Martin Doering

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since Nov 26, 2013
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Recent posts by Martin Doering

I solved the Problem:

It was the size of the exit from the heatrizer.

I enlarged it as much as possible and the temperatures of the barrel increased. And the barrel top gets over 100 degree C right away.
Usually it is at about 150-170 C in a range between 110 and 225 C meassured by a cheap chinese lasor thermometer.

Also a factor may have been, that there was a lot of half dried cob on the heater that generated a lot of wapor while drying which may have effected the burn.
After most of it dried the heater got a little warmer than before.

Also it may have been a bid finding out the best way to stick the wood and reach best temperatures. Which took a bit of try and error.
When I am burning old wood planks, I find it best to mix it with wood from apple trees. Because those branches burn hotter and get to coal earlier thus improving the burn.

I am totally satisfied with what I have now.
Thanks for everyone who answered.
1 year ago
Ok, after experimenting and measuring and using different wood, I come to the conlusion:

Applewood is fine. It is only a pain feeding in adequate amounts.
But used to start the burn and increase the burn temperature of other wood like old planks it is really usefull.

I realize that I have a burnchamber 14cm / 5.5 inch square a heatriser maybe 13cm / 5.1 square and exhaused pipes 16cm / 6.1 diameter round.
The heat generated in the burnchamber is simply not enough to heat the termal mass quickly.

The massive heat riser takes a lot of heat to warm up in the beginning as well. So it takes a while until the radiating heat reaches it peak.

After 5-6 hours running the gardenhouse is comfortable warm.
The draw is pretty strong and I have most of the time a rocket effect.

I guess, if I want to have more heat, I will need a bigger burnchamber and be burning more wood.

Or try to enlarge the opening to the exhaused pipe in the hope that it may improve the draw henche burn more wood in the recent chamber.
Also a seperate air intake may enhance performace, as I noticed that with an open door or window the rocket effect seems stronger, especially after a few hours burning.

I was a bid confused, because I thought, there was not only a rocket effect in the burnchamber but the hot gasses burning again at the top of the barrel.
1 year ago
Ok, after using different wood, the barrel reaches acceptable heat.
Obviously my applewood and branches contain more moisture than I hoped for. And bigger pieces need to be splattered before burning.

I guess it is a matter of balancing size of burnchamber, amount of thermal mass and the size of the room and isolation.

I guess for more heat from the barrel, I would need a bigger burnchamber and bigger heatriser diameter. Or construct a higher barrel to radiate more heat.
For the barrel reaching its maximum temperature quicker, something other than bricks and clay as heatriser may heat up more quickly.

I am just not sure if the woodgases should burn at the barrel top.
I got the impression from youtube videos, where the noise sounded like bangs on the barrel top.

I have just the sound from a hot burn in the burnchamber.
1 year ago

I am just about finishing my Rocket Stove Mass heater for my garden house.

I have done 3 test runs the last three days.

It has a very good draft as I have a professional build chimney at the end.

After a few hours running the thermal mass gets heated up.
My problem is, that the barrel does not get hot. At least not nearly as hot as it should. I can touch it even at the top after 2 or 3 hours burning.

I suspect the heatriser. And I think that there is no second burn of the woodgasses at the top of the barrel.

Is there a chance to solve the problem by enlarging the heatriser by a few inches?
How big should be the gap between the barrel and the riser at the top? I am using a standard oil barrel.

I could try to shorten the gap between the top of the barrel or to enlarge both barrel and heatriser. I also read in another thread, that clay is no good option for the heatriser...
Should it be something, that warms up more quickly?

The color of the exhaust gasses form the chimney is white.
I guess it should be colorless, if there was a burn of the woodgasses, should it be?

A second possibility could be the wood. I am using what I got from my garden. Mostly sticks and branches from appletrees 2 or 3 season earlier dried out.
Maybe they do not have enough energy to start up the the second burn.

Thanks a lot for your advice!

Martin (Germany)
1 year ago
Hello Peter,

the cheapest source I have found, is direct import from China. If you choose the standard ones TEC 1-12706 you get them at a resonable pricing.

I currently found the Seebeck effect values for the TEC 1-12708. It is about 49mV and 15.7mA per Kelvin. At max of 68Kelvin (68 degree Celsius tempreture difference) you get about 3.3 Watt from these.

The more common TEC 1-12706 is working at 6A while the other is 8A. My guessing is, that you can generate at max 2.47 Watt from those.

It is no cheap system considering that you need the heat exchange system as well. But it definitly can generate all the energy you need in winter. And it is a good source of energy for off grid use, because if you keep your thermal mass warm all day it does produce all day.

I definitly will try this.

I will post this, when I am finished. But I can not guarantee, that I build my rocket mass heater this winter. But I hope so.

5 years ago
Allen: Thanks a lot for seeking out the vid.

Now I understand, what you mean by the water fall. It is exactly what I was seeking for. He is using peltiers for the power and water cooling system integrating a waterfall.

I probably will not build it that way on the top of the barrel, but see if I can use the higher temperatures at the exhaust. But I probably could use a watercooling as well using the cold at the outside maybe together with a car part engine cooler.

30 Watt for such a small installation is not bad, especially in winter. And even at the top of this barrel is a lot of unused space.

And I am aware of safety precausions. It might be quite unsafe, if you use your peltier-elements at temperatures outside their specifications. And using electric energy includes the risk of fire, if done wrong.

Anyway you gave me some ideas how to work it out. I guess, I will build the bone of the mass heater and then take the actual heat at certain areas of the construction while burning and think of the best area to place the peltiers. And then build a watercooling connected to the outside.

I will report back, if I get it going.

Cheers Martin
5 years ago
Hello Allen, thanks for your reply. I hope, I can find the vid on youtube.

I am not a native speaker so I don't really get, what you mean by Rain Wall. And how this could be implemented.

What I want to use are peltier-elements, that are used to in 12V cool backs as source for cooling. But they also can produce energy, if they get a temperature difference.

Those peltiers used in cool backs are made to produce some cooling but don't use up too much energy. But there are peltiers elements that have like 60 or 80 watts if you manage to get the enough temprature difference between both sides.

As rocket stove mass heaters are quite large and those are very small, this could be a decent energy source. As I haven't yet build a mass heater, I lack the knowledge neccessary to find a good implementation.

My idea would be to mount them on a metal plate with good heat transportation on the hot side and link this also in metal to the smoke extract. And have some construction to get as much of the outside cold to the cold side of the peltiers. Maybe also a metal plate, that is linked to outside wall.

But I guess, I first have to build the mass heater then work out the temperatures and figure out how much energy a single hightecn peltier-element can produce, before buying a bunch of them.
5 years ago

has anyone used peltier-elements together with a mass heater to produce electric energy while heating?

I want to build a mass heater that produces electric energy during the heat period to support my (comming) offgrid electric energy system during the month with the least solar returns.

And I think during winter the temperature difference between the smoke extrakt near the heater and the uninsulated wall should be great to have peltier elements produce electric energy at a good rate.

I have found a source for buying peltiers elements at reasonable prices, but those have a maximum temprature of 125 Celsus or 257 Fahrenheit.

So I wonder where to place them and what construction, to allow heat to the one side and cold (from outside) to the other side of the element.

If you have any ideas for construction this as cheap as possible, please let me know.

And the peltier elements can even be used to use the thermal mass of the heater as a cooler using surplus solar energy in hot summer days.

Greetings from Germany and happy thanksgiving!

5 years ago