TLUD - Top Lit Up Draft stoves are an innovative technology for high efficiency, low emission conversion of woody biomass to biochar with plenty of useful heat available during the process for cooking and heating water.
Design and use of TLUD's is counter-intuitive to say the least.
--Rather than lighting a match to the bottom of the pile, the pile must be started on top.
--If the process is smoky, you REDUCE the process air going into the pile.
Proficiency in getting them started and adding fuel takes some experience. But in terms of efficient conversion of biomass to useful products their performance is at or very near the top among the latest world stove designs.
They offer a highly carbon negative footprint. Because they can be tuned to work with many locally obtainable biomass residues, there is no need to transport or store expensive fossil fuels. The co-product of the heat is biochar, a new-old technology that enhances crops while interring carbon in the soil long-term.
Enough banter, lets get to it.
Although tincanium and obtainium are practical when testing designs, stainless vessels offer better radiant heat properties and long term durability.
This design begins with a 2 liter vacuum insulated serving pitcher. Depending upon the number of holes and fuel quality (drier and denser is better), it finishes with a stove that boils a quart of water in 10 minutes and keeps it boiling for half an hour on a half load - one pound - of hardwood pellets.
Step 1: Remove the Bottom Cover.
Starting with a standard stainless serving pitcher, using a chisel and hammer, place the chisel in the crease near the bottom. Rap the chisel with the hammer to make the base slide down clear of the main vessel.
Keep moving around the diameter, take it a little at a time, until the base releases completely from the vessel.
The same procedure works for removing the top cap.
Step 2: Bare Vessel
Hammer and chisel make quick work of stripping vessel down to just what is needed.
Step 3: Punch Inside Process Air Holes.
A long, sharp pointed screw, with a pancake head, makes an ideal punch. Sharp is the key. Stainless is tough.
Process air holes are punched from inside and outside. Process air feeds up into the center bottom of the biomass pile. Natural draft, like a chimney, pulls air up through the pile as the process gets going.
I offset the inside from outside holes to prevent the odd hot char from dropping out the bottom of the vessel.
More holes, more power. Less holes, longer run-time.
What is ideal depends upon power needed and on-site fuel.
This stainless vessel is among the most tolerant I have ever used for various fuel types.
Step 4: Punch Outside Process Air Holes.
Match the number, but do not match the pattern of the inside holes to help prevent char dropping from vessel.
Step 5: Punch Combustion Air Holes in Base
Combustion occurs at the top of this vessel when a second round of oxygen hits gases that have been "boiled off" the pile of biomass using process air for thermal decomposition.
The outer ring of holes are the combustion air that flows from the holes in the base, up between the stainless steel skins. It is pre-heated before being introduced inside the vessel at the top. Pre-heat is a very important concept.
Roughly twice the number of holes, a 2:1 ratio of combustion to process air seems to work well in this vessel for most fuels I have tried.
The end result can be a beautiful flame pattern when a cooktop and pot are in place to "cap" the process.
Step 6: Make Top Holes
For making the top holes, a punch works. But a drill works better.
Step 7: Accessories
By sealing outside air out of the outside upper holes with a suitably sized tin can similar to the pictured chimney pipe, a basic TLUD is finished.
To use it, fill the vessel 2/3 to 3/4 full with a dry, woody biomass fuel, check that airflow is unrestricted from the bottom, and light it from the top. The most flammable pieces should be on the top of the pile for easy starting. An accelerant like lighter fluid does wonders for a quick clean start.
TLUD's cannot be made much simpler or efficiently in terms of labor input versus durability and raw material costs. I can make a half-dozen in the time it took me to do this instruct able.
If time is not an issue, they are simple to make from clay for an even lower material cost.
Testing hole sizes and shapes with various tin-can "chimneys" is a great learning tool and time sink.
For my own real world use, I add a couple of simple accessories.
A one gallon paint can with the bottom center cut out, and a short piece of pipe for a chimney/duct attachment adds great utility to the basic unit.
Step 8: Insert Vessel Into Paint Can
Apply insulation inside the paint can first if desired.
This particular vessel slides into a secure, snug fit on the paint can original opening.
Then slide the chimney down from the top.
I like to add a few small holes near the point where the chimney clears the paint can to introduce a final bit of combustion air. It generally promotes a cleaner burn as the process gets rolling.
Step 9: Ready to Run
Finished enough to suit me.
The paint can handle allows it to easily be hung on a standard T-post at preferred working height.
Step 10: Cooking Accessory Attachments
A 4" OD chimney allows using off-the-shelf sheet metal duct fittings. like the 4x7 reducer pictured here.
Slipping a water pot down into a shrouded enclosure dramatically improves water boiling performance.
Step 11: Burn, Baby, Burn
Step 12: Snuff When Flame Dies
It is possible to let the char burn for longer operating time. Carbon monoxide levels go way up (from extraordinarily low levels) in char burning mode.
For less carbon in the air, and more in the ground AKA "biochar", cap all holes when the flame disappears. On a full load of hardwood pellets, you still get several hours of gentle heat before all outer surfaces are cool to the touch.
When outside surfaces are cool, unsnuff and pour out a beautiful, light, biochar co-product that was produced IN ADDITION TO USEFUL HEAT
Char has been used for art, medicine, filtration and fuel since the earliest days of civilization.
Step 13: Build or Buy
Build or buy, what is time worth?
Artisan tooled finished product available online at The Power Mall.
Purchase there helps fund my efforts to increase the knowledge base and use of safe, cheap, obtainable, renewable biomass energy. For long term energy security, nothing else comes close.
Perception, not reality, holds back biomass - the Rodney Dangerfield of alt energy. When biomass finally gets used correctly, and garners the respect it deserves, it will change the world.
Step 14: Foundational Technology - DrTLUD and TouCan
Works by Dr. Paul Anderson, DrTLUD, one of the top biomass stove practitioners on earth, and Dr. Hugh McLaughlin, possibly the top biochar characterization authority on earth, inspired the design of the KeyStove LX.
The picture is from page 7 of "TLUD and TCHARBON Stoves for Sustainable Haitian Development" by Dr. Anderson and Christa Roth, full text available on Slideshare
Hugh McLaughlin, Alterna Biocarbon, provides more operational details than anybody cares to know in this "TouCan" pdf document hosted at bioenergylists.org
Step 15: KeyStove LX Heat Extender Adapter
It allows using the char just created for fuel, rather than saving it for later soil enhancement or liquids filtration.
Just slip it in the chimney when the yellow flames die down. Runtime heat output is much lower, but the heat continues for a VERY long time.
Twelve hours runtime from this configuration, and the char from a pound of pellets was only half consumed.
NEVER BURN CHARCOAL INDOORS!! Look at the warning label on a bag of charcoal for details.
Any can that fits down the chimney (ho ho ho) with holes punched in the old bottom-new top reduces air flow without extinguishing the char burn. Experience allows fine tuning the hole configuration and stack height to the fuel and desired runtime. Char would seem to be a standard fuel, but spacing and density varies by initial feedstock choice.
Pictures in order show:
- CO warning
- Bare attachment.