[Stoves] Cooking by conduction - plancha stoves

Sat Jun 17 17:10:07 CDT 2006

Dear Tom
----- Original Message ----- 
From: "Tom Miles" <tmiles at trmiles.com>
To: "'Kevin Chisholm'" <kchisholm at ca.inter.net>; "'Sebastian Africano'" 
<seburbanismo at yahoo.com>; "'Miranda, Rogerio'" <RMiranda at winrock.org>; 
<STOVES at LISTSERV.REPP.ORG>
Cc: "'Sebastian Africano'" <seburbanismo at yahoo.com>; "'Josh Heyne'" 
<heynejos at gmail.com>; "'Marlyng G. Buitrago Santamaria'" 
<mbprolena at hotmail.com>
Sent: Saturday, June 17, 2006 4:06 PM
Subject: RE: [Stoves] Cooking by conduction - plancha stoves

> Kevin,

> I don't understand your question or commnet. Dean, Sebastion and Rogerio
have given us good anecdotal decriptions of how rockets, ecostoves and
rocket planchas are used. They are not saying that "it is hopeless to try
and compare stove performance and to get an indication of the heat energy
required to cook a meal."

Referring back to my original question to Rogerio:

"> You mention that the Ecostove requires less than 2 kG of wood to prepare
> a meal of 3 to 4 dishes in less than an hour. How many people would this
> meal feed?

Rogerio could have replied:
"4" (or whatever)

This would give a general perspective that the EcoStove needs about 0.5 kG 
of fuel per person per meal (if the number of people fed was 4)

Now if the particular example that he was referring to was exceptional, he 
could have included qualifing comments, such as: "The Cook was making 10 
litres of stew in that pot", or "The wood used was very poor quality" or 
whatever. Instead he tells us about its capability to cook for 30 people 
under unusual circumstances.

The next time I expect 30 NGO officials to visit me, I will be sure to have 
an EcoStove on hand. :-)

> As Sebastian has illustrated the performance (energy efficiency and
emissions) of any combustion device depends on the fuel, the design of the
device and how it is used. Benchmark conditions, where you normalize the
fuel and the operation, are extremely useful in developing better devices.

Exactly!! Don't you agree that knowing the typical grams of wood required 
per meal would be an excellent starting point? Obviously, this would vary 
depending on the nature of the meal, the number of portions being served, 
whether the stove was lit for the meal, or if it was kept hot all day, etc.

> Eventually we will find the range of variation between the lab testing and
field use. Discovering those gaps should allow us to make better estimates
of fuel use and potential reduction of resource depletion in a given area,
while improving health in the cooking environment.

It seems to me that there is a huge gap between the theory and test work of 
the Lab, and reality. Reality almost always gives worse results than that 
the Developers indicate. Why not "close the loop" and relate actual 
performance? How do you start to find "the range of variation between the 
lab testing and field use."? I would suggest that we start by finding 
information on field use.

The question of improving health in the cooking environment is another 
issue. That, in my mind, is not an issue here... simply use a chimney to 
vent the noxious gases from wood burning outside. The Archives of 5 years 
ago will show that I was advocating the use of chimneys and exhaust hoods as 
a way to markedly improve, or eliminate, the serious problem of Indoor Air 
Pollution caused by stoves which vent directly into the cooking space. The 
problem of IAP is virtually a non-problem, if stoves are designed to 
accomodate a chimney.

> Comprehensive studies,
like the "Integrated Patsari Stove Monitoring Program" will give us those
answers. See:
http://www.bioenergylists.org/stovesdoc/ETHOS2006/Patsari/PatsariETHOS2006.p
df

It appears that the study is designed to show the strengths and weaknesses 
of the Patsari stove. It would not necessarily show that a different stove 
philosophy was more appropriate.

> In comparing cookstoves we are looking not only for absolute improvement 
> in
performance but for relative improvement. CFSP, for example, has adapted the
water boiling test to suit their conditions in Cambodia. They have said that
their modification is better for demonstrating relative improvement in
cookstoves in their circumstances.

That is very good, but then that is a different issue also. Such testing is 
great for improving their basic stove system, and it permits "in field 
improvement".

