[Stoves] Differences in stove testing ---- was Re: ETHOS 2017 agenda and logistics
Paul Medwell
paul.medwell at adelaide.edu.au
Tue Feb 7 15:33:19 CST 2017
Hi all,
I am fairly new to this discussion that is taking place in multiple fora
regarding the char-deducting formula. I am also heavily time-constrained
and not able to participate as much as I want. Nevertheless, I would
like to try and provide some input.
It seems that everyone in in agreement that stoves can have co-benefits
in addition to cooking. Producing char and providing space heating are
two such benefits.
Two analogies that might help put this issue in context...
1) Consider a multi-function printer -- one that is a combined
printer/scanner/photocopier. It does lots of things. Each user will
place a different emphasis on the relative importance of each feature.
For example, 'Person A' might want a very high resolution scanner, but
not really care about the print quality and never use the photocopier.
'Person B' only wants to use it as a printer (after all, that is what it
is called). How would reporting a single metric on the overall
performance help these two people choose? It seems much more meaningful
to report the quality of each feature separately. Trying to
over-simplify the reporting of the various features into a single value
causes it all to lose meaning.
If a stove does multiple things (cook, produce char, space heating) then
report each performance metric separately.
2) Consider the engine in my car.
. I put gasoline in the tank [fuel energy in...what I put in]
. I get kinetic energy from the drive shaft [useful energy out...what
I want out]
. The exhaust will contain some CO and unburned hydrocarbons, UHC
[residual fuel energy...something I could use]
. A lot of heat is produced [rejected heat...something I lose]
I could capture the CO and UHC from the exhaust and burn them in a
barbeque. Should the fuel energy that they contain be subtracted from
the 'fuel energy in'?
Cheers,
Paul
On 7/02/2017 5:27 AM, 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 <mailto: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 "m/isunderstanding", /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
> thereportedcooking 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
> disclaimedto 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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