[Stoves] CO/CO2 Ratio in the Charcoal Stoves Tested at Aprovecho

[Tom Miles]

Dean,

The reaction to your experiments has been interesting. Several people from
charcoal consuming countries in Africa, Asia, China, Southeast Asia and
Latin America have been watching the information posted to
bioenergylists.org every day. This suggests to me that if there is a
reasonable promise of improving emissions (CO, PM)and efficiency from
charcoal stoves then it is worth investigating. I think the concepts that
you have suggested for improving the stove should be developed and tested by
engineers in-country, or at least in the consuming regions with support from
the donor agencies and donor countries. 

Your experiments and the discussion on the topic from Peter Verhaart,
Crispin and others suggest that an insulated combustion chamber improves
charcoal combustion. A taller insulated combustion chamber may help explain
the improved performance by CFSP's New Lao and the acceptance in Uganda of
Mary's six brick "Sprocket Rocket" reported by Ken Goyer, compared with the
older Lao and Ugandan jikos. But an insulative combustion chamber should be
tested with indigenous fuels. That is clearly occuring in the camp in
Uganda. (According to Ken's report even balls of charcoal mixed with clay
fines (as low as 18 MJ/kg?) are burned.)  

The stability of the combustion in the Ghana jiko in your experiments
suggests to me that much is due to the high quality (low volatile) charcoal
that you used. Your jiko didn't seem to follow the pattern suggested by
Peter and Crispin or in the reports by Dan Kammen's group. What happens when
you burn the low quality (high volatile and/or high ash) charcoal? I think
you can only find that charcoal in country. Even the "low quality" imported
charcoal in the US is likely to have 75% fixed carbon. So I think the
quality of the fuel could be an important variable. (Charcoal stoves may
need to be designed more like wood stoves.) Most importantly baseline
testing needs to establish the characteristic operation of the jikos to
identify the possible areas of improvement. Fuel is an important variable
that is virtually uncharacterized for most jiko work I have seen.

When I see your rocket "take off" in the video and the persistent flame
throughout the cook it looks to me like you have no control over the
fuel/air ratio. It looks like there's too much fuel in the chamber. Can you
control this by starting out with half as much fuel? Then adding fuel during
the cook? In the end maybe someone designs the stove with a grate and
volumetric heat release appropriate to the optimum temperatures and
conditions for CO combustion, and you slow down the gas velocities to reduce
the PM emissions. There's work to be done.

Much of this combustion engineering can be done in-country or with support
by agencies like EPA, GTZ, DFID, ARECOP, and many of the universities in the
regions. Asian Institute of Technology comes to mind along with similar
institutes in India. Apro, ISU, CSU and EPA are well instrumented and can
provide comparative testing and development.  

The same is true I think of the baseline emissions testing. If you ship the
designs and specifications for the hood and instrumentation ($20,000/site?)
and arrange for support then you have stove development and emissions
reduction occurring in many regions using common test methods. ETHOS can
provide a common technical forum for development and test methods. 

So maybe you have lit off a new round of development in stove engineering.
Let's hope so. 

The other things on my "wish list" are: a well designed engineering analysis
and testing of the jikos that we see in use from a combustion engineer's
perspective - fuel analyses, stove dimensions and operation characterized
and documented for comparison and improvement; and, a complete,
state-of-the-art review of improvements made to charcoal stoves in varous
parts of the world, again from a technical point of view rather than a
policy perspective. The best of this documentation is 10 years old or more.
If we're going to improve the use of the most common fuel we need to update
our resources.          

Regards,

Tom
             

                         


-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Tom Miles
Sent: Monday, June 26, 2006 4:13 PM
To: STOVES at LISTSERV.REPP.ORG
Subject: RE: [Stoves] CO/CO2 Ratio in the Charcoal Stoves Tested at
Aprovecho

Dean,

The CO/CO2 graph provides a very different picture of the cook. 

Closing the door on the Jiko to simmer doesn't seem to have changed the
CO/CO2 ratio. Opening it to maintain the simmer doubled the CO/CO2. 

The Jiko firing looks pretty stable. The rocket is clearly unstable through
the boiling period: back to the drawing board!

What does a CO/CO2 plot look like for the WFP Wood Rocket with skirt cited
in your "Initial Development of a Charcoal Rocket Stove" report?
http://bioenergylists.org/stovesdoc/Aprovecho/charcoalstove/AprovechoCharcoa
lRocketStove.pdf 

Thanks for the stimulating graphs. 

Tom
  	

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Tom Miles
Sent: Saturday, June 24, 2006 10:49 AM
To: STOVES at LISTSERV.REPP.ORG
Subject: [Stoves] CO/CO2 Ratio in the Charcoal Stoves Tested at Aprovecho

CO/CO2 Ratio in the Charcoal Stoves Tested at Aprovecho
http://bioenergylists.org/en/COCO2charcoalrocket
 
Dean Still, Aprovecho Research Center, June 23, 2006
 
Dean presents graphed plots for the levels of CO and CO2 during one test
each of the charcoal burning rocket stove and Jiko-type charcoal stove from
Ghana.  A higher level of CO2 suggests a higher burn rate of fuel.
 
See also links to previous discussions of CO and CO/CO2 ratios and charcoal
stoves 1997-2006.