-A 20mm insulation air gap that should increase fuel efficiency while at the same time radiating some heat off the middle cylinder to the outer cylinder. The outer cylinder should be safe to touch while the stove is in operation. The theory is using a 3 cylinder stove creates a sweet spot for metal lifespan, fuel efficiency and safety. Need to compare water boiling times and outer metal surface temperatures with and without the middle cylinder
-The handles are double so 1.5mm goes to 3mm which is hopefully thick and robust enough. The double welded tabs should provide strong attachment of the handle to the outer cylinder - maybe orientate North-South so they don't act as hinges when the stove is tipped over!
-An independent pot stand that is suspended above a 1.25kg Milo tin riser and 'Permastove'. The legs are made from bamboo (any variety) and the metal cross should be able to support flat-based pans as well as round-based pans/woks. If the fuel runs out, the 'Permastove' can be easily removed and replaced with another 'Permastove' (with fuel) without any need for moving the pan/pot/wok during cooking.
-The lid tabs could be screwed into the outer cylinder with 3.2mm x 20mm galv screws which would help anchor the cylinders, increase pressure in the secondary air gap by reducing air leakage at the top
-For USB fan control I found this: https://www.coolerguys.com/products/coolerguys-manual-speed-controller-for-usb-fans It means now you can adjust the (5V USB centrifugal computer) fan speed which will adjust the flame size for better cooking control - just like a deluxe gas stove ring!
-2 spare grates per stove. The inner cylinder will eventually wear out from exposure to fire and need replacement at some stage but probably not before the grate will burn out in the middle. Replacing the grate will extend the life of the inner cylinder. For convenience the central grate should be able to be snipped out with good tin snips and replaced with a spare one that can be screwed in with 3.2mm x 20mm galv screws (can be purchased from Bunnings).
-The power bank could be the 'Zendure X6' or 'Ultron'
-The power bank could be powered from a 60W Megasolar PV panel which has USB C PD output, DC and USB A
-Why not a TLUD dehydrator? There's always the ol' solar bed frame...
-Why not a solar oven when the sun's shining and a TLUD when the sun's not shining?
Where's the CAD for 'The Permastove V3'?
I'm still saving up dollar to prototype 'The Permastove V3'. Information will be provided during the prototyping stage as there may need to be final adjustments to the CAD - which might be posted if I think the stove is worth mass producing!
The 'Permastove V4' is a '4 in 1' stove for
(1) multiday trekking/hiking/backpacking, solo or group. Day/overnighter trekking/hiking would be better served with the 'Ohuhu' TLUD stove which can also take solid fuel tablets eg.Hexamine as a backup. Note that biomass stoves probably shouldn't be used during the fire season (unless indoors)
(2) car camping
(3) backup stove for the household (if you already have a stove connected to the grid)
(4) primary stove for the household (if you're off grid)
-lightweight: made from 0.9mm 304 stainless steel - very durable too
-multi-fuel: can use plant waste (biomass) from the environment while trekking or use fuel pellets if you're alpining eg. sawdust, rice husk, coffee bean pulp etc The base/grate has many small air holes so all types of fuel won't fall through
-light ecological footprint (offsetting Carbon released by unsustainable sources and technologies eg. fossil fuel based transportation, energy production, agriculture et al like deforestation/land clearing...)
*fuel efficient with clean emissions (smokeless) via passive/non-pressurised micro-gasification (uses primary and secondary air supply)
*produces biochar (as a by-product of pyrolysis via water boiling/cooking). This can be left in the environment and will lock up Carbon for hundreds to thousands of years (eg.35,000+ years) reducing the impact of climate change/chaos
*no non-recyclable fuel (gas) canisters to deal with (that usually get turfed into the environment)
-no moving parts eg.no fan or any electronics
- to reduce volume in bag: fits in all sizes of billies eg.1.4 litre, 2 litre, 3 litre; Sigma 2.7/3.7 litre pots; Pathfinder GEN3 bottle/cup nests inside the inner cylinder
-replaceable inner cylinder
-works well with a heat shield that is elevated above the air holes on the outside of the outer cylinder
-creates local 'Green collar' jobs along the supply chains eg. fabrication, biochar collection and application
Prototyping will be done over the next few months.
