[Stoves] TLUD Summit discussion continues on Listservs

[Andrew Heggie]

On Wed, 13 Feb 2019 at 17:09, Anderson, Paul <psanders at ilstu.edu> wrote:

>
> A total of 16 tests of stoves were conducted at the January 2019 TLUD Summit held at Aprovecho.  A summary data sheet from Aprovecho is attached.   Just seeing the numbers without discussions is less than ideal, so please do not over-examine the results.

I agree that just the numbers without discussion is  not very helpful
and have waited with bated breath for other who attended this TLUD
wood burning only summit to comment.

For the purposes of this thread let's keep the topic restricted to
this summit and what it achieved. Plainly from the  banner across the
spreadsheet we can only consider the results indicative rather than
scientific.

For my part the promise of TLUD  has always been that the particulate
levels have been better than straight up draught wood burning. So your
test results quote  a number of milligrams per MJ of heat delivered to
the pot, I take it this  can be extrapolated to mg of particulates per
cooking event? Thence  are we able to relate it to the acceptable
indoor air quality, I believe WHO still recommend <10 micro grams of
particulates per m3 of indoor air.


>
> 16 tests total:
>
> 2 of one stove that was not TLUD powered (Marco – plancha stove from Guatemala)
>
> 1 test of a large TLUD-ND-Large and not intended as a cooking stove ~15 kW)  (Norm biochar maker model 16(?) )
>
> 4 tests of Kirk Harris Wonderwerks TLUD-ND
>
> 3 tests of Champion TLUD-ND
>
> 3 tests of Champion TLUD-FA (yes, forced air and not many changes to the Champion TLUD)
>
> 3 tests of FABstove TLUD-FA

Would you care to relate the particulate figures from the spreadsheet
to the stoves as tabulated above?

I did see some observations by Dan Weinshenker,  he was at the summit
, I was not? He wrote:

"Looking over the results, what really jumps out to me is how much
better the forced air units performed.  Especially the FAB.  And
especially the FAB relative to Particulate Matter.  On the order of
twice as well.  2x = 100% better !

A small computer fan doubles the power and cuts the water boil time in
half.  And moves stoves from Tiers 2-3 to essentially 5.  Again 2x =
100% better. Not just a few % here and there, but 100%.


Fundamental question and lesson: Are cookstove TLUD’s going to require
FA to reach higher tiers?

 Comparing the Champion FA tests, to the FAB FA, am wondering what
exactly about the FAB is making the difference?  Tiers of 4.6 and 4.9
are pretty amazing tentative numbers.

 A question comes up about something we were not measuring, and that
is flame temperatures?


For actual scientific based stove design, Aprovacho LENS gives bottom
line characteristics, but possibly does not allow a needed deeper more
detailed look of what exactly is effecting this output bottom line.


For example, in comparing NA to FA, what is the composition and
temperature of the wood gas prior to hitting secondary air?


PM=function(temp, dwell time, turbulence and mixing, soot size and
composition,?)  What’s the formula?  Any way to express
mathematically, or ‘rules of thumb’ at least at level of current
understanding?

 In analyzing all aspects, for each characteristic (from efficiencies
to % char generation, etc), to me it would be helpful to start with
similar word function formulas.  So in discussion and design ideas, we
can better laser down to specifics.

 Would like to see a universal set of such formulas, with to the
extent possible some level of deeper detail and relative importance of
characteristics.

 I was really impressed with everybody’s level of intuitive
understanding, but I’m guessing here at the need to use more detailed
science to optimize.

 A specific TLUD test rig design, with adjustable mechanisms?

 Yet I never forget the phrase: Don’t let perfection be the enemy of good. …


I have many other questions.  Just a few:


If the Champion in actual use is run outdoors, or in open kitchens, am
thinking PM is a secondary priority or concern, relative to simplicity
of construction and use?  Same for any other stove?  Cultural aspects
here.


For any small TLUD stove, with Impact = Technology x Adoption, is FA
the way to go?  How much will FA decrease adoption, if any?


Is FA the only way to successfully ‘compete’ with Rockets?  If Tiers
are the standard of judgment, maybe so?  But are there not more than
one category of judges: ISO yes, but also BOP cooks?


What would be the desired next series of TLUD tests?

+ Counter-flow internal risers?  Optimizing of such?  Julian’s work.

+ Stationary fans in external risers? Other designs.  Optimizing? Digging deeper

     to flesh out everything possible to learn from Kirk’s work.

+ Increased chamber insulation (reflective layers, ceramic blankets?)?

+ Simple air control turn down mechanisms to adjust primary and secondary air

     simultaneously and relatively?

            + Different FA options?

            ?



Overall, it was very exciting for me to attend.  Thank you all for
your acceptance.  This TLUD camp will be added to Stove Development
history."

I see this poses many more questions as well as pointing out that
forced air has many attributes, as Dan says perfection can be the
enemy of good enough, so to my mind I need to know what is good enough
in relation to indoor air quality. In long past discussion with Ronal
he was of of the opinion a natural draught TLUD  stove would become
"good enough" and he considered the additional cost of forced air
would  make it uncompetitive.  Natural gas hobs  do seem to be clean
with natural draught, albeit that the gas issues at 20 millibar and
the rapid expansion of products in the flame enhances this and of
course most if not all domestic gas boilers are fan flued.

Andrew

ps I do only want to concentrate on indoor air quality as to go into
things like cooking efficency will take us off on another tangent.