

From Edison’s Trunk, Direct Current Gets Another Look - lsr7
http://www.nytimes.com/2011/11/18/business/energy-environment/direct-current-technology-gets-another-look.html?hp

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colanderman
_And household appliances and much industrial equipment — everything from hair
dryers to jet planes — are built to use DC._

No, hair dryers do not use DC. That would be (a) exceedingly dangerous in the
event of a shock, since you cannot release your grasp while being shocked by
DC and (b) dumb, because neither motors nor heaters require DC.

 _In a data center redesigned to use more direct current, monthly utility
bills can be cut by 10 to 20 percent, according to Trent Waterhouse, vice
president of marketing for power electronics at General Electric.

“You can cut the number of power conversions in half,” Mr. Waterhouse said._

No you can't! Unless the DC you're getting is already the 12 V used by
computers. And not only is that dumb, because it requires 10x the amount of
copper (due to higher current), but:

 _Now, more than 145 projects using high-voltage DC, known as HVDC, are under
way worldwide._

HVDC is _not_ 12 V, so you'd still need to do DC-to-DC conversion _anyway_.
(DC-to-DC, btw, is not significantly more efficient than AC-to-DC, if using
similar technology.)

 _Direct-current transmission is also better suited to handle the electricity
produced by solar and wind farms, which starts out as direct current._

No it's not! Solar and wind produce _variable_ voltage... you need to convert
the power either way. DC-to-DC or DC-to-AC doesn't make much difference.

I really hope I'm missing something here, because HVDC is of much more limited
usefulness than this article makes it out to be.

~~~
mindslight
HVDC transmission lines aren't terribly new.
<http://en.wikipedia.org/wiki/List_of_HVDC_projects>

There probably is some savings to be had in a data center by putting the
backup batteries directly on the distribution rail. (IIRC Google's servers do
something similar with a battery in each unit)

But yeah, the rest of the article is content-free fluff and an attempt to
portray a conflict where there is none. For example:

> _Of course, AC remains by far the dominant standard for electricity, and
> many are dubious about “DC is better” arguments._

But what else would you expect from the NYT?

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Dylan16807
_Nextek Power Systems, for example, has developed a system for delivering
power via DC to lights and motion sensors through a building’s metal frame,
instead of through wires._

How.. what? A frame can provide one side of a circuit, but it can't provide
both. The FAQ on their site talks about wire gauge and length. What is this
line talking about?

~~~
mindslight
you just need to realize this article tells you more about journalism than
electricity. then it makes perfect sense.

