[Stoves] Stoves Digest, Vol 16, Issue 11
Arthur Laurent
arthur.laurent at associationmicrosol.com
Wed Oct 10 15:44:58 EDT 2007
Ya du topics qui nous interesse évidemment j'ai pas le temps de les lire...
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Envoyé : mercredi 10 octobre 2007 06:32
À : stoves at listserv.repp.org
Objet : Stoves Digest, Vol 16, Issue 11
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Today's Topics:
1. Re: [ethos] Re: Laboratory Comparison of the Global-Warming
Potential of Six Categories of Biomass Cooking Stoves (Mr. Dean Still)
2. Re: [ethos] Re: Laboratory Comparison of the Global-Warming
Potential of Six Categories of Biomass Cooking Stoves (Mr. Dean
Still)
3. Energy Calculator and data for TLUDs (Paul S. Anderson)
4. Terra preta. was Re: [Fwd: Re: Stoves in China]
(Paul S. Anderson)
----------------------------------------------------------------------
Message: 1
Date: Tue, 9 Oct 2007 22:04:39 -0700 (PDT)
From: "Mr. Dean Still" <dstill at epud.net>
Subject: Re: [Stoves] [ethos] Re: Laboratory Comparison of the
Global-Warming Potential of Six Categories of Biomass Cooking Stoves
To: crispin at newdawn.sz, "Discussion of biomass cooking stoves"
<stoves at listserv.repp.org>
Cc: 'Discussion of biomass cooking stoves' <stoves at listserv.repp.org>
Message-ID:
<60029.122.164.164.156.1191992679.squirrel at webmail.epud.net>
Content-Type: text/plain;charset=iso-8859-1
Dear Crispin,
As I pointed out to Tom, we just sponsored a very long series of tests
measuring the effect of moisture content on emissions and fuel use,
specifically responding to questions raised at ETHOS. It should be
available soon. Did anyone else investigate the effects?
The wood that we use for testing is left overs from a large carpentry
shop. It is the wood they use every day. It is not especially dried for
our tests.
It seems that you imagine that drier wood favors the rocket type
combustion. However, as you can see in the report the fan stove and Karve
gasifier did well using the same wood.
Perhaps you did not see that Rob Bailis addressed some of your points with
the WBT?
As you may remember, when we were testing the Vesto I repeatedly asked you
to come to the lab to run the tests. We try to carefully learn how to run
stoves before testing them. Having the inventor run the stove gives it the
best chance to succeed as Paul Anderson knows from testing frequently at
Aprovecho with all kinds of biomass.
I think the point is for all of us to remind funders what testing is
showing. People who are familiar with scientific investigation know that
the results of experiments only show what is investigated. Does this mean
that stovers should not do experiments for fear the results will be
misunderstood? NO, it means that more and more experiments should be done
to fill in the whole picture.
All Best,
Dean
On Tue, October 9, 2007 8:45 pm, Crispin Pemberton-Pigott wrote:
> Dear Friends
>
>
> Given the stress caused by the disagreements around testing methods I
> agree that it would be good to push forward the agenda proposed early this
> year at the ETHOS conference.
>
> The main issues have not been debated in terms of what they are. Here
> are five:
>
>
> Issue 1. The fuel is not representative of field conditions. It is
> extremely dry and does not burn like regular fuel. There seems to be no
> reason given by Aprovecho for using fuel this dry. No one presents
> justifications for it. Yet over the strenuous objections of people
> including myself, tests that purport to 'compare' stoves are still being
> made and the results published, at least on the internet, sometimes in
> documentary form.
>
> Why does it matter?
> The fuel used in these tests cannot be used to establish performance
> benchmarks.
>
> Stoves that burn sticks on the end, like the Rocket Stove, perform
> extremely well using very dry fuel. Other stoves including the Vesto,
> Juntos
> gasifiers, semi-gasifiers and any stove with a significant preheating of
> air do not do well because the fuel burns far too quickly, often running
> out of air, producing high levels of CO and particulates. The Rocket
> Stove is
> optimised to burn that fuel; the stoves it is compared with are not.
