Please help: Rocket Stove in greenhouse does not work

gelu lacusta wrote:

Michael Baer wrote:

Peter van den Berg wrote:The reason why secundary air is added just before or even in the port is because pressure is lowest, and gas velocity is highest. Air will be sucked in at that spot most efficiently, violent turbulence just behind will cause adequate mixing of the combustible gases and fresh air. When you feed air in at a later stage this isn't mixed that well. To find out all this costs me the best part of a year, and I tried literally every configuration I could think of, including something similar to yours.

So the answer to your interpretation is, broadly speaking, yes. Feeding in air at high temperature (commonly 350º C or there about, being the self-combustion level of woodgas) is also very important, nicely done by p-channel or floor channel alike.

Hi Peter,
Thanks for your answer. The theme is always more interesting to me. Slowly I get behind the connections. It raises another question for me. As intended in the drawing, I intend to direct the combustion air through a DN 160 mm pipe into the walled wreath.
Is this ok or should the greenhouse be used for combustion.
Greeting Michael

Hi Peter,
Thank you for your efforts. You mean the stove is to 70 cm sub sol and the smoke exit to 50 cm sub sol. Unfortunately, this is not possible from the effort. I have already resigned myself that I can not use the smoke gases directly. I will direct the air through the pipes. Then it will take longer until the ground is warmed.
I would now only build a reasonable oven with which I reach long burning times and which possibly does not smoke. Good is a solution in which I could also burn pellets. The combustion chamber is to be made of fire stone.
Michael

Hi Peter,
I have times tried to make a drawing as I imagine the new furnace. Everything is made of fire stone thickness 30 mm
Http://www.schamotte-shop.de/Schamotterohr-DN120-x-300mm
Http://www.schamottshop.de/index.php/cat/c40_Schamotteplatten-25-35-cm-Laenge.html/page/2
Where a <?> Is unclear to me.
Can you please say something about it.
I thank myself.
Best regards
Michael

It looks like you're trying to design a pellet fed batch box. I think this is a contradiction in terms, and is not possible.

Peter will be able to give more detailed advice on this.

As far as I know, a pellet fed batch box rocket hasn't been built yet. So there's no expertise or tested appliances on the matter.
Come to think about it, I would bet on a small one because it can be fired almost continiously as long there're pellets in a hopper. So a 4"or 5" would be adequate, short firebox, fed from the top or top side, with an auger or something like that. The top of a batch box is getting awfully hot so it isn't an option to store the pellets there, you have to feed it bit by bit to control the burn rate.

My two cents, you are in uncharted territory.

I noted the rounded bottom of the burner portion, it should be more egg shaped. The burner grill needs a certain height to get a clean burn. .5" US I have watched a dozens of youtube videos. Hope this helps.  

Hello Glenn, Peter and Larry,
Thanks for your opinions, I believe
Due to the heat I need, a batch box is not considered. This system produces a great heat and is intended for greetings rooms. Since I am a greenhouse, which I want to heat from February to May and requires rather low temperatures, I come to the conclusion that a Rocket Stove is the right one. Also I can here, as already tried pellets which guarantee me a long burning time, for example overnight. To do this, I need to rebuild my system so it works.
Larry; This post I know.
But I did not have any connections with regard to combustion, etc.
Now I'm a little further.
Please look at the picture. These are my thoughts on soil heating. Your opinions and the other Juser is very important to me.
Thank you Michael

Hello,
I have again in line with Zeros Rocket StoveTries to draw a housing. I have left the cross-sections. Starting point is with me the riser, which is from a pipeFrom fire stone. I think the round shape is fluidicCheaper than the square one. When looking at the surface, Zero has a difference from the riser to the combustion chamber of 5.7 cm². In my suggestion it is 8 cm². Can this work? This is what it should have been for this year.
In the hope of further good ideas and suggestions

I WISH ALL FORIANS A HEALTHY AND SUCCESSFUL YEAR 2017
IN GERMANY WE SAY
"SLIPS WELL"

Michael

You appear to be trying to do what this man did on a smaller scale. There are many more on the topic successes and failures.

Hans Quistorff wrote:You appear to be trying to do what this man did on a smaller scale.

There are many more on the topic successes and failures.

Good morning Hans,
Thanks for the video. This reflects my thoughts again and encourages me that it will work. Super I think the idea with the water. Unfortunately, my greenhouse is not so big that I could implement it.
Now only the question of the dimensions of the furnace is concerned.
I hope I get an answer.
Best regards
Michael

Please be aware that Torcellini's pellet-fed greenhouse rocket stove (the one shown above) had a very bad fire after about 2 or 3 years.  The pellets got warm, they put resin (tree sap) on the metal of the pellet feeder, and the pellets got stuck and the whole load of pellets caught on fire.  Very bad smoke in the greenhouse, killed some plants, luckily the heater was standing away from other things and the rest of the greenhouse was not badly damaged.  

