rocket workshops / innovators gathering / September 2014

david tyler wrote:Paul I would like to film the work shop, I have a HD sony H/C and tripod. let me know. Thanks.

David,

We have lots of HD video cameras, time lapse cameras, tripods and other mounting doohickeys here and lots of experience taking video. But apparently it takes all sorts of knowledge that is beyond my comprehension to be a DVD quality videographer.

Currently, we have two people that I know are professional videographers talking to me about coming now.

We have a videographer.

There is still one ticket left for the pyronaut laboratory.

Lots of metal working tools sounds great. i'm interested in a configuration for converting a rocket to burning waste oil which i think will be quite simple just some small off cuts of flat steel. Also i wouldn't mind trying some burn tunnel configurations where the air feeding into the feed tunnel first flows around the base of the riser and the burn tunnel and then into the feed tube. Think of it as dynamic insulation where the current of air is picking up the heat propigating through the walls of the combustion area and pre heating the primary air. My gut feel is that may help with brick style stove. If we arranged for the air flow to feed into the back bottom corner of the feed tube we would remove that area of dead air that exists and also continually blast the ash from around the base of your wood for better combustion. I would love a couple of car radiators to play with if possible please, they can be plastic tanked types or copper and it doesent matter if the very fine fins are rotted out because i would be raking these out so they don't block with ash. That reminds me has anyone thought of incorporating a cyclone into a RMH to get rid of all the ash in one spot ? Oh and i would love to play with some TEG's.

Hey Tim, your idea of a cyclone separator is excellent but where are you going to put it? Also, while you are experimenting do you have any thoughts on using venturis to improve flow?

Hi John one though is the cyclone could be built into the barrel so the heat riser is offset with a 90 deg bend introducing the gas flow to the inner circumference of the barrel and the outlet coming off the centre of the barrel near the top. Of course thats just one idea and it may be a crap one but i tend to think by stating an idea and then pulling it to pieces. For a start it would mean no hot spot on the top of the barrel to keep the billy boiling. Cheers Tim

Tim Barker wrote:If we arranged for the air flow to feed into the back bottom corner of the feed tube we would remove that area of dead air that exists and also continually blast the ash from around the base of your wood for better combustion.

Tim,
The normal J-tube do really need the down coming air in the feed, otherwise you'll get a back draft and the flame will come out the top of feed. I admit, I've tried that one but it didn't work out. Cooling the feed does work to some extent but the feed itself, at the level of the tunnel should be as hot as possible preferably. My idea was to make the top end of the feed of metal and leading part of the air around that to avoid that top end to come up to combustion temperature of the fuel. This did work admirably, no back drafting anymore as long as the chimney draft kept going.

Tim Barker wrote:That reminds me has anyone thought of incorporating a cyclone into a RMH to get rid of all the ash in one spot ?

Yes, I did, in fact it did grow out as a cyclone burner. It did work as long as the draft was very strong, beautiful results according to the Testo. When the flame is forced to go round, the stream is tripping over itself which resulted in an excellent mixing of air and combustibles. After several different set ups I gave up, the thing did work as long as the flame did go round. Anything that impaired that did cause a very dirty burn.

In general, adding air isn't a problem at all, as is high temperatures. The mixing, i.e. exact and not too much turbulence, is the real problem. Actually when the mixing is very, very good, one could reach (nearly) complete combustion with lower temperatures and much less excess air.

Using the principle as a dust separator isn't without its problems. The dust extraction is best (catching the smallest particles) with a narrow cone, the gravitational forces are the highest then. Unfortunally those forces are eating draft energy.

John Copinger wrote:Hey Tim, your idea of a cyclone separator is excellent but where are you going to put it? Also, while you are experimenting do you have any thoughts on using venturis to improve flow?

A venturi would only speed up the flow in the venturi itself, not before or behind it. In fact, it's an implementation of Bernoulli's law, in its simplest form there's a trade-off between pressure and speed. In a given duct where gas is streaming the speed will go up and the pressure will go down in a temporary narrowing. Like rapids in a river, after that there will be turbulent behavior but the stream will slow down again. So to create turbulence it's an ideal tool.

One of my plans for the upcoming gathering is to do something like that to improve mixing of air and combustibles, see my message before this one.

