[Stoves] Differences in stove testing ---- was Re: ETHOS 2017 agenda and logistics

Tue Feb 7 01:59:25 CST 2017

Dear Paul

I did not say that anything left behind after the cooking task should be
wasted – I said it should not be counted as a benefit to the cooking task.
The cooking efficiency is the useful energy delivered for cooking divided by
the energy in the raw fuel fed.  You could have another useful energy – I
used the example of space heating, the efficiency of which is the useful
space heat energy delivered divided by the energy in the raw fuel fed. The
efficiency of useful char production is the energy in the useful char
divided by the energy in the fuel fed. You could have a system that cooks,
heats space and also produces some useful char – its efficiency would be the
sum of the three separate efficiencies.

In your biogas example, the cooking efficiency is the useful energy for
cooking divided by the energy in the biogas fed. However, the biogas reactor
would produce two useful products – the biogas itself and the biogas
residue, and its efficiency would then be the energy in the biogas plus the
energy in the useful residue divided by the energy in the biomass fed.

Hope that clarifies things

Philip  

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Paul Anderson
Sent: Monday, February 6, 2017 9:29 PM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Differences in stove testing ---- was Re: ETHOS 2017
agenda and logistics

Lloyd,

My response here can be easily ignored.   But it might help clarify the
situation of char-making stoves (TLUDs).

Your comments say that whatever energy value is left behind after the
cooking task is completed should be counted as if it were wasted energy
(unless it will be used for cooking, which is not the case I am presenting.)

Biomass has energy.

When that biomass is wet, and is placed into a biodigestor for anaerobic
conversion into combustible gases (called biogas), there is a lot of energy
remaining in the digestor.  Does all of that unconverted energy get charged
against the efficiencies of cooking with biogas?

Oh.  And extreme case?  Not a case of combustible fuel?  Only look at the
biogas (not the source "stuff")??    Essentially "woodgas" is the same as
"biogas" because both were derived from biomass, but the cooking is done
with the gases, not with the biomass itself.

Splitting hairs?   Playing with definitions?  Maybe.   But something to
think about.

And I constantly object to Crispin's (and other's) switching between FUEL
measurements and ENERGY measurements when not all of the energy is extracted
from the fuel ON PURPOSE.

Personally, I am caring less and less about what is in the equations.  There
is still much more info to come about the success of the char-producing
clean-burning TLUD woodgas stoves that are being strongly accepted in very
poor areas in West Bengal, India, with a business model that includes
financial sustainability with carbon credits or simply with some financial
inputs such as have gone to other types of stoves but not to TLUDs.  

(Please note that the prevoius sentence did not use the terms WBT or ISO or
the other stuff that is getting all the discussion.   Nor am I taking sides
with Ron or others about subtracting the energy value of charcoal from the
demoninator.)

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype:   paultlud    Phone: +1-309-452-7072
Website:  www.drtlud.com

On 2/6/2017 12:57 PM, Philip Lloyd wrote:

Dear Ron

I would like you to know that Crispin’s position on the char-deducting
formula is supported by most of those working on ISO TC 285.  He is
definitely not a lone voice crying in the wilderness.

There is absolutely no doubt that the formula is wrong, if you are trying to
talk cookstove energy efficiency. Thermodynamics defines energy efficiency
in terms of useful energy delivered/ energy input, and that is the gross
energy input, not some net figure. In the case of cooking, it is the energy
used in cooking divided by the energy in the raw fuel fed to provide the
cooking heat.  If the solid stream remaining at the end of a cooking
sequence still has some components such as char that could provide
additional energy, then if they can be put back in the stove for use in a
later cooking sequence, there is no impact on the cooking efficiency, but if
they are removed from the cooking system then they represent a loss and the
cooking efficiency is reduced relative to what it would be if all the fuel
fed were reduced to ash.   That’s the science, and all arguments to the
contrary fail.

