DC Power Saves 15% Energy and Cost @ Data Center 371
Krishna Dagli writes "Engineers at the Lawrence Berkeley National Laboratory and about 20 technology vendors this month will wrap up a demonstration that they said shows DC power distribution in the data center can save up to 15 percent or more on energy consumption and cost. The proof-of-concept program, set up at Sun Microsystems' Newark, Calif., facility, offered a side-by-side comparison of a traditional AC power system and a 380-volt DC distribution system, running on both Intel-based servers and Sun systems."
Safety (Score:5, Insightful)
Re:Safety (Score:4, Insightful)
Re:Safety (Score:5, Funny)
Re:Safety (Score:5, Funny)
Oh my god! (Score:3, Funny)
Re:Safety (Score:4, Funny)
Getting one hand shocked at 220VAC is not pleasant, but it's not especially painful either...
Re:Safety (Score:2)
The electrical current that powers your heart is not really all that powerful and can be messed up pretty easily if the amps and volts are high enough.
Re:Safety (Score:5, Insightful)
Well-designed power supplies often have a bleeder resistor across the primary filter caps to drain them of juice, but note that the vaccuum tube in a CRT makes an excellent capacitor as well (it's being charged to 20 kilovolts or more), and it's dangerous to try to dead-short it to drain the residual current. 120VAC current shock can be fatal but that is very uncommon; however, the voltages inside a CRT are probably the most dangerous level of current most people have around in their homes or work environments.
Re:Safety (Score:3, Funny)
Your monitor has its own AIR CONDITIONER? Awesome....
Re:Safety (Score:2)
Also, I read somewhere on the internet that Edison got his kicks off hooking car batteries to his nipples.
Re:Safety (Score:5, Informative)
In a properly designed DC system, your no more/less safe than your already are.
(Sorry for the repost - I finally remembered my login)
Re:Safety (Score:4, Informative)
http://en.wikipedia.org/wiki/Three-phase_power [wikipedia.org]
Re:Safety (Score:2, Interesting)
In the 120/208 VAC system the phase to neutral voltage is 120 VAC - so your right. To get 120 VAC for a wall outlet you take one phase of the three phase system. You still need a transformer to get from 277/480 to 120/208.
Re:Safety (Score:3, Informative)
On a good day, there is minimal voltage difference between neutral (or common) and ground, but if the site has a poor or floating building ground, you can see some pretty severe voltage swings. Also, if the load on the three phases isn't reasonably well-balanced, that'll nudge neutral away from ground and you'll get current leaking to ground which is wasteful and even dangerous at higher amperages.
I've even seen old wiring in me
Re:Safety (Score:3, Informative)
Ummm....No.
1) 480 3 phase can be 3 wire or 4 wire. 3 wire is called Delta (floating ground or one of the legs can be tied to ground). 4 wire is called Y (typically the 4th wire is the "center" of the Y and is grounded.
2) You get 277 VAC referen
Speaking of conductor sizes.... (Score:5, Informative)
Speaking of conductor sizes, the article said this:
A DC system also would mean having to bring in larger cables than now exist with AC power.
I challenge this notion. Conductor size is not related to whether the power is AC or DC or what frequency of AC it might be; it is related to current.
Larger cables are needed when more current is passed. Traditionally, you need larger cables for DC, because traditionally, DC power systems were lower voltages (12, 24, 48) than AC systems, and these lower voltages required larger currents for same power (e.g. 100W= 830mA at 120V, but 8.3A at 12V). Running at 380V, however, you get to lower the current (excluding the reduced current caused by the 15% power savings) versus a 120V system.
Expanding on that, the reduced conductor size is proportional to the square of the reduced current. Simply by going from 120V to 380V (a factor of 3.17), you change the current flow downward by a factor of .32. This means you can change the cable cross-section area to by a factor of .1; you reduce the cable to one-tenth its original size; one tenth the copper.