I wonder what would happen if you had a setup where your gasses were reasonable rich in uncombusted products and you used the pressure drop across the venturi or any orifice for that matter to introduce secondary air.

Thanks Peter, I well remember Bernoulli and his theorem; so would it not be a good idea to put a venturi at the beggining of the burn tunnel to give a good combustion mix?
Tim, I,ve got a very good book (in French) on mass heaters generally and they recommend exactly what you say, the venturi acting as in a simple carburettor will draw air in to the burning area, and with what Peter has said that should give better combustion. I wish I could cross the puddle and come and play with you guys!!

Tim Barker wrote:I wonder what would happen if you had a setup where your gasses were reasonable rich in uncombusted products and you used the pressure drop across the venturi or any orifice for that matter to introduce secondary air.

Right Tim, that's the idea, you'd just hit the nail on its head. The resulting turbulence behind the orifice is the ideal tool to mix secondary air with combustibles. In fact, I did that before in the batch box rocket development, the p-channel implemented there is doing exactly the same thing. The above link is leading to a very lengthy thread but most of the development is described in 4 or 5 pages.

John, that's what the plan is, in a somewhat different way.

paul wheaton wrote:
64) a tiny rocket mass heater for a tiny house

Along these lines - I wonder if it would be wise to open up the idea of a 4 inch system. I wonder if the problem with a 4 inch system in the past had to do with using too much duct?

But if anybody wants to try this, we should start ordering in materials.

Hi Paul Space is key in a tiny home or caravan so an idea i would like to try is a variation on my water heater design where your mass is water and is external to the space to be heated. Imagine a 55 gallon barrel full of water heated by rocket stove that thermosyphons through hoses into a car radiator in your living space. No moving parts and you could vary output with a tap in one of the lines or even simpler draping a cloth or blanket over the radiator. Advantages would be ease of install (two holes low in the wall for hoses) and if you need move drain the system and store it inside and you would get some hot water from it.

paul wheaton wrote:Along these lines - I wonder if it would be wise to open up the idea of a 4 inch system. I wonder if the problem with a 4 inch system in the past had to do with using too much duct?

Aside from presumably using too much duct, the problems with a 4" are twofold in my opinion. The first is material related, when using bricks on its side the wall thickness of the J-tube would be something like 2" or 2.5" at the most. This will result in a certain mass versus cross section area. Scaling down the stove without taking the wall thickness into account will give you way too much mass in the J-tube. This could end up in a stove which will take hours to reach proper combustion temperature. A 4" system is less than half of the csa as compared to a 6" system. So the mass should be halved too, using split fire bricks for example or cast using castable refractory. Much better would be a feed out of spilts and tunnel and riser out of insulating fire bricks in order to slash the mass involved. Maybe done with an external steel frame, an exo skeleton so to speak. Could this be an idea for a shippable core?

The second problem could be the way gases stream in a narrow duct. The fast streaming core is much smaller in a 4" incher, due to the proportional larger wall area compared to the csa of the same duct. This will give way more friction along the walls and less turbulence, especially true for a square duct. I'd think tricks along the line of trip wires are coming into play to solve this particular difficulty.

Hello Everyone! My first post on Permies. I purchased a spot for the upcoming "Rocket Mass Heater" workshop (September 19-21), but sadly I will not be able to attend. I bought it at the earlybird price of $240. Is anyone interested in buying it from me at the same price? Let me know. Thank you, Sam

Hi Sam. I would like to buy your ticket if it's still available.

Cheers,


Daxx

Sam Graham wrote:Hello Everyone! My first post on Permies. I purchased a spot for the upcoming "Rocket Mass Heater" workshop (September 19-21), but sadly I will not be able to attend. I bought it at the earlybird price of $240. Is anyone interested in buying it from me at the same price? Let me know. Thank you, Sam

Hi Sam. I have not heard from anyone at Permies yet concerning my attending the class. Have you?

Cheers,


Daxx
m910.386.9607

Daxx,

Did you buy the ticket? If so, did Sam Graham let folks over here know about it?

I paid Sam Graham directly for the ticket and he said he would let you guys know that.

Daxx Terry Green wrote:I paid Sam Graham directly for the ticket and he said he would let you guys know that.

I just checked with Sam Barber, here at basecamp. He confirms that he received the info. He says he has sent you the information to you ... "not yet". I asked him if he could send it to you this very minute and he said "will do!"

