Dear All,<div><br></div><div>Let's take a moment and consider that the heat transfer side of cooking can be just as important as the combustion side (in any kind of stove). Great heat transfer means that the food cooks faster using less fuel. Great combustion efficiency means we produce less smoke, gases, etc. It takes both to make a great stove, right?</div>
<div><br></div><div>For example. if the pot is 4" above the heat source the water probably won't boil, etc.</div><div><br></div><div>Usually great heat transfer costs less money because lower grade refractory materials can be used and we're just changing the shape of the stove top/pot bottom interface. If we can expose the side of the pot to the hot gases using appropriately sized channel gaps, that's great too.</div>
<div><br></div><div>And system efficiency (how much fuel is used to cook) is usually more improved by great heat transfer than great combustion efficiency.</div><div><br></div><div>Best,</div><div><br></div><div>Dean<br><br>
<div class="gmail_quote">On Sat, Nov 10, 2012 at 10:03 AM, Paul Anderson <span dir="ltr"><<a href="mailto:psanders@ilstu.edu" target="_blank">psanders@ilstu.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Dear Crispin and Paal and Dean and
all, (Also to be posted at <a href="http://www.drtlud.com" target="_blank">www.drtlud.com</a> )<br>
<br>
The discussion (below by Paal and Crispin) has pointed out the
difference between the "combustion device" and the "stove
structure", and that they can be addressed separately. <br>
<br>
TINY devices do this, such as a "Steno" can or alcohol burner
(note that neither says "stove"). The heat generation unit is
separate from the stove body. In general, the combustor or
burner is too small to support a reasonable pot. Tiny tincanium
TLUDs can be in this category.<br>
<br>
When the cooking device gets larger, the heat making aspects are
generally incorporated into the stove structure, as seen in most
of the Rocket stoves and charcoal burners and simple ICS. For
the most part, the "stick wood" burner (combustion device such as
a ceramic/brick chamber or a heavy steel box) is built into the
pot-holding stove structure. For this reason, there has been
little thought to having the combustion device separate from the
pot holding.<br>
<br>
It is VERY common for people to see a simple TLUD making heat and
then asking "where do you put the pot" or declaring "that is not
a stove." Well, the pot goes above the flame, and how the pot
is supported makes little difference to the making of the heat.<br>
<br>
Also, TLUDs (because they are batch operated) need to be re-filled
(or exchanged) regularly, which favors having sheet metal
construction because of lighter weight and not being subject to
cracking like clay/ceramic constructions.<br>
<br>
Yes, there is something not appealing about moving around
containers of flaming fuel or hot charcoal, but even that problem
has been resolved in the TChar variations of TLUDs.<br>
(You do not know what is TChar??? Are you kidding me?? Check
it out at <a href="http://www.drtlud.com" target="_blank">www.drtlud.com</a> and let me know what you think.) <br>
<br>
Anyway, Wendlebo and Reed and other early TLUD developers have
been well aware that the separation of the combustion device and
the stove structure has numerous advantages, of which one is
related to the cost of the stove (stove = combustion device AND
the stove structure). <br>
<br>
NOTE: Sometimes combustion device and pot support are intertwined
such as when a chimney<br>
is important to combustion and to the stove structure, but we are
not focused on that case here. <br>
<br>
Comment about TLUDs with pots on top of them: Some of the Peko
Pe units, Reed's campstoves, the Mwoto Classic and Mwoto Quad, etc
have small pot supports on the tops. Three legs on the ground
also serve as 3 pot supports on some PP units. Three tiny pieces
of metal on Mwoto stoves are the only additional "stove structure"
to turn a TLUD combustion device into a complete stove. <br>
<br>
Less expensive than 3 little supports is unlikely on such
stoves. But it does imply that the combustion device is large
enough to support the pot on the top. Much smaller TLUDs do not
support the pots well. And for institutional cookers, because
the pots are so large that they are not easily lifted off of the
TLUDs that need refueling, the pots need to be supported
separately from the combustion device.<br>
<br>
And that is the point being made by Paal and supported by Crispin:<br>
<br>
The cost of stoves can sometimes be separated between the cost of
the combustion device and the cost of the stove structure (pot
support), especially in the case of TLUD stoves.<br>
<br>
Consider the example of the Champion TLUD manufactured by Servals
in India. The reactor (fuel unit where gas-making occurs) can be
moved from under the tripod that supports the pot and the coupling
device. The same reactor could be used under other stove
structures, and the tripod could be used above other reactors
(fuel units).<br>
<br>
In many cases, the vast majority of the expense of a stove is in
the stove structure. It is often quite visible and people want
it to look pretty. Beautiful decorative tiles and useful
attached working surfaces all add to the cost.<br>
<br>
Our discussion is about LOW cost stoves. Under US$10 for a
complete "stove" with both a combustion device and a stove
structure.<br>
<br>
A. Stove structure: make it from locally available materials,
including some possible "scrap." Use some adobe or other bricks
to make two sidewalls (and maybe a backside) to an appropriate
height, and then horizontally place 2 pieces of rebar to support
the pot. In Haiti, use rebar from some of the crumbled walls of
buildings. Or weld together a small "H-shaped" grate with 2 cross
pieces to become like " # ". One dollar? maybe $2? Before
long, the household might plaster (use dung and clay or cement?)
