From Edison’s Trunk, Direct Current Gets Another Look

http://www.nytimes.com/2011/11/18/business/energy-environment/direct-current-technology-gets-another-look.html?hp

by lsr7 • 15 years ago

4 4 15 years ago

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.

mindslight2• 15 years ago

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?

Dylan16807• 15 years ago

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?

mindslight2• 15 years ago

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

From Edison’s Trunk, Direct Current Gets Another Look

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