If you have not received anything in the next five minutes, pipe up again.

Paul, Sam is all ova it. I'm in! Can't wait. I'm a huge CouchSurfer so I'll need a little more than a week's notice on where I'm staying. Into camping as well but it was snowing like crazy here at Medicine Wheel just YESTERDAY. I'll email him these questions so don't worry friend.

Cheers!

Matt,
Could you bring a number of your insulating superwool riser pipes? Would be very handy to be able to change set ups in a quick way.

Hi Peter and all, I included a number of them in the Bill of Materials I submitted to Sam and Paul, as well as some of the castable refractory I've settled on for my builds. In both cases I requested enough that you and others could use the material for your experiments since I assumed you wouldn't be familiar enough with what materials are available here to guide the purchasing. I have had great communication with Sam, (Thanks Sam!), and let him know what I needed for what I hope to accomplish as well as some for you and the others to play with. I expect we will have plenty of the risers and hopefully enough castable. In the case of the castable, I requested two densities, 130 lb/cu.ft and 60 lb/cu.ft. I have settled on the low density for most of my stuff, but use the high density for oven shells and the like. You are welcome to any of those materials I included in my BOM as far as a I'm concerned.

Sam, if there may be a shortage let me know and I'll bring a few risers we can use as well. I am getting short on space though so I would rather not if at all possible.

We have spent about $3000 on materials. I think there is one more order to be placed this morning and it is depending on one other item that we think would be significantly cheaper in missoula - but we are still trying to nail that down.

My guess is that there will be a HUGE amount of cross pollination between the innovators.

Hello everybody, Rick Edwards here. Currently acting as Wheaton Laboratories Base Camp Fireman.
We are just now receiving the last of all the items requested for the event.
Very exciting times!

The current Fire to put out so I can get to all my other fires is peltier electricity generation from the rocket mass heaters.
We want the ability to have a Peltier (also known as TEG, TEC and TEM) setup on a RMH to generate enough electricity to run a fan that would be installed at the end of the duct run to offer positive pull through the system.
As I'm looking into this, the options and variables seem dizzying.

There are cheap ones, expensive ones, regular heat ones, high heat ones, varrying wattage ones. so on, so on, so on.

They need heat sinks, vents to the winter air, forced fan cooling or water cooling.

Google, amazon, youtube all have tons of info and i'm sure all the answers. They also have tons of B.S. to sift through to get the nuggets of quality info.

I'm hoping that some of you have played in this space and know the minimums and limits of actual install parameters of the variables and the add-ons.

The fan part I've got down, but happy to accept any low power options that people have tried with these. It needs to be fairly durable and Fit in-line of the 8" ductwork.
I've installed many fans in ducts for many custom applications but of course all of those were 110V AC.

Thanks to all the Permies out there that can and cannot help.
Sooner the better, I think I smell myself roasting.

Rick, I haven't worked with peltiers before but I've done some other similar stuff. I'm gonna try to come up with my recommendation from what I know, on the assumption that someone more knowledgeable than myself might not see this in time to be helpful. More soon!

Just sharing general strategy off the top of my head: I think it'd be real nice if we could figure something out that has the fewest number of pieces possible. Unfortunately it might not be possible that the peltier power source gets fully worked out for this so it might be nice if we set it up to run on a 12V battery as a backup plan...with the intention of working out the peltier system after the workshop. That being said I'll try my best!

Rick Edwards wrote:Hello everybody, Rick Edwards here. Currently acting as Wheaton Laboratories Base Camp Fireman.
We are just now receiving the last of all the items requested for the event.
Very exciting times!

The current Fire to put out so I can get to all my other fires is peltier electricity generation from the rocket mass heaters.
We want the ability to have a Peltier (also known as TEG, TEC and TEM) setup on a RMH to generate enough electricity to run a fan that would be installed at the end of the duct run to offer positive pull through the system.
As I'm looking into this, the options and variables seem dizzying.

There are cheap ones, expensive ones, regular heat ones, high heat ones, varrying wattage ones. so on, so on, so on.

Actually, Peltier arrays are optimized to generate thermal differences with an input of electricity instead of using a thermal input to generate an output of electricity. An additional problem is that Peltier arrays are made using semiconductor materials which are sensitive to overall heat and can be destroyed with over temperature.

