Off Grid Rocket Stove Water Heater

Started by BiggKidd, February 11, 2014, 01:23:50 PM

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Is this something you could use?

Yes
No
yes If the grid goes down
At your camp or cabin
for full time year round use

BiggKidd

I haven't been over here much lately but though I should share this with the good folks here. I just finished building a rocket stove water heater. As soon as mother nature will allow I will get it hooked up at home but we did the first test with water yesterday.

This is the majority of the materials I used.



Plus some metal from an old oil tank.

Basic design idea.



The stove part.



Test fire of just the stove.





Internals mostly built.





With the outer shell.



  First test with water.





A Short video showing the therm-o-siphon effect. Click on last picture to see video.

 

  It works pretty well that bucket of water started at 50* and ended at 105* 15 minutes later. (Pat had a thermometer) Also note how clean it burns, and that was white oak cut last week.

You all have a nice day.

Larry
A World Away

PS I am using a 50 gal. electric water heater for a holding tank for this once it's installed.
A hard life only makes you stronger.

Larry

Ernest T. Bass

Pretty cool project.. We've had a copper coil heat exchanger on the top of our rocket mass heater barrel for years, but the thermal-siphon has always been sluggish due to the flat coil shape. I just installed a little circulation pump, and it's amazing how much more hot water we're getting. We're able to get by without the electric heater now, and I'll be curious to see how much the bill drops at the end of the month..

Our family's homestead adventure blog; sharing the goodness and fun!


BiggKidd

Quote from: Ernest T. Bass on February 12, 2014, 12:43:32 AM
Pretty cool project.. We've had a copper coil heat exchanger on the top of our rocket mass heater barrel for years, but the thermal-siphon has always been sluggish due to the flat coil shape. I just installed a little circulation pump, and it's amazing how much more hot water we're getting. We're able to get by without the electric heater now, and I'll be curious to see how much the bill drops at the end of the month..

  That's great I would love to see pictures of your rocket mass heater.

This one seems to flow pretty well but then again the coil is also about 24 foot long tube and roughly 16-18 inches tall wrapped about 10 inch diameter. Using 1/2 inch id copper tube.

  Thanks Larry
A hard life only makes you stronger.

Larry

glenn kangiser

Wow Larry... that looks like a good project and looks like it is going to work great.  :)

Andrew..... you are always on top of it.... I have been so busy lately don't get around to all of the topics much anymore but I was actually just thinking of you a couple days ago....

I hope all is well with both of you.  ;D
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

BiggKidd

Thanks Glenn,

  I can't wait to hook it up to the system. The weather just doesn't want to cooperate.  I expect it to heat much faster than a conventional water heater. Time will tell. I have it getting plumbed in to a 50 gallon tank. I will time it a few times to get an idea how long it has to burn to get a full tank hot (150*) We have had the wettest year I can remember & more snow in just a few days then two or three years combined. Soon I hope real soon to get it hooked up. I'm tired of carrying 7 gal at a time from the wood stove for dishes and baths. Sure beats nothing though.  :)

Larry 
A hard life only makes you stronger.

Larry


BiggKidd

Well we got the hot water rocket stove in today, after cutting some firewood. It does work as advertised! I decided after finding gauges that only started reading @120 to drop that idea. I did come up with a way to know the temp though, sort of. Hook a LED to the thermostat that came with the heater tank.

Overall it works real well from what I have seen so far. It has had a workout since it was hooked up. It has been burning the whole time. Through two baths and showers. A load of dishes, and general clean up. The water has steady gotten hotter. So it would also work as a on demand type of water heater I believe.

I do see several things I would do differently. Mostly just to improve longevity and efficiency . The size of the hopper, burn chamber, and reburn seem to work pretty well. I would use more and larger coil, a lot more. A whole lot of heat is being wasted.

If anyone decides to build one or if I build another. (which I probably will) These are the changes I would make. Make the fire box large enough to line completely with fire brick. Use a refractory coating inside the reburn chamber and up to the top of the coil or to the exhaust stack. Both on the walls and on the baffle. Using this basic size I would likely go up to a 3/4" X 60' coil, at minimum 1/2"x 60'. Like I stated a LOT of heat is being wasted. One other thing I might change if height isn't an issue. I would move the hopper in till you are loading the wood right in the bottom of the reburn chamber and do away with the fire box tunnel. The burn/reburn chamber would need to be taller by about a foot.

I will try and get some times from start up to hot to use and hot to cut off sometime when we are not using it.


  You all have a nice night!  :)
A hard life only makes you stronger.

Larry

Ernest T. Bass

Great to be having success right off the bat! I think we could use more coil as well, now that the water is cycling faster, but I don't know if upping the diameter would help too much with heat exchange.. It seems to me that the reduced friction and exponentially less water contacting the pipe walls wouldn't be desirable.