>Look at Aprovecho's modification of a charcoal stove. Does it matter 
>whether
it actually takes 21,000 kJ of charcoal to perform a defined cooking task
(WBT)? Or does it matter more that by using the benchmark Aprovecho
demonstrated a relative improvement in CO reduction (75%), time to boil
(24%), fuel efficiency (13%)and PM (5%)
http://bioenergylists.org/en/node/551 Even if the measure of charcoal use is
off the improvements are useful.

Stoves can be designed to score high in the Lab, or with WBT's, yet perform 
relatively poorly in "day to day" use.

> There is already a wide menu of stoves. To name a few see
http://bioenergylists.org/en/stoves

Wouldn't it be neat to be able to compare this wide variety of stoves based 
on their energy performance? Within different Cultures, a "standard" meal 
could be configured, and the "energy per meal" could be reported as a way to 
compare stoves for a similar task.

> The important questions are really what stoves are appropriate for
particular sites, application and circumstances and how can those be
modified to improve performance, reduce fuel use and improve health.

EXACTLY! A stove that can cook for 30 is not likely to be as good for single 
family use, as would be a stove designed for single family use. The "energy 
per meal" is a real "bottom line indicator" of real world stove performance.

Best wishes,

Kevin

Tom

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Kevin Chisholm
Sent: Saturday, June 17, 2006 10:58 AM
To: Sebastian Africano; Miranda, Rogerio; STOVES at LISTSERV.REPP.ORG
Cc: Sebastian Africano; Josh Heyne; Marlyng G. Buitrago Santamaria
Subject: Re: [Stoves] Cooking by conduction - plancha stoves

Dear Rogerio and Sebastian

So, basically what you are saying is that it is hopeless to try and compare
stove performance, and to get an indication of the heat  energy required to
cook a meal. You seem to be saying that it is a hopeless issue, and that it
is not possible to get a reasonable indication of how various stoves perform
in a similar situation. You seem to be bringing up exceptions and obstacles,
rather than looking for a way to find a solution.

I would suggest that any stove that is capable of cooking a meal for 30
people is inappropriate for a small family. The Ecostove seems to be more of
a commercial cooker or "small institutional" cooker, rather than a Family
Cooker. Obviously, if it is big and fast enough for a commercial or small
institutional application, it is oversized for a small family application.

Obviously, if there were "good guidelines" for how much biomass was required
to good various foodstuffs, this would be a great help in determination if
one stove system was better for a given application than another.

What about basic guidelines, such as
"A serving of Food "A" requires "X" grams of biomass"

for various foods. Obviously, these numbers would vary as quantities
prepared at one time varied. Perhaps there could be several classes:
Single Family
Small Institutional
Commercial
Other?

It is not helpful to simply shrug our shoulders and say "It can't be done."

Best wishes,

Kevin

----- Original Message -----
From: "Sebastian Africano" <seburbanismo at yahoo.com>
To: "Miranda, Rogerio" <RMiranda at winrock.org>; "Kevin Chisholm"
<kchisholm at ca.inter.net>; <STOVES at LISTSERV.REPP.ORG>
Cc: "Josh Heyne" <heynejos at gmail.com>; "Marlyng G. Buitrago Santamaria"
<mbprolena at hotmail.com>; "Sebastian Africano" <seburbanismo at yahoo.com>
Sent: Friday, June 16, 2006 4:54 PM
Subject: RE: [Stoves] Cooking by conduction - plancha stoves

> Greetings - this is Sebastian from Honduras.
>
>  All these numbers also depend greatly on the type of firewood used and
> the state it´s in when used (girth, dampness, etc...), as well as the type

> of food cooked.  There are so so many variables that we can´t just tack
> numbers together for a fuel:food ratio.  One example, we have 2 ladies
> that cart an EcoStove around in their pickup truck and sell pupusas on
> street corners(a stuffed tortilla treat, directly on the plancha).  From
> the time they spark the match, they´ve sold their first pupusas in 10
> minutes.
>
>  With pots, heat transfer does take longer - you have to get the plancha
> up to a high temperature before it can transfer heat adequately.  But once

