[Stoves] practical usere and boiling beans

Sun Dec 4 19:13:25 CST 2011

Dear Paal

It is this point (your last one) that I have been trying for two years now
to bring to your attention: the inclusion of the entire energy chain, as
well as the costing of the whole process.

Your point about turning down the charcoal stove is well taken – a stove
that has not ability to be turned down is not as practical as one that can
be, but if the cook chooses to move the pot aside instead of turning it
down, the usefulness of the invention is lost.

There are charcoal stoves that can be turned down, and simple ones, but
people do not promote them. People tend to promote whatever they invent or
represent, no matter how practical it is in the circumstances.

As you have reported several times, the Peko Pe can cook with a high heat
for some time (I understand it is about 30 minutes) followed by a lower heat
when burning the charcoal produced by the initial fire. Is this true?

This is perfect for a cooking task that requires this burn cycle. A ‘burn
cycle’ is the power and duration profile of a cooking event. Notice please
that I did not say the ‘temperature and duration’. The temperature of a fire
is not the same as the power because if the fire is very small or large, the
power is quite different even if the temperature is the same. This is an
important point that Roger was picking up when he first joined the stoves
group.

Now consider the cooking of beans as you described. The burn cycle should be
a larger fire to get the water boiling followed by a low power simmer for
several hours. If you used a Peko Pe this would be appropriate and one could
imagine that the cook would learn just how much fuel to put into the stove
to begin with in order to have the perfect burn.

What happens when the fire is not large enough to keep the simmering going?
Can you add some fuel and keep it going at a low power for another 2 hours?
Is there any control of the firepower or is it what we call ‘fuel metered’?
By that I mean the power is controlled by enough adding fuel at a time to
give the correct heat output to match the cooking need.

Generally speaking (and I think this applies to the Peko Pe) there are no
controls on a batch-loaded TLUD stove. The gasifiers that Paul Anderson was
promoting 5 years ago did, but I am not sure about ‘most’ of the simple
stoves. Controlling the primary air supply certain can control the firepower
during the initial part of the burn when creating the charcoal, correct? The
problem I see in practice (and it seems it will surprise you that I test
stoves with actual cooking) is that TLUD’s in general cannot be fuelled in
any practical sense. This makes it a problem to cook the beans. To keep a
fire going for a long time at a controlled heat is quite difficult. It is
common in Kenya for example for people to cook beans for 5 or 6 hours. The
beans can be softened by soaking them overnight but people cook them anyway.

With regard to your question about factoring in the loss of energy during
charcoal production (which could be used for cooking or some process heat
like drying mangoes or fish or generating electricity) and the transport: I
can recommend you study the calculations I have provided from time to time
to see how costs and energy are account for to see if you see a way to
improve the whole situation. Improving some part of it is not difficult and
I encourage you to continue to do so. 

What will be a ‘difficult sell’ for you and Otto is the idea that we should
be opposed to all production, transport and use of charcoal. It is easy to
be ‘against something’ but far more difficult to understand all the
implications of an entire fuel industry and food preparation industry to
implement radical changes based on an ideological opposition to a major
fuel. 

In closing I want to reiterate that there are charcoal stoves that can be
refuelled, turned down, that have low emissions, that can burn a wide range
of charcoals and they have some advantages people really like: high thermal
efficiency, high power, clean pots, low smoke, portability, low cost, and
local fabrication. These are very strong selling points.

If the fuel supply were improved instead of removed, the overall energy
chain is pretty attractive in some places. In other not. There is no ‘one
size fits all’. 

Suppose the water lily that is clogging Lake Victoria could be turned into
charcoal powder! That would be wonderful: a non-wood fuel supply right next
to a huge market in Kampala and it would turn a dreadful environmental mess
into a clean, valuable fuel.

Regards

Crispin

+++++

Dear Stovers and especial Crispin and Richard  

            There is a big difference between practical cooking and
scientific tests.

A cook used to cook on charcoal will automatically remove the pot from the
hot zone for simmering and will do the same while cooking on an el hotplate

We had that situation in a huge institutional kitchen in Uganda in the
middle of the 90ties.  11 of 12 five kWh hot plates were out of order due to
the fact  the cooks removed the pots for simmering and let the hotplate
glowing instead of switching down. I saw the same in Zambia in 2008. The
reason could not be anything else than the fact it is not possible to switch
down a charcoal stove.

Crispin is always talking about you are transporting more “mj” by
transporting charcoal than biomass. When 50-60% or even more of heat is lost
by the use, how do’s this occur on the transport costs at the calculation of
the efficient of the stove?

            Another thing, while cooking small quantities of beans 900 °C is
to hot and you have to constantly to ad more cold water due to evaporation.
How do’s that enter the calculation? To boil un- soaked beans on a TLUD-ND
like Peko Pe you will bring 1 kg un-soaked beans to a boil on the loss of
energy producing charcoal, and then continue simmering for two hours
directly on the charcoal produced emptied on a tray. How will that occur on
the calculation.     It’s the practical use, which are the reality and let
us have a real calculation based on all facts, losses and costs included, on
all levels of the process of clean cooking.

With regards Paal W

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