Thermal Piles

It is possible for you to do this but the amount of energy you get will depend on how much effort and how well you fabricate the elements. Basically, a thermopile (I think a thermal pile is some kind of disease) can be made with just about any two dis-similar metals. So let's say you have iron and copper available. You will need to weld the wires together at one end and a voltage is developed between the open ends of the wires when a temperature difference exists between the open ends and the welded end. So you would likely want to attach the welded end to your heat source and then get power from the other ends that would need to be as much colder than the hot end as you can get them. You will only get in the order of tens of microvolts per degree in temperature difference so connection resistance will be something to consider. You will have to put quite a few of these in series to get up to a useful voltage. Seriously, I doubt it is worthwhile to attempt but you might build a few and get an idea of what it would take and if you want to keep going. We power space probes with "hot" radioactive material but of course NASA can afford the rocket science to make it work. Good luck!

Thanks for the ideas guys , I guess this creation Id have to build would be way bigger then a bread box and weigh a bunch. As always us solar guys are looking to be independant and diy some contraption from expired pattent descriptions from the 1800's

But on further research I found a sorce, again made in China, for T.E.Gs Thermal electric generators. Semieconductors. Fair pricey 185 bucks for 20w,though low voltage 4.2v

Im not sure weather u have to use a dc to dc converter to raise the voltage or if u go series, parelle to get the desired watts. It dosent sound much more expensive then solar pannels about 10 bucks a watt, except these would be running 24/7 so youd need much less TEG watts then solar pannels. These puppies are only 1.5"x1.5'', though fairly sofisticated in set up, they need water cooling and special mounting.

http://www.thermonamic.com/home.html

Another thought, in the summer I could dismount the TEG from the stove and make a soler reflecting dish with solar tracking and produce power from the sun.

Greg

Hi Greg,

This is totally possible. You can purchase 5.6 watt Power Thermal Couples from

Tellurex.They cost about $40.00. Thus 20 will work for you & arrange them in parallel

& series to get around 13 volts for your batteries. You need a temperature difference of around 100 degrees between the hot & cold side.Thus cooling fins may be needed on the cold side.

Yah I know all about buying them. I now own 8 from a different manufacturer I have to get my cold side colder and they shouild work. Thanks for the link for the TEG,s.

Greg

Have you thought of using Preparation H

http://en.wikipedia.org/wiki/Preparation_H

I hear it's good for the treatment of thermal piles!!

Seriously though you only get a few mV per junction and bugger all current. You would need hundreds in series to produce any sort of usable voltage and thousands of banks in parallel to get any sort of current. If you add up the amount of energy you are going to expend making a thermopile I doubt that you will ever get that back from operating it. It might sound like an elegant solution but I can't see it being practical or economical.

Since you need to generate your own power have you ever thought about a wind turbine. Here is a do it yourself wind turbine

http://www.otherpower.com/17page1.html

personally I prefer the concept of a vertical wind turbine that was discussed in this thread some time ago.

http://cr4.globalspec.com/blogentry/485/Urban-Turbine-Runs-Quiet

While they will probably not be able to cover you 100% of the time the two together will more than likely go fairly close.

In theory you could do it. However it is not practical.

You need peltie devices. They are the same as thermocouples, but short and flat... having a lot more surface. Maybe you could start collecting electric coolers... electric ice chests. There are solar versions and version that run on batteries, etc... They all have these bimetal thermo-electric peltie devices or thermapiles (not sure spelling) inside the walls.

A peltie device is a thermocouple run backwards. Instead of producing a voltage and current due to a termperature differential, it generatates a temperature differential when you drive a current through it. The flat ones inside the walls of these ice chests are optimized via geometery to generate the temp difference, but could be used as temperature sensors.

You could gather broken "ice chests" with the peltie devices in them. (Check craigslist and salvation army... etc.) You might find a volume of these peltie devices on the internet at an electronics salvage site, such as Haltech in Santa Clara... but they will likeley be expensive. I too want to figure out how to make my own. Maybe take one of these peltie devices and examine it carefull to find out. They sell those little solar icechests pretty cheap at Target, Wallmart, etc. . Check solar and 12V rechargeable, etc...

These devices are about 1" x 1" or so. You could put them together to form your large thermapile (sp?). Good idea on locating outside face of exhaust stack. Also, since lots of heat out the stack... maybe fuild a reservoir (upside down heat capture vessel) that doesn't restrict flow... with a flat top (angled for runnoff), but boxed down sides to capture the hot air. These peltie devices would tile well onto such a flat (metal) top. Makes sense to use the winter heat differntial at the stack! Good idea!.

I don't know how much power is available, but pretty large currents are used to drive these things; maybe an Amp or two or three or so. So you might get some good fraction of an amp from each. Probably pretty low voltage, but withing each peltie device are probably lots of seriesed junctions. Each junction generates a very small voltage. When dissasembling the ice boxes, note how they are wired. Will give you an idea of how much voltage is delivered to each, and thus what kind of voltage to expect out of each. 100W sounds feasible to me.