When you are building a rocket stove to heat with wood pellets, you are doing something new.  
We cannot tell you "it will work" or "it will have THIS problem."  It will have NEW problems, and you will have a voyage of discovery. (Like Magellan or Cook or Ericsson, if successful you become famous.  But if you are lost at sea, only the family remembers the name.)

Each stove builder has their own method, and some are more reliable than others.  
If you mix two methods, then you are trying something new, and nobody can give you reliable advice.

Peter is very reliable about the batch box, he helped develop it, and did many tests.  He has good experience with J-style rockets also.  And he has some experience with 200mm, but more with 100 and 150mm.  
If you are happy taking advice from Peter, he is very good.  Listen to him, and do not include advice from other people who build a different style of stove.

I am mostly experienced with the J-style, I have helped build dozens.... maybe hundreds ... counting practice systems for tests.  I do not own a greenhouse, but have helped and received reports from at least 4 greenhouse heaters.
I have only made two very small batch boxes.  With pellets, I have no experience at all.

Everyone says that is a lot of pipes.  I agree.  (when he says looooooong it means very long, plus more long than that.)
The energy from the fire makes the exhaust move, and it only has enough energy to go a certain distance.  For each method of rocket stove, this distance is learned from experience.
If doing a 160 mm J-style design, with sticks of wood as fuel, I would suggest to remove about half the pipes.  
You have over 40 feet (Almost 20 meters?) plus 7 turns.  
The J-style stove could be happy with about 20 feet (6 to 8 meters) and 4 turns.  
So you could connect the first pipe to the last pipe, making one loop from the stove, around the greenhouse, to the exit, and it should be about right.
...

Some people suggest a fan, to overcome this long pipe, or even instead of a chimney.    

I personally don't like fans.  They break, I forget to turn them on or off, and they always pull the same whether the fire is hot or cold.  
(Maybe with pellets, you can match the fan and the fuel and it can be OK.  But be careful.)  
If the fan pulls too fast (when the fire is cool/cold) or too slow (when the fire is hot), you can get smoke.  Cold pipes collect smoke and make creosote (like tar).  Dirty pipes are a fire hazard.  
Also, fans and other machines don't like creosote.
Also, a fan that runs when the fire goes out makes the place colder, not warmer.

If the stove runs clean, and you use a fan outside the stove to stir the air, no problem.  There are some heat-activated fans that are pretty cool, although not perfect.

I like to have a vertical exit chimney, near the warm part of the stove, and the right length of pipes so the stove can run naturally.
Fast when it's hot in the fire and cold outdoors, slower when the fire is low.  
A chimney that releases exhaust above the roof is reliable even if the electricity goes out.  
...

The pipes are plastic for 62C.  Not good.
The temperatures when burning a 6" J-style with sticks of dry wood can be 300 C at the first pipe.  Maybe more in some cases, especially if you use a fan.
You need metal, steel, from the fire to the exhaust exit chimney, or baked clay if you can get that kind of pipe (sometimes used for drains).  
Even concrete will not be as good for this heat, though it will last longer and be safer than plastic.  Aluminum is not very good, but better than plastic.  You could use some aluminum after about 3 meters (10 feet) if you must.

If you are not using the plastic pipes, that is good.

The temperatures for clean fire itself are 550 C to about 1100 C.  Colder, and it becomes smoky and dirty.
Sometimes with pellets you can isolate the fire in a smaller space, but you don't get as much heat from a tiny fire.  If you have long flames, you need materials that can survive hot flames.
You will be happy you used the chamotte/shamotte bricks instead of metal.  It will last much longer.

...

Also, with respect, I would disagree with Michael about the sizes of the pipes.  Here is his opinion:

martyn parish wrote:Hi Micheal
I would like to add something to all the good advice on this this thread. I have built three rocket stoves and hope I can help a little.

