Mini-rocket stove on wheels (hot water and electricity)

I just built my first mini-rocket stove as a mock-up for a future build. I added a cooking stove section and used TEC modules to make electricity.(also a first) I added a copper coil to heat water. Of course that worked. I’m impressed with rocket stoves and their virsatility. I’ll add a couple of pics.

Hi Toby; Welcome to Permies!
Very cool , nice looking stove you have built !
In your experiments be very cautious around water heating.  We call it boom squish when water flashes to steam and explodes... not something I wish to experience in person.

Keep building and experimenting and be sure to keep us posted on your progress.

Toby Craighorn wrote: used TEC modules to make electricity

Will you give a brief description of how that works? My googling only turned up heating and refrigeration applications.

Toby that stove looks great! ... a few questions if you don't mind.
There is only one picture of what looks to be your core. Is it made from soft clay brick?
I'm assuming that the heat from the top of the burn tunnel is what is heating up the oven? Again curious about what material you used to do this.
The steel tank seems small in diameter....are you using ceramic fiber blanket for the heat riser to keep the space between the tank and the riser large enough to allow proper air flow?
Thanks and keep up the good work.

Toby, I imagine a whole lot of work went into that "mini" rocket stove.  Looks great!  But I must correct you.  That is not a "mini" rocket stove.  THIS is a mini rocket stove!  I built the mold out of plywood, poured concrete in the bottom section (with hacksawed BBQ grill embedded in intake to set sticks and short branches on), then poured the top part.  It is heavy, probably about fifty or sixty pounds, but still transportable.  I've used it quite a few times.  It works great.  It is amazing how efficiently it burns the wood, and how much heat it produces.  But now I'm looking at your rocket stove again and thinking I would love to have one not just on wheels like yours, but also better built from the ground up.  My design is simple and cheap to make.  I guess it has that going for it...  Nice job!

thomas rubino wrote:Hi Toby; Welcome to Permies!
Very cool , nice looking stove you have built !
In your experiments be very cautious around water heating.  We call it boom squish when water flashes to steam and explodes... not something I wish to experience in person.

Keep building and experimenting and be sure to keep us posted on your progress.

Thanks for the encouragement and warning. It’s an open system with circulating water. Used a small DC pump so it heated slowly. Haven’t heard the term boom squish. I’ll look it up.

Gerry Parent wrote:Toby that stove looks great! ... a few questions if you don't mind.
There is only one picture of what looks to be your core. Is it made from soft clay brick?
I'm assuming that the heat from the top of the burn tunnel is what is heating up the oven? Again curious about what material you used to do this.
The steel tank seems small in diameter....are you using ceramic fiber blanket for the heat riser to keep the space between the tank and the riser large enough to allow proper air flow?
Thanks and keep up the good work.

I only used a few bricks in the base. I used fiber board in the heat riser but coated it inside and out in a layer of cob. Kept at least 4” all throughout. Some was round, some square. It’s a cut propane bottle in top. Has about 1 1/2-2” of space all around the outside of the riser.  Heat for the oven comes from the burn chamber but also I put a peice of metal in the common wall of the oven and part below the tank.

Lindon Rose wrote:Toby, I imagine a whole lot of work went into that "mini" rocket stove.  Looks great!  But I must correct you.  That is not a "mini" rocket stove.  THIS is a mini rocket stove!  I built the mold out of plywood, poured concrete in the bottom section (with hacksawed BBQ grill embedded in intake to set sticks and short branches on), then poured the top part.  It is heavy, probably about fifty or sixty pounds, but still transportable.  I've used it quite a few times.  It works great.  It is amazing how efficiently it burns the wood, and how much heat it produces.  But now I'm looking at your rocket stove again and thinking I would love to have one not just on wheels like yours, but also better built from the ground up.  My design is simple and cheap to make.  I guess it has that going for it...  Nice job!

That’s awesome! Definitely more portable.

Burl Smith wrote:

Toby Craighorn wrote: used TEC modules to make electricity

Will you give a brief description of how that works? My googling only turned up heating and refrigeration applications.