An analogy may make this clearer.  Some cookstoves also provide useful space
heating.  In this case the efficiency of use of fuel for cooking and heating
is (useful heat provided for cooking + useful heat released for space
heating)/energy in fuel fed.   The efficiency for cooking remains useful
heat provided for cooking/energy in fuel fed, and the efficiency for space
heating is useful heat released for space heating/energy in fuel fed, and
the two efficiencies are additive as they should be – and which they
wouldn’t be if the CDF were correct. 

Please accept that the cdf is DEAD.

Prof Philip Lloyd

Energy Institute, CPUT

SARETEC, Sachs Circle

Bellville

Tel 021 959 4323

Cell 083 441 5247

PA Nadia 021 959 4330

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Ronal W. Larson
Sent: Monday, February 6, 2017 5:34 PM
To: Discussion of biomass; Crispin Pemberton-Pigott
Subject: Re: [Stoves] Differences in stove testing ---- was Re: ETHOS 2017
agenda and logistics

List and Crispin

            The following in response to Crispin’s message of last night
(delayed in part by the Super Bowl - sheesh - what an ending!)

            Inserts below.

On Feb 5, 2017, at 6:28 PM, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

Dear Ron

“
I went a lot further reporting on the test experts I talked to at ETHOS -
NONE of whom agreed with Crispin on the topic of this reply - the way to
handle char in reporting efficiencies.  

That provides a comment on the poor understanding of the principles of
engineering and performance rating amount those who you contacted at ETHOS.
It is sad that those how claim to lead are so at sea when it comes to making
such simple determinations. Perhaps you are not aware that the
‘char-deducted formula’ is unique in the world when reporting the % of fuel
energy delivered as ‘work’.

            [RWL1’:  Re sentences #1 and #2 - it is truly amazing that ALL
of the experts on this topic are incorrect - and only you have the true
knowledge.  It reminds me of the way the “97%” of climate change experts are
dismissed by deniers.

            Re sentence #3 - you are correct - I am “unaware” of the
uniqueness - because it is not true.  As one example, the CSI methodology
used in the Philippines uses it.  The CSU methodology does (incidentally,
Jessica Tryner’s doctoral thesis includes this CDF = “char-deducting
formula” - and is terrific).  

            I hope readers will note that below there is NO mention of how
Crispin would handle the situation of most interest to those of us working
with TLUDs - using something other than the CDF for tier placement purposes.
I say the CDF undervalues char when looking at tiers - but I can live with
it.  Crispin is silent on how to merge char making and tiers - repeat TIERS,
not the CDF alone.

            The CDF is not different in principle than subtracting the
energy in unused wood (or do you think that should not be allowed also?)

Char making is not ‘work’ when it comes to cooking energy delivered.

            [RWL2’:  We are getting off topic here, but since it takes
energy to make char (about double that retained in the char), www could
argue about whether this is “work:.

>John Mitchell supports the existing “denominator equation” - as does
EVERYBODY I talked to at the ETHOS conference.  

Ditto – if true, it is significant that the ETHOS participants you discussed
this with do not follow this list, read about the problems and understand
the implications, or consider that scientific norms should apply to stove
testing.

            [RWL3’:   Right,  because you say so, we should disregard all
the other expert statements (I mean official in the TAG discussions - not on
this list or at ETHOS).   

            I can assure you the experts at ETHOS have been reading this
list.   EVERY one I talked to was fully aware of the controversy.  You
underestimate (and insult) their ability as well to “understand the
implications or consider the scientific norms
”

>[RWL1:  I am agreeing with decades of usage to make the “cooking efficiency
metric number" more accurate.  

The cooking efficiency is the ratio of cooking energy to the energy in the
fuel fed into the stove. Comparing the rating of two stoves calculated on
that basis gives a direct comparison of the fuel consumption to accomplish a
task. More on that below.

            [RWL4’:   You would be correct if that was the accepted method
of comparing stoves.  The accepted method, when char was trivial, is/has
been to make the CDF calculation more accurate  (less unexplained
variation).  

>The ONLY accurate denominator is one with the char being subtracted - as
the ratio is the heat into the cook pot divided by the total energy that
COULD BE available for that measure of energy into the cookpot.  

