University Switches To DC Workstations

An anonymous reader writes "Researchers at the University of Bath, UK are undertaking an in-depth study of energy consumption within the new network, with the aim of demonstrating that running a large network of devices on DC rather than AC is both more secure and more energy efficient. AC electric power from the grid is converted to DC and runs 50 specially adapted computers in the University Library. Students using the system have noticed that the new computers are more compact and much quieter than the previous systems. The immediate advantages of the new system are not only for the user but for the energy bill payer and the environment."

Comments

So... what?

[MobileTatsu-NJG]

They switched to laptops?

Re:So... what?

[somersault]

Tesla is giggling in his grave

Re:So... what?

[Opportunist]

Too bad, if he was rotating it would probably generate some power.

Re:So... what?

[ShakaUVM]

Edison: "Genius is one percent inspiration and ninety-nine percent perspiration."

Tesla: "If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found the object of his search. I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety percent of his labor."

Re:So... what?

[danlip]

Truthfully both approaches are valuable, and we would be a poorer planet without either of these men. It's a shame they disliked each other so much.

Edison: "Genius is one percent inspiration and ninety-nine percent perspiration."

Edison contracted out all his perspiration. That's genius.

Re:So... what?

[Junior J. Junior III]

Tesla was the one who advocated for AC power. Edison was the one who argued for DC as the safer choice, and publicly electrocuted horses and other animals using AC to show how unsafe it was.

Re:So... what?

[GooberToo]

Ummm...no. I'm pretty sure people understand how a power receptacle works.

Engergy efficiency has little to do with the device itself.

Completely wrong as you're not looking in the right place. Massive amounts of power in wasted on inefficient power converters. Many are frequently in the 80%. Part of this is higher efficiencies demand higher prices. So, frequently to save money, low efficiency converters are provided with consumer goods. Even many PC's have efficiencies which which range from very high 80s to very high 90s. The difference is almost always dictated by price.

Now then, if a house had a single converter, you would have a single, high efficiency unit which need only be purchased once rather than for every consumer purchase. This in turn, lowers the cost of consumer goods which dramatically increasing consumer household efficiency for many, many electronic goods. The vast majority of all electronic goods in the world comes with yet another converter; needlessly.

Most studies clearly indicate as much as 20% of American's power demands could be reduced by such moves. That's massive despite your hand waving.

Re:So... what?

[solarnetone]

12VDC at infinite amps will do nothing to you, as 12V in not enough pressure to overcome the resistance of human flesh. The wire needs to be a bit larger for the lower potential source, tho.

Re:So... what?

[Amouth]

i'd rather be hit with 120vac on a 15amp breaker than 120vdc on a 15amp fuse any day

AC will throw you - DC will make you clinch to it.

Re:So... what?

[guruevi]

DO NOT DO THIS!!! If you have cuts and/or your hands are wet/moist you could still get a tingle. Car batteries are made to give ~120A, plenty of Amps to seriously hurt you if something goes wrong (eg. your ring/watch/other jewelry makes contact between your hand and the ground of the car).

To see what a car battery can do, put starter cables on the battery, close the hood and then push the other two ends together with a long wooden or plastic stick. Close the hood just in case your battery explodes. It might catch fire if you weld the other ends together so have a non-water based extinguisher at the ready.

Re:So... what?

[labnet]

You yanks are pussies. In Australia we flick 240vac with the back of our hand to see if its live or not.

Re:So... what?

[Grishnakh]

AC is still the prime motive force in electrical generation and always will be.

No, not necessarily.

We've already started moving away from AC for long-distance power transmission, using "HVDC" instead for things like 2MV transmission lines.

The main advantage of AC is that, with no semiconductor technology available, you can easily step it up and down between different voltages using an iron-core transformer, nothing more than a bunch of iron and some copper wire wrapped around it. High voltage is absolutely necessary for power transmission, because I^2*R losses are too high at lower voltages, but high voltage isn't usable by end-users because of safety and other concerns.

Nowadays, with power electronics (giant power transistors capable of handling thousands of volts and amps) and high-frequency switch-mode power conversion, that stuff is mainly obsolete, so it's fully possible to eliminate AC for power transmission, and even get better conversion efficiency than transformers. The only reason it's really still used is 1) our infrastructure already uses AC, so you can only replace it in certain places where it won't be too disruptive (like long-distance links), and 2) iron-core transformers are still much cheaper than electronic alternatives, so it's only economically feasible to switch to DC for certain large-scale projects, not for every transformer in a subdivision.

