[Stoves] Adjusting the stove to the cook and the cook to the stove options

[Thomas Reed]

Dear Dean and Stovers:

Dean's description of matching the stove to the cooks needs sounds like 
a long task. Obviously we must match the stove to the cook's needs, but 
maybe not her prejudices. So, should we try to match the stove to the 
perceived needs of a primative cook who has had to adjust to terrible 
fuels and a mother-in-law recommending the old ways?  OR to a housewife 
in developed countries who knows the options and picks her favorite?
------------------------------------------------------------------------
We did this adjusting of cook to stove between 1800 (cooking in 
fireplaces) and 2000 in the US and Europe.  In 1800 Count Rumford 
(Benjamin Thompson) observed that the stoves available "cooked the cook 
more than the food".  He built the first range for cooking (a 
plancha/stove/heater).  Since then we have been continually improving 
the stove by continually developing better wood, then coal, then gas, 
then electric stoves.  The modern housewife has a lot of choices and is 
completely spoiled, but we must presume that the stoves on the market 
satisfy her needs.

In the developing countries we need to bring as many advantages as 
possible to the cooks, but with alternate fuels. That is why we have 
focussed on WoodGas stoves.  They give the advantages of "cooking with 
gas" while using locally available trash fuels.

Most stoves in developed countries have two small burners (~1.5 kW) and 
two large burners and use gas or electricity. So this would probably be 
suitable for developing countries if it could use wood, pellets or 
chunkettes.  The Ward stove is the closest approximation to this for 
wood that we have seen.  (See 
http://picasaweb.google.com/tombreed100/WardStove )

Yours truly,

TOM REED          BEF

Dean Still wrote:
> Dear Charlie,
>
> This reply will be short because I'm heading out of town. I don't type as
> fast as you do, anyway.
>
> So, in my opinion:
>
> 1.) When we start designing a stove we build a prototype after checking with
> local cooks to see what they want. Checking with the local cooks takes as
> long as needed or as much time as we have (weeks to months). The prototype
> starts with equal cross sectional area. Then we test it (WBT) under the
> emission hood changing the gaps. This can take weeks or longer until the
> stove has the best balance between fuel used, CO and PM to boil 5 liters and
> simmer it for 45 minutes. We use both the standard 7 liter flat bottomed pot
> and local pots. If we notice a big difference we design the stove to best
> suit the local pots, like round bottom pots in India.  Also using the
> standard pot gives us a way to compare the stove to make sure it is as good
> as other similar stoves.
>
> 2.) Then the prototype is given to local cooks to get their input using
> local food, local wood, local pots, etc. (CCT) The feedback is then
> incorporated into a new prototype which is tested as above. The process goes
> back and forth between WBT and CCT until the stove pleases local cooks and
> also uses less than 850 grams wood, makes less than 20 g of CO, and less
> than 1500mg of PM. So we and funders can feel confident that we have an
> improved stove.
>
> Durability of materials is harder. If you can throw a super heated floor
> tile into a cold bucket of water and it doesn't crack it will probably last
> long enough to please folks. Great if you can make the floor tile combustion
> chamber easily replaceable.
>
> Testing, developing of prototypes in the field determines gaps, materials,
> configurations. If we don't have a way to test emissions, then using the CCT
> to compare new and traditional stoves is great too. In my opinion, the new
> stove should improve fuel used by at least one third to one half and make
> considerably less observable smoke. The cooks should hopefully want to take
> the stove home without a rich funder standing close by with possibly more
> goodies, etc.
>
> Best of luck, my dear friend!
>
> Dean
>
>
>
> -----Original Message-----
> From: stoves-bounces at listserv.repp.org
> [mailto:stoves-bounces at listserv.repp.org] On Behalf Of Charlie Sellers
> Sent: Wednesday, August 08, 2007 10:35 AM
> To: Discussion of biomass cooking stoves
> Subject: Somewhat urgent question¿ Interior ross sectional area of a plancha
> stove.
>
> I can get to town/electricity every few days and am on line on and off for a
> few hours right now.  The dimensions of our planch stove design here in Peru
> are somewhat limited by the dimensions of the types of hollow brick
> available (I can only cut tile - or break bricks in a clumsy fashion - and
> have only simple tools) so various dimensions of the stoves are limited.
> Particularly the chimneys - only scrap iron pipe or stacked hollow bricks
> are here - so I want to be a little flexible in the open area of the stove
> at various places in the cross section.
>
> One šrulešof the rocket is constant cross sectional area throughout the
> stove but it seems that the exit/chimney really only needs a larger area
> than the rocket entrance - true?  I use the analogy of a river flowing into
> a new channel - if the area diminishes then smoke backs up into the room.
> And if the new channel is smaller then the flow out needs everything is
> fine.  And if there is a temporary wide spot inside the stove then there is
> no problem, as long as the exit is larger than the entrance?
>    
>   I am trying to increase the size of the combustion chamber as much as I
> can, since the plancha will slow the time to boil (and other perceived
> problems), to increase the firepower a little.  But I only have limited size
> possibilities for either the entrance and exit, and I donŽt yet know how to
> exactly take into account that there is an expansion of gas as it heats, and
> there is a net increase in gas volume during combustion.  How does the equal
> area rule take such things into account¿  I am taking some risks, but as
> long as I increse the chimney area I hope to be fine.  As always, I want the
> best conditions to increase the burning of the smoke before it leaves.
>    
>   Any advice on whether commercial floor tiles can generally be the walls of
> the combustion chamber¿  What exactly is baldosa tilešš - specifications¿  I
> tested mine (and also the hollow bricks) in a very hot fire with no
> problems, but success in the longer run is too important to take too many
> risks.
>    
>   thanks in advance!
>    
>   Charlie
>    
>
>
> http://improvedstoves.blogspot.com/ - just R&D related to fuel efficient
> biomass stove issues
>   http://travelswithcharlie.blogspot.com/ - most recent travel posts
> http://new.photos.yahoo.com/csellers42/ - travel photos, of everywhere -
> click on the country albumns on the left
> http://huiplesofguatemala.blogspot.com/ - my textile project in Guatemala -
> what colors!
> http://travelswithcharlie2.blogspot.com/ - older travel posts, including
> Nepal travelogue 
> http://ewbappropriatetechnology.blogspot.com/ - just posts for the ATDT of
> the EWB-SFP; AT for developing countries
>
>        
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