DIY greenhouse heatsink.

[matchat]

I have just seen this ground source heat sink discussed on the Beechgrove Garden where it has been used to heat a 6x8 to a minimum of 7°C over winter. It's made using a beer pump cooler.

Do any of our resident techies rate it? I wondered if it would be a cost effective alternative to a regular fan heater and how it might scale up for larger greenhouses.

(The explanation begins halfway through page 2 of the PDF).

[agavedave]

Looks interesting.

I think the key point is having a large enough area to lay the pipe so that you suck in heat from a wide area as possible. Commercial systems sometimes drill down very deep vertically if space is restricted.

Also circulating water through pipework during winter is always a recipe for disaster. I would probably want to dose it with propylene glycol.

Having looked into this option previously, you need to be running it for a long time to recover initial investment, unless you can get a bargain of a beer cooler.

Regards
Dave

[makleodss]

In place where I am from Heat pumps are pretty popular method of heating as it can get out 4 units of heat to one unit of electricity if we compare to electrical only heating which can get out 1:1. I have seen loads of perfect setups and loads of fails. Fails may include as pipework is not buried deep enough and soil cools down from top. Pipework is too short and after a while soil just freeze around pipes and then there is no economy. The best way definately is to have chat with heat pump specialists if they are available in UK.

[Ambrose]

I looked at heat pumps for my greenhouse, but with no mains electrickery on the allotment I opted for a heat storage system. First you have to get a grip on the Laws of Thermodynamics. Then you check on historical solar radiation for your area, but what percentage of that can you collect?
Black hose pipe undulating along the ridge, solar powered pump, 5 x 1000 litre IBC tanks linked as the heat store.
Tops cut off the tanks to stop the rain water going sour, add fish to eat the bugs that then breed in the water.
Figuring out that solar alone is not sufficient you add a wood burning mass storage rocket stove and buy a chainsaw.
The wood stove puts heat into the water of four of the IBC tanks with a gravity feed system, leaving one tank for the fish (so as not to cook them) The fish seem to accept the temperature variation, and a maximum temperature of 30 centigrade.
Four winters have shown the system works, keeps the frost out of a 36ft x 12ft greenhouse. Temperatures of below -5 over when the wind chill is excessive require you to sit up all night feeding the stove with wood so being retired is an advantage

[Mike P]

Ambrose - visions of the Victorian & Edwardian gardener feeding the fire day and night to keep the stove house warm pop into my mind.

[Ambrose]

Ambrose - visions of the Victorian & Edwardian gardener feeding the fire day and night to keep the stove house warm pop into my mind.

More like an idiot with time on his hands.
Only required when there is a really hard frost, so twice last winter.
12 volt LED lights, a good book, comfy chain and unlimited supply of pallets

[Mike P]

Yes we have been blessed with very mild winters since that blip six or so years ago.