Guest Post by Willis Eschenbach
This one is for fun and also for real. The theme of this post is “There’s never enough time.” I worked in the villages of the developing world off and on for a number of years. A recurring issue is the inefficiency of most stoves. The simplest is the “three stone” variety, made with three stones to put the pot on.
Figure 1. An obviously ancient three-stone fire with a modern cookpot in Tanzania. Photo Source
This is hugely wasteful of fuel, particularly in lands where wood and even branches and twigs are scarce. Among my known defects is that I’m an inventor. Over the years I’ve worked on making and designing a variety of stoves to try to improve stove efficiency. As a result, in one of my peregrinations around the web a few days ago I was intrigued to stumble across the “Kelly Kettle”.
The Kelly Kettle was used in Ireland by the shepherds to brew their cuppa tea. Here’s one at work on a beach somewhere.
Figure 2. Kelly Kettle cooking on a beach. Note the fire coming out the chimney.
The brilliance of the plan is that the water in the kettle surrounds the fire. I looked at that, and my inventor’s soul rose to the fore, and I thought “Man, I could make the radical Dutch Oven using that plan. Here’s what I think it might look like.
Figure 3. What I call the “Magic Cookpot”. Note the split (two part) lids, one of which has been removed, flipped over, and laid on the ground for clarity. Lids will have handles in the final version.
And here’s a cross-section:
Figure 4. Cross-section of Magic Cookpot without the lids.
No good to throw away waste heat, so the Kelly Kettles have a pan-holder that fits in the chimney to allow you to cook another pot of food on top.
Figure 5. Kelly Kettle with cookpot. Source.
Looks good to me, so here’s my version of the same. This would allow you to cook soup or stew and have a frypan on top …
Figure 6. Potholder inserts into chimney of Magic Cookpot.
OK, advantages of this plan:
• Efficiency, efficiency, efficiency. Even without cooking anything on the top, this will heat water with less fuel than any design I’ve ever seen.
• Cost. Because the stove and the cookpot are one, you don’t need to buy both.
• Portability. It can be moved easily.
• Adaptability. It can use a variety of fuels, including a propane burner.
• Speed. It will heat water fast.
As I mentioned, the theme of this post is the theme of life—there’s never enough time.
In a perfect world, I’d take this idea and run with it and make a big difference in the amount of wood burned around the planet. I don’t have time, I have a bunch of other projects going on. But I’d hate to see this idea die, it’s a really good one that could make a big difference. So I figure I’ll cast the idea free on the web, make a gift of it to the world of stoves, and see what becomes of it out in the greater marketplace of ideas.
How could this rough plan be improved? It needs a damper to control the draft, and some kind of flap to control the air intake. You could probably increase the heat transfer (fire to liquid) by putting some spiral fins up the chimney. This would increase the surface area and transfer extra heat to the cookpot.
In any case, there it is, and I encourage anyone with the time and energy to become the champion of the idea. You’ll make a name for yourself and have women blessing you all around the planet. All it needs are a couple of sharp Brazilian or Indian or Chinese (or European or American) college students who’d like to make a difference in the world.
w.
Alexander Feht says:
May 10, 2011 at 10:28 am
Russians will declare a samovar to be their “national heritage device,” and demand a huge royalty from anybody trying to sell anything resembling it.
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Good point Alexander Feht,
Here’s a modern example that’s very similar to Willis’s idea but its a design patent not a mechanical patent. The original idea is so old it isn’t patentable and design patents are only as good as your ability to protect them.
http://www.manworksdesign.com/sam_eng.html
Mongolian Hot Pot…
http://www.chinarecipe.net/beef_and_mutton/images/14.gif
With lid on
http://www.creativecookware.com/images/mongolian%20hot%20pot%202.jpg
Years of income to purchase one…
Mike Bromley the Kurd says:
May 10, 2011 at 2:49 am
If it’s cheap (in terms of energy) you can boil water, which protects your kids today from any germs, bacteria, or parasites in the water. Waiting for clean water to arrive takes time. I know it doesn’t solve some water problems (heavy metal content), but it’s a huge step.
w.
Lots of good work has been done by many people on cheap 3rd world cookstoves, most based on gasifying the wood to provide clean burning and high efficiency a google search on _top lit updraft gasifier stove_ will give you many interesting hits. I built a demo unit myself from two soup cans and some steel hardware cloth, with excellent results. Actually much simpler than your design, and more versatile, check it out.