Re:Speaking of conductor sizes.... (Score:3, Informative)
Not really correct: as the frequency increases, the current tends to flow in the outer regions ('skin') of the conductors, known as the skin effect [wikipedia.org]. Because the core of the conductor is not used, the effective area is reduced and therefore the resistance increased. For this reason hollow or flat conductors are used for high frequency applications.
Re:Safety (Score:2)
State-sponsored electrocutions used AC ...
Re:Safety (Score:4, Interesting)
Re:Safety (Score:2)
Re:Safety (Score:2)
Re:Safety (Score:5, Informative)
DC is harmless unless it has a path to carry it. You can grab a 380 volt DC line and not feel a thing. now if you then touch a grounded object, or the return path you are dead. But you have to make the connection. AC is lethal at 220v. As others posted it does have the advantage of forcing the mucsles to spasm so you can let go of the wire, But still zaps you every time you touch the cable.
Go look up the history of Edison vs Westinghouse. Edison wanted DC power all around because it is inherently safer. a Broken AC wire can zap you, were as a broken DC wire can be touched with bare hands.
Re:Safety (Score:4, Informative)
Re:Safety (Score:5, Insightful)
Yourself also?
ANY electrical path must be joined from source to drain or no power will flow. It doesn't matter if it is DC or AC. Period.
An AC path, however, has an easier to isolate ground because it works with simple transformers. A 1:1 transformer will allow you to grab a 220 volt line without being shocked, assuming you do not touch any path that leads back to the other side of the transformer. This is why in the ICU in hospitals you will find them being used: If a patients equipment shorts in a manner that the electricity reaches the patient, it will not shock the patient unless the patient grabs ahold of the equipment.
Unfortunately DC does not offer this sort of simplicity of isolation.
Edison was a sadistic nutbag that actually enjoyed electrocuting animals like cats, dogs, and elephants by joining them to an AC power path. His DC power was no less dangerous, the only reason it never electrocuted the animals was that the voltage was low enough skin (or fur) resistance did not allow enough current to pass through the animal's body to kill them. Furthermore, due to the low voltage/high current nature of his system, the amount of energy wasted through heating the conductors limited electricity runs to less than about 2 km.
The exact same ridiculousness in power cable AWG requirements can be seen in "modern" car stereo upgrades. People will run a 4 AWG cable to their subwoofer amplifier to power an "800 watt" 12 VDC amplifier. The same 800 watts can be generated from a 16 AWG cable hooked into a 120 VAC amplifier. The difference being that the car amplifiers are often unfused because fuses in the 100 - 200 Amp range are expensive, and circuit breaks even more so, and that 15 amp fuses and circuit breakers for home electricity are incredibly cheap. The unfused car system when shorted will burn the car down in no time. The fused circuit in houses when shorted will burn nothing down, and, when repaired, the wiring can even be reused.
Edison created a useless power system that never worked properly for anyone at all. He also enjoyed electrocuting animals for no apparent reason other than to hookwink customers. He also helped develop one of today's most popular capital punishments: The electric chair. Oh, and he stole credit for several inventions (not the least of which is the light bulb). All around, he's just not a cool guy.
So, basically, for Edison's idea to have worked, we'd all have 0000 AWG cables running to our homes, and we'd probably be melting several of them causing fires, not to mention that the DC power will cause the conductors to be damaged through electroplating. But, we wouldn't get shocked. Of course, the exact same benefits, along with the additional benefit of no electroplating, could be had by running the same conductors with the same voltage AC current at a frequency outside of 50 - 60 Hz.
Of course, at 50 - 60 Hz AC power is most dangerous. But then again, at the voltage levels required for modern electricity, the frequency makes very little difference.
Tesla (Score:3, Informative)
No, he just had good marketing. People keep repeating a lot of things he never actually invented, just proposed some vague idea, together with other things that proved totally impractical. I wonder why they never quote this:
"The aeroplane is fatally defective. It is merely a toy-a sporting play-thing. It can never become commercially practical. It has fatal defects."
