Mini cooler/fridge in fermentation chamber ?

[Kingtj]

Hi,

I don't have space for a fermentation FRIDGE.
So has anyone ever tried one of those mini cooler/fridge. Like this
Robot Check

Would it work if used in a fermentation chamber made from polystyrene insulation ?

 

[DonBon]

I'm completely new to brewing and haven't got around to building myself a temp-controlled chamber yet, but figured I'd give my thoughts:

It seems to me that the benefit of a fermentation fridge is that your bucket or carboy can fit inside it. You can build an extension chamber out from the fridge, but ultimately I don't see why you can't just use a fridge on its own. The mini fridge wouldn't be able to fit much inside of it, so you would presumably have to account for the size of the fridge plus any bucket you planned to use.

So far as whether it would work, I don't see any reason why not. So long as the chamber you build is suitably insulated, the internal temperatures would stay chilled by the fridge. You might find the fridge struggles to drop the temperature as quickly as you would like in response to doors opening or closing or different temperature ferments being put in the chamber, but ultimately the temperature would probably stay fairly stable so long as you're careful in how you use it.

I saw links recently to a Son of a Fermentation Chamber which seems like it might meet your needs. It's quite involved in terms of the build process, but if you're planning on modifying a fridge anyway, the SoF Chamber is probably within your skill set.

Hope that helps!

 

[Gruel]

The solid state (Peltier) cooler in that fridge probably uses something like 50W electrical power. I would guess maybe a third of that (15W or so) is available as cooling power at normal fridge temperatures, and at steady state (inside of fridge is cold, and stays at the same temperature) it is just enough to balance the heat gain from the outside through the insulation. (Compare that to a mechanical refrigerator with about 3W of cooling power per 1W of electrical power- SEER of 12(*)). So, to use the same cooler to cool a much larger surface area fermentation chamber, you need much thicker insulation, avoid any air or humidity leakage, and you need to take into account the heat produced by the sugar conversion to CO2 and alcohol inside your fermenter. I think 5 gallons of 1.05 wort converted to beer in 3 days produces about 6W (see How much heat does a fermentation produce (**)).
I'm afraid 15W is just not enough, no matter how good you make your insulation. And you then end up with a bulky container for your fermentation chamber, not very much unlike a small fridge. If you try it, make sure there are fans on both the hot side and the cold side of the cooling element.

All that being said, I built a 270W (total electrical power) solid state cooling system (with liquid-to-liquid-to-liquid-to-air heat transfer) for my fermenters and kegs, since I don't have space for a large enough fridge in our kitchen. It's just very inefficient compared to a normal mechanical refrigerator.

TL;DR: It's certainly possible to build a solid state cooling system. The peltier cooling elements are very inefficient compared to mechanical refrigerators. The problem people usually run into is efficient heat transfer.


(*) SEER = BTU/(W * hr), 1 BTU ~ 1000 W seconds, so 12 SEER = 12,000 W s/(W hr) = 3.3 W cooling power per W electrical power.
(**) this link seems to give an energy output from fermentation a factor two higher than this one: How to Size a Brewery Chiller | BV Thermal Systems ; or maybe it's just too late in the evening to do the math correctly....

 

[Gazint]

I built one by turning the mini fridge on its back.

 

[wsmith1625]

I built one by turning the mini fridge on its back.

Yours is a full mini fridge. The OP linked to a small one that can only hold a 6 pack of soda or beer. I would not recommend his fridge for a fermentation chamber build.

However, if he is planning to build a chamber large enough for the fermenter, it will likely be the same size as your mini fridge standing upright.

Cool idea turning it on it's back. I have never seen that before.

 

[garzlok]

I built one by turning the mini fridge on its back.

I’m going to assume you rotated the compressor to be in the proper position?

 

[Gazint]

Yes, and moved the cooling plate to be between the fermenters.
I may add a fan if necessary.