I've been using water baths with frozen water bottles to "control" fermentation temperatures. This has worked to some degree, but there isn't much control. See for example.
Borrowing an idea from work, I wanted to try a Thermoelectric Cooler (TEC) to cool (and potentially heat up) the water rather than relying on me to remember to put in frozen bottles daily or so. This would also allow me to dial in the temperature precisely. TECs typically run 12V and turn electron movement into heat movement, this is a 92W version available on amazon for 7$.
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| http://a.co/g7bkNtu |
To cool the water, the TEC moves heat from the water block (blue) into the heat-sink (silver) where a fan dissipates it into the air. A pump moves the water in the cooler through the cold water block and that is what cools the fermenter.
I use a towl to keep the heat out so things are more efficient. The TEC is switched on and off by a simple temperature controller: http://a.co/g69nd9F
The temperature controller has a sensor which you put in the water and it can switch a relay to control when to cool (and also heat) the water. The only thing left was a beefy power supply that can output ~10A at 12V. All in all a pretty cheap system. Next post will probably be about the ultimate performance after I attempt to cold crash this beer. For now it's holding fermentation temps at 65F no problem.
