[Stoves] burning rice husk

[Crispin Pemberton-Pigott]

Dear Christa

 

>There are other initiatives to make stoves based on the approach Alexis has
taken. Paul has other models that show some promise as well.

CR: Which Paul do you mean? I was talking of Paul Olivier below, who has
taken Belonios concept to a new era.


Yes I meant Paul Olivier. I have been assisting him on the QT. The new
secondary air heating system looks promising. The main advantages are that
the flames are initiating much close to the pot centre, the excess air
could/should be reduced a lot (which is a big problem with Alexis' version
of the stove) and there is less total material.

 

>The Mayon Turbo Stove is not perfected yet and I don't think much is being
invested in trying. It holds promise from the point that it does not require
a fan. I worked on one here (in Waterloo) earlier this year together with
two interns from REAP.  We doubled the overall efficiency but created new
problems that it got too hot. It needs additional work to keep the fuel
cool. There are of course other ways to burn the fuel with natural draft.
Maybe with the advent of cheap power from TEGs we will all make fan stoves
and not worry about natural draft any more.

 

>The MTS has the important advantage that is can be refuelled continuously
at your convenience. It does not need to be loaded in batches.

 

 

CR: But the disadvantage I noted is that it needs a lot of attention: we had
to tap the stove every two minutes last year in Belchertown with the
colleagues from REAP to assist gravity and make the rice husks fall down,
otherwise there was no continuous feed adn the fire would go out. Maybe that
'spoonfeeding' can be reduced with skills and acquired habits, but as an
unskilled user I found it rather inconvenient.

 

I completely agree with the assessment. The user convenience is an issue and
it needs to be worked on. In the same way that several of the more promising
devices seen in the past few years, it will work much better when some
effort has been put into refining the principles. Several stoves work in
principle and that has been demonstrated.  The no-fan option for rice hull
stoves is a very attractive alternative for rural manufacture. In principle
I like the idea of having the fuel enter from a single point instead of all
around so that a smaller quantity is heated by the stove body at a time, and
that it feeds in at a higher rate at that single point. This will help to
keep the fuel temperature down. The heating issue came to the fore when the
interns went to the Gambia and set the fuel hoppers on fire! I had reduced
the (very high) excess air to the point that the heat transfer efficiency
doubled (!) but the result is that the single layer combustion chamber
overheats the fuel. Oh well! It needs a longer re-think than the two days we
had available. I made 4 changes to it but it looks pretty much the same.

 

Actually it works really well as a natural draft pellet stove, if anyone
wants to try it. I found the best size is 6 or 7mm. It might do well with
5mm which is hard to burn in a regular stove, even a TLUD without a fan
because it packs so densely. The frequency of tapping is greatly reduced
with the denser fuel which addresses your main complaint.

 

Regards

Crispin

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