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Biochar-ists, (and to Stovers only because the comment started in
a Stoves Listserv message. I think this topic can best be at the
Biochar Listserv.)<br>
<br>
Subject line changed because this is NOT about WBT. But from a
message (found below) by Crispin about the WBT measurements, the
following comment should be considered by those who have involvement
with Gold Standard (GS) and CDM measurements. Crispin wrote:<br>
<br>
<blockquote type="cite"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">....the
performance of the [stove] under investigation has to be
reported correctly with respect to fuel consumption from the
supply, because that is how the Gold Standard and CDM and most
projects conceive of it. They have been using the heat transfer
efficiency proxy which is quite misleading for a lot of stoves.
The more char typically produced, the more misleading the
rating, and the scale of the error runs to more than 200% of
value.</span></blockquote>
This relates (I think) to the GS and CDM issues about whether or not
char-production and sequestration of carbon as biochar should be
factored into the GS and CDM calculations and rewards about
carbon-related projects.<br>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
<div class="moz-cite-prefix">On 2/27/2015 9:27 AM, Crispin
Pemberton-Pigott wrote:<br>
</div>
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<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Dear
Jiddu<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">You
are in the same position as several others, with the unusual
difference that you are in a private company. For that
reason I will be careful to share things on this public
space and not press you for results which belong to the
company.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">For
everyone else, we have to be careful that we provide ‘fair
and balanced’ advice so on one has an unfair advantage, and
also to try to agree on reporting metrics that are providing
useful information. These corrections to the spreadsheet are
only for the purpose of providing as much up-to-date
understanding as is publicly available. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Your
questions are:<o:p></o:p></span></p>
<div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">1. You give different changes for the
PEMS and WBT sheets. Are the PEMS and WBT giving different
performance results for the exact same measurements (ie.
stove) now? <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">If
you enter the same raw data into the PEMS older version
or newer versions of the (unique WBT) spreadsheet you
will find that the general layout of the “WBT” page is
the same. There are a number of versions of this sheet
and they have different corrections in them so if you
have an ‘old’ version prior to (I think) serial number
2021 there are a number of changes to be included to
bring it up to date and if you wish, to remove some of
the old invalid metrics (and some new ones). Please
remove references to the ‘efficiency of simmering’. This
has been dismissed by reviewers as long as 30 years ago.
No one is yet measuring the ‘efficiency of simmering’
because there <i>is</i> no such thing. You either did,
or did not, meet the requirements of simmering. Y/N.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Entering
the same raw data into WBT 3.1, 4.1.2, 4.2.3 and any of
the PEMS WBT pages gives significantly different ratings
of performance. They also do not report the same
metrics. You will notice a large different between
4.1.2 (referenced in the IWA) and 4.2.3 (current under
the custodianship of the GACC) any time there is a lot
of char produced and where there is a moderate fuel
moisture of perhaps 12-15%. Similarly there is a large
difference in performance between the current WBT 4.2.3
and PEMS 2013 if there was a lot of water evaporated
during boiling (tending to be the case with high power
stoves) because as pointed out in the previous message,
one uses the initial mass of water (which is correct)
and the other uses the final mass (which is not).<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Because
the differences do not apply equally to each stove, the
only way to find out what the actual result is, is to
make the changes necessary and have a look. It is too
complicated to make a conversion spreadsheet.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal">2. I am currently fitting the 'raw
data' and 'logger data' tabs into our own customised sheet
that uses a lot of the HTP protocol. I would like to be
able to fit errors and confidence to my data, but I am
unaware of the accuracy of all parts of the calculations.
Mainly the accuracy of the flow, PM, CO and CO2 I would
like to figure out. For CO and CO2 I can do a cross check
with gas analyser sampling in the same position, which I'm
planning to carry out next week. Do you have any
advice/thoughts or previous accuracy measurements you can
share? <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">The
biggest problem we will face with using the test
approach of the PEMS (hood x volume corrected for temp
and pressure) is that it was designed for fuels are
burned continuously, and which contain no oxygen, and
which produce no char. It is based on an EPA method for
stationary sources and gas furnaces don’t produce
charcoal. Thus there are assumptions in the
calculations, for example the mass of fuel burned, in
which it is expected that all the detected carbon
represents all the fuel burned. Wood contains carbon
and hydrogen. The equipment does not detect water
vapour from hydrogen combustion so it cannot tell if you
are burning wood gas and thus making charcoal, or not.
