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Are Data Centers Finally Ready For DC Power?
1sockchuck writes "It's been five years since a landmark study outlined the potential benefits of DC power distribution in data centers. But adoption of DC in data centers remains limited, even as the industry aggressively pursues a wide array of other energy savings strategies. Advocates of DC distribution are hoping a new study will jump start the conversation about DC distribution, which can save energy by eliminating several wasteful AC-to-DC conversions within a data center. Meanwhile, an industry association for DC power adoption, the EMerge Alliance, has formed a new technical standards committee for data centers, and is advancing a 380-volt DC power standard. Will DC distribution ever gain momentum in data centers?"
I told you bitches I would prevail one day!
DC power is the standard in the telecom industry.
I design systems based around HP's BladeSystem, and the DC power modules just drop in and go. It's very easy, works great, and most of all, my telecom customers love them.
There's no particular reason that 380 VDC distribution should help efficiency. You still need about two more levels of switching power supply before power reaches the ICs.
Google's proposal that motherboards should need only 12VDC made more sense. Drives already run on 12VDC, and there's already a level of power conversion near the CPU to get the desired CPU voltage. The USB devices do need +5, but a 12VDC to 5VDC switching converter can handle that. And single-voltage power supplies are more efficient and simpler than multi-voltage ones.
Lower voltages require larger conductors to carry the same current. Copper isn't that cheap.
If one has worked in a telco, we already have a standard, and that is 48VDC. This is the domain of the Sun Netras of yore.
If I were to recommend a voltage, why not plain old 12VDC? Yes, the amps have to be high, but we already have a connector for this (beats wiring up things by hand and throwing a breaker), and it is not hard to find off the shelf hardware to support this, be it batteries, power distribution units, inverters/converters, solar panels with MPPT controllers, and so on. We have two large markets (RV/marine) that are dedicated to 12VDC.
Why not just use an established standard? 12VDC works and has a lot of support, or if a higher voltage is needed, then 48VDC.
384VDC just seems to be asking for trouble. It would require yet another separate connector that can't be plugged into 120VAC or 240VAC, generators would have to have an adapter for it. It would require a complete retooling to get to that standard.
Making another voltage level is throwing the baby out with the bathwater. Why not just go with an established DC voltage level?
Take 12VDC. Most generators, from the expensive inverters by Honda or Yamaha can generate that, as well as the construction grade open-framed ones.
440 * sin(120) = 381.05 ....
3 phase has 2 ways of looking at the voltages, Y or delta.
The 3 phase delta is 440v when you measure between any pair of the 3 wires. The center point is ground. You don't see that in delta, but you do when measuring it in Y form. The same signals that are 440v when measured as a pair are 3 x 380v when looked at in the Y configuration.
So 3 phase 440v gives you 3x 380v to ground.
As to the 12v/5v/1.5v/ whatever you are going to have to do DC to DC all over the place. Better to have as high a voltage as possible for less current and less losses.
For certain you'd want to have a different kind of plug for DC devices, but even that would give us an opportunity to 1) standardize on one global plug standard, at least for DC, and 2) allow us to design a small, rugged, safe type of plug.
Aka the famous (in some circles) Anderson Power Pole. Go ask a ham radio guy.
The thing I love about in house DC distribution, which I have in my house, is it forces at least a token effect at "green power reduction". Suddenly given the choice of a 12 volt 6 watt LED fed by $2 of small gauge wire vs something resembling welding cable wire to run a 200 watt halogen, you make the ecologically correct choice.
I used to use cast off surplus 200 watt desktops for my mythtv frontends. Unholy pain to run on 12 V. Now I use 5 watt Zotac boxes. Good for everyone in every way.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
Would an AC current be generated by Tesla spinning in his grave?
I'll see your senator, and I'll raise you two judges.
What bothers me is all the new LED bulbs that have transformers in them (guessing, because they get hot! ... feels like wasted energy)
High power LEDs get hot because you are running good amounts of current through them, not because there is a transformer. Transformers are pretty much useless with the DC current that runs LEDs.
I'd think it would be more efficient to run DC to lighting and certain outlets like those where small devices would sit ...
The problem comes in deciding what voltage to use. 12V means you need rather hefty wires to get the required current for some devices. A 6W LED needs half an amp at 12V. If you use a voltage that makes the current resonable, then you need to convert that voltage to what your device needs, every place you have a device.
Sending 380V means you can use the same or smaller wires than you'd use for 120V systems, but you'll be busy converting that 380V DC to 12V DC or 5V DC or 1.2V DC -- and while DC-DC conversion has gotten a lot better, it is still more complicated than a simple transformer.
Hall effect.
In the presence of a static magnetic field (as around a conductor carrying a constant current), electrons in the clamp circuit, which also carries a DC current, will be pushed to one side of the clamp conductor, inducing a voltage relative to the other side. Measure the voltage and you know the current in the wire it's clamped around.