Maybe I missed it but what is your goal? Hot water for potable use? Hot water to heat the house or greenhouse? Electricity to go off grid? Maybe all of the above? Do you have any wind or solar resources?
The plan as written so far in this thread (not written in stone... this is presently in brainstorm space/time continuum!) was to have the gasifier heater in the greenhouse, directly beside the main storage unit, which is the 800 gallon hot water tank surrounded by solid thermal mass (cob, rock, buckets with sand and rocks). The piped hot water would be to the house, and that would not be used for heating, but for hot water use in the taps. I'm considering having the house close, or right up to the greenhouse in order to eliminate the problem of long distance piping, and of trenching and insulation of the pipes. The house will be heated by passive solar design, combined with RMH, an old fashion cook stove, a cob bread oven... etc.
If you're trying to heat a greenhouse it seems to me that it would be simpler to heat it directly with a rocket mass heater than to heat water and transport that to the greenhouse and get the heat to go into the greenhouse. Unless getting heat piped into grow beds is you goal and then maybe hot water is the way to go...
1.)My thoughts are to put the compost inside the greenhouse so the heat is right where you need it. 2.) I'm still working on my greenhouse design but I'm leaning towards an A frame shape with straw bale insulation on the North, East and West. 3) I'm also thinking about a solar pool cover for the glazing. It's like really beefy bubble wrap.
Mainly, in my present plan, the thermal mass is designed to be within the greenhouse glazed catchment only. This would be in the extremely deep damp warm microbe and fungi rich soils, in the stones in the keyholes, in the water tank/aggregate storage zone, in the back wall of stone/buckets filled with aggregate, cob... etc. The foundation will be insulated downwards four feet from the bottom of windows on the South wall , and the outer area insulated outwards, maybe 10 feet. In this case, the area outside does not act as thermal mass, and is not expected to contribute to thermal mass, but instead it adds a huge amount of additional insulation to the foundation, thus it creates isolation from the outside environment in winter, enveloping a large area of external Earth. This increases the thermal inertia. I could just go with insulation outwards, just below the sod, and not have the insulated wall. It would be cheaper (pretty much free, because the duff just takes some time to gather and haul), so there is that, and then the area under this insulation on the outside becomes part of the thermal mass, which seems to be what you are saying. But I'm not sure if that is the best way to do it yet. I'd rather keep more of the main heat stored in the living greenhouse soil area and not outside. But this way with thermal mass extending outside (without an insulated wall) is possibly the way to go, and I'm open to trying to figure out what is the best way to do it to maximize solar gain, while minimizing heat loss, while doing all of it with as few resources/time/money/ etc as possible. I'd like to be convinced that that is the way to go. But, like with how I started this thread, I'm willing to spend some to save more in the future, and so if I have to pay to insulated downwards at the wall because that is the best way to do it, then that's what I will do. Right now I have a steady good paying job, but I plan to quit it within three years, as I find it to be an ethical compromise. It's paying the mortgage and getting the infrastructure together... after that... I want to do permaculture/market farming here.
I'm also planning on insulating outside the foundation. I debated enclosing some of the dirt outside the foundation wofati style so that it becomes thermal mass for the greenhouse. But I'm not sure how likely that is to work properly. And if you do that as you proposed, would the insulation against the below grade foundation negate the effect of the thermal mass just outside it (block heat from getting to/from that mass)?
The thermophilic community seems to respond well to these dimensions or greater in my experience. Clearly if a person wants a long term project (heating for the winter) it will have to be much bigger, or that person will be building piles all the time.
Somewhere (not necessarily in that book) I heard that you need to have a compost pile at least 4' to a side in order to generate good heat.
Yes. True. Not when compared to hot compost.
I don't know if biodegrading hugulkultur beds generate heat or not.
I'm not sure if Pain did that. It seems that the structure of the shredded wood being piled up had enough aeration. All I have found on the subject is piling it up and moistening it in layers.
Aeration is part of the bacterial process as I understand it so you need to get air into a Jean Pain system.
I'm hoping for tempered glass, but this does sound intriguing.
references to pool covers being used on greenhouses.
This makes sense. The only thing that might throw it off is that condensation might happen between those layers.
They put it bumpy side down so the snow will slide off of it. I'm wondering if you put it bumpy side up and then covered it with a layer of greenhouse plastic if you would get even better insulation (more air pockets between the air pockets).
This might not be as complicated as you think. You might want to try creating a different permies thread for this, or try posting something on a different forum altogether. You are definitely not reinventing the wheel on this one, or the Sterling Engine, though, like I said, I know little about the potential of your Sterling proposal. Keep at it.
My only other idea...and it had progressed some...is biogas from my sheep farm manure, but it seems problematic at this time.
I agree. I've made fairly dense compost piles that were quite wet and they generated so much heat that I could not put my hand in it.
we are getting a lot of heat, so hot you cannot stick your hand into the feed very long. It has to cool off a bit before the cows/sheep will eat it. So honestly I don't think you would need aeration.
I've heard of this, and read of this, including some having a heater blower (instead of just a fan) blowing warm air in the gap between glazing layers (usually plastic) so that it isolates/buffers the outside to inside temperatures creating a high thermal inertia for internal temperatures to be lost to the outside. Of course using heat/fan energy is resource intensive, so this is not optimum.
I know many people use two layers of plastic with air inflated between them.
I might be imagining your idea wrong, but here's what I'm thinking with the condensation idea:
If that doesn't have condensation issues, I don't know why it wouldn't work with a pool cover as one (or two) of the layers.