JohnL says:
May 10, 2011 at 3:51 am
Thanks, JohnL. That works. What I’m trying to do in addition to increasing heat transfer through existing surface area (as you rightly propose) is to increase the surface area. For this purpose spiral fins are better.
As a thunderstorm man I’ve always been fascinated by vortices. I’ve made working Hilsch vortex tubes from the design in the magazine back when Scientific American was actually scientific.
So I figure that I need to set up my own little fiery inverted tornado inside the magic cookpot. Put spiral fins in. Round off all of the corners. Set up the air intake to introduce air in a spiral direction. Make the shape of the funnel up the middle like a trumpet bell for the best coupling.
The advantages to this method are
• Longer contact time. The spiral path up the chimney is longer than a straight-up path.
• Increased turbulence at the metal surface. The air will be better mixed near the metal.
• Increased pressure at the metal surface. The centripetal force will press the air into close contact with the metal walls. This will increase the heat transfer rate.
• Increased surface area. The fins will transfer their heat to the metal container and thus to the water.
I haven’t drawn it up yet. I’ll post it when I do.
w.
Also, TLUD gasifiers overlap strongly with biochar, which puts crop waste to good use while improving clayey and sandy soils. The AGW folks ought to love biochar because it can sequester carbon _as carbon_ for thousands of years, but somehow saving the world from that debbil CO2 *without* requiring massive government intervention doesn’t seem to appeal to the usual suspects.
It’s hard not to become more cynical when cost effective, positive value solutions are downplayed in favor of taxes and cap-and-trade schemes. It’s just too damn hard to skim off enough graft from a hundred million small biochar operations.
I designed and build an solar oven, it works great. I did a 4lb tri-tip roast in it in about 4 hours in the Sierra Nevada summer sun. I had to move it twice or so because there are a lot of tall trees around.
It ought to work well in a place like Tanzania.
Willis Eschenbach says:
May 10, 2011 at 9:32 am
Tallbloke, awesome photos. I love the undying ingenuity of the human species.
A Brit’s desire for a truly fresh cup of tea is the mother of invention.
Cheers. 🙂
2Hotel9 says:
May 10, 2011 at 8:28 am
Tall Bloke, my brother from another mother!!! I have made camp stoves using various sizes of metal coffee and soup/food cans, for use with wood, charcoal, trioxine tabs and even candles. Have made candle lanterns from beer cans, one from a Fosters can that we used for several years.
Cheers to you too. I love tinkering with lightweight metal materials. One design I have in progress uses some high tech. It’s a woodstove with three peltiers on the side which drive a motor and fan. The heat from the stove generates electricity via the peltiers. The fan cools the peltiers and a duct forces the warm exhaust into the base of the stove for enhanced heating rates.
The tricky bit I’m trying to perfect is a titanium strip which deforms at the correct temperature to shut off the forced air supply before the soldered joints in the peltiers melt…
A few ideas:
Nice idea – it isn’t new, but it is innovative.
1. The lid needs handles.
2. If the lid was one piece you could add a hook to one of the pot handles to hang the lid on. This would keep dirt off the lid while stirring whatever is in the pot.
3. Make the base separate from the pot so the pot can easily be removed and put back without disturbing the fire.
tallbloke,
Maybe this is what you’re looking for.
Using the KISS principle, how about just using a pot like an angle food cake pan with the central chimney on the three rock system. Accessible to put stuff in the hot water, more surface area to transfer heat, already available in mass production, just not available in the areas of the world that need a more efficient stove/pot.
If you were custom designing such a pot, replace the conventional conical chimney with a hyperbolic chimney as used in cooling towers to produce a better draft, and add a central swirl insert to lengthen the residence time of the hot gases, and if bonded to the walls of the chimney, act as fins to increase heat conduction.
Add a small fitted lid like a dutch oven and you have an easy to clean pot that has multiple uses, the top could be used to increase heat by putting hot coals on the top like dutch oven or could be used as a food warmer from the steam produced by the boiling water.
Teach the users to make a clay outer jacket the pot fits in for insulation and you have additional heating surface and ducted exhaust around the outside surface too.
Larry
Nice refinement of the Thermette Willis. Brought back many memories of camping alongside the NZ South Island Alpine rivers.
Nice idea!
Cast iron,china price and bobs your uncle!
Willis Eschenbach says:
May 10, 2011 at 12:03 pm
• Longer contact time. The spiral path up the chimney is longer than a straight-up path.
• Increased turbulence at the metal surface. The air will be better mixed near the metal.
