Topic: Thermal Mass

[tidymeup]

Does anyone use a thermal mass in their greenhouse to help stabilise temperatures on warm days and maintain heat throughout the night ?

Thanks

[Curryandchips]

I don't personally, but I have neighbours who use concrete slabs on the floor, or a large (200 litre) drum of water in the centre of the greenhouse. It is difficult to compare results though.

[MikeB]

Yes I've got a full size waterbutt in the GH to help stabilise the temperature.  This was discussed last year  I believe the thread title was ' early tomatoes ' and Tim provided a site address that went into this.  A rule of thumb was 1 gallon of water for every square foot of glazing.  You would need a lot of water to be truly useful.

[Columbus]

hi all,

My potting shed / plant house shares a wall with my tool shed which acts as a thermal mass - even at this time of year its toasty in there.

The tool shed is stained black to absorb heat.
But the water in the barrels on the shady side of the tool shed never gets warm even on the hottest days

Its almost as if it was planned  ;D
Col

[tim]

Funny that this should come up just as I was considering putting the hot ashes from the solid fuel stove in there every day?

But mass? Our lean-to leans against a 4' thick south wall ,with the AGA behind it , & it's bloody freezing in there at present!!

[tidymeup]

The idea is intriguing to me as i though perhaps it would be possible to heat the water some how using a low cost solar panel or something throughout the day in the winter months to help provide heat at night.

In summer i am sure the water would get hot enough during the day to provide protection at night.

cheers for the info i will search for the topic.

[derbex]

Try painting an old radiator black and piping the water around through it, should work. Again it will depend on how much water and how well lagged the tank is.

I was starting to think about a heat pump -but the other half would lynch me if I dug the lawn up :)

Years ago I vaguely remember seeing a trick that used latent heats and crystallization to store heat, I'll have to have a look on google.

Jeremy

[tidymeup]

Good idea regarding the radiator it should work in theory, perhaps it's worth experementing with.

yes you could use geo thermal heat to keep to place toast warm all day all year round as the temperature underground only vary a few degrees.

You could use bore holes rather then something like an earthloop.

[euronerd]

I've thought about this for years. One idea was to use an auxiliary fuel tank from a lorry (black polyprop, about 6ft square and a few inches thick, so maximum surface area to volume) full of water, facing the sun and using thermo-siphon via a large-ish pipe around the greenhouse. The theory's good but the maths didn't stack up very well and there were too many variables to be sure of reliability. Quite apart from having to make holes in my greenhouse for the pipe, and the visual pollution.
My current pet idea is to make cement slabs using seed trays as moulds, to go in the bases of the two mini-greenhouses I have inside the main greenhouse. The temperature inside these is a full 5C warmer than in the main greenhouse during the day, but exactly the same at night.
As usual, I've probably left it too late for this season.
OK, done waffling.

Geoff.

[derbex]

From what I remember the radiator does work, probably even better in a greenhouse, it's just not as efficient as a real solar panel. I think it's more the store I'd worry about.

Maybe large rocks immersed in water to get decent thermal transfer? All in a well lagged tank. I should have dug down further when I did that greenhouse bed, a tank a few ft down topped off with soil would work -or a large lump of concrete with pipes running through it. They're re-doing the A12 near me -I wonder where the workers drink.

I wasn't thinking of drilling deep enough to use geo-thermal energy -might strike oil first :)

I'm enjoying this :)

[jennym]

Somewhere, once, I read a very basic way of collecting heat using waste materials.
Can't remember all the details, but it involved painting a hosepipe matt black, and threading it through large clear plastic coca cola bottles so the pipe was covered.
This loop of pipe was then laid in a sunny, south facing spot. An tank of water was placed inside the area to be warmed, with the hose connected, inlet to top of tank, outlet at bottom.
Somewhere there was a small pump, maybe solar, which gently pumped the water around the system.
The black pipe covered by the coke bottles absorbed the heat, the warm water ended up in the tank. This may have been for supplementing a hot water system, but there could be scope for using it to take the chill off a growing area.

[Gardenantics]

I saw a plan once for a Solar greenhouse, that was a lean-too whose back wall was constructed from large 55gallon blue plastic drums full of water, and built into the breeze block wall, that was then painted black. I think the drums were piped together, and connected to the gutter to fill up, and use as a water butt too. Sounds as though it would work, but too expensive to put on an allotment I think.

Brian