>
> Issue 2. The use of lids on pots for stove tests. This has been
> discussed many times. Stoves that are designed to operate at a certain
> power level are apparently tested with no lids on the pots, forcing the
> operator to run the stove above its design power output in order to boil
> the water in a reasonable time. This affects emissions. During simmering,
> more fuel than normal is required to maintain the water temperature, even
> though the stove may be optimised to simmer at a very low power level.
> The Rocket
> Stove is optimised to operate a power level to boil pots without lids -
> years of research reports show this. While some concession was made this
> year with regard to lids, it is not yet clear to me that the tests
> recently published were done according to the stove design parameters, or
> according to the UCB-WBT.
>
> Why does it matter?
> Unrepresentative tests give unrepresentative results. Very important fund
> decisions are made on the basis of test results, such as the level of
> CO2
> offset funding a stove type is going to receive. If the test is
> unrealistic, the funder and manufacturer are being compromised.
>
> Issue 3. Fuel heat rating. There is a portion of the WBT that
> calculates the heat yielded during a test. This means that taking into
> consideration the heat in dry fuel, the moisture content of that fuel and
> the char remaining, an amount of heat offered to the pot is calculated.
> The
> UCB-WBT method is very accurate for only one species of wood and one
> charcoal type, but quite inaccurate for different wood species, different
> fuels, high moisture levels and different charcoal heat contents.
>
> Why does it matter?
> Tests done at different locations are difficult to compare with the ones
> done at Aprovecho unless the actual lab data is made available so the
> tests can be recalculated. This data, in general, has not been made
> available by Aprovecho so the tests cannot be re-evaluated, nor can the
> claims made for comparative efficiency or fuel consumption be verified.
> The results from
> several months of testing different fuel moisture levels are not rendered
> acceptable because so much money and effort was put into them. They
> become acceptable when the protocol is realistic and the calculations made
> as accurately as possible.
>
> Issue 4. Thermal efficiency calculation method. The formula used to
> calculate the efficiency of a stove involves comparing the heat offered to
> the pot with the heat absorbed by the pot. The one used in the UCB-WBT
> is not accurate. There are errors introduced by the lack of lids: no
> account is taken of radiation from the hot upper water surface and the
> excessive evaporation with no lid. The bigger error is the one that
> starts in the fuel heat rating and is then transferred to the efficiency
> calculation. As the amount of charcoal remaining increases, as the heat
> content of the fuel decreases and as the moisture content of the fuel
> rises, the error gets larger and larger. For gasifiers and users of low
> heat content fuels, the error can be well over 100%. By this I mean that
> the calculated heat released can be double the actual value, giving the
> impression that the thermal efficiency of the stove is only 1/2 what it
> really is. In other cases, the calculated value is very accurate. Such
> calculation errors render meaningless comparisons made between stoves
> using wood of different species and moisture contents and, for example,
> rice hulls, as has been done with the latest set of published tests.
>
> The forthcoming test results for higher levels of fuel moisture mentioned
> by Dean are probably going to be presented within the UCB-WBT framework.
> If
> so, the thermal efficiency calculations and specific fuel consumption
> figures are invalid because of deficiencies in the methodology and
> formulae. The only immediate solution would be that the raw data for the
> tests be published so that the real performance can be calculated using
> various other methods, though that would still not solve the fuel moisture
> problem.
>
> Why does it matter?
> The UCB-WBT in its present form cannot be used to establish realistic
> performance benchmarks.
>
> Issue 5. Variable and incompetent operation of stoves being tested.
> It is always a problem to get people who do not know how to use a stove
> really well to test it. The problem will not easily go away. The best
> answer I have seen is for developers to run their own stoves using fuel
> of their choice. To do that at a central facility is very expensive.
> Testing
> a different places in the world and comparing notes requires an agreed
> protocol.
