[Stoves] Gold Standard & CDM regarding char-making stoves ....Re: Updating your WBT and PEMS/LEMS Spreadsheet

Paul Anderson psanders at ilstu.edu
Fri Feb 27 10:45:42 CST 2015


Biochar-ists,    (and to Stovers only because the comment started in a 
Stoves Listserv message.   I think this topic can best be at the Biochar 
Listserv.)

Subject line changed because this is NOT about WBT.   But from a message 
(found below) by Crispin about the WBT measurements, the following 
comment should be considered by those who have involvement with Gold 
Standard (GS) and CDM measurements.  Crispin wrote:

> ....the performance of the [stove] under investigation has to be 
> reported correctly with respect to fuel consumption from the supply, 
> because that is how the Gold Standard and CDM and most projects 
> conceive of it. They have been using the heat transfer efficiency 
> proxy which is quite misleading for a lot of stoves. The more char 
> typically produced, the more misleading the rating, and the scale of 
> the error runs to more than 200% of value.
This relates (I think) to the GS and CDM issues about whether or not 
char-production and sequestration of carbon as biochar should be 
factored into the GS and CDM calculations and rewards about 
carbon-related projects.

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