[Stoves] Chimneys

[Crispin Pemberton-Pigott]

Dear Bob

I want to highlight the chart on the top left on your page
http://www.maasaistovessolar.org/data.html to the other readers of this
group.

There is a reasonably clear indication of the CO following the PM spikes.
The is the result of smouldering at the edges of a reducing fire even when
there is a good flame under the pot. Put simply, smoke precedes CO.

One could say it is a 'classic' burn cycle.

I also draw your attention to the work done independently of the SeTAR
Centre on burn cycle replication. Omar Masera from the University of Mexico
has also been looking at the ways stoves and fuels (some markedly different)
can be tested in the lab to give realistic projections of fuel use and
emissions. It starts with doing what is shown in your first chart. Then the
cooking cycle complete with food, fuels and pots is reproduced in the lab.
The emissions are monitored while the stove is developed and when there is a
significant benefit, the stove can be put into the field. When the family
cooks their usual mean (the same one being investigated) the emissions are
measured again, as you have done.

Although the portions of the cooking (the burn) are not labelled, they
easily could be and the emissions from different firepower or activities
noted. Analysed separately, these can be used to produce a chart of the
emissions from that type of stove under different operating conditions - a
performance chart.

We are calling this a heterogeneous test protocol in that it reports on the
how a stove performs when used under different conditions. Someone else who
is using one or more portions of a well analysed test to reasonably predict
the performance during a cooking cycle that has not specifically been
analysed before.

It is important for people new to testing stoves that if one is measuring
the emissions directly from the stove, not the conditions in the room, the
chart should not show the direct measurement of the CO and PM, but that
number multiplied by the air factor prevailing at that moment. The reason is
that one cannot derive meaning from a CO measurement that has been diluted
by an unknown amount of excess air coming through the stove. The exposure in
the room is a valuable metric on its own. The measurement of the undiluted
emissions (determined by calculation) is relevant to the designer of the
stove.

Put simply, the former is a measure of the performance of the room and the
latter a measure of the performance of the stove. One could ventilate the
room and improve the 'system' without changing the stove at all. As a lesson
this could be titled "Stoves 001".

Regards
Crispin

We do use chimneys in our Tanzanian Maasai project stove.  You can see an
animation on the stoves page of www.maasaistovessolar.org
The Maasai live in unventilated homes and our sampling particulate and CO
meters show them burning wood indoors five or so hours a day. They need a
stove they don't need to tend while cooking as they sometimes simmer corn
and bean mixtures for hours.  The data page on our web site shows how
terrible their former way of cooking had been. Note they were near
symptomatic levels of CO.  One of the most important to the Maasai women
subjectively is no more smoke and soot around where it used to go out the
door.   There houses are clean. A nice improvement for them
Bob Lange
Sent from my BlackBerryR smartphone provided by Airtel Tanzania.
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