[Stoves] Designs

Mon Aug 7 09:43:58 CDT 2006

Dear Dr. Tom Miles,

Thanks for the e-mail intending to get in touch with me. My own interests
in stove designs is at least 24 years old. I was spending time intensely
on stoves till about 1990 and shifted to looking at gasification for
thermal and electrical applications. This has occupied (in the midst of
aerospace activities and teaching) most of the time till recently. It has
got rekindled with the invitation of ARECOP for the training program at
Kunming. I had occasion to seriously examine the stove developments
through the Bio Energy Lists website operated and maintained by all of
you. I must express my appreciation for this effort on maintaining the
website.

Regarding the Swosthee stove about which you have specific questions - 
About a thousand were built during 1990 - 1884 and field tested. The key
problem has been the life of the stove. Because the inner metal walls
experience temperatures of 750 to 1000 C, the hardware lasts only a few
months. One of the key things that we uncovered in this period was that we
cannot get higher effioiencies unless the air-to-fuel ratio is close to
stoichiometric value. It was also clear that any of the stoves that
utilized free convection process for delivering the air won;t be able to
maintain the correct air-to-fuel ratio for the duration of the operation
of the stove. This is the reason that further development in this
direction was not pursued, We examined the possibility of using a fan to
deliver the air, some thing that we did in laboratory experiments to
determine the role of air-to-fuel ratio. Unfprtunately, during 1990 to
1994, there was no cheap harware for delivering the air at a fixed flow
rate. And even after we saw the fixed fuel stove with Dr. thomas Reed in
1996 or so, we could not identify for a long time a reasonable source of
fans. It is only in the last three years that computer fans that are
really cheap have arrived in the market. This as given life to the reverse
downdraft stoves all over the place. We have done some serious scientific
study over the last four years and uncovered features of the stove that
will give high efficiencies. We have been able to get up to 55 % thermal
efficiency through various optimization strategies. We are still exploring
how to get up to values in excess of 60 % particularly because the
kerosene and gas stoves promise 70 to 75 % efficiency. This has ben our
aim over the last twentyfour years.

The meeting at Kunming was very interesting. I met with three stove people
from US working on stoves for long time. What became clear to me at the
end of the workshop is that very few have clue to the science and
technology. They are genuine enthusiasts and other people. As soon as they
see something working, they want to ruch and adopt. For instance, at a
factory in Kunming, every body saw a beautiful concept on steam injection
to obtain clean combustion. Almost the next day some wanted to introduce
it into their designs without (a) really understanding how things work
or(b)care or sensitivity to intellectual property protection aspects. This
is a tragedy that stove enthusiasts have to face.

I was told in addition, that a stove performance test protocol was being
developed at Berkeley with the support of many people. After some
conversation I learnt that serious sceintists are not involved in this
activity. A set of data that were presented that showed the amount of fuel
required to heat 5 L to boil and associated emissions, in my view is very
faulty as the power level is not a subject of consideration. Th epower
level makes a seroius differnce to every thing. I also explained in a
strong way that neither candle nr a furnace can be used for deriving
cooking heat and I do not know if it went across.

In summary I have concerns on less-than-scientifically correct input going
into the stove design aspects. I have just expressed it to you here.

We will continue our efforts to produce a high efficiency clean burning
continuous feed biomass stove in coming times.

I will be happy to interact with you or others on any scientific aspects.
The paper that you enquired is available on a web site for downloading. i
shall intimate you the address on Monday/Tuesday.

I am sorry for the long mail and Thanks for the inspiration to express my
thoughts. - H S` Mukunda

> Paul,
>
> If you have a current email address for Dr. Mukunda could you invite him
> to discuss the Swothsee stove? We have been asking what the actual use
> of the stove has been and whether it would be a good candidate for a
> FAN. We have also been discussing vortex combustion in stoves (Vesto,
> Maputo,
> V-Sidewinder, Woodgas) which should still be a topic of interest to him.
> We have many questions.
> See
>
http://listserv.repp.org/pipermail/stoves_listserv.repp.org/2006-August/date
> .html
>
> We are also looking for a copy of his paper:
> H.S. Mukunda, U. Shrinivasa, S. Dasappa, S.B. Sunil Kumar, SWOSTHEE -
> Portable Single Pan Wood Stoves of High Efficiency for Domestic use,
> Sadhana, J.I.A.Sc, 13, pp. 237-270, 1988.
>
> So far we have only some photos from Auke Koopmans (1998) and a
> BUN-India report:
> http://bioenergylists.org/en/swosthee
>
> Thanks,
>
> Tom Miles
> tmiles at trmiles.com
>
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: stoves-bounces at listserv.repp.org
> [mailto:stoves-bounces at listserv.repp.org] On Behalf Of Paul S. Anderson
> Sent: Saturday, August 05, 2006 6:45 AM
> To: Kevin Chisholm
> Cc: stoves at listserv.repp.org
> Subject: Re: [Stoves] Designs
>
> Ian, Steve, Kevin and all,
>
> The steps that Kevin has enumerated below are basicially the same
> approach that Dr. Makunda used at the ARECOP workshop in China last
> week.  I will post more about it soon, but I want to reinforce what
> Kevin wrote.  Analyze the application, then find the solution(s), then
> make the stoves/heaters. Sort of like computer programming:  application
> defines the system-analysis which defines the steps of programming to
> accomplish the task.
>
> It certainly helps if you have an already operational application and
> are seeking an alternative source of heat.  That was the case in 7 of
> the 8 projects proposed at the ARECOP meeting.
>
> Paul
> --
> Paul S. Anderson, Ph.D., Geography professor - Emeritus
> Telephone:  USA-309-452-7072 (residence and office) Internet site:
> www.ilstu.edu/~psanders For my gasifier stoves info, go to:
> http://bioenergylists.org/contributors#Paul_Anderson
>
> Quoting Kevin Chisholm <kchisholm at ca.inter.net>:
>
>> Dear Ian
>>
>> ...del...
>>
>> Rather than starting with a search for stoves designs and evaluating
>> whether or not they are appropriate, may I suggest that you "start at
>> the
> other end"
>> and define the problem and opportunity? Once you have the problem
>> described, it is much easier to recognize or design a solution.
>>
>> 1: What production rate do you require, in terms of kG of dried Kava
>> product per hour?
>>
>> 2: What is the moisture content range of the raw kava?
>>
>> 3: What is the desired moisture content range of the finished kava?
> ....snipped....
>
>
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