Note that the 3D model is for illustrative purposes only. Unfortunately, a software bug prevented lining up the base perfectly central with the inner cylinder - it's not a design fault :)
Managed to get a burn for 2 hours 40 minutes using wood pellets. The fire took about 15 minutes to stabilise. I used a ss bowl with ss pollen mesh lid, filled with water, on the stove and it was able to get up to boiling no problem. I had to top it up every half an hour to replace evaporated water lost during water boiling. I used a hexagonal heat shield around the stove/bowl which protected the flame nicely as it was a little gusty. The wood pellet biochar produced from the burns looks like good quality which I will need to test in a lab for confirmation. The air jets worked ok during the burn but only worked very effectively when the pyrolysis front was near the bottom of the reactor/inner cylinder. Presumably, this was because there was more airflow available to the fire and more wood gas was getting sucked up to the air jets. I'm going to try sealing the stove lid with high temperature silicone which I think will increase the secondary air pressure in the air gap and through the jets which will add more oxygen for cleaner and hotter secondary air combustion. I'm also going to try adding a fan when it arrives and close off the outer cylinder air holes at the base. I hypothesize that the forced air/fan assisted burn will produce faster pyrolysis, shorter burn time, higher temperature fire and improved secondary air combustion.
Run time was 1h40m. Shorter compared to the first run due to better secondary combustion now that the lid is sealed properly with high temperature silicone on the top/outside edge. The silicone shows no loss of structure after the burn which may have even helped bed in the silicone. The wood pellets with kerosene shaken in a small container worked great as a firestarter. These charged pellets were placed as a thin top layer on top of the rest of the wood pellets up to the level of the first air jets. The heat shield worked perfectly. The Pathfinder boiled in 5 minutes but I allowed it to boil over which almost put the fire out. So. needs to be removed with leather gloves before boiling over. When the fire began to smoke, that signalled the end of the burn. At this point, I poured the pellets into a bucket with water. I never pour water directly on to the stove as it will deform it while it is hot. The resultant biochar looks clean and crumbles cleanly which is a good sign.
So here's my latest attempt at a TLUD outdoor kitchen, perfect for an alternative/backup way to cook at home or for car camping or base camping at lower altitudes (with a lightweight heat shield (no bucket) and using the TLUD as a portable stove, using environmental biomass as feedstock (for even more mobility) or carrying in solid fuel wood pellets). I used a 20 litre stainless steel bucket as a heat shield/reflector, wind shield and 'base plate' for stove stability. Buckets have many uses! I filled the TLUD half full with pine sawdust solid fuel pellets from 'BBQs Galore'. I used a Livingstone frypan from 'Snowy's'. A 'Barbie Mate' (found in many shops in Oz) for flipping the eggs which is also a very useful BBQ tool. I used a standard mild steel kettle for boiling water for that tea/coffee/hot chocolate, rehydrating instant food, doing the dishes afterwards in the bucket (after the stove has cooled down and removed). I used a couple of reclaimed mild steel rods as a stabiliser for the frypan and air spacer, allowing plenty of air for the pyrolysis in the stove. The wood pellet byproduct of pyrolysis is biochar which can be added back to the Earth/collected for many other uses eg. pot gardens, humanure toilets, water filtration et al. for a 'Carbon negative' kitchen, offsetting fossil fuels for cooking (or even if the BBQ gas bottle runs out) and reducing Carbon in the atmosphere and using it in a 'cascade of uses'. I should mention too that this is a completely solid state system with no moving parts and no electronics to fail.
If you are interested in purchasing one or more stoves, I have parts for four (4) I can fabricate. Please use the 'Contact' form to get in touch and I can do you a deal...
This rapid prototyping is addictive and expensive. So, the prototype of the 'Permastove' V4 was 2D laser cut, rolled and welded. It turns out that my laser cutter has a 3D laser cutter for tube. A couple of wise men recommended I used preformed tube for the chambers to save cost and I think they are right in terms of what's appropriate and available. As I've mentioned before, a good design should take into account locally available tools, materials and labour. So, it is appropriate that I redesign V4 to take advantage of 3d laser cutting and available 304 stainless steel tube in South Australia. Ideally in the future it would be Carbon negative 'Green steel', using Australian iron ore and manufactured in Australia. One can only hope...
