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rocket mass heaters

My self feeding, wood chip burning Rocket Stove

Michael Newby

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Location: Mount Shasta, CA Zone 8a Mediterranean climate

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posted 13 years ago

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So I finally built a rocket stove that I don't mind showing off (version 4, not too bad) and I thought that I would post the videos I took of it here first, see what you guys think.

It's mostly scrap materials from around the property, fire bricks, 8" stove-pipe, a 12" diameter old oil barrel, some local rock and one bag of fireclay that I bought for about $6.

I've managed to get aluminum to melt in the riser tube, about 4" from the top. I've also dropped a copper coil into the riser tube and made some decent steam.

You'll have to forgive the videos, they were taken with my cell phone and I was more concerned with documenting than with cinematography.

Stove cold so you can see inside the burn tube and how I install the louvers:
[youtube]http://www.youtube.com/watch?v=HYjfofnWVvw[/youtube]

Stove Burning:
[youtube]http://www.youtube.com/watch?v=Hop25uBJp90[/youtube]

Making Steam:
[youtube]http://www.youtube.com/watch?v=buaeS-okWPc[/youtube]

Let me know what you all think!

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Michael Newby

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Posts: 697

Location: Mount Shasta, CA Zone 8a Mediterranean climate

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posted 13 years ago

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The chip feed tube (the one in the front) is a 6" stove pipe. The chips gravity feed into the burn tube with no external input. I get around 30 minutes of burn from one full pipe (~.75 cu in).

I have ideas about routing the exhaust into the house and back through a large heat sink. If the return came back to right above the heat riser, you could re-heat the exhaust after it exits the house to help with the draft. I'm currently collecting the materials (junk) to try this out in my house, which has no heat in the lower floor.

The footprint of the stove is roughly 18" x 36" and the heat riser would be very easy to make as a single unit that would drop into the burn chamber. The chip feed tube is removable, also. The base/burn tube is the heaviest part and it is still something that 2 men could move together. I have a few more tweaks to make to the system, but I think that it would be a good, portable unit, not counting the heat sink inside the house, which isn't an insurmountable challenge.

Abe Connally

Posts: 1502

Location: Chihuahua Desert

posted 13 years ago

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this is very nice, I like it!

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Kathleen Sanderson

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Location: Zone 6b

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posted 13 years ago

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Is there any way to measure how hot the bottom of the unit gets? I've been trying to figure out something that could be installed inside an existing structure without tearing a hole in the floor for a foundation. Not sure that's what I'll end up needing, but it would be nice to know something is available if it is needed.

Kathleen

Michael Newby

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Location: Mount Shasta, CA Zone 8a Mediterranean climate

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posted 13 years ago

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I don't have any means of measuring the temp in the burn chamber, but when I stuck my wife's candy thermometer in the exhaust tube (about 3" in) the thermometer wrapped around more than 3 times in less than a minute before I pulled it out. Needless to say the thermometer's ruined. The lower barrel and burn tube bricks are getting too hot to touch, that I can tell you. I think that you could place the entire system on a sheet of fireboard and be just fine, though.

The base of this stove is a small concrete slab, approx. 18"x28"x4". I built the burn tube up from this using the 2.25" thick fire brick on the inside and 4.5" fire brick around that. I mortared everything using straight fireclay ($6 per bag, used half a bag) and put about a .25" thick layer around the inside of the entire burn tube.

I'm now working on a larger chip storage - with the burn rates I'm getting I would need around 3 cu ft of chips to get a good 2 hour burn which I think would be plenty of burn to heat a large mass or for hot water production.

I'm also brainstorming on how I'm going to redirect the exhaust through a large mass to harvest all that heat out of it. I'm thinking that I can push it through a large brick or rock wall then have the cool exhaust coming out of the mass go directly over the burn tube to re-heat the exhaust and help increase my draft.

Rob Seagrist

Posts: 717

Location: NC-Zone 7

posted 13 years ago

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Very cool. Im curiuos to know where the steam is coming from. just ambient moisture inside the coils that have condensed or is it attached to water somewhere?

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Michael Newby

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Location: Mount Shasta, CA Zone 8a Mediterranean climate

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posted 13 years ago

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I'm feeding the coil with water from my water hose. I'm making decent dry steam with the hose pushing around 5 gallons per hour. I know that I could do much better - there's lot's of room for improvement in my coil system, but the 12' of copper tubing was as much of a purchase I could justify to the wife for this little experiment.

The tap water flowing in is around 43F, great for drinking, making steam not so much. I'm certain that just preheating the incoming water will drastically improve the performance and there's plenty of heat in that exhaust. I'm thinking about using an old radiator placed in the exhaust to run the water through for preheating, but my old toyota radiator is a little big. A good heater core would probably work great.

on another note, anyone know a good place to source a pressure gauge that would be easy to hook up to this set up? I'd really like to know what kind of pressure I can make at what flow rates!

R Hasting

Posts: 188

Location: Mineola, Texas

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posted 13 years ago

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mnewby wrote:
I have ideas about routing the exhaust into the house and back through a large heat sink. If the return came back to right above the heat riser, you could re-heat the exhaust after it exits the house to help with the draft. I'm currently collecting the materials (junk) to try this out in my house, which has no heat in the lower floor.

