Heat sink

[Paul D]

Plans are afoot, at last, to get a new greenhouse. It'll be a big one and I'm thinking seriously about the design of it. Something that I remember seeing Dick Strawbridge doing on TV is building a heat sink- effectively a drainpipe going up to the highest point of the greenhouse, containing a couple of small fans, pulling the warm air from the top down to floor level. The bottom end is then sunk into an insulated pit containing a heat store, e.g. water-filled plastic pop bottles. The effect of this, apparently, is to take excess heat during the day and release it gradually over night, raising the temperature by a small amount and saving on heating cost.
Has anyone here done this? Is it worth doing?
I wonder if it will be effective at the time when it is most needed (i.e. in winter) especially with our short day length and low max temperature here in the north of Scotland.

[BryanW]

If I remember correctly, didn't DS also use chunks of polystyrene to help retain that heat?

[Paul D]

If I remember correctly, didn't DS also use chunks of polystyrene to help retain that heat?

Yes, polystyrene to insulate the sink- I think he then filled it with crushed glass which retains heat well. I've heard water is also good, pea gravel, a variety of other things.

[BryanW]

I've always wanted to try it but haven't a greenhouse of my own, also wanted to do the black copper pipe heater too ho hum.
I've found this site link for those that are not familiar with the heat sink.
http://www.reuk.co.uk/wordpress/solar/s ... heat-sink/

[agavedave]

Water will have the highest heat capacity so perhaps some kind of combined underground water storage that can double up as a heat store in winter.

Alternatively a ground source heat pump as the main source of heating. I remember reading somewhere that someone had used some old beer chillers to good effect.

Looking at the temp logs for my set up and comparing the inside to outside temps there are very few days where there would be surplus heat to store, if you were efficient in storing that heat then this would probably lower the day time temps. The heat needs to come from somewhere else.


Regards
Dave

[ralphrmartin]

I enquired about a "real" ground source heat pump to reduce my heating bills. It takes advantage of the ground a few feet down being a more or less constant temperature, to leverage the energy input for heating. Unfortunately, the cost would have pretty horrendous, and it would have taken maybe 20 years to pay for itself - and I'm not sure I'd ever live to get a return...

[Paul D]

Yes I don't think ground-source would be cost effective (nor practical in my case- not enough ground) but the heat sink idea looks cheap and clever- just wondered if anyone had tried it, and if it makes a difference.

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