I have had this idea for a while and finally got some time to build a proof of concept. It is a 6.5 gallon carboy, thin copper sheet, peltier element, heat sink, fan, and an exercise mat jacket. I used arctic silver thermal adhesive to bond the copper to the peltier and the peltier to the heat sink. While testing the peltier on the bench it could get to below freezing using that heat sink/fan(I believe it has around a 40 degree temp differential). So I crudely put it together last night to test it and am not very happy with the result. I suspended a temp probe in the empty carboy to monitor temps and over night it only got down to 65 degrees. I think my copper may be too big for my peltier so it's not efficient enough to drop the temp of the copper well enough. Thoughts?