That is a description of the heat transfer efficiency. It is unfortunate you
are not learning from this interchange. I have explained in detail how to
calculate the heat transfer efficiency and it starts by deducting the char
energy (all of it, not just some recoverable portion).  You are calling the
heat transfer efficiency the cooking efficiency. That is the root of the
problem. They are different when the stove produces a solid residue
containing unreleased energy.

            [RWL5’:  I have no idea why you are claiming that I am “calling
the heat transfer efficiency the cooking efficiency”.    If you would leave
all of the exchange instead of cherry-picking it, our audience would see
that In my sentence labeled “RWL1” above, where I have “cooking efficiency
metric number”  in quotes,  I did so because your immediately preceding
sentence (from the 4th) was "You want to increase the cooking efficiency
metric number by deducting the energy content of the recovered char energy,
is that correct?”    So you use a term “improperly", then accuse me of its
improper usage, even though I had it in quotes.  The “root of the problem”
(your term, not mine) is your unwillingness to give char the credit it needs
in the only equation around for setting tier levels.

>Energy that is in the char was NOT available to go into the cookpot.  

That is why it is deducted when calculating the heat transfer efficiency.

            [RWL6’:   And it is this “heat transfer efficiency” quantity
that is being used in the setting of the tier levels.  So why are we
arguing?  The quantity you insist is the only one that is important is
already being obtained and reported.  The issue is tiers - and you are not
addressing that topic.

>It HAS to be subtracted to get a valid efficiency when you are running
different tests with relatively arbitrary and unintentional amounts of char
being produced.

That is correct, if you want to calculate the heat transfer efficiency.

            [RWL7’:  Yes I want to calculate that efficiency - because it is
the one used for setting tiers. 

             Is the problem that you object to tiers?

>You are the only person I have heard say this is improper.  Your view has
been dismissed by dozens of others - especially in “official”polling.

Obviously you are not in all conversations on the matter. You are in no
position to conduct an ‘official poll’. Science does not operate on
‘official polls’ of people whether or not they are informed on the subject.
In fact, opinion counts for little in a mathematical calculation.

            [RWL8’:  All four of these sentences are off-base.  1):  I never
said I was in “all” conversations;  I reported what was said to me at
ETHOS.,  2)  Official polls have been conducted (and you have lost by votes
of roughly 30:1);  I didn’t conduct these or claim to have done so;  3)
Agreed that science doesn’t operate with polls, but ISO groups do, because
one person in the group can be holding up progress;  4)  You have agreed a
few lines up that the equation in question (used to establish tiers) is OK -
so why are you raising an issue of opinions?

>          I think the “denominator equation” formula undervalues (not
overvalues) the energy in the char.  

The equation does not report the cooking efficiency, nor the energy in the
char nor its fraction of the original energy. It is an error to use it for
anything. It has no standard name because it is not accepted as a standard
calculation save as a rough guide to the heat transfer efficiency, which I
remind you was the original intention of the authors of the VITA test. The
approach was used in a much more refined form in the BUCT paper of 1 year
ago. When it was pointed out on this list that the calculation of the
relative fuel consumption was in error because of this, one of the authors,
Kirk Smith, made a comment on this group that the error would be corrected
‘if the paper was published’. In fact the paper was already published. The
error is to think that the relative heat transfer efficiencies of two stoves
is the same as the relative fuel consumptions. This error is common to the
WBT (all versions) the CCT and the KPT. (With the KPT it is only considered
in certain circumstances so there is a caveat there – the KPT sometimes
gives the correct answer.)

            [RWL9’:  You continue to make no sense.  First you say (above) :
“That is correct, if you want to calculate the heat transfer efficiency.”

Then you turn around and say (second sentence above)  “It is an error to use
it for anything.”

            If you give a cite to the “BUCT paper of 1 year ago”,  I’ll read
it. Despite your inferences, I think we have already established that Kirk
Smith is OK with this equation - and certainly the Berkeley Air Monitoring
Group (BAMG) is.

