I've spent the last year determining how I can combat the hot temperatures to brew beer. I resort to a swamp cooler and spend significant time adding frozen water bottles in order to bring the temperature down.

This kickstarter claims that via its "patent pending solid state cooling system that pumps heat out of your fermenting beer using tiny heat exchange chips" it can reduce your fermentation temperature to LAGER TEMPS.

Surely if this is possible it can be replicated, DIY, with a Raspberry Pi and/or Arduino. I don't even care about lager temps at this point; If I can simply reduce temperature to ale temps that would be great!

As an aside, I'm not about to make a donation to this at the moment. BeerBug is a very cool idea (measures specific gravity of your wort as it ferments) that was started by kickstarter, but it costs $250 for each carboy. I have 8 carboys brewing simultaneously and would rather do it myself.

TL/DR How is it possible to reduce temperature without a fridgerator or swamp cooler or other prehistoric device?

  • Sounds like you need both the beer bug and the brewjacket!
    – mdma
    Commented Apr 12, 2014 at 12:54
  • 8 fermentors? In your shoes I'd be looking at how to reduce beer turnaround time. With the right treatment you can go grain to glass in a week for a regular strength beer.
    – mdma
    Commented Apr 12, 2014 at 12:56
  • Why don't you want to use a fridge or chest freezer?
    – Denny Conn
    Commented Apr 12, 2014 at 17:29
  • @mdma I only extract brew for now, and the Northern Brewer recommended time frame is generally 2-4 weeks (with an additional 2 weeks for bottling). Are they just being overly cautious? Commented Apr 14, 2014 at 19:33
  • @DennyConn To fit by 8 carboys it will cost me around $1,000 for a large enough chest freezer. Commented Apr 14, 2014 at 19:34

1 Answer 1


It uses peltier devices - a thermoelectric cooling/heating device - when a current is applied they chill on one side and warm the other. They're quite common but relatively inefficient in terms of energy compared to a compressor that you'd find in a fridge. Their efficiency is based on how quickly you can dissipate the heat generated. Thermal design is a key factor to being successful with these devices.

Peltier with heatsink and fan

The image above shows the peltier - the white square at the bottom, above that is the heatsink and above that the fan.

If you want to start building a DIY version, you'll need a few things:

  • a large heatsink (or better called a cooling fan) or metal rod that goes into the beer
  • a heat sink and fan to dissipate heat produced by the peltier
  • thermal grease to bond the peltier to both hot and cold heatsinks.
  • a DC power supply or suitable battery
  • Insulation for the carboy - this is necessary to maintain any kind of reasonable energy efficiency.
  • an H-bridge - this allows you to reverse the polarity so that you could also use the same device to heat. (This is optional.)

This is just off the top of my head, but those are the main components to building any kind of cooler with peltiers.

An interesting point of the brewjacket is that it uses the same rod to cool and also measure temperature. This requires some smarts in software to know when the temperature read then accurately reflects the temperature of the beer.

  • I wonder what material they use for their 'heat transfer rod'. Copper? Aluminum? I suspect copper because of it's high thermal consuctivity, plus it makes an excellent based for electro plating.
    – BrianV
    Commented Apr 12, 2014 at 14:13
  • 1
    You wouldn't want either copper or AL in fermenting beer. The pH of the beer would leach undesirable compounds from them.
    – Denny Conn
    Commented Apr 12, 2014 at 15:02

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