[Stoves] Test methods for cook stoves

Crispin Pemberton-Pigott crispinpigott at outlook.com
Thu Mar 19 14:35:27 CDT 2015


Dear Frank

>
stove has been made a ‘better stove’ it is sent to the independent Stove
Lab for testing and compared to the other stoves. This is the only fair way
to do this and until the stoves are tested this way there will always be
suspect and bias. 

You are on the right track vis-à-vis the testing of labs to see that they
can ‘do it’. No problem. I have only heard of one attempt to compare stove
labs and the result was not good.

 

Testing stoves is another matter.  Biomass stoves are not like liquid fuels
stoves because the fuel is completely different – it burns inhomogeneously
and what is left over is not ‘raw fuel’ as is the case with a kerosene
stove. It is not like vehicles either because cars don’t produce charcoal. 

 

Like cars, there is a start and warm-up cycle which has to be included in
the test because that is part of real life. Power stations and fixed
boilers, however, are usually run continuously and testing them under
‘constant conditions’ is the norm (and is reasonable). 

 

Stoves are almost never run continuously and certainly not at a constant
power. Thus performance needs to consider not only the starting cycle, but
the running cycle with its ups and downs. When testing vehicles, this is
done: the car is put through a driving cycle on a test bed. It does not have
to go on the road because the road slope and the power requirement can be
modelled and reproduced in the lab. All Formula 1 cars are set up this way,
per race. The fuel loaded and suspension and wing settings are tuned in the
lab to the track conditions. The engines are tested by computer operated
servos while bolted to a frame, not even in the car! The engine and gearbox
are ‘run around the circuit’ for a whole race to see if the gearing is
correct and how much fuel is needed.

 

Sticking with that analogy, we can test the stoves in the lab using known
conditions and requirements of the ‘real track’. Each race track has a name
like Indianapolis which represents it cycle of distance, speed, elevation
changes, acceleration and braking requirements.  In vehicle testing each
driving cycle is given a name and number and represents a different type of
use.

 

There is no point in comparing the performance of an F1 car set up for Monza
with a car set up for Monte Carlo. You can do it, but it is pointless.  It
does not predict performance on any other track and the teams are well aware
of this so they don’t do it.

 

You cannot pick one race track and say every car must be compared using that
track. Which track? Where is the ‘average track’?  The reason is obvious: a
car can be tuned to the test track, say, a dirt oval in Charlotte, North
Carolina, and get an optimal result, yet in real life it will be used as a
taxi on tar roads in Jakarta. If you want to test cars that will be used as
a taxi in Jakarta, you should use a Jakarta driving cycle, and proper tires.

 

The core lessons are: 

-          A test protocol can be created that captures the performance no
matter what the track or conditions.

-          Sets of conditions – cooking cycles or ‘burn cycles’ – can be
described and named or numbered. 

These ‘conditions’ are not part of the protocol. The protocol is the
measurement and assessment tool. The conditions are from the list of
available, properly characterised cooking cycles.

 

Comparing performance means comparing stoves doing the same thing – this is
agreed. However it should also be agreed that having everything race on a
dirt oval in North Carolina is not an appropriate way to characterise the
performance of a Jakarta taxi.

 

Innovation:  A motorcycle may far outperform any Jakarta car-taxi, and that
is why there are taxi-motorcycles in Jakarta. If the goal is to use less
fuel, take a motorcycle. If the goal is to stay dry, taker a car.  Customers
(and cooks) have different goals. We have to measure appropriately and use
relevant conditions when stating comparative performance.

 

It is how everything else is done, so why not stoves?

 

Your fan

Crispin

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