>It says the inefficiency is larger than it is. 

The formula doesn’t calculate the inefficiency of anything.

            [RWL10’:  In my world (I have been primarily involved in energy
matters since 1973), inefficiency is the complement of efficiency:  i = 1-e.

> I accept  the formula only because the tier structure is based on its use.

You are correct that the tier structure (which has its own additional
defects) is based on the WBT 4.1.2. which miscalculates the cooking
efficiency. I invite you and everyone else on this list to obtain one of the
(at least) three versions of the WBT 4.1.2 and run a set of measurements
through it to get the ‘thermal efficiency’.  Then run the same set of
measurements through v 4.2.3 and see what the answer is. Be amazed. To get
the real answer, delete the contents of the ‘char’ cell and set the char
catching container to zero. Compare that with the other results. Be shocked.

            [RWL11’:  Again, you put the effort off onto the reader.  Why
don’t you just show the results?   Some of us have other things to do than
run around looking for “three versions of the WBT 4.1.2.”.  You are correct
that I will be “amazed/shocked” if anything related to charcoal and the tier
system is different in any of these procedures.  So please enlighten us with
your demonstration.

>I would have been happier with a tier structure based on overall
efficiency, but I know that is impractical - especially at this late date.

Interesting. So getting the correct answer is not important, expediency is?
How long would you be willing to wait under normal circumstances?

            [RWL12’:  I am misusing my time in this endless exchange because
the correct answer IS important.  I have no idea what you are driving at in
the last sentence.  Your wasting everyone’s time claiming that charcoal is
being mishandled and the right answer is to drop char computations when
placing a stove into tier structure  does not seem “normal” to me (reminding
you and this readership that you are routinely out-voted by 30:1 (as you
have yourself also implied a few messages back)

>>This deduction raises the reported fuel efficiency.

>[RWL:  For small amounts of char it makes the reported efficiency more
accurate.  

No, it mis-reports the metric that claims to represent the fuel consumption.
The more char you make, the greater the misrepresentation of the fuel
economy.

            [RWL13’:  That is your belief on
“mis-reports/misrepresentation”. The rest of the world seems to believe the
CDF/WBT is the best/only equation around - especially for establishing
tiers.  

            And I support the tier structure as being important at this
early point in (possibly) moving to standards.  Please tell us how you feel
about tiers.

>It undervalues the overall (more than heat transfer) efficiency of stoves
that are trying to make char.

You are correct on this point insofar as the formula does indeed calculate
the heat transfer efficiency (or a reasonable proxy of it). I am not cure
why you have contradicted your earlier points above.

            [RWL14’:  I see no contradiction.  Perhaps you are not reading
closely enough.    I presume “cure” should be “sure” - but maybe there is
something else possible here.   

            Please expand on “reasonable proxy”.

            The great point here is that we are in agreement on what the CDF
is doing.  I did not expect this sentence.

>>Are you OK with that as the result?

[RWL:  Marginally.   Only in the tier heat rating sense.

So having the wrong answer is not an issue as long as the heat transfer
efficiency tiers are not changed? Did you ever buy a product based on the
heat transfer efficiency?

            [RWL15’:  Of course getting a wrong answer is an issue.   That
is why I am willing to argue with you (and will continue to do so).  Your
view oj the unimportance of char needs to be fought.   Yes - I have bought
many products on the basis of heat transfer efficiency - thank god that the
EPA has provided those numbers.

>Example:   If energy into the boiling water and charcoal each are
one-third, then the sum of all inefficiencies MUST also be one-third.  

That is incorrect. Please read on.

            [RWL16’:  If my value of 1/3 is incorrect, it would seem
incumbent on someone claiming so to give us the right answer.  Good lord!  I
do not see a corrected answer below.

>You argue for a heat transfer efficiency of 1/3 (dropping all consideration
of the char).  

No, I argue that the cooking efficiency is 1/3. Please correct your
misunderstanding.

