DC Power Saves 15% Energy and Cost @ Data Center

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."

dc / dc converter

[wwwillem]

Would be interesting to know what the efficiency is of a 380 -> 12/5 DC-DC converter, compared to a traditional 110 AC -> 12/5 DC converter. This is of course only just a part of the total picture, but in the past this has often been mentioned as the reason for _not_ going DC. Maybe with modern switching power supplies, that problem has disappeared.

Working Models and Cost Issues

[miller60]

This issue has a been a hot topic [datacenterknowledge.com] at conferences for data center professionals, with a lot of debate about timetables. Several facility designers are advocating DC distribution as the solution to the current power/cooling challenges. Corporate data center managers like the cost savings projections, but want to see it work in someone else's facility before they put their neck on the line and pitch a DC conversion to their bosses. That's the real value of the Livermore project discussed in TFA - it provides a working model.

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:Safety

[MindStalker]

Yea DC is a strange beast, a small jolt or small voltage of DC is safer. The dangerous part of DC is
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:Here, here!

[cswiger2005]

Agreed-- that level of DC voltage is actively dangerous, and I wonder why they are running that high a voltage when most of the equipment in the racks is gonna want +5VDC & +12VDC rails. Perhaps they are using it to power big DC motors in fans and AC/cooling/dehumidifying equipment, but it would seem to make more sense to feed those with 3-phase AC and use a more sensible VDC delivery at, say, 48V, which is a telco standard...

Re:The Telcos have known this for years

[hauntingthunder]

re 48V in telco buildings

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 bussbars - which then shorted - an explosive way of painting a room.

I once had to help install some sun servers in an exchange (CAPITAL) and walking around - the building most of the old stuff had been taken out - was quite eerie lots of clicking and odd buzzes.

CAPITAL is/was one of the main exchanges in the uk its actually in Edinburgh not London Rgds M

Re:Safety

[gurps_npc]

You have your facts backwards. Human beings are far more sucpetible to Alternating current than to Direct Current. One of the reasons Edison prefereed using Direct Current was that if everything else is the same, house hold Alternating Current will kill you, while the same amount of electricity transformed to Direct Current will not.

residential DC

[tmbailey123]

I wonder if you would see the same 15% power saving if a home was outfitted for DC use ? When you think about it most electronic devices in the home have power supplies embedded which are nothing more than AC-DC coverters, which in and of themselves waste energy.

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.

Re:Safety

[Engineering_bully]

In the 277/480 VAC system the phase to neutral (and typically ground) voltage is 277 VAC. The difference phase angle makes the phase to phase voltage 480 VAC (not 277*3 = 831 VAC).

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.

AC conversion vs DC conversion and voltage FACTS

[viking2000]

1. DC/DC conversion is cheaper and simpler bacause with a 60Hz AC signal, you have *no* power during the zero crossing. The PS has to store the energy in a capacitor or a coil to deliver during the 120 "outages" a second. A DC/DC converter operates at hundreds of kHz, so components are much smaller, and since the conversion uses square waves, it does not have the "outages" a sine function has on the input.

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

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Goodnight Tesla

[Doc Ruby]

Don't hydrogen fuelcells generate DC? I can't wait to hook my home gaspipe to more than just my stove, and suck in the MWs direct to my devices. Without all those AC adapters left over from the 20th Century cluttering my home, getting hot, drawing power when "off", getting lost and mixed up...

Maybe we can use the old AC network as a 3rd broadband line, after telco and cableco.

At 48V, couldn't you go solar too?

[denis-The-menace]

Instead of using a 380-volt DC distribution system, why not use the telephone standard: 48V? Then you could use the same 48V connectors (STD equipment, lower cost) to plug into converters that would be in the same form factor as regular AC power supplies. Then, if you really what to save money, have solar panels (or other means of power generation) to charge batteries that would feed the 48V system. Built-in UPS!
Hum, I might be too idealist, here...

Re:Safety

[VAXcat]

This reminds me of one of the troubleshooting steps taught to me by my old motorcycle gang bros...when you're troubleshooting an engine fails to start problem, first step is decide if it is a fuel delivery or no-spark problem. If you're sure it's a no-spark problem, then firmly grasp the metal part of the spark plug lead and kick the engine over...what's that, you're not willing to do that? Then, you aren't really sure it's a no-spark problem - keep thinking and testing until you are.

Re:Here, here!

[quoll]

That's true for transmission over longer distances, but what about those short distances in the data room? Or for that matter, in my home office?

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:What about 220VAC as an easier, partial solutio

[BCW2]

The freq switch smoothed out the motor in the tape drive. There was almost no hum detectable compared to 60 hertz. When listening to Soviet boats we would alter 60 hertz up or down (58, 59, 61, 62) to alter our own background noise and unmask tones on that line from the contact.

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.

DC at home

[FrankMachine]

Forget DataCenters.
How about 12V DC at home, so that I can get rid of the half dozen little tranformers plugged-in under my desk?

What are the real objections to 12V in the home?

The most sensible one I've heard is most digital devices need a fairly fixed voltage drop, which probably means that need to be in parallel. That pushs your current thru the entire system up, perhaps to dangerous levels.