Great Rocket Stove
I love the way that functions, and I love the self feed. mechanism. I'd like to see what 1-3" logs would do in this hopper.
But I'm a little confused here. Aren't you looking for a rocket mass heater
http://www.youtube.com/watch?v=LfKHVoCY2so

Michael Newby

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Location: Mount Shasta, CA Zone 8a Mediterranean climate

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posted 13 years ago

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Richard Hasting wrote:
Great Rocket Stove
I love the way that functions, and I love the self feed. mechanism. I'd like to see what 1-3" logs would do in this hopper.
But I'm a little confused here. Aren't you looking for a rocket mass heater
http://www.youtube.com/watch?v=LfKHVoCY2so

I've used 16" firewood split into roughly 1"-3" pieces, but I was having real problems with burning up into the feed tube. This was partially solved by plugging the feed tube so that there's no draft up or down the tube. Performance is much better with chips, though, as that's what I've been designing my system around - you see, I'm an arborist in NorCal and therefore I have an abundance of chips.

As far as what I'm calling the unit, I figure that right now it's a rocket stove since there's no large thermal mass in the system. From what I understand, once I start pushing the exhaust through that thermal mass I might run into drafting issues that I'll have to overcome. Once I overcome those potential issues, then I'll feel comfortable calling it a RMH - call it splitting hairs if you will.

I've been fascinated with Rocket Stoves and RMH's ever since I first stumbled across them about a year ago while researching the GEK (Gasifiers Experimenters Kit) and I am just now at a point where I can afford the time to try out some of the many ideas that I have. Right now I don't have the supplies to do the thermal mass so I have been playing more with making steam, with my latest run making steam with the water flowing at about 15 GPH. I'd love to make enough steam to turn a gen set that could charge up a battery bank for an off grid house.

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posted 13 years ago

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nice work M...

has the tube ever clogged? I wonder how much smaller diameter feed tube (so you could get a slower / longer burn) you could get and still have smooth fuel flow with that sized chips.

Brice Moss

Posts: 700

Location: rainier OR

posted 13 years ago

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Be very very careful working with steam it gets dangerous at lower pressures than it gets useful, I worked on steam plants for over ten years, and saw some things that give me nightmares on occasion.

Dale Hodgins

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Location: Victoria British Columbia-Canada

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posted 13 years ago

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In just about every city there are tree companies who need to get rid of vast amounts of wood chips. Anyone who creates a proper system to burn chips will never have to gather firewood again. I've had free loads of wood chips delivered to put under my kids playset and to build pathways at a muddy jobsite. There seems to be no end to this free resource. I've even received calls asking if I'd like more

Michael Newby

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Location: Mount Shasta, CA Zone 8a Mediterranean climate

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posted 13 years ago

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Scott911 wrote:
nice work M...

has the tube ever clogged? I wonder how much smaller diameter feed tube (so you could get a slower / longer burn) you could get and still have smooth fuel flow with that sized chips.

No, I haven't had any clogging problems with the 6" tube. I'm keeping my eyes out for some cheap (read:free) sheet metal to see what kind of problems will arise with a square shaped feed tube having sloped sides - I'm trying to increase the amount of fuel I can hold without increasing the feed tube size. If you want a slower burn rate, I think that changing the amount of air allowed in, always ensuring that the air comes into a focused area to prevent smoldering will achieve that.

dale hodgins wrote:
In just about every city there are tree companies who need to get rid of vast amounts of wood chips. Anyone who creates a proper system to burn chips will never have to gather firewood again. I've had free loads of wood chips delivered to put under my kids playset and to build pathways at a muddy jobsite. There seems to be no end to this free resource. I've even received calls asking if I'd like more

This is very true. I'm an Arborist and although my business is in a rural area, I have plenty of chips. This is one of the main reasons I've started this project - much easier to chip small trees and branches than to cut them into a bunch of short, woodstove sized sticks.

Sam Green

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posted 10 years ago

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I was thinking the same thing as the guy from Victoria and was directed her from another thread re: the wood chips, they might not be ideal in terms of dryness, but after watching Return to Eden the whole wood chips on gardens has me hooked, so I figured what if the highway service wanted to give you waaaay more than you needed, could you burn them??? Ive seen chicken feed on compost so i figured nothings impossible. Might not be what a person sets out on, but if theyre local conditions mean theyre up to their eyes in wood chip mulch, could it be burnt in a rocket type stove?

Michael Newby

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Location: Mount Shasta, CA Zone 8a Mediterranean climate

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posted 10 years ago

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Hi Sam,

So far I've had great success with burning wood chips in a rocket stove.

Once I don't have more pressing projects going I plan on building one that has a built in wood chip drying rack or bin. I think if I had a perforated metal enclosure of the right dimensions and placement (I'm thinking think x-section for maximum air penetration of the chips) above/near the heat riser I could fill it with green wood chips and have pretty dry chips by the time I'm ready for another burn. Might be a while before I can do that one though, so many things to do around here...

Rj Howell

Posts: 67

Location: New Hampshire, USA

posted 10 years ago

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Nicely done!

I've built a couple of versions myself more on the goal of a cooker vs. a heater.
I've also toy'ed with the idea steam and running a steam powered generator.
The feeding of the stove made it impractical, but you've overcome the issue.

I'm impressed!

Can't wait to see the next progression in your journey.

Old in age, not in mind

Mart Hale

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posted 6 years ago

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Wow, just wow. Exactly what I needed, I have been wanting to build a system that I did not need to stand there and feed. I have a huge dump load of wood chips, and I have dried some of them A 30 min burn with no moving parts is exactly what I am looking for. Combine this with Thermal mass and bam!.

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