            [RWL17’:  This exchange, from my perspective, is about tiers,
which are based on this CDF equation.  I see no “misunderstanding” on my
part to correct.   And if I have a “misunderstanding”, it seems to be widely
shared.     

            I repeat that I see none or very few on your side of any part of
this argument.  Since you are not convincing me, I invite someone else to
explain it better,

>The “denominator equation” (used by everyone but yourself as near as I can
determine) says the “heat transfer efficiency” is  (1/3)/(1-1/3) = (1/3) /
(2/3) = 1/2.    

First, virtually no one outside the USA uses this formula in any official
capacity (CDM/Gold Standard excepted) , and within the USA it is shunned for
regulatory purposes by the EPA.

            RWL18’:  I ask for a citation for this “shunned” statement .
John Mitchell and Jim Jetter (both of EPA) strongly support this CDF
equation - as well as everyone else I have queried.

Second, that is how to calculate the heat transfer efficiency, not the
cooking efficiency.

            [RWL19’:  I have found nothing in the literature on the WBT  (I
again recommend 4 cites by Jim Jetter that a I gave a week or so ago), to
say the equation in question should be called a “cooking efficiency”.  I see
no reason to start calling the CDF equation in question a “cooking” equation
- and again note that you have earlier called this equation a heat transfer
efficiency equation.  Your “cooking efficiency” equation is already being
used and reported.  It would help this dialog a lot if you would explain how
your preference on reporting can help with tiers.

>I can live with this, but I also think it important to say that the
inefficiency is NOT also 1/2.  

The formula does not calculate an inefficiency, it calculates the heat
transfer efficiency. The heat transfer efficiency is not useful for
calculating fuel savings.

            [RWL20’:  In the EE world I have inhabited for quite a few
decades, efficiencies are the ONLY way “for calculating fuel savings”.  I
hope you can show us a method for avoiding that term/quantity.

>The overall efficiency, when one is trying to produce char, is 1/3 +1/3 =
2/3.  This last is clearly NOT the “heat transfer efficiency”

Correct. It is not the heat transfer efficiency. It does not have a name as
you are adding the cooking efficiency to the % of energy in the original
fuel that was not burned. As I pointed out to you and Paul, this metric is
non-standard and does not have a name.

            [RWL21’:  I see no problem with calling this “2/3” number the
“overall efficiency”.  I dispute that this metric is “non-standard”, as  it
is the ONLY way to get the inefficiency value (here of magnitude 1/3).

>but the overall efficiency should be reported as well if we are trying to
promote more valuable stoves, and it is not being reported.

What do you consider to be the ‘overall efficiency’?

            [RWL22’:  I think you are not reading carefully enough.  it is
2/3 in this example.

>Now the reverse question -  WHY are YOU so unhappy with the subtraction in
the denominator?  

Because as applied in the WBT (all versions) it gives a misleading number
which is used to calculate the relative fuel savings of stoves, comparing
them with a baseline product. It gives the wrong answer. You indicated above
that while the cooking efficiency is 1/3 and the WBT reports it to be ½, you
are OK with that misrepresentation. I am not.

            [RWL23’:  You continue to avoid the “why” question.  It is not
enough to call it “misleading” or a “misrepresentation”.  A lot of
knowledgeable people have concluded that tiers are appropriate at this time
for improved stoves and this CDF equation is the right/only one.  You offer
no alternative.

>Is it your opinion that this char production was an inefficiency?    

In standard terms char production is reported as a % of the dry fuel input.
Where it is not a desired product, it is a mechanical loss.

            [RWL24’:  Now we have gotten to the bottom of the issue.  For
you, char is NOT a “desired product”.    Pity.    But consistent with every
other comment over at least a decade on the relationships between you and
charcoal.   

            I see no reason to call char a “mechanical loss” - neither
mechanical nor loss.

>You have expressed great unhappiness with the “denominator equation”, but I
don’t recall ever seeing a reason.  

Then you have not been reading my posts.

            [RWL25’ :  Obviously I have been reading your posts - primarily
to protect char-making.    I contend that you have again not given a reason
other than your (much-disputed) put down on char.