Nikola Tesla
Edison, it's true, had his personality defects. In many cases he was not quit
Re:Safety (Score:2, Interesting)
It constricts all your muscles which stops your heart and your ability to move until the power is removed. If you happen to grab a DC power line this is especially dangerous, as an AC line with throw you off while a DC line will cause you to simply grab harder and you can't let go.
Fun hu?
Re:Safety (Score:3, Funny)
You claim to know the "Fun Hu" technique? Teach it to me immediately, or I will kill your master just as I killed his other students.!
Re:Safety (Score:3, Informative)
Which is why my sister-in-law once told me to use the back on ones hand if you aren't sure if a line is still live or dead. Your hand will contract around nothing thus giving you a slightly better chance of survival.
Re:Safety (Score:4, Interesting)
Re:Safety (Score:3, Informative)
Re:Safety (Score:5, Informative)
From http://www.andamooka.org/reader.pl?pgid=liecDCDC_
Note to the wise: Wherever possible, always approach a circuit with the back of your hand. If it is DC, the muscle reaction in case of contact/shock will tend to pull your arm away. If it is AC, same thing will happen. Depending on the voltage present on the conductor, you may even feel the hairs on the back of your hand react to the field produced, i.e., they will 'stand up'.
CPD.
Re:Safety (Score:3, Funny)
And this my friend is why you have more male electricians (who on average have harrier hands) than female. And if the back of your hands don't grow hair anymore, you shouldn't be an electrician anymore.
Re:Here, here! (Score:3, Interesting)
Re:Here, here! (Score:2, Informative)
Re:Here, here! (Score:3, Informative)
Except that the only reason you see 48vdc for telephone over those tiny 22ga wires is that there's no load. As soon as you go off hook the voltage drops to around 10vdc. This works because telephone circuits don't actually do much work-- they mostly just transmit analog data. The size of the copper you'd need to feed an actual load at 48vdc is prohibitive, particula
Re:Here, here! (Score:3, Informative)
Although, you're right that they don't use 22-gauge wire for that purpose; one of the PBXes at a client site has a 15 or 20amp/48VDC power supply, for example, which seemed to be using 14 gauge wiring, for example.
Re:Here, here! (Score:4, Informative)
The power conductors in central offices are oversized out of paranoia, and because sometimes you have a foot-thick pileup of power cables leaving a fuse bay and you want to make really sure resistive heating is negligible. Also, most equipment has redundant power feeds, A and B, but either feed is large enough to handle the entire load. During normal operation when both sides are sharing the load, the resistive drop in the wires is absurdly low.
The other advantage of 48v is that it's below the 50v "low voltage" standard in the NEC, which means it's easier, legally, to work with. The 300-plus voltage they're using in this study loses that advantage.
Also consider this: AC voltage and power are measured RMS, but the insulation has to withstand P-P voltage. So to deliever the same power on the same conductors, the DC system's insulation has a greater margin of safety.
Re:Here, here! (Score:3, Informative)
Stick a voltmeter across tip and ring. If the line is on-hook, you'll see 48V DC. If someone calls, 90V AC will be superimposed on it to run the ringer. Take the line off-hook and the voltage goes down to somewhere around 6V DC.
Re:Here, here! (Score:5, Informative)
Conversely, if you halve your current by boosting the voltage, you can reduce your transmission losses by 75%. Thats a pretty good reason to go with higher voltage. And since this is in the datacenter, you can train your people not to pee on the red wire.
A black wire question. (Score:3, Funny)
Re:Here, here! (Score:4, Funny)
We have dedicated and colocated server in various datacenters, so I have a fair amount of experience with them, and so I need to ask you... PLEASE give me an example! An example of a datacenter staffed with people who can be trained not to pee on a red wire, because if they can be trained to do that... hell they might even be able to reboot the right machine from time to time!
