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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."
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
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.
GE is what became of the Edison General Electric Company, the losing proponent of DC Municipal Power a century ago.
I can see the fnords!
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.
SIG: HUP
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
OH look, a TROLL!!
Whoever modded this informative is an IDIOT.
In reality:
"Low frequency (50-60 Hz) alternating currents can be more dangerous than similar levels of DC since the alternating fluctuations can cause the heart to lose coordination, inducing ventricular fibrillation, which then rapidly leads to death within six to eight minutes from anoxia of the brain and medulla.[9] However, any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow, whether it uses alternating or direct current. Since the precautions against electrocution are similar, ultimately, the advantages of AC power transmission outweighed this theoretical risk, and it was eventually adopted as the standard worldwide."
Here is a whole thread about the subject:
http://cr4.globalspec.com/thread/3212/Which-is-More-Dangerous-AC-or-DC
DC power lost the "current wars" because we didn't have solid state transformers capable of doing voltage step up/down like we did with AC back in the day (simple wound transformers).
These days even the cost of really high power DC transformers (>500,000 volts) is offset by more efficient transmission and a number of notable long-distance power lines are actually DC for that reason (lower losses offset cost of transformers).
By stepping up the voltage, such as to 48v, you can significantly lower the losses, shrink required conductor sizes, make the circuit breakers cheaper, and still derive the same benefits (48v->12v->5v->3.3v DC transformers are actually fairly cheap, unlike their high-power cousins).
Why do you think some car makers are switching to 48v DC on-board power and 48v batteries? You can greatly increase efficiency and lower weight since so many devices are electrical on modern cars.
Natural != (nontoxic || beneficial)
The concept is actually to go with a European 240/415V system rather than ever using US voltages of 480/277 and 120/208V; you step down from medium voltage directly to the 400V. "Best practices" would be to have an offline or line-interactive UPS.
The biggest gain is actually in the power supplies and not the electrical distribution system. I'm a fan of 600VDC in the data center from an engineering perspective, but there are huge safety issues that need to be resolved to make it viable. (DC arcs don't self extinguish as there is never a zero crossing.)
When discussions were first being done five years or so ago, my theory was that for it to be practical you would need a 3N design rather than today's 2N system, as all work would need to be done on cold busses and you still had to maintain 2N redundancy.
> 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
It isn't half as many amps, it is only a 15% reduction since 208V is used in the US for data centers. The benefit (albeit at the expense of fault current) is eliminating one AC:AC transition in the process. The same could be said for getting equipment to operate at 277VAC similar to lighting in the US.
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
In fact AC loses slightly more at a given voltage, up to a lot more for really long wires.
Whiskey. Tango. Foxtrot. Line losses are based on current not voltage. And with AC you can convert current and voltage with a transformer with a very high Q. That's why AC (Tesla) beat DC (Edison) at the turn of the century for power distribution. Also, direct current generates more heat than alternating current. -_-
#fuckbeta #iamslashdot #dicemustdie
These days they are usually switching power supplies, which are quite efficient (not to mention smaller).
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.
It should be noted that the only savings is in the infrastructure, not in ongoing energy costs. Power = current * volts, so whether you're using 240V or 120V, the overall power (measured in watts) is the same, and thus the overall power bill is practically the same. There will be slight differences in efficiencies, but you really won't gain all that much.
The biggest difference is, yes, you could get away with less overall wiring costs to carry the same amount of power.
For those running on equipment that is currently running on 110-120v, it's a 50% amperage reduction, especially since anything designed to run on 208V will also handle 220v-240v just fine.
Kevin Smith on Prince
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).
Opportunity for some power supply manufacturer here.
Some time ago I was tasked with solving the brick proliferation problem for a national retailer. The cheap little wall-plug PSU's that were proliferating under the POS lanes were considered dangerous.
My response was to talk to a power supply manufacturer and get them to design a single wall-mount PSU with multiple DC leads using a variety of connectors to fit the various POS peripherals (fortunately they all used a standard DC voltage).
The output leads were separate wires with plug-in connectors at each end so as to offer choice of length and to match the connector requirements of the periphs. If you're going after a couple hundred units or so, these firms will be glad to design and produce a unit for you, with your choice of leads & all. If you have multiple bricks with the same output voltage, this could be your solution. But some retailer would have to step forward I'd think, to order the minimum quantity.
Do not mock my vision of impractical footwear
No WTF.
At a given voltage/amperage, DC will lose less power per mile than AC. However, AC transformation equipment is cheaper/more efficient than DC.
At a couple hundred miles, DC becomes the more cost effective solution for a high power run.
Also, direct current generates more heat than alternating current
Not at the same wattage.
I don't read AC A human right
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.