There's no technical reason that, in the future, DC couldn't become the standard, with electronic "transformers" stepping the voltage up and down as necessary.

Re:So... what?

[Grishnakh]

You're missing the point. Much of our electronics run on 5V DC. If you put a big 5V converter on the side of your house, and a bus system to connect this to all your 5V gadgets, the losses would be greater than just having all those wall-warts. Even worse, your gadgets wouldn't work, because the voltage drop between your converter and your gadgets would be so great, you'd end up getting 4V at the gadget, and worse, the drop would vary depending on how much current that gadget is drawing (and other gadgets on that run).

If you want to be more efficient, the answer is simple: throw away all those wasteful transformer-based wall-warts, and replace them with high-quality switching wall-warts instead. They're lighter and also have better efficiency, both when under load and when not loaded. The problem is that switching wall-warts cost more than the crappy Indian and Chinese-made transformer-based ones, so gadget makers don't usually bother to include them.

Switching to DC isn't a magic bullet to solve energy efficiency problems, despite this idiotic (and just plain wrong) article.

Re:So... what?

[vivian]

You are not quite comparing apples to apples. 12VDC at 10A would only be 120W of power - not enough to run most desktops.
At 120VAC, this would only be 1A.

120VAC like used in US houses is supplied at something like 15 to 20A. (I live in Australia - household power here is 240v, 10A.)

If you needed to supply enough DC for several computers, TV's, and pretty much anything which doesn't have a high power motor or heating element in it, you would need to be able to supply a lot more than 120 Watts. My PC + monitors alone are drawing 280 Watts.

So say you wanted a household DC supply that needed to be able to provide a 12v rail at 600 Watts - possibly just enough to run two computers and monitors.
The current needed would be 50 Amps - and you would need wiring that's about thick as car jumper leads.

This would make wiring very expensive. There is also an additional danger of having such large currents - it is a lot easier to have a fire due to resistive heating of a weak connection or damaged wire.

Re:So... what?

[thedarknite]

120VAC like used in US houses is supplied at something like 15 to 20A. (I live in Australia - household power here is 240v, 10A.)

Electrical supply in Australia is 230V/50Hz. Residential switchboards have an 80A fuse to the mains and the individual circuits have 5/10/15/20A fuses/breakers depending on the age of the house and the expected circuit usage. In my current house the lights are wired into a 5A circuit, living areas are on 10A circuits, kitchen and laundry are a 15A circuit and the garage is a 20A circuit.

secure?

[Hazel Bergeron]

There is no evidence or reason for DC to be more "secure". If some lame argument about it being harder to bring your own power source / utilise their outlets when you have a custom system is put forward, then, well... no.

I can understand the efficiency argument to a certain extent, although if a workstation needs enough power that a fanless AC PSU is unsuitable then the more efficient AC PSUs will be enjoying enough load to reach over 80% efficiency. Are the centralised rectifiers + wires + in-computer DC-to-DC converters as efficient?

Re:secure?

[Hazel Bergeron]

Doesn't the most basic 80 PLUS rating require 80% efficiency at 20% load?

Re:secure?

[rAiNsT0rm]

That is the claim but many fail that and don't actually get close until 50% or higher, a few sites have done real world testing and have proven it. The other thing is that people always way over estimate the draw of components or simply go for the "bigger is better" mentality. I've seen so many 1KW PSU's in systems drawing 200watts or less. The wiki page gets into it all a little bit: http://en.wikipedia.org/wiki/80_PLUS

Re:secure?

[LordLimecat]

Its not that you can't design build and sell a 99% AC supply, its just you can't do so and survive in this weird confuseopoly market where the only thing that matters is price

Lets see if it really makes sense to get that 99% AC supply, since you think its such a brilliant idea.

My Core2Duo system w/ graphics card chews up a whopping 225 watts under full load (measured with wattmeter), with an 80% efficiency PSU. That means the PSU is wasting an astonishing 225 * .20 = 45 watts. The kWh rate here is around $0.062 after generation and distribution. That means per month, it costs me about 8.37 cents for having such an inefficient PSU. I purchased it about 5 years ago (June 2006 I believe), and it has run for the most part 24/7-- we will assume full load and constant operation. This means over the past 5 years, I have spent 5*12 * 0.0837 = $5.02 on electricity for said PSU.

Now for the kicker, this fine Antec PSU cost around $50. Show me your 99% efficient AC PSU for $55-- not even taking into account this was 5 years ago, or that actual average load is likely to be closer to 160watts.

In no sense does it make sense to spend what would likely be several hundred dollars, and a boatload more emissions, on manufacturing a PSU with such high performances, to save a measly $5 and around 15kWh per year.