The volume of each part of the stove is the critical factor. Each section of the construction should hold more volume of air than the last, if not you get poor air flow. It looks like the space above your internal chimeney riser between the enclosing drum/lid/barrel is too small. I would suggest either raising the drum, or shortening the riser. I had exactly this problem with my first rocket. The next ratio is the side space between the drum and the internal chimney riser. I use an 18 cm riser and 68 cm old oil barrels. This gives lots of space for the air at the top to fall to the exit pipe.
I agree with other comments about the exit pipe, it is too small in diameter. I estimate that with your current rocket dimensions your exit pipe must be at least 30 cm, but also the length of the pipe is too much and has too many angle bends. For best effect have a maximum of two angle bends. After each angle increase pipe diameter by about 20%. The pipe should be metal or ceramic. Not plastic or anything with a heat compustion temperature less than 200 degrees celcius!! Otherwise it can be very dangerous.
You could have the exit pipe not fully horizontal but at a few degrees angled up to encourage air flow in the right direction. Consider a 12 volt fan at the final outlet of the pipe. With these considerations you should be able to maximise the length of pipe in the ground, but it will require experimentation to see how much length you can have in this setup. I suggest buildling the rocket itself first without the exit chimney, test and get it burning well before adding the chimney pipes piece by piece to find the limits of your system. The performance will depend on some critical factors: ambient temperature and humidity, internal temperature and humidity (a rocket already warm inside will light much faster than a cold one, so the first time you light it is normally the most difficult), also the airflow into the greenhouse must be sufficient to keep the fire alight. An external cold air inlet tube is a good idea I think.
It takes some time to understand these little miracles and it it working, but it's well worth it! So have fun my friend!
If you have any further questions I am happy to help

Once I thought the same as Michael, that larger pipes give less resistance.  So we used different sizes, always growing larger.  It did not work, and it failed badly, one of our worst stoves.

Now we prefer not to change the size of the pipes after they start going horizontal.  
In a few cases, where we have used larger pipe toward the end, the stove had a big problem and the exhaust would not draft.  
In a few cases, where we have used pipes 20% smaller (200mm going down to about 170mm) at the END of the stove, it was OK.

We think this is because the exhaust cools as it goes down the pipe.

In some parts of the stoves, like right after the fire, where the exhaust goes downward and drops ashes, more volume is useful.  Anything from 2 to 4 times the size of the chimney can be good here.  
However, once the exhaust has cooled, especially at the exit chimney, the volume should decrease again to a standard size.  
Too much volume, and the exhaust gets too cold.  It becomes dense and will not rise up the chimney.  If you have no chimney, or too cold exhaust, the stove can run backwards on a bad day.
(Wood, and pellets, and most fuels, produce water when they burn.  If this water condenses in the exhaust and makes droplets of fog, the exhaust will become heavier than air and it can choke the stove.  Peter gives a very good explanation of this "chimney stall" process.)

The exhaust will cool at different places, depending on the weather, and how long you run the stove.  So it is not easy to change the pipe size to match the exhaust temperature.

I think it is simplest to build with pipes all the same size.  The J-style firebox, pipes, and chimney are all the same size inside.  When I say "size," I mean the cross-sectional area, you can imagine it as the smallest piece of flat paper that could block the pipe.  Every gap should have at least the same size as the chimney, with very few exceptions.  Watch out for small gaps when you change directions, especially near the firebox connection to the pipes or chimney.

The batch box uses the heat riser diameter and chimney about the same size, and other dimensions are proportions on this.  A few specific air channels are smaller than the system size.

The second simplest method is to make a very big volume - more than 4 times the size of the firebox or chimney - and bring the exhaust out down low, and then up the chimney.  
In English, masonry heater builders call this a "bell." Some popular designs that use it are called Russian Bell Stoves.  This is like what Paul Wheaton calls a "Stratification Chamber," because it allows the hot air to go to the top, the coolest escapes at the bottom.  This is simple to imagine, but sometimes harder to build because you must do good masonry or metal work to air-seal the box.  Pipes are sometimes easier to connect.  

Peter has some rough numbers for the size of this box - it is about surface area to collect heat, not exactly volume.  I don't know if these numbers would be useful to you, because your fire will be different with pellets.  You may need to know how fast the stove burns fuel (how many kg/hour or g/hour), before we can give you good advice about how big to make the pipes.  
The J-style 6" heater might burn less than 10 kg for about 4 hours, and it can run about 20 to 25 feet of pipe (6 or 7 meters), with 4 bends.  Or 35 feet of pipe with 2 bends.
The batch-box 6" heater could burn about 10 kg in maybe 2 loads, 2 hours.  Peter might use about 5 to 7 square meters of internal surface area if I remember correctly.  Counting the top and sides, not the bottom internal surfaces.

I do agree with Michael, and others, who warn that you are doing something new.    
Because of the pellets, and your unique firebox design, it is not possible for someone else to tell you "here is how to do it."  
You will have to test your design.  If it has a problem, you will have to fix the problem, and try again.
We can give you ideas based on other projects, but these ideas may not be correct for your project.


If you want plans for a J-style greenhouse heater that other people have already tested, we do sell plans for an 8" J-style greenhouse heater. The Greenhouse Heater is in our online store: www.ErnieAndErica.info/shop.  