the sides, and even whitewash it. Voila', stove structure that
is inexpensive, and quite sturdy. <br>
<br>
B. Combustion devices: <br>
<br>
1. The Mwoto TLUD gasifiers in Uganda are already sold at only
US$14 with pot supports (and no subsidies). And that is for a
full size unit with about 7 inch diameter fuel chamber. And the
Awamu Biomass Energy company (GACC Partner in Uganda) is fully
engaged on making it for less than $10 by using concepts such as
the Mwoto Quad design, smaller sizes, TChar versions, and less
metal (which is the major cost). (Full transparency: Awamu is
owned by Nolbert Muhumuza and Paul Anderson, and they are looking
for others to join them. Awamu means "together" in the Lugandan
language.)<br>
<br>
2. Paal Wendelbo and his associates have Peko Pe models (mainly
in Zambia, I believe) that also could probably be reduced to under
the $10 price. <br>
<br>
3. Prof. M. Nurhuda in Indonesia is making excellent progress
with his low cost TLUD stoves.<br>
<br>
So, the target of very clean stoves for under $10 can be met. <br>
<br>
But the nay-sayers will quickly point out that people want better
looking stoves, or have fuel preparation problems, or do not want
to change out the TLUD batch. (Conveniently forgetting that the
fire has run UNattended - but not out of sight - for 10 or 20 or
40 or more minutes, depending on the fuel types. TLUDs do not
need the 3 to 5 minute attendance cycle that Crispin so correctly
pointed out as a major problem with the vast majority of
stick-burning Rocket and simple ICS stoves.)<br>
<br>
In conclusion, if you are not into the TLUD stoves yet, please
reconsider. We welcome your participation.<br>
<br>
Paul<br>
<br>
<br>
<pre cols="72">Paul S. Anderson, PhD aka "Dr TLUD"
Email: <a href="mailto:psanders@ilstu.edu" target="_blank">psanders@ilstu.edu</a> Skype: paultlud Phone: <a href="tel:%2B1-309-452-7072" value="+13094527072" target="_blank">+1-309-452-7072</a>
Website: <a href="http://www.drtlud.com" target="_blank">www.drtlud.com</a></pre>
On 11/10/2012 5:03 AM, Crispin Pemberton-Pigott wrote:<br>
</div>
<blockquote type="cite">
<pre>Dear Paal and All
This idea of making a replaceable combustor has additional benefits. The idea is already in use though it may not at first be obvious to a casual observer.
++++++++++Paal Wendelbo wrote:
Dean and Paul are right if they also adopt the original idea with the TLUD-ND from the 1980ties and see the TLUD as a kind of a wrapping for the fuel; a unit loaded with energy to be put into a stove. Then you will have a lot of more possibilities.
++++++++++Crispin continues:
I will post a photo of a stove I have recently seen in Cambodia which has a very substantial built-in brick and cement three-pot layout. There is a single chimney against the wall and three pot-holes. There is a wood fire space under or in front of each pot with a horizontal channel to the chimney behind it.
