need to re-fit, heavier power cables from down-converter to the individual machines and the underfloor area becomes much more hazardous (600VDC = 3rd rail).
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.
I have a bad feeling about this...
Half as many amps == half as many power strips, half as many UPS devices, half as much wire, etc.
In the split-single-phase arrangement that is used in the USA, the only difference is whether there's a neutral wire in the conduit. For a given wire gauge you don't get any more power from a 240V circuit, because they're fundamentally the same thing, just one has kind of a "center tap". That copper is a very marginal savings (3 conductors vs 4) when you figure all the labor, conduit, breakers etc that's going to be put in anyway. And if you're dealing with 3-phase it's even less (4 vs 5 conductors).
In a colo environment it would be smarter to run 120 (with shared neutral) so people can use the normal plugs and cables that they have on hand, although in a single-customer datacenter where all your equipment is sure to have modern power supplies, fine, go with 240. But it's not hard to wire 240V outlets as needed (eg for a high density unit like a blade chassis or cisco gear).
You don't use any fewer power strips because you still need a plug per computer regardless of the voltage, and you still need to same amount of UPS equipment because your VA and WH would be the same for a 120 vs 240v UPS of a given price or physical size. It may surprise you that 120V and 240V UPSes generally have the same internals, the only difference is the plugs and cables that they're outfitted with on the back panel. Try measuring the voltage across two hots on different plugs of a "120V" UPS - you'll probably see 240V.
You're better off buying high efficiency power supplies on your computer and fully shutting off entertainment stuff (which you can often only do by unplugging it).
Well, tube warmers used to be the major source of abuse, but other then CRT TVs is there really any equipment with a meaninful power draw in "standby"?
Socialism: a lie told by totalitarians and believed by fools.
The responses to this here where highly predictible, and many af them are quite naive.
Modern DC-DC converters have excellent Efficiency over a wide dynamic range of loads. This holds true for the small, nice isolating ones which every designer of instruments likes very much, and also for larger ones. No transformers, smaller capacitors, easier redundant designs, easier buffering. In a time when computers are more and more designed to vary their input power according to their load, all these things could provide a savings of energy (and money). Even if this saves only a few percent, the investment will be payed off in a reasonable time.
Here's a table:
http://standby.lbl.gov/summary-table.html
Doesn't look like they have a breakdown on lcd and plasmas, but rear projection TVs are listed as 6 W when off. Non-DVR set-top boxes for satellites are about 15.5W, and DVR types are almost 30W when not even recording anything.
Not a typewriter