So what's in V5?
*Still a multi biomass fuel stove that produces biochar as a byproduct of pyrolysis/burning for a Carbon negative footprint
*The smaller version is suitable for single/multi-day trekking or a backup household stove.
*The larger version is suitable for car camping, base camps for group trekking or a primary/backup household stove.
*1.6mm 304 ss for the inner chamber and outer chamber - I would use thinner steel but it is not available for 304 ss tubes at these diameters in South Australia (if at all).
*1.2mm 304 ss for the base and lid which should be OK for the tabs and provide better durability than the 0.9mm used in V4.
*Perforated tabs will be used throughout the design.
*No tack welding of the base to the outer chamber. Large tabs on the outer of the base will be folded down to support the inner chamber. The inner chamber will still use tab guides that worked well in V4 but will be longer for added stability.
*V5 won't be Fan Assisted/Forced Air (FA) and remain a Natural Draft (ND) TLUD
*There will be less air jets for secondary combustion on the inner chamber. All these jets are not needed and less of them will save money/less time needed on the 3D laser cutter
*The lid won't be screwed on to the outer cylinder and should fit perfectly with no air leaks using folded down tabs as a guide. No high temperature silicone required either.
*The pot stand will be a circular section cut from the inner chamber with circular air holes similar to the primary air holes at the bottom of the outer chamber. This will be much more stable that the cross design used in V4.
*The smaller V5 version fits inside a 2L (14cm diameter) Zebra billy and the larger version fits inside a 3 litre (16cm diameter) Zebra billy (with a 4cm height overlap). Zebra billies are also made of 304 stainless steel and are available from a number of stores in Australia.
The stoves will hopefully be available for sale by 3/2023!
Made using TLUD first principles and some old junk (and a couple of parts from the 'Permastove V1') I had lying around. Works great! Completely 'solid state' during operation - no moving parts eg.fans. No external power source needed - just biomass for micro-gasification during operation. Modular - parts can be assembled and pulled apart with easy replacement if parts wear out. Manual operation.
The bottom air hole system (four air holes that can be opened or closed) allows the user to find the optimal air flow given the variation between feedstocks, moisture content of the feedstocks and amount of flame desired for cooking/boiling water.
Tested with wood pellets, thin bamboo pieces and sticks from an acacia. Good for wok cooking, boils a kettle very quickly and works perfectly with Carbon steel cookware.
Also, I doubt a biochar biocomposite saucepan would work very well...
'Carbon negative' 'Green steel' would be ideal for all the steel used:
304ss for the TLUD two inner chambers (15 litre stockpot and chimney flue section), conical steel mesh base insert and possibly lid; repurposed 5 gallon oil drum made from mild steel; Milo mild steel + tin chimney; mild steel pot holder; Carbon steel for the cookware
Also HW350, mild steel and galvanised steel for the Kon-Tiki kilns.
The steel dilemma:
I want to be able to tell customers that both TLUDs and Kon-Tiki kilns follow this new definition I am proposing of a 'Carbon negative technology footprint', taking a 'Cradle to Grave' approach:
The Carbon removed and probably offset over the lifespan of the technology is more than the Carbon required to 'mine'* the raw materials, refine the raw materials, produce the final materials, build the technology with the materials, transport the technology to the user, use the technology then repurpose or recycle the technology at the end of the service life.
*which could include direct air capture (DAC) of Carbon or include biochar Carbon from biomass to produce Carbon-based materials, just to muddy the waters.
But, the longer I wait for the ideal steel, the less time there is for customers/DIY builders/field testers to 'Burn: Using fire to Cool the Earth' (referring to the book by Albert Bates and Kathleen Draper).
An interesting point to note here is that the same technology built from the same materials might have a different 'Carbon negative technology footprint' and that's not even taking into account the Carbon removed and possibly offset over it's service life. So, to avoid accounting confusion, maybe a more Carbon negative inclusive definition of 'Appropriate Technology' is needed. Any ideas?