>
> I have suffered many times with products (other than stoves) being badly
> run by 'independent' testers so the problem is not unique to stoves. In
> the case of the recent rice hull stove evaluation, the tester ran out of
> fuel part way through the test, yet reports the result which a reader must
> assume as being representative of the stove's performance. This is not
> reasonable. Previous tests showed the CO emission to be 1/7 of this test.
> This is
> inconsistent and frankly, unbelievable.
>
> Why does it matter?
> It is dangerous because unfair accusations of bias can emerge if a stove
> is underperforming at Aprovecho when being tested alongside other expertly
> run stoves and the comparative results published as representative of the
> stoves performance in general.
>
> Improving the situation:
> A very large amount of goodwill have been shown to the people and
> institution of Aprovecho by many skilled and experienced people. No one
> will benefit from the publication of results that are correctly critiqued
> followed by more of the same. A year ago these same five issues came up
> at a meeting in Bonn on the development of stove performance benchmarks. A
> year later the issues are largely unaddressed, with quite serious
> consequences for one of the stoves recently tested, the dissemination of
> which is dependant on funding determined by the CO2 and GHG mitigation
> value. Suppose these tests are believed?
>
> Failure to address these five fundamental scientific issues, now, at
> Aprovecho, can only lead to further complications and disaffection in the
> stove developers community. If they are not addressed, there is a real
> danger that their results will be increasingly ignored.
>
> A lot of talented people are willing to contribute to this process. We
> must enhance the store of goodwill that already exists between this
> eminent group of peers and deliver superior services to the world.
>
> Sincerely
> Crispin
>
>
>
> _______________________________________________
> Stoves mailing list
> Stoves at listserv.repp.org
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> http://info.bioenergylists.org
>
>
------------------------------
Message: 2
Date: Tue, 9 Oct 2007 22:23:13 -0700 (PDT)
From: "Mr. Dean Still" <dstill at epud.net>
Subject: Re: [Stoves] [ethos] Re: Laboratory Comparison of the
Global-Warming Potential of Six Categories of Biomass Cooking
Stoves
To: "Tom Miles" <tmiles at trmiles.com>
Cc: methods at bioenergylists.org, ethos at vrac.iastate.edu, 'Discussion of
biomass cooking stoves' <stoves at listserv.repp.org>
Message-ID:
<60175.122.164.174.183.1191993793.squirrel at webmail.epud.net>
Content-Type: text/plain;charset=iso-8859-1
Hi Tom,
I'm glad that you appreciate the time and effort we put into testing. We
do not get paid for a lot of the testing we do, it is a part of our
committment to improve stoves.
As I said to Crispin, the wood we use is dumped into my pick up truck from
a local carpentry shop. We do not wet it or dry it.
The same was true for the rice hulls. If I remember correctly, they came
from UC Davis in a bag and were used directly from the bag. Should we have
poured water into the bag?
This is what we had to do, by the way, when testing the effect of moisture
on fuel use and emissions recently. The wood was placed in a sealed
container over water. Getting it to 20% and 30% was not easy requiring
frequent measuring by placing samples in an oven.
All Best,
Dean
On Tue, October 9, 2007 1:19 pm, Tom Miles wrote:
> Dean,
>
>
> I understand your intent and appreciate your good work. I like the
> direction but we still need to apply rigorous testing and evaluation
> criteria so that the results are meaningful.
>
> I'm not too concerned about where the rocket falls. It may perform well
> under many conditions. I am concerned that if we are generating
> information about emissions that it be as close to actual use (e.g. CCT,
> KPT) conditions
> as possible. And the performance conditions should be well documented. Our
> purpose should be to find the best point of performance of these stoves
> and encourage their use in those conditions. That may actually require
> different types of fuels, densities and moisture contents for different
> stove designs. Charcoal testing should include improved stoves like the
> New Lo Trau.
