[Stoves] A debate about “efficiencies”….. was Re: ABCEG deceit and conceit

All is in reference to:

an important stove reporting equation of the form e3 = e1 / (1- e2).  

I am not great at such equations.   But it seems to me that the letter  e    is used both as   efficiency   and as    energy.     Whatever.  That is not my key point.   Rather,

Both sides have their appropriate strong points.   
1.  Biomass fuel is consumed, and any remaining charcoal is NOT the same as the original fuel.  So, 100% of the original fuel is gone.  –Crispin is correct about FUEL efficiency.

2.  The charcoal is different from the biomass fuel, but it is still a viable, usable form of energy that came directly from the original biomass.  So there needs to be some recognition of its ENERGY value.   (If the char has other, non-energy value (such as being good for filters), and may or may not be eventually consumed as energy, that is NOT part of this discussion.)

3.  On an ENERGY basis (not fuel basis), only the actual released energy in the biomass (after subtracting the energy that is still in the charcoal) should be used to calculate the heat transfer efficiency of the stove.   So the formula (and Ron’s second table) can be considered correct, but it should be perhaps emphasized that the column heading should be:     EE-stove   (ENERGY Efficiency of stove)    and is not     FE-stove  (Fuel efficiency of stove). 

************
I want to pick up on what Crispin wrote:

Char produced as a co-benefit goes in the top line, not deducted from the bottom.

That realization might have great merit.   Can the math-competent people please do that, and we can see the result.   

Basically it says that ALL of the fuel (in the denominator) is used, but there are two products in the nominator.     I do not know how to add “Energy captured in the pot” AND “charcoal created (as weight or volume)”.  Maybe convert the charcoal into units of energy.  And then add them.   And that sum is divided by the energy of the fuel that is consumed and is no longer in its original biomass form.

Does this work?   Ron,  please put another column or two into your second table and send us the results. 

Another way to look at “efficiency” of fuel and of energy is to convert everything into monetary amounts.

$ value of having heated the pot       PLUS      $ value of the created char    / divided by     $ value of the biomass fuel.

For use in this monetary equation, there can be multiple different values for each of the 3 variables.  

Extreme values are possible, such as “if the pot does not get hot, the food is not cooked, and the baby dies” (a very high value for the heat to the pot.)      Also, biomass fuel that is actually expensive wooden furniture would command a high dollar value.  

On the low side, some biomass fuel could be invasive species that must be burned, so burning has no cost, and the act of doing the burning could receive payment. 

But just sticking to common, defendable values, we can find ways to COMPARE the economic value of using one stove type (that makes char, for example) with another type that does not.   

This will become increasingly important if and when the world recognizes special values of charcoal, as in water filters or fo carbon sequestration (without being biochar into soils) or as biochar with increased food production (with sequestration as an added benefit.).   

Stove stuff.   I find it interesting.

Paul

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

YTOPR01MB0235921B77C8DA5567CF2DA5B1790@YTOPR01MB0235.CANPRD01.PROD.OUTLOOK.COM” type=”cite”>

Dear Ron

 

The problems I have with the equation applied in the WBT are:

 

1. The resulting number is not what it claims to be (the thermal efficiency). It is also not the energy efficiency, nor the heat transfer efficiency, nor the % of energy available from ‘missing fuel’ that was transferred to the pot.
2. It does not report a number that can be used to compare the fuel efficiency of two or more stoves, its primary function and specific claim, as applied in UN contracts, the GACC contracts, as well as the CDM and Gold Standard methodologies. Relative fuel consumption in those projects are all calculated incorrectly.
3. Producing char (or not) is not a cooking task and does not enter its efficiency rating. Anything that interferes with the energy in the denominator misleads the reader as to the product’s cooking performance.
4. The energy content of recovered char is not the same number as the energy ‘not used for cooking’. It is a portion of the ‘not used’ number. In short, if the stove made a lot of small ‘unrecoverable bits of char’ the energy in the recoverable char is significantly less than the energy in the residual solids. Subtracting the energy ‘not released by burning’ from the total energy available in the fuel fed in, would give a close approximation of the heat transfer efficiency (the error being partially combusted gases). But that is not what is happens with the WBT formula. Only a portion of the energy in the solid residue is subtracted – the ‘recoverable portion’. Well, who says what is recoverable and what is not? Opinions differ. And, after making this subtraction, what is the proper description of the result of the calculation? It describes no standard reporting metric of thermal performance. It is just a number. It is not even a useful number.
5. Users of the WBT have, for years, been led to believe that it represents the fuel consumption and that comparing the two ‘WBT efficiency’ numbers from two stoves will show the comparative fuel savings by using the formula

(1-(Stove 1/Stove2))*100%

The answer is the fuel saved in % (or increase). The answer is only correct if the energy in remnant char. Recoverable or not, is not subtracted from the denominator.

 

Using the WBT ‘thermal efficiency’ numbers, it gives the wrong answer. The fuel use is under-reported.  The reason it gives the wrong answer is because it makes the calculation incorrectly. Mathematically, the method employed treats the recoverable portion of the remnant char as if it is unburned raw fuel.