Re:Here, here! (Score:5, Interesting)
Almost every device I own uses 4.7V or 12V. I look around at work here, and I can see power strips full of transformers, all of which are knocking back the AC power to one of a couple of DC voltage levels. Every one of those transformers has its own losses, most of which dissipates as heat. They're also large, making it difficult to fit them all into a strip, and their heavy, making it difficult to balance or hang the strip where it's most needed. At home I have DC transformers for the monitor, the switch, the firewall/router, the WiFi, the PDA recharger, the BT mouse recharging dock, the USB hub, the TV tuner box, etc, etc. It's got to be a safety hazard.
Then we have the PCs, which are also using 2 (OK, 4) predefined levels of DC voltage, and have their own transformers and rectifiers to do it. These get so hot they even need their own fans!
Why isn't this stuff standardized, and power strips can instead contain one single transformer/recitifer package, with DC sockets, or retractable DC wires coming out of them? Even if we ignored PCs and only did the external peripherals for now, we'd still get a big saving in power just by having fewer transformers.
Re:Here, here! (Score:3, Insightful)
The cynic in me suggests it's because your typical wall-wart costs about 50 cents to make in bulk and are commonly marked up by a factor of 20 to 100 or so, so when the company sells you a repla
Let Go (Score:3, Informative)
Re:Let Go (Score:3, Insightful)
Riight... Whichever muscle in a muscle group is stronger presents the dominant force in a convulsion. In the human arm, the gripping muscles are far stronger than the hand-opening muscles. DC or (low frequency) AC, the result is the mostly the same - the hand will grip. If that grip is responsible for the zapping, good luck. DC is worse than AC in this aspect.
That said, fibrillation is more of a risk with A
Bye bye Tesla (Score:3, Funny)
DC power can be a good thing... (Score:3, Informative)
When they used to talk about DC power systems be less efficient, you have to remember that most of them were talking about 12-48 volt systems.
From the article:Not according to my electronics class, if they're really going to be running at 380 volts. They'll need more insulation instead. I'd also want to be real careful around those wires. DC will kill you much quicker than AC of the same voltage/amperage. Then again, you don't have to worry about shorting yourself to ground with DC.
For now.
Deadly DC? (Score:5, Informative)
I always thought the opposite was true. Here is a wiki quote that also supports that:
Taken from http://en.wikipedia.org/wiki/War_of_Currents/ [wikipedia.org]
Re:Deadly DC? (Score:2)
Re:Deadly DC? (Score:4, Funny)
Just make sure that the article that you are quoting wasn't edited by Stephen Colbert...
Re:DC power can be a good thing... (Score:2)
That statement makes no sense at all.
Re:DC power can be a good thing... (Score:2, Informative)
Re:DC power can be a good thing... (Score:2)
Industroal systems do this all the time (Score:4, Informative)
But as for DC killing you quicker, I would disagree that its the type of system that kills you, it will depend on the type of damage that the shock causes. You can use a 9VDC battery to kill yourself if you apply it in a manner that a small current (mA level) flows to your heart and I would guess that the same level of AC current would also do the trick. On the other hand if you pass a large current through your body that causes physical damage (major burns etc) then it won't matter if its AC or DC if the so much of the body is destroyed as you will die eventually.
As for not worrying about grounding yourself with DC
Re:DC power can be a good thing... (Score:2, Informative)
The savings will be somewhat in components and somewhat in power. After your UPS system (in which AC power is converted to DC for battery storage) there will be no need for the DC/AC conversion and then AC/DC in the silver box. This deletes one conversion stage, in theory (in theory communism works, in theory...)
AC supply -> UPS AC/DC -> battery storage -> bus converter -> several servers
rather than
AC supply -> UPS AC/DC ->
Re:DC power can be a good thing... (Score:2)
Yes, they will save on resistance losses by about 1/3. (120/380)
(1/3)**2 = 1/9 actually.