>
>
> In my experience very dry fuels make more CO. Wet fuels make more PM. We
> need to narrow the gap between the artificial environment of kiln dried
> fuel and fuel that is conditioned (humidified) to simulate fuels in actual
> use. The 3.6-4% MC fuel you used corresponds to fuels stored for a long
> time in a dry inside environment (60F 15% relative humidity). That's about
> the same equilibrium moisture content (EMC) as furniture in a house. I
> have hundreds of analyses of rice husks from thousands of tons that I have
> burned, mostly in Thailand. I have never burned rice husks as dry as 4%.
> With the weather
> today in Bangkok, Manila or Phnom Penh (80F, 79% RH) the rice husk EMC
> would be about 16% MC. With higher moisture CO will come down. PM may
> increase. Your previous "benchmarks" may all move up.
>
>
> Previous tests on heating stoves have been done using 18% MC and 35% MC.
> 15%-18% is typical of air dry wood. 35% is representative of partially air
> dry green wood. Your 10, 20 and 30% MC tests will fall somewhere in
> between. We look forward to the results. Hopefully the tests will include
> references to similar tests on heating stoves.
>
> If there is more information about the performance tests of the six
> stoves then it should be referenced in the study cited. I didn't see a
> reference or link to the detailed test data which should include
> information not reported in your summary.
>
> I appreciate that these tests take time and resources. As we have
> discussed before we need to have more labs around the world doing these
> tests. I do not know what funding is available for this kind of testing
> but we should have more of it. At ETHOS 2006 EPA's Jim Jetter described
> proposed testing but we have not seen any results.
>
> I invite everyone to suggests ways that we can improve testing so that
> the results can be more representative of actual use.
>
> Regards,
>
>
> Tom
>
>
>
>
>
>
>
>> -----Original Message-----
>> From: owner-ethos at vrac.iastate.edu [mailto:owner-
>> ethos at vrac.iastate.edu] On Behalf Of Mr. Dean Still Sent: Tuesday,
>> October 09, 2007 1:44 AM
>> To: Discussion of biomass cooking stoves
>> Cc: 'Discussion of biomass cooking stoves'; methods at bioenergylists.org;
>> ethos at vrac.iastate.edu Subject: [ethos] Re: [Stoves] Laboratory
>> Comparison of the Global-
>> Warming Potential of Six Categories of Biomass Cooking Stoves
>>
>>
>> Hi Tom,
>>
>>
>> I'm in India trying to make great, inexpensive stoves so this will be
>> short because the net seems to drop out whenever I write a long message.
>>
>> Haven't we discussed that in response to these questions we sponsored a
>> woman from Cameroon to spend a couple of months at the lab? She did a
>> very long series of experiments with various stoves using wood at 10,
>> 20,
>> 30%
>> moisture content. She looked at fuel use and emissions. This study should
>> be out soon.
>>
>> We are not doing anything to favor the rocket, Tom. I think it odd that
>> you would suggest it. As it turns out the rocket, gasifier, and fan
>> all were improvements. The fan stove was amazing. I have to say that our
>> lab takes advice to heart, we respond by studying the question, which
>> takes time and great effort. The questions you and Crispin raised at
>> ETHOS
>> are being addressed through experimentation which will hopefully give us
>> answers. We encourage everyone to do research as we do.
>>
>> All Best,
>>
>>
>> Dean
>>
>>
>> On Tue, October 9, 2007 12:25 am, Tom Miles wrote:
>>
>>> All,
>>>
>>>
>>>
>>> My impression on reading this work is that it is an impressive first
>>>
>> test
>>> of a series of methodologies but I think the results suffer from the
>> same
>>> problems we have discussed previously with the UBC WBT. While the
>> tests
>>> as used by Aprovecho may show relative differences between stoves for
>>>
>> the
>>> same fuel (7% MC Douglas Fir), when applied to emissions fuels should
>>>
>> be
>>> used that are appropriate to the stoves being tested. I very much
>> doubt
>>> that even fuels of the same density as douglas fir are burned at 3.4%
>>>
>> MC.