This has been addressed somewhat in the later versions
but the root problem remains. The early PEMS numbers are
much less reliable. But the bottom line is unless you
have a combination of gas readings <i>and</i> the mass
change, you will not be able to work out, even by
estimating, what burned.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">How
that affects the calculated outputs is this: supposed
the volume of gas flow is constant. Suppose the
concentration of CO2 and CO is low in the beginning of
the fire. How do you know if that is a TLUD burning
hydrogen-rich woodgas, or is it just a small charcoal
fire? So the Carbon totals are tracked and summed, but
without knowing if the mass charge as large, you don’t
know if you have a small fire in the chamber, or a large
gasifier operating beautifully.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">There
is a fundamental difference between trying to measure
the emissions from a liquid fuel stove and a biomass
stove because a biomass fire almost never burns the fuel
‘evenly’. The ‘hood’ method of emissions measurement
assumes at the outset that the fuel is burned
continuously the same way, which we all known is almost
never the case.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">There
is an alternative EPA method - a carbon balance method –
used to determine emissions for vehicles, but that too
has a fatal flaw for us. It assumes that if you detect
carbon, you have detected fuel. So, if late in the fire,
you are burning mostly charcoal, then the C level of the
emissions is quite high relative to the ‘average’ for
the wood. Then the heat theoretically available is
incorrect because there is almost no hydrogen burning. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Taking
the overall average might not be helpful either because
that could only provide the ‘correct answer’ if the
firepower, or the mass change (one of them) was constant
throughout. The water vapour dilution is a major issue
because it contains a combustion product that is not
measured. Suppose a lot of left-over fuel at the end is
totally dry…or not? If you draw some combustion volume
charts using various scenarios you will quickly spot the
problems.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">What
works, then, is a filter on the PM (which gives a total
mass), but what to do with the CO? That can be said to
have been (within its limits of detection and
quantification) been measured correctly. As long as no
inference is made from the CO about what heat was
available and when, or the total mass burned, the CO
measurement has value. It is not used to correct for the
energy lost in the calculation of the heat transfer
efficiency. If you are interested in the HTE you should
make that correction as the number is available. Do not
include WBT low power in such a measurement – you don’t
have enough information to be able to determine the heat
transfer efficiency to a hot pot.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Lastly,
the matter of system efficiency v.s. heat transfer
efficiency (proxy, because no one is measuring the
actual heat transfer efficiency) has been discussed
already. If the remaining char has no value for the next
fire, then it is discarded and cannot be considered
mathematically ‘unburned fuel’ because it is ‘consumed’.
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Paul
raises the point that more metrics are needed on this
matter. Fine. No objections there, but the performance
of the product under investigation has to be reported
correctly with respect to fuel consumption from the
supply, because that is how the Gold Standard and CDM
and most projects conceive of it. They have been using
the heat transfer efficiency proxy which is quite
misleading for a lot of stoves. The more char typically
produced, the more misleading the rating, and the scale
of the error runs to more than 200% of value.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Assuming
you were to correct all the formulas and metrics, the
PEMS or some other hood-based approach will correctly
give real time performance for ethanol and kerosene and
LPG stoves because like cars, they do not make
charcoal. Biomass and coal are fundamentally different.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I
am very interested to see what you produce as a working
sheet. I had a stab at guessing how much moisture was in
the emissions at YDD and applied it to the SeTAR SOP
1.57 heat transfer efficiency spreadsheet which is part
of the current Indonesian National Standard. It was a
surprise. The heat transfer efficiency curve (which is
real time) straightened a lot to an almost horizontal
line. I didn’t expect it would be that good, or that it
was that constant. The SEET Lab measures humidity now
and we are in a position to reasonably estimate the
effect of dilution and hydrogen combustion. Still
working on it…<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">The
evaporation of water from the fuel acts as a dilutant
for all emissions and if it is not tracked, you don’t
know by how much. The absolute humidity can exceed 150
g/m<sup>3</sup> in a chimney (!) some of which is from
combustion and some from drying the fuel. But which? And
when? As you will understand implicitly by using a scale
and the hood, combining the information provides
something close to a picture of what is going on in the
fire, within the limitations of the equipment.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">If
we can first get the structure of the experiment
correct, we can then go to the topics of accuracy and
precision. The team at CAU is very anxious to tackle
this during the coming year. The SeTAR Team is going
address the issue of measuring performance during
simmering.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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</pre>
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