Re:secure?

[Hazel Bergeron]

Erm, wasted this month: 45W * (24 * 31) hours = 33.5kWh = $2.08.

Also, that kWh rate is fairly cheap...

AC?

[Anonymous Coward]

The only thing inside a computer that actually runs on AC is the computer's powersupply. The powersupply regulates this to DC voltages! The powersupply is also quite bulky and noisy compared to the other components.

"Initial tests show that the system in Bath emits approximately half as much energy as heat than the previous AC powered system while running much faster."

Yes, I'm sure it'll generate less heat when most of that heat comes from converting AC to DC, but why the hell would it run faster when everything else in the computer is still the same?

Dumb idea

[Animats]

There's something to be said for DC distribution within data center racks, but building a plug-in DC infrastructure seems like a PR stunt. They need a whole rack of power conversion gear to serve 50 desktop computers.

Google at one point proposed that rackmount computers should be built to run on 12VDC only, so you could have a single 12VDC supply in the rack and get rid of the individual power supplies for the server. Whatever happened to that?

Much industrial automation gear and military equipment runs off 24VDC. That's low enough that you don't have a shock hazard, but high enough that the wire sizes are reasonable.

Re:Tesla v. Edison

[Corporate Troll]

AC is the tool for killing Elephants though. linky

More Secure? Regionalism, maybe?

[rwade]

Selective quotes from TFA:

Researchers at the University are undertaking an in-depth study of energy consumption within the new network, with the aim of demonstrating that running a large network of devices on DC rather than AC is both more secure and more energy efficient.

The new DC network also offers greater security. DC power supply units have a simpler design, with fewer parts that could fail and need replacing. The system at the University also charges a number of batteries when usage levels are low to allow the system to run independently from the grid for up to eight hours should a cut in power be experienced.

The above two paragraphs are the only I could find in TFA that mention security. I gotta ask -- can anyone speculate how centralizing the PSU would lead to a more secure system? Is it possible that there is a regional definition of "secure" to mean "very reliabile" or "very available." As in, we have "secured" a constant municipal water supply?

Re:More Secure? Regionalism, maybe?

[xs650]

"Is it possible that there is a regional definition of "secure" to mean "very reliabile" or "very available."

Yes, it's regional, as in "The wankers will stop nicking the computers if they can't use them at home."

AC vs DC

[prakslash]

The major drawback to DC power is in the wiring. Direct current requires larger gauge wiring than AC power, which increases material costs considerably. In general, DC power is economical only if the wiring between the computers and the DC source is less than 35 feet in length. More than that, AC power becomes more economical.

Re:AC vs DC

[TDyl]

I guess I could swing either way on this one.

Re:AC vs DC

[Muad'Dave]

I'm not sure how you came to that conclusion. AC suffers from several effects that make it less efficient and/or more expensive over long distances.

For DC, the power delivered is V*I. For AC, it's similar except the V is really Vrms - you must insulate for Vpeak, but you only get Vrms * I power. For sinusoidal AC, the difference is a factor of 1.414.

With AC circuits that have non-zero reactance, you must choose a conductor that can carry Imax, but the power delivered to the load is only Vrms * Imax * cos(phi), phi being the phase angle between the voltage and current.

AC circuits suffer from the skin effect where the power travels more on the surface of the conductor rather than equally throughout its cross-section. This requires a larger solid or stranded conductor than would be required for DC.

AC has a few things going for it - the ease with which voltage can be transformed, the ease of generation with rotating generators, and ability to drive large, multiphase motors efficiently.

Re:AC vs DC

[vlm]

The major drawback to DC power is in the wiring. Direct current requires larger gauge wiring than AC power, which increases material costs considerably. In general, DC power is economical only if the wiring between the computers and the DC source is less than 35 feet in length. More than that, AC power becomes more economical.

FTFA:

the project team moved the one tonne AC converter through the University library and into the roof space, removing and rebuilding walls to transport it

Somehow, I suspect that the cable run to the individual machines is more than 35 feet.

His figure of 35 feet is of course completely made up, or at best applies only to one very specific situation. Its a rather complex non-linear solution that depends on current level, local union labor contracts, price of copper wire, UPS and battery capacity, etc.

Obviously, if you are charging an ipod at a zillionth an amp after a 12V to 5V converter, you can run that thru thousands of feet of small gauge (cheap) speaker wire before the voltage drop will matter. And if you're doing the thousand watt gamer PC or NAS farm you'll need something approaching welding cable to keep the voltage drop low enough. In between, well, its in between. But by no means as simple as a 35 foot cutoff.

