smokeless woodstove

[greenkarson]

Bought a new woodstove this fall a nice drolet with the secondary gas burner.  Very happy with it.  Wood is our primary source of heat.  That being said i'v been thinking even with all the advancements in woodstove in the last few years most of the heat is still going out the chimney.
  So i'v been thinking about a totally different design. A air injected firebox with a large water scrubber/heat sink.

Lets see if i can discribe what im thinking. First of all a airtight firebox with no air intakes other then a variable speed power vent. So the power vent total controls the burn rate and forces the smoke out the chimney vent on the top of the fire box.  The smoke still being forced by the power vent enters the pipe into the water filled scrubber.  Which i believe would capture almost all of the heat out of the smoke.  The top of the scrubber could be then vented out side.  But because the ''smoke'' is now cold and still being forced by the power vent.  It could be vented straight out of a wall instead of a costly chimney.

The water scrubber could be quite large to hold the heat.  Maybe it could be used to run a radiant floor system or just used by it self  as a large radiant heater. 

Pros
No smoke
More even heat
Maybe could go days between fires depending on size of scrubber
Finer control of burn rate with the varible speedpower vent

Cons
Power vent would have to be running when ever fire is going
Large size
Probably need to change water every season
Here are some pros and cons

[greenkarson]

Sorry typing on a tablet.  Here are some pros and cons was supposed to be on top of the list not on the bottom

[kensue49]

Check out the pellet stoves.
They solve the problem of variable moisture content, uniform sized burn material and excess creosote production.

If you can overcome these problems with your design then it could work nicely.
Good luck.
Kenneth

[thirteen]

You might run across a fire code violation. If your off grid you would end up using a lot of power unless it is planned for that type usage. Just an idea  I think that you would need a bypass system to operate things until all of the piping got to operating temperature. They do make a heater that goes into the exhaust piping that blows the air thru tubes that are in the stove pipe. I do not know how well they work. If your stove is working right you should have clean air going out of the exhaust pipe. You would need an air tight system the way I'm thinking. I think that you might need to shut everything down to put wood inside to burn. It sound like it might work best of luck.

[JimB]

Check out mha.net for masonry heater. I have one that does just about everything you are trying to accomplish. It is also very simple and requires no electricity.

[greenkarson]

I checked out the masonry heaters.  They are very nice looking but still put most of the heat from the fire out the top of the chimney. And they are stationary with no way to move the heat from room to room. 

I'm thinking with a propery designed scrubber the air from the chimney  should be allmost cold with the majority of the heat captured in the water. That could be piped to a radiant heating system.  I think that it probably  would need a bypass on the chimney before scrubber for lighting.

So far this is just a ideathat was on my mind.  But the more i think about it the more i want to build a prototype.
Thanks everyone for your feedback

[wewantutopia]

Sounds like a great idea.

The power vent blower could be on the exhaust side after the scrubber pulling the air through like a bong/hookah.

The hot water then used for radiant hydronic heat.

[electrondady1]

bong water gets pretty nasty after a while,
 but yeah, a viable speed fan on end the exhaust  side pulling air into the fire box is a lot less likely to kill you.
i think you would need to get some really complete combustion.
maybe by injecting more air at some point.
hydrogen ?oxygen?
a plasma arc ?
if you bubble the smoke through the water it won't be water for very long.
some kind of acidic industrial waste.

i keep looking at those commercial natural gas radiant heaters with a very long exhaust pipe up near the ceiling.
if you could get a hot enough, complete enough combustion going on inside a pipe like that you could run a water/coolant pipe in parallel and pull the heat out.

[birdhouse]

i heat my home with a wood stove, and also think a lot about how much heat goes out the chimney. 

i've come up with a possible good solution to this, though never tried it. 

basically, put the chimney on one end of a room, and have the woodstove on another.  a long exposed piece of stove pipe running near horizontal to connect the two.  the pipe coming off the stove emits an awful lot of heat.  the more exposed interior pipe the more heat is emitted.

you could even take this one step further, and wrap the pipe in soft copper and connect it to radiant floor heat, or storage tank ect.   

the down side, is cooling the exhaust air will create more creosote in the chimney.  so regular cleaning would have to be a priority! 

adam

[thirteen]

You will also need to look at the type of wood you will be burning. You may need to try and circle the exhaust pipe with copper pipe and use it to circulate a liquid thru it for the floors for radiant heat. I sounds like a good idea but one of the main problems is the final exhaust. You would carry allot of water vapor and would need a good supply. You might also need a circulating pump so there would be a settling tank beside the exhaust. Just a thought or idea.

[JW]

The design you mention sounds alot like a wood gasifier. I have some really cool picture of various "homemade" gasifiers, most of what I have seen is thru email correspondence, mostly from Russia. I cant post the images in my email, here, unless I get permission.

jw 

[greenkarson]

Yes similar to a gasifire.  But i think the blower would have to be blowing into the firebox not pulling from it. That way there would be less chance of getting smoke back out through the fan.  The dirty water would not be a problem.  Maybe a discharge pump built right in.

[richhagen]

As pointed out above, if you cool wood fire exhaust too much, you get lots of condensation of creosote type stuff that is flamable, which increases the odds of having a chimney fire all else equal.  With high efficiency natural gas, this is used without issue because you don't generally have much condensing other than the water formed in the cumbustion process and that tends to flush out the chimney and exchanger to some extent.  With a forced air fire box with gas you need pressure switches or some other cutoff to prevent the flow of gas and flame if the fan pulling it into the box should fail.  For wood, I would think you would need to ensure that your design could not back vent if the fan failed you in the middle of the night, for example.  For the case of bubbling the exhaust gases through water for example, it would require a reasonable pressure difference to accomplish this which would be dependent upon the depth of the water through which it was to be forced, as well as having all of those condensates accumulate in your water.

[greenkarson]

I was thinking about somesort of well built flapper valve the fan would pull open it could even have a rubber seal and could be on the intake end of the power vent pipe.  to be away from the heat so seals won't burn.  That way when the fan was off the fire would smother its self

[machinemaker]

you might want to look at rocket mass heaters or RMH stoves. the concept is similar to masonary heaters in that you are burning a hot effiicient fire for a short period and capturing the heat in a large mass to radiate slowly into your living space. the RMH stove are fairly easy for the DIY builder. You might want to look here for a forum on them:  http://donkey32.proboards.com/index.cgi
kent

[nick1234]

i have a  drolet air tight and when the wood is burning good  i close the air vent after a short while with the air vent closed the stove pipe is cool enough that i can put my hand on it with out burning it and all you see thought the window is burning red wood with a gaseous flame   the pipe goes straight into the chimney as per drolet's instructions  and i use less than 1/3 the wood i used before  it's 8 years that i own a airtight and i will not switch to any other type now
nick

[bdubay]

I have an older Kent wood stove from New Zealand. I think they make them now in the U.S. It was the first non-cataltytic stove with an afterburner, a chamber above the fire where the fumes burn more completely before going up the chimney. I live in Washington State and burn a lot of fir.

Once it develops a small bed of coals, I turn it down. Even a small fire will burn 5-8 hours with no flames and with white smoke coming out the chimney.

I am interested in the findings that air-tight stoves create more fumes than a regular stove. I wonder if that is true of stoves with afterburners in them.

Bill DuBay
Whidbey Island