rocket stove mass heater

[Prepper1]

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



rocket mass heaters in a nutshell:

heat your home with 80% to 90% less wood
exhaust is nearly pure steam and CO2 (a little smoke at the beginning)
the heat from one fire can last for days
you can build one in a day and half
folks have built them spending less than $20



the verbose details on rocket mass heaters:

This could be the cleanest and most sustainable way to heat a conventional home. Some people have reported that they heat their home with nothing more than the dead branches that fall off the trees in their yard. And they burn so clean, that a lot of sneaky people are using them illegally, in cities, without detection.

When somebody first told me about rocket mass heaters, none of it made sense. The fire burns sideways? No smoke? If a conventional wood stove is 75% efficient, doesn't that mean the most wood you could possibly save is something like 25%? How do you have a big hole right over the fire and not have the house fill with smoke? I was skeptical.

And then I saw one in action. The fire really does burn sideways. The exhaust is near room temperature - and very clean. The smoke doesn't come back up because a huge amount of air is getting sucked into the wood hole. Neat! I sat on one that had not had a fire in it for 24 hours - it was still hot!

how it works:

The sticks stand straight up. Only the bottom ends of the sticks burn. The fire burns sideways. Since the heat riser is insulated, it gets freaky hot. This causes a strong convective current. When the hot gasses hit the barrel, it gives off a lot of heat, which cools the gasses which get much smaller and easier to push around. The gasses that exit are usually just carbon dioxide and steam.
rocket mass heater

The real magic happens with the heat riser. The strong convective current is what makes the air get sucked in through the wood feed so that the fire burns sideways and the smoke doesn't come out. It is also the place where it gets so hot that all of the smoke is burned.

Here is a much better image showing the mighty power of the insulated heat riser, reburning the smoke and powering the whole system.



The first picture below represents the most thorough rocket mass heater design I have ever seen. Followed by the rocket mass heater that was created from that design. These are both the products of the leaders in rocket mass heater innovation, Ernie and Erica Wisner, who have built more than 700 rocket mass heaters.





rocket mass heater vs. conventional wood stove
conventional wood stove

a conventional wood stove uses a lot of the heat to push the smoke out of the house

rocket mass heater house

a rocket mass heater extracts as much heat as possible before releasing the exhaust

I've now given presentations and taught people how to make these. The question I am most often asked is: "If my current wood stove is 75% efficient, it seems the most room for improvement is about 25%. But you say you can heat a home with a tenth of the wood. Isn't that claiming that a rocket mass heater is 750% efficient? Wouldn't 100% efficient be the maximum?" There are two ways to answer this.

1) Measure the temperature and volume of the smoke leaving a conventional wood stove (very hot and a large volume) and compare that to the exhaust of a rocket mass heater (a little more than room temperature and a trickle). Far more heat stays inside with a rocket mass heater.

2) Let's do the math.

a) A rating of "75% efficient" does not account for some of the heat that goes up the chimney to remove the smoke. The testing labs will use a number of either 14% or 16% for smoke going up the chimney. So the 75% number is actually 64%. Saying 75% is allowed and sells more wood stoves.

b) The rating of 75% was the most efficient result experienced in a laboratory with experts trying to get the most efficient numbers. So while a wood stove might be able to achieve 75% efficiency in a lab, it rarely does in a home. An experienced wood stove operator will probably experience something more like 35%. Somebody using wet/green wood and shutting the dampers down a lot for a "slow burn" will probably experience something more like 5% efficiency (or less!) with a 75% efficient wood stove. Thus leaving a lot of room for improvement. Rocket mass heaters have no way to reduce the air flow for a slow, inefficient burn. An inexperienced wood burner will probably have a 90% efficient burn every time.

Another question is about creosote. In a conventional wood stove, under inefficient conditions, creosote can build up in the chimney and start a chimney fire. The "chimney" in the rocket stove is the same thing as the heat riser. The rocket stove is designed to have a controlled chimney fire every burn.






For more facinating information, videos etc please visit...
http://www.richsoil.com/rocket-stove-mass-heater.jsp

[Scythe13]

I hope to be building one of these when we move into our new house in the next couple of months. It'll be a summer project though, for when I have the polytunnel up and running.