>>
>>> (We have
>>> discussed here the need to look at emissions at 15% MC and 35% MC
>> with the
>>> same stove to test performance with more commonly used moisture
>>> contents.) I also seriously doubt that rice hulls are actually burned
>>>
>> at
>>> 4% MC. The very
>>> low moisture would show much higher CO levels in various stove types
>> than
>>> probably actually occur. This leads me to believe that the
>> performance of
>>> these stoves is misrepresented by the tests and therefore the
>> emission
>>> data is useless. What is the best performance of each of these
>> stoves;
>>> what are the conditions that cause that performance; and, how does
>> that
>>> compare with the performance reported here? How is it that the stoves
>>>
>> are
>>> compared under circumstances that seem to favor the rocket design?
>>>
>>> We have questions of methods and results to settle. Let's go back and
>>> compare the performance of the stoves in these tests with a range of
>>> performance parameters before drawing conclusions about performance
>> and
>>> emissions. The questions raised in the January PCIA and ETHOS
>> meetings
>>> are still unanswered.
>>>
>>> Perhaps those many coauthors of this report (Bond, Macarty, Ogle,
>>>
>> Roden,
>>
>>> Still and Willson) can show us how the performance reflected in this
>>> report compares with previous tests and more typical fuels.
>>>
>>> Let's use discussion of this study as a vehicle to resolve these
>>>
>> issues.
>>>
>>>
>>> Thanks
>>>
>>>
>>>
>>> Tom
>>>
>
>
------------------------------
Message: 3
Date: Wed, 10 Oct 2007 05:35:03 -0500
From: "Paul S. Anderson" <psanders at ilstu.edu>
Subject: [Stoves] Energy Calculator and data for TLUDs
To: crispin at newdawn.sz, Discussion of biomass cooking stoves
<stoves at listserv.repp.org>, Crispin Pemberton-Pigott
<crispinpigott at gmail.com>
Cc: 'Discussion of biomass cooking stoves' <stoves at listserv.repp.org>
Message-ID: <20071010053503.uyhrbtrjzs0kggc4 at webmail2.ilstu.edu>
Content-Type: text/plain; charset=ISO-8859-1; format="flowed"
Crispin, Tom Reed, Nordica, and all,
Your good message is appreciated. However, I must refer it to Tom Reed. I
do
not have WBT results except what has been done at Stove Camps. (Here, maybe
Nordica can assist because she has the raw data. Please reply, Nordica and
Tom).
In my development work, I have not measured the moisture content of the
fuels
used (except maybe 3 times.). I know that I have some sundried woody fuels
that work, and then I keep comparing the different stoves while using the
same
basic fuels.
I am in India until 18 Nov with a TLUD gasifier stove project. So my focus
is
on the specific situation here. I will report the results later, and
at ETHOS.
All looks very very good so far.
Paul
--
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone: USA-309-452-7072 (residence and office)
Internet site: www.ilstu.edu/~psanders
For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson
Quoting Crispin Pemberton-Pigott <crispinpigott at gmail.com>:
> Dear Paul
>
> I think it is important that you try the results of a few old stove tests
in
> the dry fuel equivalent calculator. Nigel and I tried to accommodate a
wide
> variety of fuels in the sheet so that you get information that is close to
> the truth about the thermal performance of your designs and design
changes.
>
> Where there is a significant difference in the moisture content or
charcoal
> yield, you will see some interesting results.
>
> I am very interested to hear from you what the results are for actual test
> data plugged in from gasifiers, and from gasifiers where the charcoal
yield
> is pretty low.
>
> If you have been using any of the standard tests or have been using the
WBT
> in its present form, you might try putting in the data to see what the
> differences are.
>
> We noticed in particular that the low quality fuels like grass, waste
> agricultural materials and rice husks are performing far better than was
> thought in terms of thermal efficiency. Roger Samson and I have been
> talking about this and how it affects the CO2 offset value of improved
> stoves. The difference in CO2 emissions are significant if the thermal
> performance is not accurately reflected. He is doing a lot with grass
which
> has a low heat content.
