Topic: greenhouse heat sink

[Niamh]

Has anyone seen the heat sink system that they installed in the ground under the greenhouse in the BBC series "It's not easy being green"? There's a video clip on teletext 630 on the BBC channels showing some of the details.

What I'd like to know is a) does anybody out there have a similiar existing system, and how well does it work? b) could any of the technically minded geniuses who frequent this site pass comment on how well they think it would work, if they have seen the system in question?

Just about to put up greenhouse in next few days and would have to get the polystyrene lined box, crushed glass and piping in place if I'm going to do it, so comments, advice etc welcome!

thanks,

Niamh

[kitty]

i 'spect someone of a technical mind will pop along here an assist you-me?
i think the bbc throw money at stuff without a single freakin clue if anything REALLY works...if it did, i daresay the money -canny commercial growers would be doing it in droves...either they are keeping it a well guarded secret or..like me,they'd rather be gardening! ;D
good luck!
kitty

[timnsal]

I didn't see that bit on the series, but OH bought me the book. It uses an awful lot of glass. :o

It will work - just. The idea is that the glass is warmed up by passing warm air over it all day, and releases the heat back at night when the air is colder. I don't know how much heat glass will store. Wouldn't have thought it was that much though, especially in winter when even the daytime temperature won't be that high.
They claim in the book it kept the greenhouse above freezing the first winter. I got the impression it was done mostly because they had a lot of glass.

If you want to do something similar, there are probably more effective materials to use. Try searching for 'thermal mass' for ideas.

Sally

[rbull]

The system should work, since all they are seeking are marginally increased night temperatures.

Glass is quite good, but I gather they used it because they wanted to re-cycle a lot of bottles and they needed something that would allow air to pass permeate easily.  If anyone wants to copy the principle, house bricks, especially high-density ones, should give a similar if not better result.

Roger

[Niamh]

Thanks everyone,

would definitely agree with the theory that glass wouldn't store huge amounts of heat for rerelease into the greenhouse. The idea did look nifty, though I suspect that if I painted the huge wall that the greenhouse is built against black, that might work also!

Niamh

[timnsal]

I agree. Probably be more effective, as the wall will be heated directly.

Sally