OT [sdiy] Peltier Elements

[The Peasant]

Quoting harrybissell at prodigy.net:

> Not directly related... but i saw the most ridiculous
> product yesterday. It as called eco-fan (or similar
> iirc)...
> it was a fan with an aluminum extruded heatsink... for
> use inside
> a cooking oven. The fins were arranged so that the cool
> side
> of the peltier device was "cooler" than the hot side, it
> worked
> on temperature differential from top to bottom. The
> Peltier device drove a small electric motor.

LOL! Harry, somebody here is just a bit confused. The 
device that you refer to is NOT for use *inside* the oven, 
it is designed to be used on top of woodstoves to circulate 
the heat coming off of the top. If you read the 
instructions on the box carefully you will find this.

It does generate it's own electricity, from the heat 
difference between the stove top and the air above, using a 
peltier chip. That's right, you can generate power with a 
peltier, its just a 4 quadrant heat pump - in-out/up-down, 
it's all the same. This device is very environmentally 
friendly, as it runs off of a stove that would be burning 
just as much fuel anyways, but it really makes a big 
difference if you rely on wood heat and don't have ac 
power. So Ecofan is an appropriate name.

The only problem is that peltiers are soldered together 
with fairly low temp solder, so it's very easy to damage 
them with excessive heat. The Ecofan has a bimetallic strip 
in the base that lifts the device off of the stovetop a bit 
when it gets too hot, but even then, it's not very hard to 
damage them if you are not careful. There are manufacturers 
who make higher temperature peltiers specifically for 
thermal power generation, but they are very expensive.


*****DISCLAIMER*****
I don't sell Ecofans or have anything to do with them, I 
have just used the product myself and think that it's a 
great idea. I also spend significant amounts of time in 
wood heated dwellings without mains power in a cold climate 
and have experimented with heat to power conversion and 
other alternative energy sources. YMMV.
*****DISCLAIMER*****


Take care,
Doug
______________________ 
The Electronic Peasant

www.electronicpeasant.com