[Stoves] Fan-blaster Combustors, Stove Camp 2006, andtheDell-Point Pellet Stove

[Tom Miles]

Paul,

Thank you for explaining the process in detail. It helps to understand what
was actually tested. 

It is interesting to note that the performance results for the Woodflame
(Dean's Fan) are actually very similar between the benchmark tests and the
Stove Camp 2006 tests. If you took the Open Fire, Phillips, Reed and
Woodflame stove back through the standard WBT you might get numbers
comparable to the January benchmarks.

It does appear that the primary benefit of the forced draft is lower
emissions. Although some of the natural draft stoves reported in January
perform very well. The anecdotal reports from the field for the natural
draft stoves seem to confirm both the fuel savings and emissions reductions.
So I think the results may be encouraging but it would be good to have
corroborating tests. 

Tom
 

-----Original Message-----
From: psanders at ilstu.edu [mailto:psanders at ilstu.edu] 
Sent: Tuesday, September 19, 2006 11:39 PM
To: Tom Miles
Cc: 'STOVES - Listserve'
Subject: RE: [Stoves] Fan-blaster Combustors, Stove Camp
2006,andtheDell-Point Pellet Stove

Tom and all,

Lessons from Stove Camp 2006:

Your excellent observations (below) relate to ALL of the stove 
emissions testing
at Stove Camp 2006.  It is important to note that the testing procedures
were
changed from the previous Stove Camp and other testing.

The 2006 results were derived from an "Abbreviated WBT" that involved
boiling
2.5 liters of water in a 3 liter pot that was almost the same diameter 
as the 7
liter pot used with the "Official WBT" that uses 5 liters of water.  The
A-WBT
versus the O-WBT.

I believe this makes a difference in the heat transfer.  The same
bottom-surface-area with less depth of water in the pot should/could/might
yield better results on the PER LITER basis that is reported in the graphs.

Also, after boiling, the simmering was for only 30 minutes instead of 45
minutes.  That could relate to the total fuel used, again reported on a per
liter basis.  The table says "Time to Boil and Fuel Use."  It does not say
"Simmer", but we did NOT weigh the fuel after the boil was attained, so the
fuel use must include the simmer time.

Basically, the results of the Stove Camp 2006 emissions testing can 
only be used
for comparisons of the 8 reported stove results, of which one set if 
results was
for the 3-stone fire.  I believe that the 3-stone fire was tested with the
2.5
liter and 30 minute simmer conditions, so that comparison is valid.

Perhaps the best way to make some comparisons would be to look at the
measured
results from the 3-stone fire data of the A-WBT versus data from the O-WBT.
I
do not have that data.  Perhaps Nordica or Dean or Damon could assist.

I understand that the time availability of the emissions hood at Stove 
Camp 2006
was limited.  Personally, I could have used an additional 3 to 6 tests of
stoves.  I stayed an extra day, but Aprovecho commitments also needed to be
met.  So I learned not to bring so many stoves and to lower my expectations
of
the number of testings that can be accomplished.

Furthermore, there is some disappointment to realize that the Stove Camp
2006
emissions results cannot be directly compared with the results of previous
testing at the Aprovecho Research Center.  Also, that means that that they
cannot be compared with the benchmarks that were established using the 
official
WBT, in my opinion.

This leads to 2 observations:

1.  ANY reasonable arrangement of emissions testing can be valid testing
provided that the proceedures are consistantly applied and that a sufficient
number of tests are conducted.  The results are compared WITHIN the
population
of tested stoves.  The only problem comes when the results from different
testing methods cannot be compared.  Sort of like Beta vs VHS video 
systems. Both show a picture and the winner is the one with the market 
dominance, not
necessarily the best quality or price.

2.  Having more locations where testing can be conducted will be 
useful, even if
results from any two locations might not be very comparable.  I drove 
over 4000
miles (6400 km) round trip to Stove Camp, and I am glad that I did for 
the many
reasons of interaction and discussion with great people involved with 
stoves. But I am not so happy when I count only 4 trials under the 
emissions hood for
my stoves.  4 is a large percentage of the total tested and reported, 
but I was
expecting that this year we as a group would have tested 15 or more.  I do
not
want this to be viewed as a complaint, but rather as an observation that
supports the need for more testing locations.

Linked to the above 2 observations, I should register my reservations 
about the
"official wood" that is used in the emissions testing.  A standardized wood
is
necessary for comparisions to be made.  But what has become the standard is
kiln-dried quality wood that is obtained from some factory.

The question is, are some stoves disadvantaged by the required fuel?  
The answer
is yes.

