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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."
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
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.