Seriously, only burning over a little of a half cord of wood for an entire winter in Montana? I guess my real question is if he is just blowing smoke?
No. As a proponent of Rocket Stoves myself, they are impressive and certainly efficient. That style is not EPA approved (maybe should have been posted here? "Non-EPA Woodstoves and Fireplaces ). Builders of other styles, which more closely approximate masonry heaters, are looking to gain EPA approval. I, as well as BrianK, and member NW Walker have a thread or two about our efforts....
If we all could get by burning only a half cord of wood, then we wouldn't need the stove to be EPA approved because we would all be putting less CO2 into the atmosphere.
I find the consumption questionable but size of dwelling not stated. The other thing is he is using the rocket stove with quite a bit of mass and that is the key. If we were to locate our more conventional wood stoves in an alcove of say a ton of granite and proceed to get the granite all nice and toasty, likely wood see the fuel consumption drop as well. Think of a rumford fire place system - mass being warmed by fire then radiating out into area long after fire dies out. Nothing new. Rocket stoves are fairly quick on consuming fuel but at a very high heat factor & hence burn clean, rather than a slow burn which we are more accustomed to. With out mass the rocket stove
I’m building one of these plus a 55 gallon barrel rocket heater for a guy in North Carolina next week: Batchrocket.eu - Applications For Code/zoning purposes it’s technically a masonry stove (which will usually pass code and homeowner insurance regulations) but it uses a rocket heater core. They’re really efficient because they creatE an extremely hot (2200•F) burn but for a shorter time than a regular wood stove. The secret is capturing that heat in a masonry bench which absorbs the heat then gives it off slowly many hours after the fire goes out. They do use less wood per season than a wood stove, but the difference is a matter of debate. Since we’re building on a slab foundation, , in front of an existing fireplace, weight and chimney is not an issue, but in a typical American home with a basement, it is a big issue to build one of these on the first floor. A foundation must be built up from the basement to support the weight.
A properly built and insulated rocket heater core will hit 2100-2200•F, which is hot enough to burn the Firewood and reburn all the volatiles and particulates in the smoke with only natural air draft and no catalytic combustors. So from an environmental perspective they have a lot going for them. All the volatiles necessary to form creosote are incinerated so creosote accumulation isn’t a concern, and the exhaust stream can run as low as 180-220•F, thus keeping a lot more of the BTUs inside the house and not being sent up the chimney. These two facts account for much of the claimed greater efficiency and incredibly clean exhaust.
I recently developed an interest in rocket stoves. Now I know why you guys are so interested in them! Go, Jen, go! Hey wildwest she has those boots on!
reminds me of the Russian fireplaces I would run into in Richmond Me. Big masses in the middle of the home. seems all they burn is kindling. The units were huge and in the center of the house. Kept the whole place warm as well as being their stove.
I don't buy the hype, unless the efficiency numbers for our EPA stoves are way off. Suppose my 30-NC is 50% efficient (it is claimed to be more, who knows), and I burn 7 cord a year. If I install a rocket stove, and lots of mass, and somehow achieve 100% efficiency (impossible), the wood burn would be cut to 3.5 cord,1/2 of what I currently burn. I see claims all over the place to 1/4 or 1/10 even of the wood consumed in an EPA stove. Something does not add up. Greg
Has anyone approached this as a thermodynamics problem? Plus, we really don't know about the structure. A few decades ago, the rage was in building structures super insulated; 2x10 or 2x12 stud walls so that more insulation could be packed in the walls, super sealing against air infiltration; air heat exchanges (since the houses were super sealed; you had to bring in fresh air from the outside). If you really closed the system; from a thermodynamics viewpoint, then any energy put into the system is going to stay there. I just found it hard to believe that he only used a little over a half cord of wood for the entire heating season of his location. What I see about the advantages of the system is that you have a large thermal mass that helps to moderate any swings in temperature. That does not mean that you still don't have to put as much energy into the system to have the same comfort level.
It'll take a smarter guy than me to lay it out, but I agree, no such thing as a free lunch. Your home requires a certain amount of btu's to keep warm but the fact remains, the energy source is wood. You can walk in slow or run screaming in, but a piece of wood has the same energy no matter what, it's just a matter of how it's spread out.
There is some validity to the claim that Rocket Heaters extract a much higher percentage of available BTUs per pound of firewood, and that the efficiency in capturing and releasing those BTUs is much higher with a rocket heater because the exhaust stream is relatively cool. I think in the end it could be validly argued that they use less than half as much wood as a highly efficient hybrid stove like my Ideal Steel, but only because the mass extracts every last BTU of heat available, and they are more efficient at reburning the smoke than the most efficient hybrid wood stoves. Without a mass a rocket heater is useless.
Basically these stoves are mini blast furnaces, burning the wood at high levels of O2 so that the fires are releasing as much of the energy stored in the wood as possible and transferring that energy to a thermal mass that will help to moderate any temperature swings.
It would be interesting to see actual head to head testing to see the how and why. I can wrap my head around stealing the exhaust heat back, but how much more efficient can something be burning if I have no smoke out of my stack on a regular secondary burn stove (or a catalytic stove) vs a rocket stove? I'm not looking to argue, just to be convinced. Kind of like the short cut being a better way. If it was the better way, it would be the way.