Fire the Rocket!


[singlepic id=236 w=320 h=240 float=right]To heat our greenhouse we knew we wanted to use wood from our property. Normal wood stoves are a pain because you have to burn them for a long time and you lose a large amount of the woods potential heat out the chimney. Wood Boilers can work a bit better but suck electrons from the batteries. As well as not burning very cleanly.

Enter the Rocket Mass Heater(RMH). RMHs work on a simple principle. A super hot fire will burn off all the violates(the stuff that can combust) removing the risk of creosote buildup in the chimney. With the risk of creosote gone, cooling of the combustion gas in the chimney is possible without the fear of chimney fires.[singlepic id=241 w=320 h=240 float=center] The RMH is made of two parts. The stove and the mass. The stove is shaped like a J. The wood is put in vertically in the shorter of the two vertical sections. It wood burns from the bottom up but instead of the fire and smoke coming out where you put the wood in it gets pulled through the horizontal chamber by the chimney effect created by the larger vertical riser. It is the same effect that keeps your house from filling with smoke when you light up your wood stove. So far there isn’t much that is different from a normal stove. Beside the sideways fire.[singlepic id=220 w=320 h=240 float=center] The first change from norm is insulating the whole of the burn chamber and vertical risers. With the insulation around the chamber we go from normal wood stove temps of 300-600 F to 1200-1800F. And with the 1200-1800F we get a complete burn of the violates in the wood achieving a very clean burn.
Might as well keep making it different. The heat riser is surrounded by a 55 gallon drum. The hot gases come out of the riser hit the top of the 55 gallon drum and are channeled down the space between the insulated riser and the drum. At this point the temperature of the gas much lower. The drum radiates heat off like a wood stove normally does.[singlepic id=234 w=320 h=240 float=center] The gas is then collected at the bottom of the drum and funneled into an 8 inch stove pipe. It runs 25ft horizontally and then out of the greenhouse and up a chimney. The horizontal run is buried in a bench of dirt sand and rocks. As the hot gas flows through the pipe, heat is pulled off into the bench. The bench will then slowly radiate off the heat well after the fire is done burning. This is why the RMH uses significantly less wood then a normal wood stove. You don’t have to keep burning to keep the heat up. A few hours of burning will let you coast with a slow release of heat over time. The temperature of the exit gases will be around 100-200f which means we have captured a much higher percentage of the BTUs in the wood then with traditional wood stove. That means less burning, less felling, less splitting, less C02 going up into the atmosphere.[singlepic id=218 w=320 h=240 float=center] If you want to learn how to build a RMH you can purchase the book here. Check out permies wood burning forum for others doing projects and there is also a video that was just kickstarted coming out this summer.


February 10th, 2013|

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One Comment

  1. Alan February 10, 2013 at 9:47 pm - Reply

    It looks quite efficient. Way to go! I hope to see it in operation soon.

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