Re:DC power can be a good thing... (Score:2)
My question is do any systems still use 60hz as a time reference? Back in the old days a lot of internal clocks used the 60hz signal as a time reference since it was very stable over time, and it was cheap
High voltage DC would eliminate the need for the big buss bars that they used in low voltage systems.
I would take a look at some of the Navy research in the DC power area. All US d
switching costs? (Score:3, Informative)
Re:switching costs? (Score:3, Informative)
Most AC power is 80% efficient, which is where the 15% gain is coming from (and remember, it is UP TO 15%, not 15% all of the time). But AC power supplies are becoming more efficient, with IBM claiming its BladeCenter power supplies are 90% efficient. That means that DC will probably only give a 5%-7% gain in eff
The Telcos have known this for years (Score:5, Insightful)
In a telephon e exchange 48v DC is the norm.
They have huge batteries and standy generators to keep the phone syste, running.
Re:The Telcos have known this for years (Score:3, Interesting)
Yeh some where (I may have lent them out) i have a pair of 1948 GPO handbooks for technicians. Which describes the technology?
Including how to build your lead acid batteries on site (48 hours on battery power was required) and the technical details for the pneumatic tubes used in manual exchanges to send tickets up to the trunk floor
I have also hear some old timers war stores one i liked was about the guy who when painting in an exchange put a paint can on top of the main bu
Re:The Telcos have known this for years (Score:2)
They use DC because the systems originally ran completely off batteries. The battteries were charged fomr battery chargers on the power line. One of the reasons they did that was so the phones would keep working during a power outage. The original UPS.
Another reason for DC is that the early carbon element microphones required current running through them to work. You can make one work on AC, by the AC hum is then the pred
At 48V, couldn't you go solar too? (Score:3, Interesting)
Hum, I might be too idealist, here...
Edison (Score:3, Insightful)
Re:Edison (Score:5, Insightful)
> application of DC is a credit to Edison's scientific achievements.
For 19th and early twentieth century technology Tesla and Westinghouse were entirely right. They had no practical method of changing voltage.
BTW you don't want to look too closely at Edison's scientific achievements. You might find that there is less there than meets the eye.
Re:Edison (Score:2, Funny)
Re:Edison (Score:5, Insightful)
The record player was really the only truely unique thing he did. Everything else was a duplication of someone else's efforts where he succeeded and the others failed- or was something one of his employees came up with. Did you know that he'd "Westinghouse" a cat "to show the dangers of AC power" during the time where he was trying to compete with AC power versus his DC system (From which ConEd initially came from...)? This would entail hooking up a grid of alternating plates with some small amount of insulating gap to an AC power connection, place them inside a cage that one's keeping a cat and then plug it in. Edison's NOT someone to be holding up as an example of scientific achievement- unless you want to hold Mengele up as well. Sure, we got a lot further in medical science because of that "Doctor", but how he got his information, I'd rather he didn't do what he did- and it's not a good example of a scientific achievement.
DC and AC both have their place. DC is good for short-haul power distribution, but if you short out the lines you'll destroy the entire power run. AC doesn't do that anywhere near as bad- which is why electric power is distributed as AC- it doesn't have the same safety issues and it can be transmitted long distances without major losses as it's being transmitted down the wire, not conducted.
Re:Edison (Score:2)
AC can be transmited long distances without as much loss because it's easy to use a transformer to step it up to 30KV
Re:Edison (Score:2)
Edison didn't have a lot of inventions, but Edison mainly improved existing inventions like the light bulb and got boatloads of patents on that sort of thing. The money he made on these patents probably funded most of the research, so it wasn't without merit.
Your final point is something I was g
Re:Edison (Score:2)
it doesn't have the same safety issues and it can be transmitted long distances without major losses as it's being transmitted down the wire, not conducted.
