Geothermal Chillers

[sijani]

I've been thinking about different ways to exchange heat and cellar/larger e.t.c.

One of the ideas I'm thinking about trying is a geothermal chiller. They are very temp stable all year round. Very cheap to run as well.

Basically It's a heat exchanger/sink buried about 2-3 meters underground.

I was thinking of burying a 30L sealed container filled with water and about 10m of copper coil. Garden hose from container to surface. Insulate hosing and circulate.

Now this bit is where I'm getting stuck. Pump water in a closed loop HE to HE? Or circulate air through an insulated cool box/room whatever.

Anyone have this system at home?

Thoughts?

 

[jonocarroll]

Pump water in a closed loop HE to HE?

From what I understand from the chillers, 30L will heat back up pretty darn fast. You're trying to cool 20L with 30L and expect to keep a temperature gradient?

Or circulate air through an insulated cool box/room whatever.

Couldn't you then forgo the underground water vessel? Put that in the cool room too. Sorry, but I'm not sure I understand exactly why you would bury the water tank, making it reasonably thermally insulated. Wouldn't it be better to have the water tank out of the ground, and able to cool back down? I've heard a lot of success stories of people using their rainwater tanks for such a purpose.

Good luck if you get it going.

 

[Adamt]

I think sijani is referring to maintaining fermentation temperature rather than chilling post-boil wort. It'll definitely not be enough for chilling post-boil wort, and seems like complete overkill for maintaining fermentation temperature.

 

[newguy]

I think the size of your coil is too small. For a typical geothermal (heat pump) central heating/cooling application, it's recommended that about 100m of buried piping is required for every ton of heating/cooling power (12,000 btu/hr). In a typical heat pump (at least around here) the buried pipe is actually plastic and it is embedded in a special concrete-like slurry so if you're burying copper I suppose you'd likely need less than 100m per 12,000 btu. However, it's the ground itself that absorbs/sources the heat - if your coil 'concentrates' the heat in one small volume, its ability to absorb heat would decrease as the earth becomes saturated with it. You'll definitely need to circulate a water or water/glycol mixture in the system. Air won't cut it.

I'm not sure this kind of system is terribly feasible given the work to bury the line and the cooling "power" it could handle.

Edit: this may help.

 

[raven19]

Underground temperature will certainly be nice and stable, and cool.

+1 for other comments here - liquid to liquid heat transfer is much more efficient than air to liquid.

2c.

 

[jonocarroll]

My bad, but my point stands. Even a 10C temperature difference will be an issue with 20L vs 30L, and the ferment could produce that if vigorous enough. A lot of buried water... perhaps. Otherwise the tanks will have an equilibrium somewhere in the middle and I'm not sure how much of a heat sink the ground would be.

Happy to be proven wrong.

 

[sijani]

The ground is actually an excellent heat sink.

It would be easy to bury a wheelie bin 120L or even more...

Don't need glycol as it never gets cold enough here for the water to freeze. Ground temp & 3 m is about 4C year round

Will only be maintaining fermentation/conditioning.

Can run this off a small pond pump

 

[samhighley]

Just don't bury it too deep, or you'll end up with a geothermal heater

 

[sijani]

I wonder how deep I have to go to replace the elements in the kettle.

Hmmm... geothermal powered quadruple steam jacketed conical titanium space kettle...

 

[newguy]

I wonder how deep I have to go to replace the elements in the kettle.

Not deep at all if you move to Iceland.

 

[PostModern]

Not deep at all if you move to Iceland.

Or Rotarua.

 

[br33zy]

The ground is actually an excellent heat sink.

It would be easy to bury a wheelie bin 120L or even more...

Don't need glycol as it never gets cold enough here for the water to freeze. Ground temp & 3 m is about 4C year round

Will only be maintaining fermentation/conditioning.

Can run this off a small pond pump

I agree with ...well whoever it was... I don't think you need a buried reservoir; just a sufficient length of ground based piping through which you can recirculate your cooling fluid. If you get the length (and depth) correct; your fluid should come out at a constant 15 degrees all year round.

I'm really interested in this stuff; but as yet there is very little on the market here in Oz, so its a case of design and build your own unfortunately. This site looks terrible, but has some good information in it: http://www.mb-soft.com/solar/saving.html

Cheers

Breezy