Free overnight heating for greenhouses

[dtw]

I saw this on that program with Dick Strawbridge and his 'green' smallholding in Cornwall.

Basically, it's an underground storage heater.
Hot air is drawn from the top of the greenhouse using a solar powered fan, through a load of large pebbles or stones underneath the greenhouse where they are warmed during the day.
The colder air then exits the other side.
The heat is then released during the night through the ground.
The fan switches off at night, because it is dark!

I missed the rest of the series and was wondering if it worked ok, or if anybody else had tried it.

[dtw]

[Marymary]

Sounds brilliant - I'd certainly like to know more about it too.

[norfolklass]

I watched this too, the first time around. I can't remember exact details but his website http://www.itsnoteasybeinggreen.org/ says this:

"How does the greenhouse heat sink work?
Some details are in the book, but half the adventure is working out for yourself and thereby customising your solution. All you need is:

The heat sink is imploded glass - we used bottles from various parties and the local pub - imploded courtesy of Krysteline www.krysteline.net
Big hole - we lined it with polystyrene that came as packaging
Pipes were standard waste pipes for under sinks etc
Fan was a small 12V computer fan from a market £1.20 - in a box made of scrap wood
A 12V deep cycle leisure battery
Small 11w solar panel and charge controller
Old chimney cowl for the air to be pushed out the glass

Air sucked down from the apex heats the broken glass under the floor. Fan runs 24 hours a day. As the greenhouse cools the cooler air is still pumped through the glass, but when it comes out through the cowl, at floor level, the glass has warmed it so a constant supply of warm air is now being pumped through."

[dtw]

Thanks for that, I didn't know about the battery bit.
I might give it a go when I build a more permanent structure.
I've just got a cheap plastic covered tubular steel greenhouse at the moment.
Which has got lots of holes in due to UV damage.
It was only £30 from Lidl last year, I think I'll get another one.

[Marymary]

It sounds really interesting though slightly beyond my DIY skills. :(