As far as pics of our system goes, our setup isn't nearly as fancy as yours, and besides the cob bench there isn't much to see. I cut a spare barrel top to cover the coil, so it just looks like a normal rmh (or as normal as a steel can in your living room gets...).

I don't feel so "on top of it" Glenn, but you're always there to cheer me on. :) I'm still a faithful follower of your thread, even though big steel buildings scare me and I don't know what you're talking about half the time. ;)


Our family's homestead adventure blog; sharing the goodness and fun!

BiggKidd

I haven't been burning this at dusk before. So I just noticed it looks like it gets warm.



 





    Wonder just how hot that is?
Have a nice night

Larry   :)
A hard life only makes you stronger.

Larry

tommytebco

IIRC. red heat is around 1000 deg F, yellow is around 1300 deg F and  white heat pushes 2000 deg F.


tommytebco

no edit.
I just checked myself
red starts around 1000 and goes to 1500 ish Yellow is high teen to 2000 and white hot is over 2000

BiggKidd

Thank you so a brilliant orange I would guess between the two? Pretty hot for a wood fire!    [cool]

  Thanks again.

Larry
A hard life only makes you stronger.

Larry

Don_P

That looks about like the sides of my old woodstove just before it distorted heavily. I wonder what you can do to cool that zone without losing the fire's heat? I've come into most of the parts, this is looking really neat.

BiggKidd

Quote from: Don_P on March 03, 2014, 12:12:22 AM
That looks about like the sides of my old woodstove just before it distorted heavily. I wonder what you can do to cool that zone without losing the fire's heat? I've come into most of the parts, this is looking really neat.

  The next one I build will be sized to have it completely lined with fire brick and if I can swing the $$$ coated inside with a refractory coating. I have everything but the coating to build another burner. I would reuse the coil and outer shell.  But as well as this one works I doubt it will happen anytime soon.

Thanks
Larry 
A hard life only makes you stronger.

Larry

10thMTNVET

This looks great, good to hear that it performs well too. My wife has been trying to get me to look into rocket stoves for awhile. I will take your advice on the revisions if we build one. Thanks for the post.   [cool]


BiggKidd

Another update on the rocket water heater. It works really well so well in fact it could be used as an on demand type heater. I will use 50-60+ feet of coil if I ever build another. It wastes a lot of heat judging from how hot the flue gasses coming out that would be better used heating a larger coil. Which would mean less burn time and greater efficiency.

Larry  d*
A hard life only makes you stronger.

Larry

Don_P

I was talking with a friend about these the other day. He's using a rocket stove in a small greenhouse for air heating as well as heating water and pouring that into a large tub for thermal mass. I suggested making one of these and he raised a couple of safety issues that might be worth considering, especially as the tube gets longer. If the water turns to steam, even though there is a free flow out the ends the steam generation can be so rapid that the pipe will still burst. I'm not sure if a couple of popoffs along the line would counter that or not.

I also worked on an old log cabin that at one time had a wood cookstove with the water heater on the side of the firebox. The water heater froze one night and the father didn't realize that when he fired the stove the next morning. Since there was an ice plug there was nowhere for the steam that was created to go, it killed him. I'm not wanting to step on a good idea, I'd like to build something along these lines and hook it to the radiant tubing in my shop, just stuff to keep in mind.

BiggKidd

Don P

  You make good points. I have valves and drains to keep freezing from being an issue. Also put PEX pipe at the inlet and outlet as safety links. Think of the low pressure pex like a fuseable link or sacrificial link . It will blow before the pressure gets to high. I purposely tested it twice and the pex blows with no problem and without any other damage occurring. It's also wrapped loosely in foam pipe insulation to direct the steam away from the operator. If it was to heat the water to steam to fast a small pump could be used to circulate the water fast enough to keep it from being a problem.

Thanks
Larry
A hard life only makes you stronger.

Larry

BiggKidd

Hello everyone thought I would drop in and give an update on the water heater. It's been being used for about 2 years now. Had to pull it down in January 2016 and clean the coil it and the freon tank used as a diverter were just about turned to one they were so clogged. I have been burning wet green wood for two years. I have no doubt this would not have been needed with good dry wood. Good news everything came apart and went back together in about an hour without trouble. The 3/16 burn chamber metal is showing serious signs of heat damage and fatigue. So when I do build another it will have firebrick lining it. The basic design works well I do believe the coil is to short by about 1/2. I think when  I build another it will have a layered coil with each layer shaped like an electric stove eye but rising just enough with each turn to keep positive upward flow. This will also do away with the diverter plug (freon tank).

  I'll check back incase anyone has any questions.

You all take care
Larry
A hard life only makes you stronger.

Larry