[Stoves] Stove ID please - 2-pot stoves - testing needed

[Crispin Pemberton-Pigott]

Dear Paul

 

Some interesting suggestions.

 

>And I am sure that there are other 2-pot stoves, but just not being stamped
out and with such smooth edges.   Many of us have made such units.

Yes there are lots of two or three pot stoves. The overall efficiency of
even a crummy one is pretty good because.two pots are better than one.

>What is needed is some serious study of these useful features, whether
built into the stove or as an attachment.   Issues to be studied include:
heat transfer to EACH pot
types of pots used (sit on top or inserted)
insulation 
temperatures of the outside surfaces
fuel efficiencies attributed to the second pot

The reporting of the performance is of course important so that prospective
buyers can consider the aspects that related to their needs. Cecil Cook is
working on a modernised social impact assessment methodology that will make
it easier to decide what to report and how to conduct an acceptability
'test'.

And of course, the ways of supplying heat to the 2-pot stove structure.
The fact that both the Prakti and Envirofit units use Rocket combustion
structures does not exclude use with other combustors, such as TLUDs and
even fossil-fuel burners.

I have a quibble here about what is and is not a 'rocket' stove. A Rocket
stove does not have a grate and there is, provided by Dean, a fairly tight
definition of what conforms and does not conform to a Rocket stove design.
As he pointed out (re the Uganda stoves) that some people do and some people
do not make Rocket Stoves. Side-fed stoves have been around forever. Are
they all Rocket stoves? Looking at the design from the 90's it seems not.

Important note:  These 2-pot structures both (virtually all of them?) have a
chimney because horizontal flow of the hot gases must eventually have some
upward movement to maintain the draft (exceptions if there are fans in use).
For the TLUD combustors, the chimney is a nice enhancement of the draft.

There are several stoves that do not use a chimney but have cross drafting
of the fire. Provided the total draft is adequate to move the gases, it
works. There are 'improved' versions with elevated second pots.  The Anagi
is one but there are many others. The advantage of not having a chimney is
higher heat transfer efficiency because of slow moving gases and more
residence time. Putting on a chimney can greatly reduce the efficiency due
to too much excess air being drawn in. As most people to not have a
combustion analyser available, they do not know what the excess air level is
and have to guess as to whether it is improved or not. Adding a damper is
usually a hit-and-miss affair because we never know what is really going on.
Of course the chimney removes all the smoke but maintenance is then needed
as chimneys get clogged if the combustion is not good in the first place. In
Indonesia chimneys added to unimproved stoves have to be cleaned as
frequently as every 1-2 months.

I did not understand Crispin's comment about keeping the smoke and flames
together.

Yes you do - the concentrating disk idea!

>>It seems to me to be worth investigation the % of smoke that can be burned
by keeping the smoke and flames together for a while. 

>That is true for "stick-burners" like the Rockets.   But TLUDs are
"gas-burners" (that make their own gases in the close-coupled gasifier
reactors.)   What would be the best ways to get the best results with
Rockets, TLUDs, or other heat sources?



All smoke should be burned. End of short story. If the smoke can evade the
flames, it gets away.


>But the question is:   who will pay for these tests, and who will release
the results?   

 

It is likely that the easiest funding are projects that need the
information. To do that the product has to past first inspection for having
a chance. The Indonesian stove programme is likely to do this. The roadmap
calls for this. Product descriptions and performance expectations will be
generated by the recipient communities and products evaluated against them. 

 

Regards

Crispin

 

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