Re:AC vs DC

[Anonymous Coward]

AC circuits suffer from the skin effect where the power travels more on the surface of the conductor rather than equally throughout its cross-section. This requires a larger solid or stranded conductor than would be required for DC.

Did you READ the article you linked on this? "At 60 Hz in copper, the skin depth is about 8.5 mm." If you've got wires with 17+mm diameter solid conductors in them, you're DOING IT WRONG...

Re:AC vs DC

[seanadams.com]

With AC circuits that have non-zero reactance, you must choose a conductor that can carry Imax, but the power delivered to the load is only Vrms * Imax * cos(phi), phi being the phase angle between the voltage and current.

With respect to RMS vs peak, you are thinking of the *voltage* rating (what the insulation can withstand), NOT the current rating. Economically the insulation rating is not low hanging fruit for optimization - the copper conductor is by far the bulk of the cost and this can not be downsized for DC because it is the average thermal dissipation in the wire that determines its current carrying capacity. This is the same for a given DC vs AC operating voltage and load.

AC circuits suffer from the skin effect [wikipedia.org] where the power travels more on the surface of the conductor rather than equally throughout its cross-section. This requires a larger solid or stranded conductor than would be required for DC.

Stranded wire is used for electrical distribution not because of the skin effect, but because it's easier to bend, pull, and terminate (except for #12 or smaller because usually you prefer it to hold its shape). At 60Hz the skin depth is 8.5 mm - it just doesn't come into play at such a low frequency for building power distribution.

Con Edison

[The Grim Reefer2]

I guess Con Edison should have waited just a few more years. Apparently 125 was not quite enough.

I think I speak for us all when I say "Huh???"

[$RANDOMLUSER]

Initial tests show that the system in Bath emits approximately half as much energy as heat than the previous AC powered system while running much faster.

If you mean "much cooler", you already said that. If you mean "much faster", you should probably sign up for that physics (or electronics) course.

The new DC network also offers greater security. DC power supply units have a simpler design, with fewer parts that could fail and need replacing.

So you don't mean "security", you mean "reliability".

Decarbonisation will increase electricity consumption by 2030 and possibly more than double it by 2050.

I wonder how much carbon was released refining all the lead in all those batteries...

Re:I think I speak for us all when I say "Huh???"

[adonoman]

running much faster

With DC power, the electrons get to run laps, and every time they get to your computer, they can do a little bit of work, spreading it out among all the electrons. With AC power you got those electron thingies racing back and forth and back and forth, but never getting anywhere. Only the few electrons near the computer actually do any helpful work, and they get worn down really quickly, so they stop working as efficiently, and the CPU slows down, and it's just generally bad.

Where did the heat go?

[DeadCatX2]

They just move the AC/DC conversion somewhere else. All of the heat will go along with it.

Re:Where did the heat go?

[tomhudson]

From TFA:

Also:

the project team moved the one tonne AC converter through the University library and into the roof space, removing and rebuilding walls to transport it

It would have been cheaper to just use 50 energy-efficient laptops. You'd get even more power savings, and if you wanted to completely remove the heat from the transformers, just put them all in a cabinet that vents outdoors, and extend the DC power plugs.

And you wouldn't have to also invest in another ton of batteries.

wow, newer = faster and smaller, big deal

[alta]

Ok, so people have 'noticed' that these NEW computers are faster, quieter, smaller and just magically better than the old system.

This is obviously not very scientific, I'd venture to say if they replaced the entire old system with a new AC system, it would still be faster, quieter, smaller, etc...

Yes, DC may be great, but these observations can be said about any new vs old setup.

Back in (the) Black

[demonbug]

So they went AC-DC to try and get back in (the) black?
My concern is that the initial conversion would cost a touch too much, and it ain't no fun waiting for the energy savings to cover the investment - the down payment blues.
Still, in my experience the power supply is often the point of failure that finally kills the whole computer, so goodbye & good riddance to bad luck.

Actually DC is great for long distances too

[Viol8]

Its the voltage that matters when transmitting over long distances, not the type of current. In fact DC is slightly more efficient for a given voltage though you'd have to ask a physicist why.

Re:DC-DC conversion?

[vlm]

Today if you blow a power supply (one of the most common computer failures) you lose one computer. If you blow the power supply for the office floor you might lose 100 or 200 computers.

