I've built a lean-to greenhouse 1.80metre long, 1.0 metre wide, about 3 metre high. In the floor I want to put a heat sink using an old polypropylene water butt (100 litre), one of those slim ones for narrow spaces. It's split at the bottom a bit so is now useless for water. Does anyone think, given the size of the greenhouse that it will be worthwhile or not using this size butt? Plan to fill it with broken glass. Been saving beer and wine bottles. There's no room for a bigger container for the glass. Thanks.

Here's some pix

On Mar 14, 4:37*am, mojocain
wrote:



In this last issue of Garden & Greenhouse :

http://www.gardenandgreenhouse.net/i...2012&Itemid=18

mojocain wrote:
I've built a lean-to greenhouse 1.80metre long, 1.0 metre wide, about
3 metre high. In the floor I want to put a heat sink using an old
polypropylene water butt (100 litre), one of those slim ones for
narrow spaces. It's split at the bottom a bit so is now useless for
water. Does anyone think, given the size of the greenhouse that it
will be worthwhile or not using this size butt? Plan to fill it with
broken glass. Been saving beer and wine bottles. There's no room for
a bigger container for the glass. Thanks.



100 litres of bottles isn't going to do much. Water has a much greater
thermal capacity than glass, especially glass and a lot of air. Could you
patch it up and fill it with water?

D

Many years ago, I examined a PhD thesis from a student who had looked into the possibilities of using a heat store in a greenhouse in East Anglia. His calculations suggested it really wasn't worthwhile, but if you want to try it, then water would be the best storage medium. How you get any surplus heat into the store is another question; you really need a decent sized absorber (think solar water heating panles). One other possibility might be to fill the tank with largish pebbles, and arrange a fan to pull warm air through the pebble bed. But it would probably not be worth the effort.

Dick Morris