[Stoves] (no subject)

Sun Oct 13 05:37:27 CDT 2019

Dear Ron, Crispin, Kevin, dear members,

When discussing improvements to ceramic stoves by metal internals, it
should be noted that their corrosion is very temperature dependent.
Therefore the service life of metal insertions decreases, especially from
600 °C, even with a high content of chromium. I attach a diagram, which
originates from an old manual (ABC der Stahlkorrosion, Mannesmann
Dusseldorf 1958), which shows the scaling resistance (hours per mm material
loss) depending on the Cr content with the temperature as parameter.

And I fully agree with Ron that the traditional making of charcoal has
horrible consequences (see e.g. http://solarcooking.org/seifert ).

With kind regards,
Dieter

Am So., 13. Okt. 2019 um 05:30 Uhr schrieb Ronal Larson <
rongretlarson at comcast.net>:

> List and Kevin:
>
> 1.  Thanks to Crispin for one earlier response.  But the following is
> totally different, so I think it best to limit this to Kevin’s material.
>
> 2.  I have communicated off-list some with Kevin - and don’t think any of
> the following is in conflict with his thinking.
>
> 3.  I urge reading the three reports.  I see some errors in them - but not
> in the main conclusion reached in each - that there was a BIG change in
> efficiency with this very simple low-cost modification.
>
> 4.  Kevin’s simple modificafion (see the simple sketch in his message) for
> a charcoal using stove follows naturally from his previous report on a
> similar big efficiency improvement with a simple layer of small stones
> under a 3-stone fire using wood.  That was nice because it was essentially
> zero cost and possibly motivated by air management systems used in some
> (maybe now many or most) rocket stoves. This improvement to the 3-stone
> fire is apparently spreading rapidly.
>
> 5.  That experience (unique to Kevin) is obviously his reason for asking
> whether something similar might work for charcoal using stoves.  I have
> mixed feelings about this improvement - as I am so down on charcoal-using
> stoves.  They have obvious advantages - but the making of the charcoal in
> the first place is horrible.  Making charcoal in a cookstove seems much
> superior - IF the char is placed in soil.  The cost of cooking should go
> down, much less harmful emissions, and a time saver.  But that is a
> different story (with zero application to TLUD - as near as I can see)..
> Below - only picking up on Kevin’s query on a possibly pre-existing “*body
> of work on this*” (charcoal-using stoves with an added grate) .
>
> 6.  I’ve googled around a bit on this and now feel pretty sure there is
> not;  Kevin's idea seems quite new.  And not surprising that it is new.
> Why would one need/want two perforated disks?  The idea seems inherently
> un-necessary - maybe even illogical.  But my brief search also tells me
> there is now a lot of useful information out there on charcoal-using
> stoves.  Unfortunately almost all seemed to be behind a paywall.  I’d like
> to hear if anyone know of any non-fee papers we could all comment on that
> touches on charcoal-using stove improvements.  Anyone have a (free)
> computer program that might predict the improved efficiencies?
>
> 7.  But even if there is no prior analysis on a second grate for a
> jiko-type stove,  I think this list could still give some guidance on how
> now to optimize the further testing of  Kevin’s ideas.  This should be
> possible at near zero cost for any list member near users of
> charcoal-consuming stoves.  Which of there following should NOT be done?
>
> a.  My first thought is that this second upper grate may allow significant
> air flow around the edges.  The location of the modified air supply might
> be important, even though the overall flow resistance must be increased.
> b.  The added flow resistance may itself be important - so running tests
> with the same number but smaller (or larger) air holes might give better
> efficiency?
>
> c.  The air passing a second grate should be entering the charcoal at a
> higher temperature.  Maybe a few thermocouples could tell a direction to go.
>
> d.  Must be less energy lost going downward. Maybe (not likely) one should
> have three grates?
>
> f.   The same amount of char means that the average distance to the
> cook-pot is reduced.  What might the result be if that separation was
> maintained constant?
>
> g.  Did the three (or more?) operators handle the stove operation
> differently - more attention to the main lower door aperture opening?
>
> h.  Maybe there was a curious optimum rock size separating the two disks?
> Or what about tests where only the rock size changed?  (From 1 mm to
> several cm?)
>
> i.   As Crispin noted, some charcoal using stoves have been able to obtain
> very high efficiencies (> 50%).  Could these already hit efficiency be
> improved with one more gram? (The cost of running a test might be $1?)
>
> Anyway - thanks to Kevin for keeping us up to date on his very novel zero
> (or almost zero) cost ideas for saving trees.
>
> Ron
>
>
>
> On Oct 10, 2019, at 11:37 AM, K McLean <info at sun24.solar> wrote:
>
> Listmates,
>
> Has anyone tried this?
>
> We seem to have significantly increased the efficiency of charcoal jikos
> by putting a bed of rocks on the jiko's grate and putting second metal
> grate on the rock bed.  The charcoal goes on the second metal grate.   2-3
> cm rocks work.  It works in all metal jikos and clay jikos that we've
> tested.
>
> Our testing is early and unscientific, but consistent.  25-50% less fuel
> used.  Here are three reports.  The Sierra Leone report has good photos at
> the bottom.
> Sierra Leone
> <https://drive.google.com/file/d/12MvBKjxq6PCGCcCHAjSYSeVXXvl7jWjD/view?usp=sharing>
> Uganda
> <https://drive.google.com/open?id=1zQIY49E1vrfjYl7t5V_shvw70d67QirGWUrbW51tDxo>
> Kenya (very few rocks)
> <https://drive.google.com/open?id=1MPwHCwKEVqJvuybKB5Yj39nr8fbcopBP>
> (The report authors are untrained and not native English speakers.
> Especially the Kenya report contains many errors. Please focus on the
> consistent final conclusion that a rock bed and second metal grate
> significantly reduce firewood usage.)
>
> This may be a very low cost, very easy way to greatly improved the
> efficiency of charcoal jikos.  I'd like to hear if there is already a body
> of work on this.  Here is my rough drawing:
>
> <20191010_133359.jpg>
>
> Thank you,
> Kevin
>
> *Kevin McLean, President*
> *Sun24*
>
> *https://sun24.solar <https://sun24.solar/>  Sun24 Cookstoves Overview
> <https://docs.google.com/document/d/1ZryS7gQ1q3zKLZPM2KcXdtIHbOYQp4PbloPqMvrlZ5Y/edit?usp=sharing>*
> *Tampa, Florida, USA*
> *+1 (813) 505-3340*
>
>
>
>
>
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