Actually DC can also be transmitted long distances as well. It's high voltage that allows long distance power distribution, not something special about AC. The reason why we use AC for power distribution and not DC is that AC can be easily stepped up or stepped down to different voltages using simple technology. It's only recently become possible to d
Re:Edison (Score:2)
Edison died in 1931.
Tesla died in 1943.
The Bell Labs transistor was successfully built in 1947.
Neither Edison nor Tesla had the fair knowledge of the proliferation of transistors 60-70 years posthumous. I don't know about you but practically every on-grid device in my apartment is DC based. TV, computer, clocks, cordless phones, DVD player, etc. The only th
I've always liked ... (Score:5, Insightful)
That pretty much covers the entire range of possibilities.
I often wonder why they didn't say something like "up to 50 percent or more" or "up to 99 percent or more". Those would be every bit as meaningful.
Re:I've always liked ... (Score:2)
What about the conversion from 380 VDC to 5-24 V? How efficient would that be?
What's new about this? (Score:5, Informative)
You can also store DC whereas you cannot store AC, meaning UPS always need an AC-DC followed by a DC-AC stage. Since we have had large FET power transistors it has been possible to make DC/DC conversion very efficient - especially since, if you were beginning again, you would not choose 50 or 60 Hz for best efficiency.
In fact, already the PC is using a DC bus to power small peripherals (USB) and it works surprisingly well.
I may be wrong about this, but it was Edison who accused DC power of being more dangerous ("Westinghoused") only to have AC adopted for the pleasant US custom of humanely frying criminals.
Re:What's new about this? (Score:2, Informative)
Re:What's new about this? (Score:2, Informative)
How does this help? (Score:2)
- This eliminates the need for a AC->DC rectifier in each component
- But they still need to have the transformers to step down the voltage
- DC requires twice as many wires
Is the elimination of the rectifier a significant efficiency increase? Or is the real benefit in the move to a higher voltage? But doesn't that just mean they need bigger transformers to step down to the 12V they rea
Errr... So many misconceptions (Score:2)
Ummm... Transformers don't work with direct current.
Re:How does this help? (Score:2)
It may be that they distribute the DC supply which would be used in the PSUs anyway. Therefore the PSU is slightly less complex. Or they could replace the PSU wi
Re:How does this help? (Score:4, Insightful)
- But they still need to have the transformers to step down the voltage
This is done with a pulse-width modulator. An AC-DC power supply already has one of these running from 380VDC anyway. The 380VDC in that case is derived from a type of rectifier called a voltage doubler (in the case of 120V sources) or a full-wave rectifier (in the case of 240V sources). The excess voltage then comes from the fact that we are getting peak, rather than RMS, voltage from the AC to the DC side.
The savings is in that the rectifiers are all consolidated. The pulse-width modulators can have an efficiency as high as 95% easily, whereas a whole switching PS can be as bad as 50% efficient.
The savings are in the economies of scale for the rectifier. A similar savings could be realised in the pulse-width modulator, too, but would be quickly wiped out by the increase in losses by making long wire runs at low voltages (5V and 12V).
- DC requires twice as many wires
Nope. Still two to complete a circuit, just like AC.
dc / dc converter (Score:5, Interesting)
Working Models and Cost Issues (Score:4, Interesting)
Right now the cost of power is remaking the landscape of the data center industry. Yesterday there was another announcement of a huge data center in central Washington State [datacenterknowledge.com]. Sabey will invest $100 million in a facility right up the street from where Microsoft and Yahoo have data centers under construction. It's all about cheap hydro power. Both Microsoft and Yahoo have contracted for more than 40 megawatts of power [nwsource.com] from the local utility. That's why DC is one of the solutions that will begin to get serious consideration.
Re:Working Models and Cost Issues (Score:2)
What's next? Outsourcing to Canada to profit from lower ambient temperatures (=less cooling required)?
"Larger power cables" - WRONG (Score:5, Informative)
From the article:
(emphasis mine)
The power lost in the cables varies as the resistance of the cable and the current in the cable.