Example:  Two T-LUD natural draft stoves were tested under the hood.  
One was by
Ashley Airone with my assistance, looking much like a simplified 
Champion T-LUD
gasifier.  The other was using Mr. Hao's combustor with steam ejector,
called
the "Hao-Juntos" on the graphs of test results.  In both cases, the 
stoves were
prepared and tested away from the hood, using woodchips obtained near Eugene
Oregon from a large company preparing mulch, bark chips, etc.  Those 
chips were
further sun-dried for about a day at the start of Stove Camp.  When 
tested with
those chips, the stoves worked nicely and we were confident that they would
operate well in the emissions testing.

When we went under the hood, we used the official wood.  We did not want
long
pieces for the T-LUDs, so we cracked and broke the long pieces with a 
hammer to
produce reasonable chip-like splinters.  Under the emissions hood, this 
is what
happened:

The Airone stove was lit at the top and soon the fire was racing away, 
creating
far too many pyrolysis gases.  We actually aborted the test before boiling,
so
that is why it does not appear on the graphs of test results.

The Hao-Juntos stove was also overactive, but not a complete run-away 
fire.  We
were not able to reduce the fire for the simmer stage.  The graph shows that
the Time to Boil was one of the lowest, but everything else was quite high.

Experience is a great teacher, and I diagnosed that the structure of 
the airbase
of the T-LUD was allowing uncontrolled primary air to enter, resulting in
excessive flames with the official fuel but not with the regular wood chips.

To confirm my hypothesis, I switched to a different style of fuel 
container with
much more control of the primary air.  I operated both stoves (not under the
emissions hood) on the Tuesday after Stove Camp, using the official 
wood.  With
that control, the flame was quite appropriate both for the boiling 
stage and for
simmering.

I am glad that I had the chance to learn this lesson about my stoves and
about
the official fuel.

Let's look at this fuel issue from a different angle.  If a stove is tested
using the O-WBT and using the official fuel, and the stove is "certified" as
meeting the benchmarks, that is considered to be a worthy goal.  But if the
same stove is then taken to people who do not have fuels that are 
comparable to
the kiln-dried official fuel, those people might always be operating with
emissions and fuel consumption considerably above the benchmarks, but being
assured that the stove meets the benchmarks.  And that is not good.

On the other hand, if a stove does not meet the benchmarks when using the
official wood, the impression is bad.  But if in the villages that same
stove
with local fuels could reach the benchmarks, that would be excellent.

NOTE:  I am trying to make objective observations.  Please do NOT shoot the
messenger.  Just discuss the topics, please.  Others have raised similar
questions in the past.  I do not want to go back to the days before
emissions
testing.  We just need to be careful with what we are doing.  There is 
a danger
that the practitioners start to believe their own pronouncements and 
standards.

Paul

Quoting Tom Miles <tmiles at trmiles.com>:

> Paul,
>
>
> The times to boil for some of the fan stoves seem pretty short. But the
> overall fuel (700-1000 g/5L) use seems to be close to the 850 g/5L
benchmark
> proposed in January.  Phillips, Reed and Dean's Fan were all less than the
> benchmark. CO and PM emissions were all very impressive compared with the
> benchmarks. Do we conclude that in the laboratory the fan stoves boil
> faster, reduce emissions significantly but reduce overall fuel slightly
> compared with a natural draft stove? That is, if they can be fed
constantly
> with small bites of dry fuel? :-)Or, am I missing something?
>
> Stove Camp Results: http://bioenergylists.org/en/aprocamp2006
> ETHOS benchmark:
> http://bioenergylists.org/stovesdoc/ETHOS2006/Still/StillETHOS2006.pdf
> Images of fuel preparation and feeding:
> http://picasaweb.google.com/trmilesjr/OneDayAtAprovechoStovesCamp2006
>
> Tom
>
> -----Original Message-----
> From: psanders at ilstu.edu [mailto:psanders at ilstu.edu]
> Sent: Tuesday, September 19, 2006 3:22 PM
>
> And it was Dean who clearly stated to me that the Woodgas Campstove has
been
> repeatedly operated in this same way (what I am calling "fan-blaster") in
> previous emissions testing because the duration of the burning by a single
> load of fuel in the small fuel chamber of the Woodgas Campstove was not
> sufficient for completion of the WBT Water Boiling Test.  I am sure that
is
> true because the Campstove's capacity for the "official wood" used in all
> emissions testing at Aprovecho is significantly less that what is needed
to
> accomplish even the boiling of 5 liters of water, and then still to have
the
> pot simmer for 45 minutes.  I understand and accept that way of operation
> during those tests because the Woodgas Campstove is not able to be
reloaded
> for further T-LUD operation without removing the pot, emptying out the
> char/ash, partially cooling the inside of the stove to prevent ignition at
> the bottom, and then reloading and relighting for T-LUD operation, and
> replacement of the pot onto the stove.  Such a procedure is not
convenient,
> so the procedural solution was use what I am now calling "fan-blaster"
> combustion.  What is interesting is that the "fan-blaster" mode of
operation
> was not recognized or noted or reported, and we thought it was a T-LUD
> operation.
>
>
>



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