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Hydro/Wind/Wood/Geothermal And other types of alternative energy

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Old 03-11-2015, 10:42 PM
ron45 ron45 is offline
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Default Getting the most out of burning wood

We found 20 mostly wooded acres on top of a mesa in New Mexico. Juniper, cedar and pinon mostly. Because of how our land is situated we decided to participate in a fire prevention program that involve removing lower limbs to above grass fire height and thinning the standing trees to lessen the likely hood of a fire spreading. It's a crap shoot but we can use the wood.

So I'd like to discuss how to get the most out of the wood we burn. I'd rather have observational or experiential help than opinions or preferences it that's ok. We've been using wood for heat since 83 when we moved off grid and began building our passive/active solar adobe fort. We have lots of thermal mass, all the interior walls are 10" by 14 adobes the exterior wall use the longer dimention for slower heat loss.

We have passive solar gain and a radient floor system that is currently not working. When it is it cuts our wood use in half. We can have single digit and minus single digit temps a few times in winter but it can also warm up to 48 outside in January. We are at 7000 feet.

I am familiar with rocket stoves and cob construction and wonder the pros and cons of, for example, building a cob enclosure very near or contacting the outer surface of the stove. Same thing about the chimney. It's very long in the shop area... 13 or 14 feet. The stove is quarter inch steel plate with fire brick on sides back and floor. It will handle 25.5 inch wood and I can put five 8 to 10 inch logs in it if I'm careful. I don't currently have a damper in the chimney and I should and the stove is not fed outside air. YET. That one seems to be favored by most people. I hope to benefit from the experience of some of you intrepid seekers of a more serene life style.

Ron
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Old 04-11-2015, 02:31 AM
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There are a number of sites that provide the BTU's per cord of wood burned. Based on the one I reviewed your Pinion comes in first, the Juniper second and the Cedar a close third.

Living considerable further East, I have no experience with actually burning these woods, but have found the BTU's per cord charts to be very accurate on the fire woods we normally use here.

For what it's worth department, if that helps any.
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Old 04-11-2015, 04:30 AM
ron45 ron45 is offline
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Hello Jjr. I'm looking more for information about the pros and cons of enclosing the stove in thermal mass to capture more of the heat from the wood I burn.

While btu's are certainly relevant they are only part of the story and then a possibly incomplete one. I know pinon has a rep for high btu out put but it's only when the wood is full of pitch. It will burn hot alright but it's a fairly dirty burn with all that pitch in it. You'd have to keep it roaring to burn it a little more cleanly. That's a good way to burn up a single wall chimney or worse. If it's well dried it burns up rather quickly and I only use it because there is so much dead and standing pinon in the area from a bark beetle infestation. And it dosn't last as long in a stove as oak would. But I'd rather save the ceader and juniper for later. Once the dead trees hit the ground that rot very quickly.

For instance: If I build a cobb enclosure around the chimney it will change how hot the chimney gets. As does putting a copper coil there. I don't know if that's a good idea for the chimney. In I really mean I do know know and it's possible I'm wrong. If the chimney is cooler there will be more incompletely burned material to deposit itself on the walls of the chimney. This is me speculating about what will happen. I'm hoping to run across someone who understands the implications better than I do. The science of it if you will.

I appreciate you taking the time to join in and actually on the pinon, I am drawing conlusions from local lore and having it sitting near the stove in winter and seeing the sap that runs out of the wood. It's gotta be a little like burning non anthracite coal or burning diesel oil in an engine with out the turbo and other recent improvements in diesel engines. So much to know so little time.

Ron
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Old 04-17-2015, 03:35 PM
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Ron:
I'm doubtful, I can help you with the answers you seek.

But, if you have not reviewed it, insulated chimney pipe reportedly has multiple times the insulating value of brick, greatly reducing its proximity to combustible material. The insulating effect should produce a cooler overall chimney pipe, but the burn inside and its reaction is something else entirely.

If and when you get a definitive answer on the questions you raised, I for one would be interested in knowing the outcome.
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Old 04-18-2015, 04:50 AM
ron45 ron45 is offline
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Thank you Jjr, I hadn't been aware of that. But two things come to mind. The wall near our chimney is 14 inches of adobe block so there is not much danger of damage or fire. Also, Cobb the material I mentioned using is much like a normal adobe mud mix but with much more sand and for this kind of all the straw and vermiculite you can manage to mix in. This will slow down heat travel quite a lot and give that nice hot burn. But We get quite a bit of heat gain from the 13 foot metal pipe. Where it goes thru the roof it is triple wall and fiber kiln material is packed around it to keep it away from the 1 inch rough cut pine ceiling.

I'll be glad to post if I get more information. AFAIK the biggest heat gain would be from using outside air for the burn. I need to find an alternative energy forum. Someone there might have some more info for us.

Ron
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Old 04-19-2015, 12:01 AM
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Ron:
I hope you find the answer(s) to your dilemma.

Sorry I could not help you more.
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Old 11-06-2017, 07:30 PM
paul wheaton paul wheaton is offline
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First, here is a quick video about the difference between a conventional wood stove and a rocket mass heater. It includes why conventional wood stoves need insulated chimney's and why rocket mass heaters don't.

https://www.youtube.com/watch?v=fwCz8Ris79g

Next, here is a video where a guy took a conventional wood stove and modified it to have a heat riser like on a rocket mass heater and then extracted more heat out of it, before sending the exhaust outside:

https://www.youtube.com/watch?v=DMUES-34Ioc

Finally, when you are talking about a rocket mass heater for a shop, your strategy is gonna be different. With a shop, you are usually working in there for several hours, then you go away for a day or two, and then come for a few more hours. This is different from a home where you will be in it for most of the day every day and you wish to keep the temperature comfortable.

So, in this video, we are gathered around the rocket mass heater in our shop. But it has a large batch box on it and three barrels. This is so that we burn a lot of wood really fast and we extract most of the heat right away. We want to heat the shop really fast and put very little heat into the mass.

https://www.youtube.com/watch?v=t0cs8PWDfwg
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