[Stoves] Understanding Stoves

Crispin Pemberton-Pigott crispinpigott at gmail.com
Sat Dec 10 22:55:07 CST 2011


Dear Xavier

Things are going well I see.

Although the institutional stovers you make are portable (for distribution)
it is not necessary that they be moved much once they arrive at their
destination.

We found in Swaziland where people are not tall and the cooks are often
teenagers that access to the pots was important. The height of the stoves
that hold a 70 litre pot is not really reducible. Thus we build a step
beside each stove, at least two, from concrete blocks or recycled bricks. It
happens that stoves are often installed in pairs so the steps are usually
placed between them allowing access to both stoves.

There is often a third step. That is used for place the smaller pot for
serving. The smaller pot is put on top of the top stair and the food is
scooped from the 70 litre on into the smaller one. It is at just the right
height being on the top stair.

When it is necessary to lift out the pot, people climb the stairs and stand
on top of the stove. In your case that will not be possible but you could
still use a fixed concrete/brick construction to make it much easier to
service the stove.

When making the top stair check the height of the 70 litre pot and the
height of the smaller pot and make the stair suited to keep the tops at the
same level. That way it is the least effort with the least spillage.

Regards
Crispin


+++++
I found the review of the stoves principles by Dr Sai Bhaskar Reddy Nakka
just great. This is what every person beginning with stove design should
read. Because this person will necessarily face one of the problems
described, if not all.

Yes, height is the major concern for institutional stoves, so I discovered
also. I also have been progressively paying attention to the size of the
cooks, the length of their spoon, the height of their small wooden bench,
etc. The size of the earth stoves they use already : 80 cm from the ground
to the top of the pot/surface of the water. Our rocket stove for the same
size of pot was 93 cm to the top of the pot. The women also have trouble
carrying the heavy pot full of water over the tall skirt. They even needed
to put the pot on the skirt (which if fortunately a double-skirt), and then
in the stove. On the contrary, their traditional earth stoves are 50 to 60
cm high. Very practical. Our biggest stove is, or was, 110 cm high!

We decided to reduce the space between the stove and the ground, the space
and insulation under the combustion chamber. We reduced the chamber of
1/5th. Our tests showed similar performances than the normal-sized stove in
terms of time and fuel efficiency. There wasn't more smoke, but we didn't
have the instruments to measure the gas emissions. We managed to reduce size
by about 15 cm, much to do still.
The best technique I saw: the pot is put empty on the stove, filled with a
waterhose, and emptied in small containers on a trolley.
While writing this email, I am thinking: any way to make a removable skirt,
so it is more practical to move the pot in and out of the stove? But then I
am not sure removing the (greasy) skirt is very practical either ...

Regards,

Xavier





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