Burl, Awesome question! I looked and looked for hours and couldn’t find any rocket stoves and TECs either. But, it only takes a heat differential. I’ll take some more pictures. I put 6 TECs in series on a metal plate on top of the tank. Then put cold water in a pan on top of the TECs to keep the cold side cool. I think the TECs are only rated for about 250 Deg F. I couldn’t leave them there too long as it exceeded that temp after a while. I’ll probably make it so I can put the TECs on the side of the tank and not the top next. Air/fan cooled but preferably water cooled via 4” square tube is my next idea. Just not much out there except 1 commercial company using the TECs with a rocket/wood stove to charge batteries. Seems like an awesome back-up to solar. I got almost 1Volt per TEC. Could easily put 100 of them on a stove. Just gotta bleed off the heat from the outer side.

Toby Craighorn wrote:

Gerry Parent wrote:Toby that stove looks great! ... a few questions if you don't mind.
There is only one picture of what looks to be your core. Is it made from soft clay brick?
I'm assuming that the heat from the top of the burn tunnel is what is heating up the oven? Again curious about what material you used to do this.
The steel tank seems small in diameter....are you using ceramic fiber blanket for the heat riser to keep the space between the tank and the riser large enough to allow proper air flow?
Thanks and keep up the good work.

I only used a few bricks in the base. I used fiber board in the heat riser but coated it inside and out in a layer of cob. Kept at least 4” all throughout. Some was round, some square. It’s a cut propane bottle in top. Has about 1 1/2-2” of space all around the outside of the riser.  Heat for the oven comes from the burn chamber but also I put a peice of metal in the common wall of the oven and part below the tank.

Thank you for the clarification Toby. Please keep us posted as to how well it operates and anything that you might change after you use it for a bit.

Toby Craighorn wrote:I just built my first mini-rocket stove as a mock-up for a future build. I added a cooking stove section and used TEC modules to make electricity.(also a first) I added a copper coil to heat water. Of course that worked. I’m impressed with rocket stoves and their virsatility. I’ll add a couple of pics.

This is what I want to make. How did you cut the pro pain tank? Would it heat water better if the copper tubing was in the center of the heat riser ? I need a space/water heater for drying my cloths and for shower room. Will this work ? I'l have to look into the power/energy production as that wuld be great for wen power is out.

TEC ( or Pelltier module) stands for thermoelectric cooler and if you power it with electricity it will make a hot side and a cold side.
If it heated on one side and chilled on the otther side it creates electric curent and becomes a Seebeck generator or a TEG wich stands for thermo electric generator.
There are modules that are sold as TECs and TEGs with TEGs being more expensive because they are build to withstand higher temp up to 150 C while the ones made for cooling ,altough they can be used as generators perfectly,they last only up to plus 100 C temp.
They have an efficiency of just 10% and there are much better alternatives for such stove generators like the Stirling engines generators with 35% efficiency.
Now, if the energy is lost inside a house ,then you might not care about losses from poore efficiency.

Mihai Ilie wrote:TEC ( or Pelltier module) stands for thermoelectric cooler and if you power it with electricity it will make a hot side and a cold side.
If it heated on one side and chilled on the otther side it creates electric curent and becomes a Seebeck generator or a TEG wich stands for thermo electric generator.
There are modules that are sold as TECs and TEGs with TEGs being more expensive because they are build to withstand higher temp up to 150 C while the ones made for cooling ,altough they can be used as generators perfectly,they last only up to plus 100 C temp.
They have an efficiency of just 10% and there are much better alternatives for such stove generators like the Stirling engines generators with 35% efficiency.
Now, if the energy is lost inside a house ,then you might not care about losses from poore efficiency.

TY good info.

Mihai Ilie wrote:TEC ( or Pelltier module) stands for thermoelectric cooler and if you power it with electricity it will make a hot side and a cold side.
If it heated on one side and chilled on the otther side it creates electric curent and becomes a Seebeck generator or a TEG wich stands for thermo electric generator.
There are modules that are sold as TECs and TEGs with TEGs being more expensive because they are build to withstand higher temp up to 150 C while the ones made for cooling ,altough they can be used as generators perfectly,they last only up to plus 100 C temp.
They have an efficiency of just 10% and there are much better alternatives for such stove generators like the Stirling engines generators with 35% efficiency.
Now, if the energy is lost inside a house ,then you might not care about losses from poore efficiency.

I have a bio camp cooking stove that generates electricity to run the fan and the charging station. I wonder if it runs on the same principal, but on a smaller scale. It puts out quite a lot of heat for cooking just using small pieces of wood chips that I have an endless supply of (gather them after splitting wood each time, have bags of them.) You have sites to recommend on this stuff you talked about?