[Stoves] Action about Stove Testing

Mon Oct 22 10:44:29 EDT 2007

Dear Paul,

Tami Bond, Rob Bailis, Damon Ogle, Nordica MacCarty, Tom Miles, et al., are
looking at the calculations and they are responding to make sure that the
UCB revised WBT does not contain errors. I'll make sure that there is a full
respond when it's been figured out.

No worries.

Dean

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Paul S. Anderson
Sent: Monday, October 22, 2007 7:37 AM
To: crispin at newdawn.sz; Discussion of biomass cooking stoves; Crispin
Pemberton-Pigott
Cc: 'Discussion of biomass cooking stoves'
Subject: [Stoves] Action about Stove Testing

Stovers,

Crispin's message (below, partially snipped) about stove testing needs some
"authoritative" response, and then some action.

Very few of us actually get into the calculations like Crispin is doing (and
I
thank him for that).  Those who deal with originating what is in these
calculations need to respond.

Unless there are errors found in Crispin's re-working of the 
calculations, those
changes should be incorporated into the "authoritative" spreadsheets, etc
that
we are using.

Issue 1:
Crispin presents info about calculations relating to different "species" of
biomass fuels ranging from wood-types to dung.  This is important, BUT when
tests are done using only one species, there is no issue, as in the case of
using Douglas Fir at Aprovecho.  BUT, we are ALSO discussing field tests and
therefore other fuel species MUST be incorporated into the calculations.

Can anyone argue against this?  Is it too hard to put this into practice?

Issue 2:  (Moisture content  -- MC -- of the fuel):
Absolutely critical to resolve this!!!!!   Sure, there is no problem OF
CALCULATION when the kiln-dried fuel at Aprovecho is used for all the 
tests. However, Nordica wrote recently that the wood at Apro does pull 
in more
moisture during the dampness of Oregon winters (about 9 months, I think).
So
even there, MC needs to be CORRECTLY included in the calculations.

Again, those who get into the methods of calculations need to respond.  No
response means:  Person is not receiving the messages;  Person is ignoring
the
issue;  Person has other reasons for not helping get this resolved.

Summary:  This is to be objective science, not a democratic vote on past or
present formulae.

Serious doubts are quite justified concerning OUR methods of evaluating the
stoves.  If we cannot get this resolved pronto, the funders could reject our
work as being un-scientific and/or misleading.

Is there to be ProBEC-WBT different from the UCB-WBT?  Or is that difference
already a reality?  If so, can a stove developer choose which one to use?

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 Crispin Pemberton-Pigott <crispinpigott at gmail.com>:
(snipped)
>
> The noise I am making about the UCB-WBT relates to calculation errors
which
> are on my 'not negotiable' list.  Until they are fixed we will not use the
> UCB-WBT because it does not give the correct answers to very important
> questions. The fact that people get wrong answers consistently does not
> impress me at all.  Even if you yell at me or gang up or write
> tongue-in-cheek jibes, I will not be cowed.
>
> As Peter Verhaart wisely (and modestly) said, address the issues and don't
> appeal to authority.
>
>
> Problem 1
>
> We are all familiar with the following calculation of the power needed to
> heat and boil water:
>
> Water mass = M
> Spec Heat of water = 4.186 J
> Standard heating 'delta T' = 75 degrees
> Latent heat of evaporation = 2260 J
>
> Heat required to expel water from anything =
>
> [1]  M*75*4.186 + M*2260
>
> This formula is used to calculate the heat content of fuel in the UCB-WBT.
> I refer to the error I mentioned in September which was shown to have been
> corrected in a later version of the test posted on a difference site.  It
> was regarding the net heat available from moist fuel.  Fuel with moisture
> cannot be taken as being 'all wood' because some of it is water.  Some of
> the wood is required to be burned to remove the water.  What is left is
> available for cooking.  At present the calculation in that cell is made
> correctly, however as Dana pointed out, the number is not used, and by
'not
> used' she means used  in the calculation of thermal efficiency, the
specific
> fuel consumption or specific emissions per kg of fuel burned.
>
> Those are all important numbers.
>
> A second calculation is made in the spreadsheet for the heat absorbed into
> the pot.  This is also made using the same example [1] which determines
the
> power absorbed to heat the water and work out the power in the evaporated
> water that is now missing.
>
> No problem.
>
> The problem lies in an antiquated and inaccurate formula used to calculate
> how much power is required to boil the moisture out of the fuel.  You may
be
> surprised to hear this because I have just said above that the calculation
> is made correctly.  But it is made correctly to show it on the screen.  It
> is not used to make calculate what power was produced by the fuel in the
> critical cell on the spreadsheet.
>
> Now...how long do you think it would take to get a coherence discussion of
> this error going on this 'discussion list'?
>
> It should not take more than 5 minutes yet a year later here we still are
> hearing 'appeals to authorities' (so-and-so used it. It has always been
> there, Baldwin wrote it, important people use it thousands of time...)
>
> The formula used in the UCB-WBT is:
>
> Power required to remove the moisture from fuel:
>
> [2]  12% of the water mass times the heat content of the dry fuel per
> kilogram
>
> As the power required is actually [1] above, we may have a problem.
>
> The heat content of fuel is not constant across species.  A reproduced
error
> using fuels that are all very similar can give very close approximations
of
> relative performance of stoves, in a lab, only to find later that in the
> field the predictions about performance are not so good because several
> things change simultaneously.
>
> Take a 10% WWB moisture content and 1 kg of fuel. How much power is
required
> to get dir of the moisture?
>
> Red Cedar = 21.124 MJ/Kg LHV
> Using Red Cedar the result of [1] is 257,095 Joules
> Using Red Cedar the result of [2] is 253,488 Joules
>
> Cedar Mangrove = 15.400 MJ/Kg LHV
> Using Cedar Mangrove the result of [1] is 257,095 Joules
> Using Cedar Mangrove the result of [2] is 184,800 Joules
>
> Rice Husk = 14.000 MJ/Kg LHV
> Using Rice Husk the result of [1] is 257,095 Joules
> Using Rice Husk the result of [2] is 168,000 Joules
>
> Dung = 12.210 MJ/Kg LHV
> Using Dung the result of [1] is 257,095 Joules
> Using Dung the result of [2] is 146,520 Joules
>
> Do you see a pattern here with the output of [2]?  It is a part of the
> formula actually used to determine how much dry fuel is available to heat
> the pot and thus underlies every performance figure.
>
> Now, increase the moisture content to 35% and tell me what you notice
about
> the output from [2].
>
> [1] = 899,833 Joules (constant because according to two other places in
the
> spreadsheet, it is the power required)
> [2] = 887,208; 646,800; 588,000; 512,820 Joules respectively
>
> Notice that no fuel gave the correct answer using [2].
>
> That is one problem that thankfully has nothing to do with litres and
lids.
> Let's please deal with it first so we get used to the idea that the
UCB-WBT
> needs to be, and can be corrected.
>
> Thanks
> Crispin
>
>
> _______________________________________________
> Stoves mailing list
> Stoves at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org
> http://stoves.bioenergylists.org
> http://info.bioenergylists.org
>

----------------------------------------------------------------
This message was sent using Illinois State University Webmail.

_______________________________________________
Stoves mailing list
Stoves at listserv.repp.org
http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org
http://stoves.bioenergylists.org
http://info.bioenergylists.org