Re: Homemade Thermopile
- From: YD <ydtechHAT@xxxxxxxxxx>
- Date: Wed, 05 Dec 2007 00:04:34 -0300
Late at night, by candle light, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> penned this immortal
opus:
On Sun, 2 Dec 2007 04:31:07 -0800 (PST), Dunc <Dunc461@xxxxxxxxx>
wrote:
There are two major problems with thermopiles as tool to generate
electricity. Very low efficiency and high initial cost. It appears
that the only way to attack efficiency is to utilize more exotic (read
expensive) materials.
What I was wondering is could a "homemade" thermopile be constructed
using very cheap or recycled materials (nails, aluminum cans, aluminum
foil, metal scrap, etc.). If you consider sweat equity to be free you
might be able to produce a viable installation.
If possible, it would be best to utilize a natural occurring
temperature differential such as air to ground, air to water, or dry
bulb to wet bulb. I recognize that these are relatively small delta
T's, but they are completely free and universally available.
My questions are as follows:
Which, if any, commonly available materials would be best for such a
device?
What design parameters should be considered?
For example:
Do the cross-sectional area, distance between or shapes of the
junctions effect the output?
An iron-copper thermocouple can be made from hardware-store stuff. It
will give about 50 microvolts per degree C temp differential, and you
can put multiple junctions in series to get more voltage. Of course,
the resistance goes up as the heat source:sink distance goes up, and
as you add thermocouples in series. Done just right, expect thermal
efficiency on the ballpark of 0.5%. It's unlikely that you can harvest
even a couple of milliwatts from the sorts of sources you mention. A
10 degree C temp differential is about 500 uV per couple, so you'd
need ballpark 3,000 thermocouples in series to light an LED.
Older water heaters and furnaces use a thermocouple, in the pilot
flame, to hold in the gas solenoid valve. I guess they use multiple
junctions, too. 50 millivolts is typical here.
The iron will rust, too.
John
I recall reading about a transistor radio powered by a kerosene lamp.
Lots of thermocouples surrounding the chimney, looked like a
cylindrical porcupine.
- YD.
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- Homemade Thermopile
- From: Dunc
- Re: Homemade Thermopile
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- Homemade Thermopile
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