Saturday, January 7, 2012
Starting the Rocket Mass Heater
Today I finished building and fired up the rocket mass heater for the geodesic dome. Ironically, it's January and we're having record breaking warm temperatures in the 50's but I couldn't resist and started it up. I will do a full video about the construction in the future, but wanted to share a few pictures of it.
This heater is a bit different than some you may see. I wanted to be sure there was enough drafting in the chimney so I doubled up the barrels.
The entire burn tunnel is buried under the floor. It took a little while to get the drafting to start. It didn't help that the internal chimney wasn't insulated yet (missing some parts for it), but once the system got warmed up, it turned into a raging inferno.
A picture without the flash shows how well the fuel is burning in the tunnel.
I ran out of sand so I wasn't able to completely bury the horizontal exhaust. It was quite hot to the touch, but as you moved down the pipe, I could hold my hand against the duct and it was slightly warm. It was quite funny to see the sand around the duct drying out so quickly. It will be interesting to study the temperatures along the system in the future!
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7 comments:
Hey Rob, great job documenting your work, as usual. A few questions...did you stack the barrels because of the height of the dome? How many months of the year do you expect to run the heater? How often will you need to replace those barrels, if ever?
Chris
I'll do more detail when I get around to the video. I stacked the barrels because I wanted to see if I could get a stronger draft with a taller chimney...which I did. I'm hoping to just need the heater for about 2 months. I have no idea how long they will last. I would assume the top lid will go first since that takes the most heat.
Very nice series Rob, Looking forward to each addition you post.
I was wondering about the difficulty you might have starting the draft. Have you considered a propane torch for a preheater? Use the gas valve assembly from an old furnace and a 5 gal propane bottle and run it for 15 seconds or so prior to your pellet auger starting up. It could be an over-sized pellet ignition system that serves as a preheater to get the draft started.
Thanks a lot for taking the time and effort to post the videos man.
Appreciated!
Eric
This weekend, I'm going to try a small duct fan inside the exhaust to get the draft started. I got it started last weekend, but had a lot of smoke. ;-) I think it should work very well.
I am confused about your choice to double the barrels. I understand that increasing stack height, flue gas temperature and difference in air density all increase draft. My question is that would your double barrels not increase flue gas friction by fighting the overall stack height outside the greenhouse? I love your page you have done an awesome job.
I'm not a thermodynamics engineer so I'm not sure about this. My assumption would be that the overall force of the rising heat exceeds any frictional loss.
While this certainly ain't the heater like the ones from heater.com which I had in mind, both require attention and extreme care whenever you handle or operate such heaters.
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