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."

Comments

What's new about this?

[Flying pig]

DC buses have been used in military and industrial equipment since DC/DC converters were invented. (In fact, other former Cambridge undergraduates may remember the old 200V DC bus in the Cavendish labs, exposed contacts to the motors and all. Nostalgia...)

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:Safety

[Engineering_bully]

You probably don't realize that most of the lighting and mechanical systems in your data center are already 277/480 VAC. That is the standard power configuration for a new commercial building (cuts down on conductor sizes). There is a dedicated transformer to create 120 VAC for all the plug loads.

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

[peragrin]

So you also failed electrical theory, as well.

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:Here, here!

[saider]

Copper losses are created by current and are described by the equation I^2 * R. So as you double your current, you quadruple your power losses.

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.

Re:Safety

[CaptainPuppydog]

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.

From http://www.andamooka.org/reader.pl?pgid=liecDCDC_3 , AC will tend to induce fibrillation of the heart, while DC will tend to 'freeze' it. A 'frozen' heart is more likely to regain a normal beat than a fibrillating (rapid, irregular beat) heart. Either way, not a 'Good Thing'.

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.