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Post by vanderlaag on Feb 13, 2016 6:02:33 GMT -8
Hello all you pyro-geniuses. I've spent days reading through your excellent posts, but am still not sure whether or how to build a tiny batch heater for my 8' x 12' (240 x 370cm) greenhouse. I know. It sounds ridiculously small, but I do get a heluva lot of food out of it. And you might think, why bother in zone 9, but this cool, humid climate is in much more need of a heated greenhouse than where I used to grow food, in NY State.
So the building runs east-west and is built against a 9'/274cm masonry wall; the structure is of heavy-duty aluminium on a dwarf brick wall (no wood in sight); there's a door in the east wall under the gable. There will be two raised beds along the north and south sides, the soil retained by brick walls on either side of the central path. Before I build those walls I want to build the heater -- if it makes sense! I've been thinking to run pipes (clay? vitreous enamel? inside a brick tunnel?) in a horseshoe shape, up one bed under the entrance and down the other, from a batch heater in the NE corner built of fire brick (or I can get kiln brick that takes up to 1400 C). Does that sound doable? Are there plans I haven't found on this site for just such a little critter? I'm not sure how long a metal barrel will last under greenhouse circumstances, but I take it building the barrel out of brick would reduce the flow? The thing is, though, I don't need a lot of heat in the atmosphere. Most of it needs to be captured underground.
Thanks for any thoughts about this...
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Post by mkrepel on Feb 27, 2016 11:47:23 GMT -8
How high are your raised beds? Will there be enough room to install 1/2 barrels (ala Matt Walker's design) beneath the beds?
If so, you could probably build a 4" PVDB batch box with a short barrel on top (to contain the heat riser and do some air heating which would be good on really cold nights) which would then enter into the beds via half barrels. Put the flue down into the half barrels to within a couple inches of the bottom and you will have a system that should work pretty well. I don't know if you could put in a valve to direct the gasses back and forth between the beds on successive firings, but something like that should be possible.
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tomr
New Member
Posts: 2
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Post by tomr on Feb 27, 2016 22:31:46 GMT -8
I will be copying a youtube video I saw. Search greenhouse rocket stove After the rocket , the stovepipe lays on the ground, between 2 dry stacked concrete block walls. Pea gravel fills the gap between the walls I will be experimenting with water heating of 55 gallon barrels
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Post by mkrepel on Feb 28, 2016 8:11:12 GMT -8
Take a look at Matt Walker's comments concerning sand or gravel for heat storage. Also, look at Permies.com. They have done some work with it and I gather they found that the heat transfer is not as good as casting cob (or concrete) around the pipe. Still, I am sure it will work to a degree (no pun intended).
I guess the goal might be to slow down the heat storage to avoid overheating the beds and cooking the plant roots. If that is the case, you might want to use gravel to "temper" the heat.
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mudder
Junior Member
Posts: 50
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Post by mudder on Mar 1, 2016 17:07:49 GMT -8
another one here in favor of the walker half barrel bench system.
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