 

The End

 

It is junk science and always was. It is an error introduced in 1985 by VITA against the objections of Feu do Bois and Eindhoven University. Upon review in 1991 (Rani et al) it was rejected as a calculation by the government of India. Good for them.

 

I do not care how much people have invested in this WBT test. It lies. It is fatally flawed. It doesn’t give an answer people can believe. It has no place at the table. It has to go. It is cheating people out of their investments in stove programmes.  Everything based on it is fundamentally flawed – all decisions, all ratings, all money spent and wasted – and Lord knows there has been enough of that.

 

Ron: If you want to report something about the char, use conventional methods and metrics, don’t piggy-back on junk science from Berkeley. So they made a mistake. Fine. Get over it.  Extending the deception will not help anyone. At this very moment it is deceiving the UN which is purchasing 10,000 stoves for refugees that will not live up to their performance ratings – because, and only because, they were tested using the WBT 4.2.3 and its defective spreadsheet v4.2.4 (Don’t ask me why the numbers don’t match – it doesn’t matter.)

 

Char production is a function of the mass in and mass produced, expressed as a %. It also has an energy content. Fine. Report it. The downstream uses of char from char-making stoves do not affect in any way the cooking efficiency which is a measure of the fuel needed to conduct a cooking session.

 

It is pointless to try to convince us who are working in the field and spending other people’s money to report that a stove using 1.3 kg per of dry fuel cooking cycle uses 650 g ‘because it makes char’. I do not care what type of fuel is going in – if it takes 1.3 kg per time, then the fuel consumption will be reported to be 1.3 kg, efficiency x. If it produces 400 g of char doing so, and you want to report it, the report can say: dry fuel consumption is 1.3 kg per replication; char produced 400 g per 1.3 kg of fuel (31%); cooking efficiency x. There is no free lunch.

 

There is nothing wrong with reporting the fuel consumption of a stove. There is nothing wrong with reporting the mass or energy of char produced. There is a lot wrong with subtracting any number from the mass of fuel in the denominator representing the fuel needed to perform the cooking task. That is called ‘cheating’.

 

I have already reported on this list a method for calculating the performance of a pair of stoves like that produced by Dr Nurhuda wherein the second uses the char produced by the first as its input fuel. Any such evaluation can produce the correct answer for the system efficiency of the pair only by correctly calculation the performance of the first stove, which means avoiding the WBT thermal efficiency formula. This is a matter of science, not opinion.

 

Regards

Crispin

 

 

 

From: Ronal W. Larson [mailto:rongretlarson@comcast.net]
Sent: 12-Jan-17 17:08
To: Discussion of biomass <stoves@lists.bioenergylists.org&gt;; Crispin Pemberton-Pigott <crispinpigott@outlook.com&gt;
Cc: miata98@gmail.com
Subject: Re: [Stoves] ABCEG deceit and conceit (Re: Crispin, Andrew) ON THE SIDE

 

List,  

 

            This exchange below has reminded me that Crispin and I have not closed the loop on an important stove reporting equation of the form e3 = e1 / (1- e2).  About half way down in this message, Crispins says about this equation:

 

The error in the WBT is to deduct something from the denominator. This was never correct. The fuel fed is the fuel fed, not something less. Char produced as a co-benefit goes in the top line, not deducted from the bottom.

            This is to disagree with Crispin’s “never” – and to defend the WBT equation.  

 

 I will start by suggesting we look at a set of data saying that stove measurements on five successive days gave these results:

	E1=thermal(%)	E2=char( %)
Monday	30	20
Tuesday	28	23
Wednesday	32	17
Thursday	29	21
Friday	31	18
Ave’s	30	19.8
Max difference	4/28  (14%)	6/17  (35%)

 No-one following this topic would be surprised if I posited that Crispin would prefer the Wednesday stove which has 14% more water boiling than the lowest, while I should prefer Tuesday with 35% more char than his Wednesday choice.

So what does the equation in dispute say about this matter?  This additional column says that our two choices differ by only 2.2% (and my Tuesday choice is the “loser”)

	E1=thermal(%)	E2=char( %)	Estove=E1/(1-E2)
Monday	30	20	37.5
Tuesday	28	23	36.4
Wednesday	32	17	38.6
Thursday	29	21	36.7
Friday	31	18	37.8
Ave’s	30	19.8	37.4
Max difference	4/28  (14%)	6/17  (35%)	2.2/36.4  (6%)

The important point (which I have so far hidden in this hypothetical example) is that these are not different stoves. These are posited results all for the same stove.  The differences are caused by having different operators, different types of fuel, moisture content, , etc.  Multiple tests are needed (and are being undertaken) to be able to report a more accurate answer.

 

            The subtraction of E2 in the denominator is NOT leading up to a statement about charcoal production efficiency.  It is the exact opposite.  The denominator after subtraction is the amount of energy available for boiling water.  The resultant answer (about 37.5%, within about 1 %) is the efficiency of the stove if no char had been produced.

 

            So I am fully happy with using this equation, as long as there is no intent to make and keep produced char.  It is NOT an incorrect equation.  But it is meaningless if one is intentionally trying to produce char.  Crispin and I agree on this.

 

Ron