• Increased pressure at the metal surface. The centripetal force will press the air into close contact with the metal walls. This will increase the heat transfer rate.
• Increased surface area. The fins will transfer their heat to the metal container and thus to the water.
I fold my energy drink can chimneys with a concertina of ridges. This increases surface area and provides the taper which increases gas velocity near the top where the exhaust gases have cooled and contracted. a separate spiral hanging in the chimney like in a gas flue isn’t such a great idea because the heat can’t be transferred to the liquid. Making the chimney out of material as thin as possible and with as high a heat coefficient as possible helps rapid energy transfer. Aluminium is good. Copper is even better, but heavy and weak.
The spiraling intake idea is already in use on the 4 dog titanium woodstove.
http://www.fourdog.com/
Build a slightly bigger “Dakota-hole” fire pit with 3 stones (or bricks) in the bottom.
A conventional pot fits down the hole and sits on the stones with 1 or 2 inches of clearance, so it is heated on the bottom and the sides at the same time.
Efficiency would rate with the best.
A steel mesh can be placed over the top to warm your buns, grill the steaks, heat your coffee, dry your laundry, etc.
Feed the fire from the hole with long chop sticks, or from the top by removing the pot.
“Fail-Safe” Uranium fuel-electricity is so much cleaner and easier…
these ideas are so stone age… sigh.
Another cheap stove in use today to reduce fuel needs.
http://www.stovesonline.co.uk/darfur-stove.html
Looking at the Kelly Kettle, the first thing that came to mind was the Samovar . I believe this is the source of the design . . . http://en.wikipedia.org/wiki/Samovar
re Willis
But potentially harder to clean, especially if fuels are dirty. Think hexamine gunk and having a simple design that can be cleaned with a handfull of sand.
Or.. what about combining with the Multimachine initiative wsbriggs mentioned earlier to make a better version of this-
http://www.brad.ac.uk/archsci/depart/resgrp/amrg/Rievaulx02/Rievaulx.htm
similar principles seem like they could be used to make low costs smelters to turn scrap into cookpots?
It is cheaper not to boil the ants. :p
There are a couple more refinements IMNSHO.
A ‘straight-through’ air intake is a problem in windy areas, the water is still going to convect a decent amount of heat to the outer wall, and the placement of an actual pot on top has room for improvement.
The link at the end of this paragraph doesn’t have all of your improvements – but several of the ones they do have are easy – and not overwhelming pricewise – additions to yours.
http://darfurstoves.org/our-solution/science/
Note that the entire thing has a ‘double wall’. The base of the wall has cutouts for fresh air, but I’m not certain you need them – the ‘chimney’ is well away from the ‘inlet’ even if the outer wall was a simple straight cylinder with notches for the handles. The intervening space then becomes a pre-heater for the air and makes for -very- little convection from inner-to-outer wall as the air is actually flowing into the combustion chamber. The ‘outer wall’ is completely non-load-bearing, and can be whatever can stand up to the local winds.
A second thing they’ve done is shape the heater’s exhaust around the pot itself. They can do this because they’ve standardized on a specific pot. But with your ‘X on the chimney’ design, there could be different inserts for different pots. A basic ‘outer pot with hole in center and crosspiece to support inner pot’ retains that much more of the heat.
Considering making one out of a $10-20 aluminum bundt pan:
http://www.amazon.com/MIRRO-Aluminum-Bundt-Cake-Baking/dp/B003AYHX58/ref=sr_1_6?ie=UTF8&qid=1305057376&sr=8-6
Smokey says:
May 10, 2011 at 12:28 pm
tallbloke,
Maybe this is what you’re looking for.
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Thanks Smokey,
So much for the link I provided earlier related to the hydrogen car conversion. Found this from your site link related to muscle wire.
http://www.switch2hydrogen.com/h2scams.htm
There are some very ingenious solutions in use ranging from pottery and metal cans to wrapping wood sticks in aluminum foil. Use a search engine with the search term “wood gas stove” or “wood gas stove” and “Africa” The same searches on YouTube bring up some good videos. See the YouTube videos featuring “wood gas stove” and “aluminum” or “aluminum foil”. Here are a couple of links:
http://e-woodgasstove.blogspot.com/2006/06/woodgas-stoves-made-with-potters-clay.html
Smokey says:
May 10, 2011 at 12:28 pm
tallbloke,
Maybe this is what you’re looking for.
Thanks Smokey, I’ve been messing about with the arm off my busted titanium specs frame. 🙂
It’s the same design as a gas water heater in a house.