This theme is used in Indonesia as well. I saw the exact same system used in urban Jogjakarta and a multi-pot single-fire version in rural Java.
In all cases the hole is shaped so that it can take large woks and flat bottomed pots of different sizes from about 230mm to 900mm in diameter. The smaller pots are accommodated using reduction rings that fit the open hole and the pots.
The point is the holes are substantial and the fires variable. When there is a desire to cook for a long time the ring(s) are removed and a taper-bodied stove that looks a lot like a tall JIKO is placed into the hole. This is a 'burner insert' or 'combustor' just as described by Paal.
I have a photo of such a stove in operation. It has a charcoal burning stove dropped into the larger stove body. This can be done with all three holes if desired depending on what is cooking.
As the concept is already well established, all that remains is to create other combustors that will either fit into the existing holes or stove body-combustor combinations that will accept appropriate pots.
Further in our favour is that there is in Indonesia a (regionally?) established precedent for having an ash cleaning hole that is built into the floor below a clay grate. This satisfies the requirement to have a low overall height (about 300 mm) for the stove body. It means the combustor can be taller than 300 mm and still fit into the stove body.
All the drop-in burners (which are stand-alone stoves if you take them out) can be improved as they stand so the new system performance should be much better than the baseline.
Paal, in order to be able to get the PP or similar burners accepted in the same communities they will have to be 1) power controllable and 2) refuellable or the equivalent of refuellable such as a convenient swappable insert that can be managed easily.
There is a stove in Mongolia that is copied from a Japanese brand 'Royal' which has two TLUD combustors connected by a Y-shaped channel to a common chimney. It is able toi cook constantly while swapping back and forth between two fires which can be run sequentially or in parallel. If one is started say, 1 hour before the other, the heat is continuous and the cook can re-charge the used one while the second burns.
The big mis-match at the moment is the almost unchanging power output of the simple TLUD and the need for long term variable cooking for various foods, tea, palm sugar making, sea salt making, boiling chips and sterilising or heating water. People exercise quite a bit of control over the firepower during a burn cycle.
For everyone's interest the most /hated/ aspect we could determine about stoves was the time interval between needing attention. At present it is about 5 minutes for domestic stoves. Although this will be investigated in the near future in detail, the people I interviewed rated a longer time away from the stove (perhaps 10-20 minutes) more valuable than fuel saving, smoke, ignition time, cost or fuel preparation (though objection to preparation of fuel was strong).
The biggest opportunity I see at the moment with basically no change for the TLUD's is the load, fire and forget water steriliser. Lanny, don't forget. It can be a stand alone or a drop-in unit.
Regards
Crispin in Carrying Place, Ontario (is there really such a place??)</pre>
</blockquote>
This was the message from Paal Wendelbo:
<blockquote type="cite">
<p style="LINE-HEIGHT:13pt;MARGIN:0cm 0cm 10pt"><span lang="EN-US"><font style="FONT-SIZE:11pt">Stovers</font></span></p>
<p style="LINE-HEIGHT:13pt;MARGIN:0cm 0cm 10pt" class="MsoNormal"><span lang="EN-US"><font style="FONT-SIZE:11pt">Dean and Paul are
right if they also adopt the original idea with the TLUD-ND
from the 1980ties and see the TLUD as a kind of a wrapping
for the fuel; <i>a unit
loaded with energy to be put into a stove.</i> Then you
will have a lot of more possibilities. You will cover the
whole specter of energy needed for household and
institutional cooking, bakery and heating, with a lot of
warranties of types of fuel, and easy to adjust to local
needs and local resources. The technology itself is so
simple that a child with a nail, a hammer and a tin can make
a perfect clean burning unit. And the most important it will
create jobs near connected to the marked philosophy, cheap
and short time lasting. <span> </span></font><span><font style="FONT-SIZE:11pt"> </font></span></span></p>
<p style="LINE-HEIGHT:13pt;MARGIN:0cm 0cm 10pt"><span lang="EN-US"><font style="FONT-SIZE:11pt">Paal W</font></span></p>
</blockquote>
<br>
<blockquote type="cite">
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