Re: Juntos Stove text message

["Paul S. Anderson" <psanders@ilstu.edu>]

At 07:40 AM 2/22/02 -0700, Ron Larson wrote:
> Paul:
>  
>     Nice write-up.  I need
> more time to digest it all and better understand the new options you are
> suggesting.
>     I like the "shelf"
> arrangements - haven't seen anything like that
> before.

Nor have I.  All the heat seems to go so straight up through the
levels that there is very little lateral loss of heat where there are
spaces at the racks.  (I have started to call this a "heat
column".)  And with some real manufacturing (not just tin cans
in a shed), it would be possible to have the units slide in to more snug
fittings, perhaps with half-circle collars to minimize lateral loss or
impact of wind.

>    
> You may have the achieved the widest range of "turn-down"
> ratios (different fuel weight conversion (or kW) rates) - can you
> quantify what you are able to achieve in min and max
> kW?)

I honestly do not have any clue about KW output.   But as some
(I think it was Dean) have said, the fuel gives about the same heat
whether burned fast or slow.   The real issue is how much of it
can be effectively captured for useful purposes.  Therefore, another
one of the intermediate or upper units could be the "haybox"
(not made of hay or other combustible material) with an open or partially
open bottom to let in additional but VERY low heat.  The haybox
could be opened occasionally for stirring or checking by the cook. 
It could even be removed from the "heat column" (I just made up
that term, but it seems to represent what  the Juntos stove is all
about).  Then the cook would close the haybox and have the option
to  introduce additional heat from the bottom from a low-burning
gasifier or from some embers of charcoal in another heat column of the
stove complex.   

>     I
> am interested also in how you are controlling primary air flow with the
> horizontal pipes.   Their length looks longer than I might have
> expected - your reason?

Air pipes.  The ones shown are horizontal, but they could be angled
or even vertical or coiled around the gasifier.  The air pipe serves
as a handle.  The length of the air pipe allows the gasifier to be
pushed further back into the stove chambers, even so far back that
another gasifier could be place on the outer edge of the chamber.  I
envision chambers with about 4 gasifiers of different sizes able to be
turned on or off or moved into any of several places to initiate heat
columns.

Consider that the air pipe is well sealed where it enters the inner can
(or more appropriately called the "inner chamber for primary
combustion" or the "gasification cavity").  If the
air pipe  is completely closed (I use sticky-back aluminum foil
tape), there is no primary air from below the grate/fuel.  But on
the air pipe there are various holes, including the outside end of the
pipe that could be completely open to allow plenty of air to enter. 
Regulate the number and size of the holes allowed to be open, and you
have control of the primary air.  The control (increase or decrease
of heat) is not instantaneous (allow 20 to 60 seconds for internal
adjustment??), but neither is it instantaneous control on a electric
stove or hot-plate, but is virtually instantaneous on a LPG or gas
stove.

Furthermore, the conveniently long air pipe allows me to stick the
out-put end of a small bellows into the pipe and to pump in short blasts
of extra air.  I have also done that by blowing with my mouth at the
air pipe ("But I never inhaled." WJ Clinton said that before I
did.).   By far the best idea on this "supplemental
air" is to have a flexible hose from the air pipe to a place where a
cook could easily grasp the other end of the hose and give a few puffs of
air.  Also, the hose could be connected to a bellows or a blower for
continual injection of more air.  Proof that the effort is worth it
comes from Tom Reed's Turbo WoodGas stove with a battery operated blower.
(additional comment below).

Supplemental air will gasify the fuel faster, but also, after
gasification is complete, will turn the charcoal remains into blazing
embers!!!!   You can consume the charcoal in the lower unit,
but here is the problem:  the blazing charcoal is like a
forge.  It is VERY hot, and can seriously damage the gasifier. 
Not only will burning the charcoal in the gasifier hasten the destruction
of the tin can and the grate, but when I did it with an aluminum air
pipe, just one event (a couple of minutes) literally consumed (melted,
vaporized, etc) the inside end of the aluminum air pipe.  Not
cool.  The solution is to make a cast-iron grate and internal walls
(much like Crispin's "basket grate" but without holes, so it
would be a "bucket grate") and have an iron air
pipe.   But that dramatically changes the cost structure,
becoming much more expensive (?) only because of a desire to consume the
charcoal "in situ" after gasification of the
biomass.   It is MUCH easier to simple remove the tincanium
gasifer, dump the char into your preferred container, reload the
gasifier, re-light it, and place it back into the base of the heat
column.

It is really easy to make a Juntos stove.  I plan on taking all the
necessary tools to southern Africa with me in March so that I can try to
make some stoves there.

I sure hope that some readers of the Stoves list will say that they will
try to make a Juntos Stove based on the descriptions I have
given.   Then I would really be doing something Together
(Juntos) with my fellow stovers.  
 
Paul

>    
> More later - but thanks for giving such nice detail.
>  
> Ron

Paul S. Anderson, Ph.D.,  Fulbright Prof. to Mozambique 8/99 - 7/00

Rotary University Teacher Grantee to Mozambique >10 mo of 2001-2003

Dept of Geography - Geology (Box 4400), Illinois State University

Normal, IL  61790-4400   Voice:  309-438-7360;  FAX:  309-438-5310

E-mail: psanders@ilstu.edu - Internet items:
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