RMH uses EIGHT TIMES less wood to heat a house than a wood stove

[ChickenToes]

My husband and I are considering building a small (probably no larger than 4 x 8, if that) passive solar greenhouse, and my biggest concern is that it wouldn't heat it well enough in the dead of winter without a secondary heat source. It can easily reach -40 here if you include wind chill. -20 without the windchill included is not uncommon.

I think it may be one of those things that we'll just have to try and see if it works.

 

[paul wheaton]

Moments ago I uploaded a video where a rocket mass heater combustion chamber is mounted on top of a conventional wood stove.

Ernie Wisner has built over 700 rocket mass heaters and this is his third hybrid. In three minutes he covers a lot of detail about the efficiencies of conventional wood stoves, rocket mass heaters and hybrids. Including some enlightening information on how rocket mass heaters can heat a space using 90% less wood.

http://www.richsoil.com/rocket-stove-mass-heater.jsp#hybrid

 

[Leta]

Wiki has a good article on these. This helped me grasp the ideas further, too.

 

[Boogity]

Hey Paul, I have been studying rocket mass heaters for a couple of years and I have a small rocket stove that I built to process Maple Syrup. My wife owned a woodburning stove shop from the late '80s through the '90s. Being a mechanical engineer I became her technical department. Over the 12 years that she had the store I attended 6 technical workshops on creosote build up issues and smokestack design. I have two questions about the rocket stove concept.

1. My outdoor rocket stove uses 12" to 16" long sticks and the max. diameter I can use is about 1 1/2". 1" would be the norm. Using this tiny wood requires constant work at the feed area of the stove to keep the fuel supply ready. When we do our syrup thing in the early spring someone has to feed the stove almost continuously. I just cannot imagine staying up all night to stoke the fire in a mass heater in a home or greenhouse. How do you handle this issue?

2. A rocket mass heater is typically designed to extract the maximum amount of heat from the flue gasses. At first glance this sounds good and it seems that it would result in maximum efficiency. Squeezing every last BTU from the flue pipe seems like a good idea. But all open flame type heating appliances with natural draft, not fan forced, absolutely must have a temperature differential within the flue pipe to create the required draw up the chimney to extract the unburned gasses from the fire. If the chimney in a typical wood stove gets too cool you will loose draft and the fire will burn cooler and produce relatively large amounts of creosote. A poorly drafted system will allow the flue pipe to cool and this results in creosote condensation on the interior walls of the flue pipe. This creosote build up is a one way ticket to a chimney fire and a burned down house. Most of the Rocket Mass Heater designs do not seem to assure a high enough stack temperature to reduce or eliminate the creosote build up. How much creosote is deposited in the RMH flue and how is this situation remedied?

Thanks.

 

[paul wheaton]

The "chimney" is about two and a half feet tall and super hot. Reburning the smoke. No creosote.

The exhaust can cool with no problem.

As for restocking - that's what the mass is for. You heat the mass and then mass throws off heat for days.

 

[Boogity]

The "chimney" is about two and a half feet tall and super hot. Reburning the smoke. No creosote. The exhaust can cool with no problem. Hmmmm that's pretty cool. Well I guess it's really pretty hot.

As for restocking - that's what the mass is for. You heat the mass and then mass throws off heat for days. So, are you saying that you only need to fire the stove for a relatively short time and then allow it to go out? If so, that's also pretty cool or hot or something.

I'm determined to try a RMH one of these days. It'll probably be a small greenhouse project I have rattling around in my head. Thanks.

 

[paul wheaton]

I just finished a major overhaul of my rocket mass heater article. Nine new drawings, one new animation showing the path of the fire/smoke/steam, new videos and twelve new pictures.

http://www.richsoil.com/rocket-stove-mass-heater.jsp

 

[Britesea]

http://www.arizonapreppersnetwork.com/2011/09/how-to-make-16-brick-rocket-stove.html

I want to try this next summer

 

[paul wheaton]

http://www.arizonapreppersnetwork.com/2011/09/how-to-make-16-brick-rocket-stove.html

I want to try this next summer

I think most people like them much better in the winter.

 

[Britesea]

I was thinking of the small rocket stove for an outdoor kitchen, as per the video I found