>The purpose of including a char term in the denominator is NOT to say
anything about char - it is to get at the POTENTIAL heat transfer
efficiency.  

There is no such metric as the ‘potential heat transfer efficiency’ except
to say that it is always 100%, until the stove is tested.

            [RWL26’:   Yup - 100% IS possible -  as soon as we find a way to
eliminate losses via conduction, radiation, and convection (and
char-making).  Are you sure you want to hang your full argument on
dismissing the CDF (your term - see above) based on this 100% absurdity.

>To repeat - too many will think that char-making stoves are much less
efficient than they really are.

When it comes to fuel efficiency, char making stoves are usually much less
fuel-efficient than stoves that burn all the char. As usual, you are looking
for some way to over-report the fuel efficiency by pretending the char is
unburned ‘fuel’. 

            [RWL27’:  First sentence not true (relative to “much less”);
many of the EPA tests are showing BOTH a fuel saving and char production.
You were in such a discussion yesterday with Paul Anderson.

            Re second sentence,  I have been consistently saying that the
CDF under-reports.  If I had my way I would base tiers on the “Overall”
(i.e. 2/3 efficiency value).  

            I see very few people agreeing with you that the CDF
“over-reports” anything.  I think you are again here repeating that char “is
not a desired product”.

Then, you plan to bury the char in the ground (proving it was not ‘fuel’
after all) to accomplish what others call ‘sequestering carbon’.

            [RWL28’:  I think I have been clear on that - as means of both
helping stove users and of being an important start at much larger CDR
(carbon dioxide removal) - what I consider to be the world’s #1 problem.
Thanks for bringing  ‘sequestering carbon’  into the dialog.  But you are
missing the soil benefits - of huge benefit to all potential char-making
stove users.

Using your example above:

Cooking efficiency: 1/3

Char energy retention, based on the recoverable mass of the solid residue:
1/3

Heat transfer efficiency: 2/3

            [RWL29’:   What would you call the CDF equation result of 1/2?  

             Also,  I see no way that your number “2/3” can be called a heat
transfer efficiency.  In the future,  much of this valued (for soil
improvement purposes) char will be going into the ground.  Why should it be
called “heat transfer efficiency?  (I used the term heat transfer efficiency
[1/2] because it is NOT the value of 2/3 (which you are [surprisingly]
using).

Two stoves both have a cooking efficiency of 1/3. One of them makes some
measurable amount of char. Applying the WBT formula raises the reported
cooking efficiency (not the actual cooking efficiency). The actual cooking
efficiency shows that both stoves require exactly same amount of raw fuel to
cook. 

            [RWL30’:  I disagree with your second sentence.  The WBT formula
does NOT raise “the reported cooking efficiency”.

            You continue to avoid the concept of tiers - which can’t
possibly be developed with anything related to your term “cooking
efficiency”.

Applying the WBT formula one finds that the char-making stove disclaimed to
require less fuel to complete the cooking task. 

       [RWL31’:   NO.  It says that IF char (valuable its own right) had not
been produced, then more heat would have been transferred (or more cooking).
This is independent of whether the char amount was small or large,
intentional of unintentional. 

            I don’t understand the term “disclaimed”.  Was this supposed to
be “is claimed”?

That claim is false. People are being induced to pay for a reduction in fuel
use on the basis of the WBT calculation. They are being defrauded with false
claims of fuel saving. I don’t believe you are ‘OK’ with this situation.

            [RWL32’:   I suggest, with your “don’t believe”, that you aren’t
paying attention to what I am saying.   I repeat for the benefit of you and
anyone reading this that I AM “OK” with this situation.”   I thank the
(mostly) volunteers working on every part of this ISO exercise.  

            Aside:  In about an hour, I will be listening in on an announced
two hour call on the WG3 work product (for field testing) - where this same
equation  will be discussed and (presumably) endorsed.  This is NOT a topic
related only to the WBT.

Ron

Regards

Crispin

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