Fermentation space heat regulation designs

Hello, hello!

I have finally managed to get round to posting something here. Didn't even know that this forum was here before I saw Paul's email! How exciting...

Anyway, what I would very much like to ask Sandor is what are the best setups he has seen for maintaining a stable temperature for one's crocks, or even barrels (I am very interested in doing kraut in WOODEN barrels... in fact I will post about that too in a minute) that aren't heat pads or in boiler cupboards.

My question applies to both small and large scale fermenting operations (and when I say fermenting I am mostly thinking of kraut, kimchee, kombucha, kvass)... but I am sure this would apply to other sorts of fermentation.

I have thought about things like electric heaters and bubble wrap tents. But that's something of a fire risk, and I don't particularly like the idea of using electric heaters either.

I will put additional criteria on my definition of best to encompass its using renewable energy if possible, and being as lo tec as possible. I guess that some kind of thermal mass system would be the holy grail, perhaps using water to store the heat. And even better would be if it were something that could be assembled in a rented space and then easily disassembled if necessary.

Ok, I think that's my question articulated adequately! Hopefully it is answerable!

many fermentation processes create their own heat. sometimes too much. alcoholic beverages are one obvious example. koji makes a lot of heat, as does tempeh. I would imagine that lacto-ferments also create a bit of heat just through the metabolism of the organisms involved, though it might not be significant.

so what about using other fermented products to provide heat when you need it?

I love tel jetson's idea of using other heat generating ferments as a heat source. I'm not certain if that would be easy to control temperature without a lot of manual intervention, but it might be possible!

For ferments that require warmer temperatures, I built an insulated wooden box with a a light bulb as heat source. I control the temperature with a temperature controller that is accurate down to 1 degree.

it would certainly need a lot of attention if fermentation heat alone was used, at least initially. once a routine was established that maintained temperature within an acceptable range, things would get easier.

insulating well and including thermal mass in the space would prevent quick temperature swings.

a lightbulb is probably a better option if there isn't a steady production of fermented stuff, or when the volume fermenting isn't large enough.