For reasons which are a long story, I have had several servers up and running on 12V for many years now. The powerstream guys are pretty much the gold standard of ATX 12 volt power supplies, as far as I know:

http://www.powerstream.com/DC-PC-12V.htm

Note that these are "honest wattages" not the "marketing wattages" seen in the AC power industry. The price of a 300 watt DC supply seems high compared to a 100 watt AC supply from China that has a sticker claiming 300 watts. However its not too bad compared to a AC supply that actually only provides 300 watts despite having a sticker labeled 800 watts or a million watts or whatever marketing felt necessary. Also the powerstream supplies, to the best of my knowledge, are some of the few computer power supplies you can buy that do not have forged FCC and UL registries, which is worth something to me. In summary, expensive, but strongly recommend based on years of experience.

Anyway, what happens when the primary rectifier goes down, is my battery bank will run the asterisk PBX and friends for something like half a day, during which time I can source a generator and charger, or perhaps casually purchase a new supply, etc. Also I have multiple supplies any of which could theoretically power the whole works (at a cost of high heat and much shorter capacitor lifetimes, etc). So you Y-cable them to run multiple plants off one supply. Guess what, the same Y cable can be used to run multiple plants off one battery, if one fails. Etc.

Theoretically, I could run the entire phone system off an idling car, assuming you have enough gas in the tank. Unfortunately my entire plant draws just a little too much for the cigarette lighter plug, probably 15 amps total. If I could invest in new phones / new servers / etc and get total plant draw down to 5 amps, not only would my batteries be 1/3 cheaper or last 3 times longer in an outage, but I could also run the works conveniently off a car cig lighter port.

Obviously if you have zero battery capacity then you are instantly in deep doo doo, but given three or so figures of amp-hours you're good to go for a very long time.

Wire everything in Amphenol power poles, exactly like the ham radio guys so you can use their DC products, and keep a stock of extension cords and Y cables and other gadgets. Use fuses, and as a subset of that rule, only use automotive fuses because they are infinitely available. Use 12 volts as your standard because you probably own a mobile 12 volt generator (aka your car). Perhaps if you're in the .mil and have a 24 volt humvee, do 24v instead, whatever.

A DC powered system is frankly pretty straightforward and simple.

Why we have AC

[headhot]

AC is much easier to transport. DC resistance in the AC world is impedance. As impedance is complex, If you choose the correct frequency and voltage, you can move power very very far distances with extremely little loss. You cant do that with DC.

Also, when houses were getting power, all they had was lights, and motors, all of which run fine on AC.

When electronics started to come out, a house only had a handful, TV, Radio, that was it.

Now, I would say that a significant part of consumption is DC at a home, but there is no standard in the house for a parallel DC infrastructure. Would you do -48V like the phone companies? 12V? How would the in wall wiring work?

Re:DC-DC conversion?

[Big_Mamma]

Huh? The linked products are beyond horrible compared to any decent and MUCH cheaper AC PSU. Just look at any half decent review site, like the awarded products @ hardwaresecrets.

I won't be paying $280 for a 400W DC PSU with 65% efficiency when I can get a whisper silent 500W PSU at 87%+ efficiency for $99 (Enermax Pro87+), or a fanless Seasonic X-400 for $134. The numbers just don't make sense. And yes, these are "honest" wattages, the 400W one actually delivered 600 in overload testing. You do have to do your homework when it comes to buying a PSU, but it really isn't that hard nowadays - aim for 80+ Gold and it's usually safe.

I don't really care how simple and straight forward a DC system is, but if it's costing me 2-3x in purchase and wastes 30% of the input power as heat, count me out.

I vote for -48 Volts DC

[KenSeymour]

When I first had to deal with telephone equipment, I came across the -48 VDC power standard for things like SONET nodes, digital cross connects, channel banks, and telephone switches. I believe this is due to cathodic protection of buried copper cables.

You can find -48 VDC rectifiers, AB fuse panels (think redundant DC power supplies) and lots of telecom gear in racks that is powered with -48 VDC.

Re:I would love to make the conversion

[Draknor]

Third parties would spring up to provide cables to connect the router you already have to this DC outlet in place of the wall-wart.

I sort of did something like this once; for some reason or another I had an ethernet switch without a working transformer. I simply chopped off the DC power plug, soldered it onto the 12v pins on a 4-pin molex, and plugged it into my PC power supply. As long as the PC was up, so was the network! I might even have run a small LAN party this way for a weekend.

The truth is, all those wall warts could be our saviors -- many electronic devices already accept DC direct, you just need a supply for them. You just need something like a "power hub" (analogous to a USB hub) -- a single AC/DC transformer with 4-8 12v DC outputs on it, and a pile of cables (maybe with interchangeable tips), to fit the devices you have.