>
> Version 1.0 of the calculator is for getting the basics right. We are
going
> to put in a second method of determining the heat yielded by the volatiles
> which will give accurate results for gasifiers for fuels where the carbon
> content of both the raw material and char is known. We tried it and it is
OK
> but decided to go with the simpler version first for comments.
>
> There is a question you will have to address which is what happens to the
> char removed from the gasifier. If it is 'useful' then it can be counted
as
> 'not burned' but if the resulting char has to be thrown away without
> benefit, it can be viewed as having been consumed. We talked about this
once
> a couple of years ago.
>
> If you are doing a test of a stove development you will be interested in
the
> total thermal efficiency at certain times and won't worry about the char.
> In that case you will find the assessment of total energy offered to the
pot
> useful because it will tell what the thermal efficiency is when boiling,
for
> example, and the specific consumption of energy used to simmer, whether
> expressed in watts per litre simmered or the dry wood equivalent.
>
> If you are using regular woody biomass you can go with the charcoal heat
> value of 29.477 LHV if you are not sure what it is. When we know more
about
> the carbon content of char produced at different TLUD temperatures you
will
> enter the appropriate values.
>
> Good luck!
> Crispin
>
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Message: 4
Date: Wed, 10 Oct 2007 06:32:24 -0500
From: "Paul S. Anderson" <psanders at ilstu.edu>
Subject: [Stoves] Terra preta. was Re: [Fwd: Re: Stoves in China]
To: frank at compostlab.com, Discussion of biomass cooking stoves
<stoves at listserv.repp.org>
Message-ID: <20071010063224.dp82wmmo0wkwcgcg at webmail2.ilstu.edu>
Content-Type: text/plain; charset=ISO-8859-1; format="flowed"
Quoting frank <frank at compostlab.com>:
> Stovers
> I suggest there may be much better use for charcoal than returning it to
> the forest. It does contain some nutrients like potassium, phosphorus,
> calcium etc but there are better ways to add these (compost) and it may
> help improve the structure of a poor soil. I don't see the carbon being
> available to the plants as I have found it in thousand year old
> archeology sites.
Frank, the carbon (char) in terra preta old soils is not to go into the
plants,
but to help the soil be better for the plants. Carbon in compost with
be lost,
but the char is a nearly permanent improvement. Especially in the humid
tropics, the compost (incl leaf litter) is rapidly decomposed and/or
leached.
I suspect that the nutrients (P, K, Ca, etc) in the ash do become available
to
the plants.
This is especially for tropical soils. And maybe mid-latitude sandy
soils?? Nothing against composting. But char into the weak soils is
ANOTHER way of
improving soils, especially in the tropics.
Paul
I would think mixing it in with small fuel that is
> densified may be a better use.
> Frank
>
> Jeff Davis wrote:
>
>> Crispin wrote:
>>
>>
>>> As is obvious, if a person goes back into the forest to cut more wood,
>>> then there is a problem.
>>>
>>>
>>
>>
>>
>>> If I have a gasifier that requires 2 kg of wood each day, making 1 kg of
>>> charcoal is not helping the forest re-grow.
>>>
>>>
>>
>> The theory is that one would return the charcoal back to the forest.
>>
>> As a side note; truckers have a term for finding something to haul on the
>> empty leg of their trip but the term escapes me at present.
>>
>>
>> Jeff
>>
>>
>>
>>
>>
>>
>
> --
> Frank Shields
> Soil Control Lab
> 42 Hangar way
> Watsonville, CA 95076
> (831) 724-5422 tel
> (831) 724-3188 fax
> frank at compostlab.com
> www.compostlab.com
>
>
>
> _______________________________________________
> Stoves mailing list
> Stoves at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org
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> http://info.bioenergylists.org
>
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