[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
>
>
>
> _______________________________________________
> Stoves mailing list
>
> to Send a Message to the list, use the email address
> stoves at lists.bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>
> for more Biomass Cooking Stoves, News and Information see our web site:
> http://stoves.bioenergylists.org/
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20150227/1fb7fc09/attachment.html>
More information about the Stoves
mailing list