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I am designing a thermo-electric generation system that would generate electricity from the heat of my wood stove. The active components are bismuth telluride TEG cells that use the Seebeck effect in reverse to convert a temperature difference into an electrical voltage.

The surface of the flat cell facing away from the wood stove needs to be cooled by a heat sink and fan so the semiconductor is not damaged.

I would like to fashion an aluminum heat sink out of waste aluminum (foils, baking sheets, trays, etc).

Update: What I had in mind was a metal brake and bending system to fashion the fins and then bonding the fins to a flat piece of aluminum with a layer of heat sink compound adhesive. Since the waste aluminum is thin and easily malleable, this should be trivial. Melting it down and pouring into a mold in a vacuum would not be worth it.

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  • Given that you can get extruded aluminium computer heat sinks from eBay for as low as $1.76 with free international shipping, I'm not sure why you would want to DIY one. Nonetheless, if you want to spend more than $1.76 in fuel/energy, you could use propane/electricity to melt down a whole pile of random aluminium scraps and pour it into a sand cast. A flat base plate with an array of rods sticking out of it (made using straws or knitting needles) would probably give you the conductivity and surface area you need.
    – Tim
    Feb 22, 2018 at 6:09
  • You need a low O2 (ideally no O2) environment to melt aluminum. If you heat aluminum in an O2 environment you'll just get aluminum oxide. A propane torch definitely will not work.
    – Jean-Paul Calderone
    Feb 22, 2018 at 15:45
  • lol... You might want to tell that to the tens/hundreds of thousands of people that smelt and sand cast aluminium for small projects every week. ;) duckduckgo.com/?q=sand+cast+aluminium+propane
    – Tim
    Feb 26, 2018 at 13:08

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Forget the foil. Even if you laminate it, you'll never eliminate tiny air gaps, which will make it into a fairly effective insulator.

I've seen (copper) heatsinks made from thin precision-cut fins, soldered to a thicker spreader plate. Solder is better than thermal epoxy, but doesn't work on aluminium. This was necessary for a specific purpose, but not as effective as a similar-sized extruded aluminium heatsink despite the higher thermal conductivity of copper.

If you want to use recycled heatsinks, I suggest you use recycled heatsinks: Old computer heatsinks are effective (I had a collection from Pentium 2s that were very useful; they were huge as the only fan in those systems was a pathetic one in the PSU, with a duct pulling from the CPU heatsink.

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  • Would brazing the copper be better than soldering since we are working with higher temperatures?
    – 0tyranny0poverty
    Feb 25, 2018 at 2:55
  • @0tyranny0poverty. Quite possibly. We didn't have the facilities to try, also soldering with paste in an oven is much quicker. I know in bike manufacturer aluminium is usually welded. It's not the easiest metal to weld but the strength you need is much less.
    – Chris H
    Feb 25, 2018 at 7:45

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