DC equivalent of Light Dimmer, to save energy?

i was reading the package of a light dimmer yesterday, and it read something like (don't remember exactly):

Dimmed by 20% ---- energy cost reduced by 15% ---- increase bulb life by 2 times
....
....
Dimmed by 70% ---- energy cost reduced by 60% ---- increase bulb life by more than 20 times

or something like that. now im wondering if there was a way to use such a device on dc computer fans, or maybe a DC equivalent?

and i recently asked if a rheobus or fan controller saves energy and the answer was no. and i don't know much about electricity, but im guessing the rheobus/fc doesn't reduce energy cost, because it doesn't change how much energy is being fed into the line, it just takes some off before it gets to the fan??? if so would it be worthwhile/possible/beneficial to adjust a psu to say 7v(12v line) across the board(in a dual psu set up of course), dedicated to running my fans?

Well, as far as I know, there isn't such thing as saving energy.
Dimming is done by building an adjustable resistor. It actually drains energy, so there's less energy left in the circuit behind the dimmer (where you mount the fan).

this looks like the dimmer i was looking at:
http://www.cornerhardware.com/howto/ht02.html

"They save money, too, dramatically increasing bulb life while reducing electricity use. According to one industry source, dimming an incandescent bulb 10 percent can save 5 percent on electricity and double the bulb life. Dimming it 50 percent saves 25 percent on electricity and extends bulb life 20 times."

Well, I said "As far as I know" ...

I agree that it can save money by extending lifetime, but I'm still skeptical if it really saves that much energy.

Light dimmers do save energy, they just dissapate some of the energy as heat, as well. You can use a rheostat or a potentiometer, or even more efficient is a PWM controller. Do a google search and you should be able to learn how they all work.

YetAnotherNoob said:

i was reading the package of a light dimmer and i recently asked if a rheobus or fan controller saves energy and the answer was no.

Click to expand...

Rheostats do save energy, just not 100% proportionally. You lose just a little bit to heat. However, the savings in power and longevity of the device are substantial, percentage wise. The more power the devices use, the more a rheostat can reduce your power bill.

Having said that, computer fans draw miniscule amounts of current, so monetary savings would be perhaps a nickel or 2 per year. Going for longevity would make more sense.

Look at this computer with 3 rheostat fans, with rheostats front mounted. I didn't have power savings in mind, but it pays off big in reducing noise and dust.
http://webpages.charter.net/bobad/cool.htm (look at Pic1 in particular)