[Stoves] Testing stoves for their intended use

Crispin Pemberton-Pigott crispinpigott at gmail.com
Wed Jan 22 10:59:21 CST 2014


Dear Teddy

 

>This is indeed a very interesting issue you have brought up. Here are some
of my personal anecdotes in regards to this in Kenya.

 

You have run head-on into probably the most important need in the stove
sector: the need for a comprehensive toolbox of test methods, or the
principles for constructing them, within an agree framework of metrics and
definitions not only of performance but of 'everything'.

 

You have a string of products that are not well suited to a GACC-WBT or a
UCB-WBT and you are understandably frustrated by this.

 

Something to note (and this is good timing because there is a conference
focussing on Kenya in a couple of weeks) is that the tests I have seen
recently that were performed in Kenya at a university were done using the
UCB-WBT 3.0 from 10 years ago which I admit shocked me. There is no
meaningful way to correlate the calculated outputs of that test method with
either the GACC's 4.1 or 4.2 series (which themselves are meaningfully
different). 

 

So the question immediately arises: what test are you getting when you ask
for one? 

 

Re charcoal ovens:  Ovens have to be tested on cooking efficacy, fuel
consumption and emissions. There are several ways to do this and that will
have to be negotiated with regulator (presuming there is a desire to have a
national regulation covering them).

 

Charcoal ovens and in fact large cookers can be very efficient, thermally,
and might be efficient on emissions if they are properly ignited. I
occasionally invite people to calculate the whole system efficiency of the
energy available in a tree and the amount of cooking done with a wood-fired
device and the conversion of that tree into charcoal and used in a charcoal
burning device. Because charcoal can burn quite completely in a very low
excess air environment, the heat transfer efficiency to an oven can be above
90%. This is most easily determined using a combustion analyser though it
can be calculated using individual CO, CO2 and O2 cells and a thermocouple,
applying the Siegert formula.

 

Together with the CO/CO2 ratio and a fuel consumption rate per hour, you
would have a very good assessment of performance in continuous operation. As
you can imagine, using a 'task-based approach' to a bakery is inappropriate.
That is where a testing toolbox is really helpful. You would have in the
toolbox validated procedures for measuring the CO/CO2 ration, for example,
and apply it. You would also find a validated method of measuring fuel
consumption with definitions and metrics. Applying that would give you a way
to evaluate the product over a typical day.

 

Typical in every case means according to local practices and conditions. A
test intended to rate relative performance if only meaningful in a context.
Thus the test should be relative to the general conditions prevailing either
in Kenya or the region where the product is used. If it is a bread bakery
that operates 10 hours a day that is pretty common and would delineate the
burn cycle (including refueling).

 

Im thinking we just roast chickens and bake bread, but I imagine that would
just be more delicious then scientific. 

 

There is nothing that prevents you doing proper measurements and using
appropriate metrics. Using the relevant set of 'sub-tests' from the stove
testing toolbox, you would construct (or they would) a protocol that
consisted of validated elements. If the test is created using valid tools
then the result, calculated using validated methods and metrics, creates a
scientifically valid report.

 

Work on such a toolbox has been going on for some time. A presentation was
made on the progress at the GACCC conference in Phnom Penh in March last
year.

 

Then there also is the issue of how in the world do we begin to afford test
the other products (that are already being copied by jua kali) like the .

 

Tests cost money. What we all need is a test that is relevant to the product
and which reports what the performance will be in use in the target
community, which might be al the baker all the urban food vendors and so on.
One stove test does not fit all products any more than one food satisfies
all palates.

 

This is considering that the charge appx. 60,000ksh (700USD) per test and
they take months and will probably need to be individually designed etc.  

 

Once a test of a product type has been constructed, it is a matter of
applying it. The $700 figure is realistic.  A rough guide is that a testing
facility has to charge about 1% of the value of the equipment used per day.
Equipment has to be calibrated. A certification level lab will spend about 1
full day per week only on system calibration. Measuring relative performance
is much, much cheaper and requires much less expensive equipment. The
testing toolbox could contain procedures for both.

 

We try our best with our own in house testing (largely based on things iv
learned from my dad and the bioenergysite info) and we work hard with our
customers who after all, more or less are the ones who fund, design, test
and market our new products.

 

If you want to test on an individual scale you need a scale, a combustion
analyser, some thermocouples (two at least) and some training. Training is
occasionally available at the SeTAR Centre in Johannesburg on how to do
this. We have trained people in 7 universities (at least) but the most
northerly was from Dar es Salaam.

 

And one last small thing is the testing of the KCJ... how is that inevitably
the particular KCJ tested always somehow seems to be the one that looks like
it was made by a drunk fundi using old rusty sheet metal and then run over
by a herd of cows and was lit using wet charcoal? 

 

Again the question arises as to which version of which test, and what was
the intended use of the result?

 

Was the stove dried (fired) before testing? Did the test protocol include
the ignition emissions in the overall result? I heard that some tests are
omitting the ignition period, using only the emissions from when the pot is
placed on the stove. Obviously this gives an inaccurate answer to the
question, "What is the cook's exposure to emissions?"  As you will be aware,
not all IKJ's are created equal. And it is so easy to improve an IKJ! The
shape of the ceramic chamber is awful and the holes are too big and ...
another time.

 

If anyone on this listserve would like to test a real original Kenya Ceramic
Jiko, made to the exact original specs, please contact us to get one on
loan, completely for free if you pay shipping. (and testing.) 

 

Well, which test, and to what would you compare the 'result'? An IKJ is
reasonable, but the ignition method is going to improve/worsen the emissions
far more than small variations in shape and size. Try lighting it with an
ignition cone and drop the smoke total 50%. Then all you have to do is
quibble about durability.

 

Regards

Crispin

 

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