[Stoves] Peru Stove Projects?

[Crispin Pemberton-Pigott]

Dear Laurie and Steve

Thanks for 'going on' as you did. It was informative and 'real world'.

I want to draw your attention to:

>(d) finally the metal rocket, for the folks who did try 
>to use the stove properly, developed holes in spite 
>of its thickness and weight of 7 kg.  

If you put anything vaguely insulating behind a combustion chamber made of
metal, is it not going to last, even though cast iron, in this case, should
normally last a century.

As you apparently have access to a cast iron combustion chamber, there is
something you can do with it, actually two things:

1.	Build the stove with air that enters behind and below the combustion
chamber, air not to enter in the same direction as the fuel;
2.	Make it so that the air that gets there passes around the combustion
chamber wall cooling it. This will lower the temperature of the metal and it
will last much longer, possibly decades in the case of cast iron.

The heat that is pulled off the cast iron increases the temperature of the
air that goes to the bottom of the fire. This is called Primary Air or Under
Air as it comes from underneath. The heat is not lost, it is carried back
the fire so there is no loss of heat, but actually provides two benefits.
First, conservation of heat and second, you can always burn damper wood
better if the primary air is heated.

In a cold climate this is an important way to reduce emissions as it
increases the temperature of the fire, providing again, two benefits: lower
particulate matter and lower CO.

I am very please to hear you might be using a brick chimney (I think it says
that in your text) because metal is often sold or used for something else as
chimneys are new to many people. Later you write:

>we have a local welder who has made us chimneys and 
>grates, and painted the part of the chimney that is outside 
>with a waterproof paint.

The change of location seems to be using metal chimneys. These can be
changed to small brick ones, not metal. It is important that the chimney not
be large in cross-section (as many assume it should be). The inside diameter
(square) can be 3 or 4 inches. Don't make it huge. Too much cooling surface
takes too long to get hot on the inside surface. In a  cold climate, a mud
chimney can work better than a metal one because it doesn't get as cold
towards the top from heat loss. Put the metal cap on top, or a flat rock
with a cross-gap underneath (not one side).

>...and the retention cooker and various other things aiding 
>in improved hygiene.

Good for you. Remember that the retained heat cooker (RTC) can be a box
under the end of the stove that has no fire box. It can be constructed with
a plancha on top passing over the RTC - a sort of oven that is not really
heated by the fire, but the stove body can act as additional (hot)
insulation.  Cheaper, better.  

As far as I know there is no version of the Onil Stove (or similar) that has
an RTC in the 'far' end of the stove, but you can do it, easily, and three
of the sides are already in place. It is often hollow so put the RTC in
there.

>soon we will be posting pictures on our blog and also the 
>design of our stove and the survey tool.  
>the address is http://pencilsforperu.blogspot.com

Great!

For an example of how to use bricks to bring air behind and under the fuel
entrance, have a look at
http://www.newdawnengineering.com/projects/probec/lionstove/ 

It is not what you are making, but you can learn from the design and 'make a
plan' (leave a lot of things off). You can test any layout by just laying
bricks on the ground and then lighting a fire in it. If a design looks
promising, put a little mud on the joints and try it again. You should be
able to make a great stove with less than 100 standard bricks.

I am jealous that you have access to cast iron chambers! Try for a cast iron
grate as well, using the chimney money saved by using mud bricks. It will
last a lot longer (because it is cooled by the air supply).

Best regards
Crispin

Sustainable Energy Technology and Research Centre (SeTAR)
Johannesburg