> it´s up to temp, you can keep pots of food hot for an hour, and warm for 2

> hours with just the coals from the fire.  Even better, you can dry your
> wood on the warm griddle overnight to use the next morning.  Frying isn´t
> a problem in flat bottom pots and pans, but ladies that fry food for sale
> typically do it in a round-bottom, wok style pot, that doesn´t work at all

> with planchas.  There I would recommend another model which exposes the
> pot to the flame.
>
>  With the Rocket Plancha stoves, I´ve cooked a large pot of hearty
> vegetable soup with tortillas on the side using pine cones, corn cobs and
> coconut husks as fuel - probably as 60% of the fuel mix, with wood making
> up the other 40%.  If we can get people to cook in this way, the answer to

> the fuel:food question would be, "not much firewood at all..."
>
>  The ticket, as Rogerio mentions, is using the plancha as a complete
> tool - cooking on the hot spot and preheating or maintaining foods hot on
> the rest of the plancha.  Boil your rice, then slide it to the back to
> simmer.  People here cook a huge pot of beans for the week, and then they
> only have to reheat them, which doesn´t take long at all.  Many folks cook

> a big pot of corn daily for the next days´ tortillas, but will typically
> put it on after dinner, when the plancha has been heated all day.  Since
> the custom here is to keep a stove lit from 6 - 16 hours straight, a
> plancha stove remains the healthiest and most economic option for cooking
> lots of food over long periods of time.
>
>  All the best,
>
>  Sebastian
>
>
>
> "Miranda, Rogerio" <RMiranda at winrock.org> wrote:
>  Kevin:
>
> When I was living in Brazil, at my home there every day my cook Lucia
> used the Ecostove to prepare our meals. There usually I had 6 to 7
> people for lunch.
>
> While I was in Nicaragua, one day we invited 30 people from NGO's for a
> demonstration, and our cook there Luiza cooked rice, beans(with pressure
> cooker), fried platanos and meat in one in a half hour for this big
> crow.
>
> With the Ecostove in general does not matter how many dishes or how many
> people are you feeding, because once the griddle is hot it accommodates
> small or larger families easily, given that it has a wide cooking
> surface (56 x 56 cm griddle). So, of course as much you cook using the
> griddle surface, more efficient the Ecostove will be at the end of the
> day.
>
> Rogerio
>
> -----Original Message-----
> From: Kevin Chisholm [mailto:kchisholm at ca.inter.net]
> Sent: Friday, June 16, 2006 11:21 AM
> To: Miranda, Rogerio; STOVES at LISTSERV.REPP.ORG
> Cc: Josh Heyne; Marlyng G. Buitrago Santamaria; Sebastian Africano
> Subject: Re: [Stoves] Cooking by conduction - plancha stoves
>
> Dear Rogerio
> ...del...
>
> Thanks very much for your information on cooking temperatures for
> Tortillas.
>
> You mention that the Ecostove requires less than 2 kG of wood to prepare
> a
> meal of 3 to 4 dishes in less than an hour. How many people would this
> meal
> feed?
>
> More particularily, I am interested in getting a general perspective on
> "How
> much fuel wood is required to prepare a meal?"
>
> This would be a very practical way to compare "real world stoves."
>
> Best wishes,
>
> Kevin
>
>>To cook tortillas you need around 200 C to cook it well. To test a
> stove
> to see if it is hot enough for tortillas, throw drops of water on it,
> and the water should jump and evaporated immediately, that is when you
> are about 200C.
>
>
>
>> As for real cooking the Ecostove reaches between 350 to 500 C on the
> center, while goes down to 200 on the edges. If you have 400 C, you
> should be Ok, 500C usually is overheating, which is not good for the
> griddle in the long time.
>
>
>
>> The trick with the Ecostove is that you should have all your pots on
> top
> of it, pre heating, while the main dish being cooked on the hottest
> spot. Usually the Ecostove can deliver a meal of 3 to four dishes in
> less than an hour with 2 kg or less of wood.
>
>
>
> Rogerio
>
>
>
>
>
>
>
>
>
>
>
> ---------------------------------
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