The power delivered to the equipment varies as the current in the cable and the voltage on the cable.
A 380 volt DC system can deliver as much power per unit current in the cables as a 380 volt AC system (assuming a near-unity power factor).
Ergo, the size of the cables for a 380VDC system will be the same as the size of cables for a 380VAC system.
So, if the comparison is against a 240VAC system, then a 380VDC system will have SMALLER cables, not larger. Only if the system being compared against is a 440VAC system will the cables be larger.
Also - a 380VRMS AC system will have a peak voltage of about 540 volts (two significant digits in, two significant digits out), and thus will require MORE insulation than a 380VDC system.
Also - the first things a switching power supply does is rectify the AC into DC and dump it into a capacitor (and usually do power factor correction): so a power supply designed to run from DC needs neither the power factor correction nor the big capacitor (a smaller cap will still be needed, but not one that can carry the system through the bulk of the AC cycle when the voltage is below peak). This makes the power supply simpler, and removes switching losses from the rectifier (granted, a modern synchronous rectifier based on IGBJTs will have a very low loss - but it still is a loss.)
Also - creating a backup for 380VDC is pretty easy - you use a battery bank floated at the 380VDC level. No need to "switch" from mains power to battery - you are ALWAYS running on battery, and the mains power is just charging the battery. This is how the phone company does it - the central office has a bank of batteries providing 48VDC, which is float charged from the mains. Lose mains power, and the system doesn't even blink.
(Yes, you need to have fusing to prevent those batteries from going nuclear if shorted, but that is a much simpler problem to solve than the issues of switching to backup power for an AC system.).
Yes, you have to design the equipment to run off the 380VDC - so you need different power supply front ends: most power supplies are split into 2 parts - the front end that takes mains power and makes about 300VDC on a cap, and the back end that makes the lower voltages from that - so the back end of the power supply does not need to be redesigned. Moreover, most power supplies use an off-the-shelf front end module, and any "magic" is in the back end - so this is NOT a major issue.
I see the reason, sort of. (Score:2)
That being said, you have to GET to 380V. My guess is they are simply rectifying 440VAC to DC.
Seems like a cleaver, efficient idea.
residential DC (Score:3, Interesting)
A DC power home would lend itself more readily to home based power generation. I believe most solar panels and windmill generate DC power which then has to be converted back to AC before it can be put on a powerline or used with conventional home appliances. With the new high efficiecy LED DC lights available the AC light bulb (a hundred year old device) is a real power hog and also generates enomrmous amounts of heat.
100 yrs ago when they were first bring electrical power to the masses perhaps AC was the right answer, but I believe our needs and priorities have changed in the past 100 yrs and perhaps the way we generate, distribute and use electricity is due for a new analysis.
AC conversion vs DC conversion and voltage FACTS (Score:3, Interesting)
2. A lot of AC/DC switching power supplies is a constant power load on the grid. It tends to draw more Amps as the Voltage decreases, producing a lot of harmonics in the mains power line, and a worse power factor than regular "resistive" equipment. Therefore the mains must be overdesigned to support this kind of load.
2. 220V AC means 220V *RMS*; 110V is just one of the wires tied to ground. The peak-peak is around 311V. Not that different from 380V
Comment removed (Score:5, Interesting)
What about 220VAC as an easier, partial solution? (Score:2)
Most computer equipment is still powered by 110VAC while mearly all of it is not only capable of running on 220VAC it runs more efficiently .
At my last job we were expanding our data center and put in a small handful of 220V circuits, by hooking up our biggest servers to 220 we were able to increase our UPS runtime by almost 10% and reduce our HVAC duty cycle by a bit in the process.
BITD when I went through Compaq ASE training the instructor mentioned that some server configurations (maxed out drive bay
Re:What about 220VAC as an easier, partial solutio (Score:3, Interesting)
When operating on exercises with our own or allied forces we used a special transducer and amp to play tapes of various Soviet boats. I wish I had the 500watt McIntosh tube amp we used.
