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

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

037901d280aa$d78be170$86a3a450$@co.za” type=”cite”>

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@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@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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