Or you could look for the dimensions for J-style pipes and fireboxes in our book.  Peter's batch box dimensions are available on the internet for free, or also in the back of our book.  
The book is at Amazon or at our publishers, New Society: www.newsociety.com/affil.mvc?Affil=ERWI&Page=../Books/R/The-Rocket-Mass-Heater-Builder-s-Guide

Peter and Satamax, if you are familiar with sites discussing J-style rockets in German, could you share them please?  
I wonder if we know someone who has built a 6" J-style and speaks fluent German.  It might not be exactly the same as with pellets, but it could help.

Yours,
Erica W

German, don't know. There was a good Dutch forum, but it seems it has vanished.
But there must be a few sites or parts of sites, discussing rockets in German.

Hello Erica, Hello Satamax,
I thank you for your advice and opinions.
After ample consideration, I have come to the following opinion which I will try to implement.
First I will reduce the diameter of the riser to 120 mm. So I hope the stove will burn better. I will derive the exhaust gases directly over roof.
With regard to warming the soil, I will transport the warm air in the upper part of the house with a fan into the collector pipes. In addition, I intend to have a heat exchanger at the chimney and the stove
To radiate this radiated heat into the ground. I'm curious if this works.
In any case, I will report here no matter whether I achieve success or failure.
Best regards
Michael

Something that just occurred to me, using copper pipe. put sand into it to prevent crushing, and wrap it around the riser put both ends into an open 55 gallon drum. make sure the exhaust is higher than the intake. the boiling water should create a siphon effect. causing it to create a heat sink in the drum and you can water your plants with the warmed water use a thermostatic controller to prevent scalding your crops. I see what you are doing. but wonder about how you are going to keep your soil at 75F for proper growth.

Larry Monroe wrote:Something that just occurred to me, using copper pipe. put sand into it to prevent crushing, and wrap it around the riser put both ends into an open 55 gallon drum. make sure the exhaust is higher than the intake. the boiling water should create a siphon effect. causing it to create a heat sink in the drum and you can water your plants with the warmed water use a thermostatic controller to prevent scalding your crops. I see what you are doing. but wonder about how you are going to keep your soil at 75F for proper growth.

Good morning Larry, Thank you for the advice. I have now received so many ideas and am creating a concept for me.
On 08.02. I am back in Germany and will start to insulate the foundations with 30 mm Styrodur plates.
In the next step, I will install a ground collector in 40 cm depth.
For this I will install a d 100 mm PVC pipe on each side of the gables. These two pipes are connected with 32 mm PE pipes. The distance between the 32 mm pipes is 100 mm.
The warm air in the upper part of the house is passed through the collector and will heat the ground. I hope this will work.
Greeting Michael

Michael Baer wrote:

Hans Quistorff wrote:

The energy for the fan will be generated by a thermoelectric generator. This is when the oven burns a battery as well as feed the fan. The battery should serve as a buffer. And for the time when the stove does not burn.
The fan is controlled via a temperature difference module. The visualization is then done in my home control. Now I have but still work to optimize the furnace.
Greeting Michael

Just a small side note . . . I purchased a wood stove fan - with a thermoelectric generator too turn the blades . . . and I can't use it . . . seems the unit is only rated for about 500 - 600 F.  ( REALLY hot box style wood stoves) My rocket stove is just starting up and goes by that temp in about 10 minutes . .  . I am pretty sure that if I left the fan on top of my stove at full temp (1100 F) it would melt the Thermoelectric coupler . . .

Something to keep in mind .. .

Two  pictures . . warm up  . . . and max temp.

The Rocket stove is best built above ground.  It will keep the ground warm anyway.   20 feet or six meters of pipe is about the max before the pipe is exited.  When you install it build a way to circulate just a very little of your smoke into the green house, your plants will love it.  Use the top of the mass heater to start your seeds.

Just thought something else.  The space from the top of the insulated (required) riser to the barrel can be no more then 2 inches.

I feel compelled to point out that many people spend time and effort trying to help others, who haven't apparently done initial reading and planning themselves. And most continue to be respectful and helpful without condescension. I have little engineering experience, but even I thought "Is this person seriously using polyvinyl to transfer heated air?"

In my case, a RMB that works really well, the surface of A is quit similair to B. The distance in my case, of the arrow in B, the distance form the heatriser to the covering barrel is only 3cm/1.18 inch.
Further there is hardly any -burn tunnel-. I think because the absence of the -burn tunnel- there is no push-pull reaction in the rocket. As far as I understand the burner tunnel has the smallest diameter of the whole system and will be very important.