In Wisconsin, we NEED the HEAT (Score:2)
This reminds me of a recent discussion I overheard here at work, yesterday. Some vendors were talking about an experiment they had heard of, where an entire office building was converted from fluorescent lighting over to LED lights. They claimed that the long-term cost was higher for LEDs due to an unexpected increase in heating costs, since the ballasts from the fluorescents had been helping to heat the building in the winter.
Here in Wisconsin, the heat "wasted" by computer systems isn't a complete l
Same data, different conclusion (Score:3, Funny)
My headline would read "DC Power Results in 15% Increase in Equipment in Data Centers"
Goodnight Tesla (Score:3, Interesting)
Maybe we can use the old AC network as a 3rd broadband line, after telco and cableco.
where does that DC come from? (Score:4, Insightful)
To get DC you, um, spin a coil in a magnetic field, then rectify it, then put a huge capacitor on there to flatten out the humps.
There's just no good method for generating DC. And even if there were, electric companies aren't going to run two new phases (DC+ and DC-) to get it to you from the source.
Instead, the power is going to come to near you as 3-phase, then be rectified. There is a loss in that rectification, but sadly, you can't eliminate it, just change where it happens. Moving it to the other side of your power meter will have an advantage since you theoretically wouldn't have to pay for the losses, although the electric companies would surely change their rates to recoup this lost money. But note that even if they don't change their rates, you haven't saved any energy, just not paid for as much.
So my guess is this experiment bought into this fallacy, that they measured their power usage at DC levels, found it was lower and reported that as a win, when without a source of DC power that doesn't involve rectification it really isn't.
I'm sure they save some electricity due to the increased voltage. That reduces current, which decreases power lost. This is the same reason electric companies use high voltages for power transmission.
The article seems to imply that power supplies convert 120VAC to 381VDC internally. This just isn't true. They never raise the voltage, and 120VAC peaks at 175V or something like that. Even 240V input would peak at 350V. So I don't get this. I think they just messed up a few numbers and really in the experiment connected rectified 240V (UK 240V, which is one phase double high, not the US one 120V phase over another) directly into the power supplies after the point where the rectifier would normally be.
From what I can tell, going to DC just would save you the cost of lots of little rectifiers in favor of the cost of one big one. To be honest, since the small rectifiers come in commodity ATX power supplies, you're paying almost nothing for them anyway. So I don't see that it's all that valueable to consolidate them.
I would recommend that if we wanted to save the most power on servers, we should just go to 3-phase 440V AC power supplies. A new connector would have to be designed, as the current 440V 3-phase connector would barely fit on the back of a tower, and wouldn't fit on a 1U server. This would save the most possible in losses without having to buy external rectifiers or force the electric companies to install one on site (and charge you back in increased rates).
Re:where does that DC come from? (Score:3, Informative)
A datacenter takes 3-phase 440VAC in, which goes directly into the backup power system. This converts the the AC into DC to be fed into the batteries, then the batteries are fed into a DC-AC converter to put out 60Hz sine wave AC. The AC from that converter then gets distributed to each computer. Each computer in turn takes that AC and converts it into 12/5/3.3VDC. Unfortunately all those AC-DC converters sitting in each computer are unne
Re:where does that DC come from? (Score:3, Insightful)
A switching mode PSU needs DC so AC from the wall goes first to a rectifier and then to at HF generator (100KHz or more), then to a relativly small transformer (HF = small loss = high efficiency on a transformer), then again to a rectifier and then to some voltage regulators (+12V, -12V, +5V, -5V, +3.3V).
It is littlt oversimpl
Just ask Telecom companies (Score:3, Insightful)
Re:Old time rivals at it again... (Score:5, Funny)
At 60 revolutions per second.
Re:Old time rivals at it again... (Score:2)
The main reason... (Score:3, Insightful)