At the end of the day there are many factors at play in producing the first not Carbon negative 'Green steel' in Australia - in fact, it has been achieved by SIMEC Mining in Whyalla,SA, which they describe as being 'low carbon intensive'.
'Carbon negative' should be the end game but it's a great start for Australia and the rest of the world!! I couldn't help chuckling when I read the name of their pellets as 'GREENSTEEL' - great for SEO rankings :)
What to do with the biochar?
Biochar produced as a by-product from the TLUD can be used for water and air filtration if needed (then down a cascade of uses) or straight into a piss bucket for 'hot charging' the biochar with Nitrogen for fixation plus Carbon removal and fertiliser or into an indoor or outdoor humanure system then onto the garden for Carbon removal and fertiliser not to mention all the other benefits highlighted throughout the website.
Note other ingredients could be added to the piss bucket or humanure system to customise the biochar fertiliser. See the 'Permafert' page for some ideas...
The stove mainframe for metal 3D printing. I reckon in 5 years (2028) it will be economically viable but it could be sooner or later. Just depends on the 3D printing tech and the cost of the metal powders. The only support structures needed were for the flat ring on the base. The ellipses and 55 degrees minimum angles worked perfectly for the plastic prototype. I would say at this point it's a fairly niche area. The best option right now would be 3D tube laser cutting and 2D laser cutting - but the tube steel is too thick at 1.6mm for a lightweight stove. Keep in mind too that 3D designs are totally scalable. This design could be used for larger institutional stoves or smaller super light backpacking/hiking/trekking stoves. I should mention too that it's only one part - no parts to lose other than the stove itself when you're out bush. No maintenance either. No volatile liquid fuels. The only byproduct of your fuel, which you could take with you as wood/rice husk pellets, or use locally acquired biomass, is biochar. So over it's lifetime of use I would call it a 'Carbon negative' technology.
In the future, it could be fuelled by Cyanobacteria pellets on Mars or whatever biomass happened to be abundant on a different future Planet.
NORI's lightning sale has just been joined by the Schwarzenegger Institute, offsetting the footprint of their operations. So what I am thinking is if I can work out the supply chains for the Permastove V5, I could embed the purchase of NORI CRCs into the cost of buying the stove in order to offset Carbon emissions of manufacturing/production. Then, if a village or co-op down the track wanted to buy stoves (or even produce their own stove on the coop level with 2D and/or 3D laser cutter purchases via public/private philanthropy), biochar produced could be reimbursed with CRC purchases providing NORI tokens proportional to how much biochar they produce.
The 'Permastove' is more complicated to build compared with the 'Carbon' V3 (See the Flat-Tiki 'Carbon' page). There are more parts and more things need to be done to the metal. I've been told that the double fold on the 'Carbon' V3 is tricky but doable for a skilled press brake operator. The 'Permastove' V2, V3, V4 however requires rolling, bending (with the exception of V4) and welding in addition to 2D laser cutting (which is a skill in itself). The 'Permastove' V5 requires 3d tube laser cutting and 2d flatbed laser cutting. I'm thinking that 500W fiber optic 2D laser cutters and 3d tube laser cutters could be purchased in a given region (maybe with Nori tokens) and located at a centralised workshop for both the kilns and stoves. The 'Permastove' V2, V3, V4 could be distributed as a flatpacked kit to local workshops that can do rolling, bending (with the exception of V4) and welding. The 'Permastove' V5 doesn't need any additional fabrication after laser cutting so should be made at a centralised workshop. These workshops could then act as stove and fuel distrubution hubs. For stoves, I prefer this model over a centralised workshop that does everything but only creates distant jobs through the biochar related supply chains but in some cases centralisation may be the only option (eg. 'Permastove' V5). It makes more sense to do the cutting and folding of the 'Carbon' V3 at a centralised workshop then distribute it from there. For both stoves and kilns it depends on local preferences too eg. What's the most appropriate way of doing business? Where is the unemployment? What transportation links are available? Most importantly, where is the market?