What you are looking for is a thermopile which is another word for an array of thermocouples. You can use copper and iron wire to make these but the output voltage is very very low (high current though).

The best supplier of peltier panels / thermal electric generators I know is this company in germany: http://thermalforce.de/
Here is the list of products they offer: http://thermalforce.de/de/product/module/index.php
For use with a RMH my be usefull these items:

LED-Generator with 3,2 to 3,8 V, 5 to 30 mA.

Datasheet: http://thermalforce.de/de/download/m201d.pdf

Accu charger

Data sheet: http://thermalforce.de/de/download/m2503.pdf

30W generator

Data sheet: http://thermalforce.de/de/download/m1225.pdf

For use in gas fired systems they do have also different solutions, bis the temperature in RMH-chimneys is too low and RMH is fired with wood.






This one is also usable in wood fired systems:
12 V; 2 to 3,5 A
max temp of gas: 400°C / water temp 25°C
diameter: 150 mm


Data sheet: http://thermalforce.de/de/download/m2070.pdf

Then there is one more system to use on top of the chimney. But you need there a
temperature of about 70 to 130°C


This company offers also the parts to construct something specialised. Look at this page:
http://thermalforce.de/de/product/thermogenerator/index.php

You find this item:

This is made for temperature up to 1000°C
Data sheet: http://thermalforce.de/de/product/thermogenerator/097-300-33.pdf

They offer so many things, may be they have much more which is not shown on the website.
Just ask them

Konstantin

I have looked at TEG's a bit and they certainly hold some promise. You generally use the term Peltier when you are using an electrical current to generate a temperature difference and use the term seebeck effect when using a temp difference to generate an electrical current. There are certainly a few TLUD's on the market that have TEGs incorporated in them and i remember seeing somewhere a canadian company selling stove top fans with a TEG built into the base to blow the warm air around. It was a neat design as the TEG was built into a bi metallic strip so if it started to overheat the TEG would rise clear of the stove top. OF course it was a copy of an earlier design using a stirling engine and an alcohol burner (lake breeze). I also found you can buy off the shelf tegs out of China built into heat exchangers capable of generating 200v DC, of course these need a lot of hot fluid to do the job. So great if your getting some TEGs to experiment with great ! Just don't expect any electrical expertise from me.

I think the information posted regarding the German manufacturer 'ThermalForce' is really good. the Unit that sits on top of a burner called '40 watts generator for fireplace heater' looks like the most promising. As an Engineer, I do not like the solutions which sit within the flue - however clean the burn is for the RMH, the last thing you want is a solution that is heavy on maintenance time. The surface mounting ones may be 'ugly' compared to an in-flue design, but practicality of something that sits on top of, or is attached against a surface would be my choice.

Tim Barker wrote: There are certainly a few TLUD's on the market that have TEGs incorporated in them and i remember seeing somewhere a canadian company selling stove top fans with a TEG built into the base to blow the warm air around.

I have two of those canadian fans, one for our gas fireplace and one for the wood stove in the wall tent. They both work wonderfully! In fact, sometimes to well. I have had the temp well over 100 F in the wall tent, but with it that warm it does dry out the hunting clothes nice! They just move the warmed air in the direction the fan is pointing. It would have to sit on top of the RMH to move the warm air around the room.

The Canadian fans are from a company called Caframo. I have two of these too - they work great.... as long as all you wish to do is move air around. The trade name for the product is Ecofan. I have had one for over 10 years now and just replaced the motor (was a bit warn and made a ticking noise at certain speeds. So all in all a repairable, eco-friendly device that does just what it is intended to do - move air around your stove without creating a massive draught.

But is Paul trying to generate electricity to charge batteries and things?

Hi Rick and all, here's what I've done along these lines so far....



I haven't gone much beyond this as I haven't had much interest in investing much more than a few tens of dollars in it, since I don't have much of a need for it. It's a novelty project for me, although I sure have fun playing with them.