Linear power supplies in consumer devices disappeared years ago. I don't think I ever saw a wall-wart that actually had linear regulators in it, even back in the 80's. They're all switching supplies now, running very efficiently at very high frequencies, which is why you can get 50-100 watts out of that little brick that powers your laptop.
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
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
Having a standardized DC plug would be a good thing. There could be power bars and UPSes which provide it, and eventually household outlets could have DC sockets, alongside the 120V sockets.
USB would almost be a good choice, but unfortunately it only provides 5V, and 500 mA. Enough to power/charge some small devices, but not everything. PoweredUSB comes a step closer, but it is proprietary and the current is probably still too low to be useful for everything.
A connector/plug like Serial ATA power is probably getting closer to being a good general purpose connector, although the current is again still too low to be useful for things like computers or TVs. The nice thing about SATA power is it provides 3.3V, 5V, and 12V, which covers voltage requirements for most devices. You'd obviously use a cable more suited to the outside world than the typical cables used inside PC cases.
If this connector (or something similar) could be scaled up so it was bigger, and supported higher current ratings, it would probably be ideal.
In your house, alongside your AC breaker panel, you'd have a DC transformer and another breaker panel for it.
Speak before you think
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.
Half as many amps == half as many power strips, half as many UPS devices, half as much wire, etc.
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This is all utterly and completely false. Number of amps does not affect number of power strips as other posters have proven with math the first computer could have done. (20 == 20 => true)
The number of amps does not affect the number or capacity of UPS devices; it is Watts (commonly referred to as volt-amps) which dictates this, and it remains constant for a specific device no matter the supply voltage.
Your wire savings formula is flawed, unless the 240/415V technique is used as proposed (sort of) by another poster.
As mentioned by another poster, data centers are 3 phase electrical installations. This means there are three wires with alternating voltage in them, and they are all at peak at different times. A wiring technique is used in many installations called "Edison Three Wire" (I have no idea if they use this in data centers, but if they don't, they're stupid) This brings two live wires and one neutral wire to a location requiring two circuits of a given amperage. Let's call it 30A since this requires 10GA wire on a short run from the panel. Two Circuits, three wires. If you remove the ability to use Edison three wire by using 208 V circuits involving no neutral and two live wires, you increase the wire usage by 50%. An up in voltage yields a down in voltage by the same factor. The savings in current is only 42%. 150% of the number of wires times 57% as much ampacity. 17A requires 12GA wire, or run 14GA wire and a 15A circuit breaker which you pray no one trips on a daily basis. (Wow that's reliable) This does not factor in the need by law for each circuit to have a separate ground wire, adding to the number of wires.
10GA wire has a cross sectional area of 10.4 thousand circular mils or kcmil. (mil = 0.001 inch) (1 circular mil is when you have circle radius 0.001 inch.)
12GA wire is 6.53kcmil
14GA wire is 4.11kcmil
Wikipedia on AWG
For arguments sake and the fact that calculations dictated that a circuit now needs 17A down from 30A, we'll use 12GA wire. If you want to argue that it could be 14GA consider the fact that if you cut the available current by 2A you will likely need to increase the number of circuits to an enclosure or other fixture such as cooling or lighting. This will require larger distribution panels, bigger feeder cables, larger conduits, and all around more electrical capacity when dealing with things such as generators and UPS. This will eat into the savings.
Your new wire is 65% as much copper as the old wire. You require 150% as many wires not counting grounding/bonding. Your total mass of copper used is now 97.5% as much as before. A total savings of: precisely dick.
Or, you can double the voltage of every circuit in the data center and leave the electrical network topology the same. This requires new transformers, new distribution equipment, and now run the risk of never being able to provide a customer a 120V circuit for their wall-wart powered device. (I'm assuming that's a transformer block, many of which are now supporting 240V anyway) You could save about 60% as much copper mass, and then spend 10x more replacing all the other equipment which delivers the electricity around the data center, keeping in mind the cost of hiring a certified electrician to install this is tremendous.
Wire is the cheapest piece of equipment in the entire building, and it's the only thing that will be saved in the 240V datacenter, even if you start a brand new building from scratch with this in mind from the first mark on the design plan. Get over it. No one wants to do it.
Perhaps an electrical engineer could come up with some more promising data for converting data centers to 240V up from 120V, however I'm quite certain an EE wouldn't say "WHERE'S MY FISH YOU IDIOT"
Topic Change
Drifting away from t
Sadly, a Libertarian cannot force his views on another, and freedom cannot spread as does the cancer known as religion.
uhh, the common D cell is 1.5v (ok carbon-zinc) so, by my calculations you only need 320 of them too make 480v :P
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Or, better yet, strips of IEC-C13 jacks. Anyone who's plugged in a computer will be familiar with those:
http://www.geistmfg.com/_Apps/catalog/images/items/Item_260_1.jpg