I'm quite sure we can come up with a solution for you, but it's going to take some fiddling for sure. The biggest challenge/expense to my mind is going to be purchasing a Seebeck unit that is robust enough for long term use and can handle a wide temperature range. The little TECs I use here are great for playing with since they are less than $3, but I haven't been able to make one last much more than a month or so. Like I said, that's a problem that could be easily handled by throwing some more money at it. So, Rick, I'd say buy some cheapo TECs, some low voltage DC motors of various flavors, and we'll play with them in coming weeks and work towards a solution that could be coupled to a better Seebeck unit for long term use. That's my thoughts on the subject, anyway. Hope it helps a bit. If you want to email me I'll try to find the model numbers of stuff I've played with for you, although I'm doing earthworks today and tomorrow, then heading your way tomorrow night so I may not get you a whole lot farther along until I see you next week.

Rick Edwards wrote:
The current Fire to put out so I can get to all my other fires is peltier electricity generation from the rocket mass heaters.
We want the ability to have a Peltier (also known as TEG, TEC and TEM) setup on a RMH to generate enough electricity to run a fan that would be installed at the end of the duct run to offer positive pull through the system.
As I'm looking into this, the options and variables seem dizzying.

I'm wondering what the objective is here. Is the fan simply to improve the performance of a RMH with airflow problems? I'm hoping there is more to it than that. Otherwise it seems like a lot of tech to throw at a problem when much simpler solutions likely exist.

Mike, Thanks for the input. The battery wont work on this RMH install permanently, but I like the idea of using it for the short test if necessary while we take more time to configure number and type of TEGs.

Dave, interesting info. No time now but I'll look into that after the workshop. Any links to picks or products?

Konstantin, That stuff looks great. Giving me lots of ideas.

Tim, thanks for the clarification.

Glyn, I agree, the TEG unit would not be in the flue. The TEG module would be near the manifold on the duct or on the barrell. Positioning would depend on operating temperatures. The electricity generated would be used at the end of the duct run for an axially mounted "Duct fan" (of custom build most likely). Might buy a cheap duct fan and pull the motor and mount the fan blades onto a small dc motor instead. This fan would have to be easily accessible for cleaning and/or replacement. It would also need to be a pretty tough and/or cheap combo. Tough motor/blade combo is preferred for less waste obviously. The first prototype might be cheap to get us a test though.

Dennis & Glyn, I've also seen those Caframo fans and know people that are very happy with them. For this use though they don't work unless i take the blade off and unhook or remove the motor and reinstall down line. I also dont think that the Caframo fans will move enough cfm for the draw through the system but maybe.

Glyn, only trying to run a fan to improve draw through the duct work. This RMH is VERY experimental in a number of ways intentionally to prove or disprove a few innovations. This modification if it works will help us learn more things about the other innovations. And of course let us get to play with and learn about new gadgets and "Bat Features".

Matt & everybody else, This is exactly the info I was hoping for. Thank you so much. Also exactly what I assumed would be the case. If you or anyone else can throw up suggestions for the cheap TEGs and/or good ones and some motor/ fan blade options as well that would be an incredible function stack. Right now I've got to get finishing the Leviathon and the saved Internet legwork would be greatly appreciated. Links to amazon prime items are the favorite but any source is welcome.

Micky, See Glyn's reply above. I stated pretty clearly the desired use. "We want the ability to have a Peltier (also known as TEG, TEC and TEM) setup on a RMH to generate enough electricity to run a fan that would be installed at the end of the duct run to offer positive pull through the system." There is definitely more to it than that and it seems to me pretty simple tech using waste heat. There is room for debate on the low tech high tech aspect and i can see both sides, but that is another discussion for another thread. Gets quickly into social justice and invested energy issues pretty quick as does the metals for the barrels and the duct work and any other materials we didn't dig up on our land. There are simpler solutions, but we are trying to push the knowledge and understanding of the limits of the working parameters of the RMH to a new level. This we cannot do using the obvious easy answers. This RMH mod is not to show and help others how to cheat a bad design. All the experiments going on with the 3 RMHs here are kind of like racing cars compared to production cars. The things we learn here during the R & D might help many others in the future build better easier systems in more applications with less failure.

Rick Edwards wrote:


Glyn, I agree, the TEG unit would not be in the flue. The TEG module would be near the manifold on the duct or on the barrell. Positioning would depend on operating temperatures. The electricity generated would be used at the end of the duct run for an axially mounted "Duct fan" (of custom build most likely). Might buy a cheap duct fan and pull the motor and mount the fan blades onto a small dc motor instead. This fan would have to be easily accessible for cleaning and/or replacement. It would also need to be a pretty tough and/or cheap combo. Tough motor/blade combo is preferred for less waste obviously. The first prototype might be cheap to get us a test though.

Would it be cheaply possible to add a motor to a galvanized steel wind turbine attic vent? (one of the ball vent things). The motor could be out of the gas gas stream. In windy conditions the motor wouldn't be required at all. Though adding the extra variable of wind velocity into the RMH management equation may be more complicating than it is worth.

quick note: all spots for all events are now sold out.

Tom, possibly. I dont know how frictionless they are. A low power dc motor would have to spin it and probably driven by a Belt. That might take too much power. Or it could be mounted top center but again in the gas stream. Ive never seen one up close or had in my hands. Ill take a look next time at the store. Also i think they might need to be vertical which adds another 90.

Having thought about this thread over the weekend - I admire the laboratory approach that you guys are taking, if mechanically assisted flue systems are not explored, then a definitive conclusion based on experimentation will be lacking in the development of the RMH. However, I cannot help wondering why just designing a flue that is efficient in the first place is not a prerequisite for any heating system that burns 'stuff'. The principle objective of a flue is twofold; firstly to take away the poisonous fumes (CO, CO2 etc.) and secondly to provide a draw of fresh air containing that useful ingredient for combustion O2.

Is the problem that the RMH is too effective at drawing heat our of the exhaust gases that by the time the exhaust flue in the designed system starts the 'exit' path that they are too cold to create a thermal draw to the outside?

Clearly this state would exist upon start-up and if not designed into the system would mean that the RMH would never be easy to light. The traditional solution to this problem would be to have a bypass baffle in the flue circuit that would enable the initial flue gasses to bypass any heat sink route and exit directly to the 'chimney' part of the system. Once started the baffle would be set in the usual position (perhaps gradually) to enable the whole flue to be used. I have seen examples in country houses in England where in the 18th century, to maintain the architectural integrity, a house would be built without chimneys in the main building, but a separate chimney being built higher up on a nearby hill (Chatsworth House is one of these examples), of course, the initial draw of the cold system meant that no fires could be started in the house without pre-heating the flue, so the solution was to have miniature fires in 2 or 3 places in the flue connecting the house with the stack - once warm, the draw in the house was sufficient to maintain the overall system of fires.

So another solution could be a smaller 'fire hole' in the flue that enables the initial draw.....

I'm just offering these alternative ideas because any system that requires additional technology to keep it running relies on expensive and energy-intensive production processes, for me the simpler ideas would take preference over the more complicated ones due to their reliance on less resources. I love the idea that the RMH could produce electricity to charge batteries etc., but is the problem we are looking for here simply that we are designing RMH flue circuits for steady-state operation which has created a problem with the initial start-up do to the lack of draw in the flue? If it is a question of aiding flue efficiency the surely a passive improvement is more durable (and cheaper) than an active 'fan-assisted' type design?

By the way, I installed an Okofen wood pellet boiler last year and have just realised that the initial circuit within the burner/water boiler section is similar to the RMH. Initial burn with controlled air feed produces the primary combustion, with an additional air injection a little way above the base 'pyramid' for secondary combustion. the hot gasses then pass down the internal surface of the boiler and then up through holes within the water jacket, then out of the flue (see http://outilssolaires.com/pro/fabricants-distributeurs/okofen-france+e1051.html). The temperature of the outgoing gasses is rarely above 80°C and the ash I minimal - requiring a monthly check and dump. I know that this is far removed from the RMH design, but even with electronic controls and monitoring (and fan assisted air feeds and flue control) we still get ash and a warm chimney. If the problem is balancing steady-state energy extraction from the flue versus initial start-up effectiveness, then yes - I agree that some initial burn design feature should be used, just as the Okofen boiler has controls in the initial ignition cycle.

... gosh, that was a long post! I hope it provides some food for thought!

There are simpler solutions, but we are trying to push the knowledge and understanding of the limits of the working parameters of the RMH to a new level. This we cannot do using the obvious easy answers. This RMH mod is not to show and help others how to cheat a bad design. All the experiments going on with the 3 RMHs here are kind of like racing cars compared to production cars. The things we learn here during the R & D might help many others in the future build better easier systems in more applications with less failure.

I cannot wait for the findings! Best of luck with the fan-assist experiments.