[Stoves] Examples of results of simmer efficiency Re: [Ethos] Additional presentations at ETHOS 2015

[Dean Still]

Dear Philip,

The Low Power test works well when the fuel use is normalized using a set
simmering temperature.

Sam and I are writing up some characteristics of the WBT and I'll post the
paper here. Lots of work to do and I look forward to our continued
collaboration.

Best,

Dean

On Sun, Feb 15, 2015 at 11:43 AM, Philip Lloyd <plloyd at mweb.co.za> wrote:

> Dear Dean
>
>
>
> Crispin said it well:
> “The three low power metrics are invalid. The variables selected are
> inappropriately chosen. The calculated results are misleading and contrary
> to any claim [that] they provide guidance for product development or
> selection. We have to move on.”
>
>
>
> I have looked at the simmering metrics in WBT 4.3.2 and can only concur.
> That is why I do not think we should waste much more time arguing about
> them – they are fundamentally wrong. Yes, stove designers need to be
> concerned with simmering and turndown; no, the WBT simmering metrics do not
> provide them with guidance, and can be positively misleading, which is
> worse.
>
>
>
> Kind regards
>
>
>
> Philip Lloyd
>
>
>
>
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
> Behalf Of *Dean Still
> *Sent:* 15 February 2015 06:38
> *To:* Discussion of biomass cooking stoves
> *Subject:* Re: [Stoves] Examples of results of simmer efficiency Re:
> [Ethos] Additional presentations at ETHOS 2015
>
>
>
> Dear Prof Loyd,
>
>
>
> As I pointed out, when the stoves do the same work (hold the water at 97
> C, for example) the stove with greater heat transfer efficiency scores
> better. Simmering tests are important and simmering is an important part of
> cooking.
>
>
>
> The ISO process is creating new history and approaches to old problems.
> Whatever emerges will certainly be defensible as the new approaches are
> forged by consensus.
>
>
>
> Best,
>
>
>
> Dean
>
>
>
> On Sun, Feb 15, 2015 at 12:58 AM, Philip Lloyd <plloyd at mweb.co.za> wrote:
>
> I am concerned that this is turning into a very fruitless discussion.
>
>
>
> On fundamental grounds the simmering test does not provide anything
> meaningful.  Crispin has demonstrated that rigorously, and others have
> pointed out that the test can score an efficient stove poorly and an
> inefficient stove well, so it does not provide any useful measure.  To go
> on defending the indefensible does not make sense, even if it did
> accentuate the need for turndown – but that need was always there, it was
> not the product of the WBT.
>
>
>
> We need defensible measures of stove performance.  Can we please turn our
> attention to developing those, and leave the indefensible to history?
>
>
>
> Prof Philip Lloyd
>
> Energy Institute
>
> Cape Peninsula University of Technology
>
> PO Box 652, Cape Town 8000
>
> Tel:021 460 4216
>
> Fax:021 460 3828
>
> Cell: 083 441 5247
>
>
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
> Behalf Of *Paul Anderson
> *Sent:* 15 February 2015 02:26
> *To:* Discussion of biomass cooking stoves
> *Subject:* Re: [Stoves] Examples of results of simmer efficiency Re:
> [Ethos] Additional presentations at ETHOS 2015
>
>
>
> Dear Dean,    my reply is below:
>
> 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 2/14/2015 1:06 PM, Dean Still wrote:
>
> Dear Paul,
>
>
>
> To do well on the Low Power Specific Consumption metrics the stove has to
> have a good Turn Down Ratio. In other words, the stove has to have high
> power and low power.
>
> I totally agree with this.   But it is not the whole story of LPSC.
> Other factors influence LPSC, especially concerning the measurement of the
> variables that are used to make the calculation.   These can include the
> insulation of the pot (incl. skirts), lid on pot, pot characteristics such
> as size, quantity of water in the pot at the start, and at the finish.
>
>
>
> Specific Consumption is based on how much energy was used to create
> simmered water.
>
> Simmered water is not created.   It was already hot at the start of the
> simmer phase of testing.   We are interested in how much energy is used to
> MAINTAIN the required temperature near boiling, but preferable about 3
> degrees C lower than that boiling temperature.   In fact, a
> super-insulative pot could need barely a flicker of a flame, and therefore
> even a well turned-down stove could cause the water to boil and
> evaporate.
>
> If the stove only operates at high power there is more steam made and [at
> the end of testing] less simmered water remains....
>
> that is true.   but continue.
>
> ..... so energy was used to create less product.
>
> Stove simmering is not creating a product.   It is maintaining a
> temperature.   The steam that is driven off does not represent loss of
> "product" which should be understood to be "cooked food" (and not meaning
> water that can be added to the pot by any attentive cook in a household.)
>
>
>
> I like Specific Consumption because it forces stove designers to make
> stoves that simmer successfully, not just boil water.
>
> I agree.   But the measurement procedures need to accurately document the
> ability to have that strong turn-down ratio, without calculations that can
> yield ambiguous or mis-leading results.
>
> For example, new TLUDs are better stoves because they have both high power
> and low power. In my opinion, the WBT 4.2.3 helped to create these more
> successful TLUDs.
>
> The cause-and-effect relationship is not totally clear.   We have wanted
> turn-down capabilities in TLUDs for many years.
>
>
>
> As Sam says, we are working on a paper showing characteristics of the WBT
> 4.2.3 for the ISO work. Knowing the characteristics lets folks evolve a
> perfect test.
>
> I question the above wording to "evolve a perfect test" (which is a test
> run, not the test procedures.)   Maybe the statement should be that
> "knowing the characteristics let's folks operate their stoves in special
> ways to obtain superior results that are not realistic for average users."
> OR "... let's folks 'game the metrics' to present 'perfected' test-results
> BASED ON OPERATIONAL PROCEDURES AND NOT ON IMPROVEMENTS TO THE STOVES
> THEMSELVES."
>
> OR it could be that flawed protocols /procedures (such as dividing by the
> volume of remaining water after simmering) can yield numerical results that
> are questionable and perhaps disadvantageous to the development of clean
> cookstoves.
>
>
>
> Sam is doing great work as he crunches all the data....
>
> absolutely.   But we are questioning if the numbers are as valid and
> useful as claimed.
>
>  and gives ISO real numbers to work with in their discussions.
>
>
> Concluding statement:   The topic of Low Power Specific Consumption is too
> important to just brush aside the stated issues.   More "expert testimony"
> would be useful, including a mathematical analysis of the impact of the
> parts of the calculations.
>
> Paul
>
>
>
>
> Best,
>
>
>
> Dean
>
>
>
> On Sat, Feb 14, 2015 at 8:18 AM, Paul Anderson <psanders at ilstu.edu> wrote:
>
> Dear Tom H.,         and to all who are interested in proper testing of
> stoves.
>
> Your reply about your experiences is helpful.   Sounds like you had
> qualified testing center do the testing, in accordance with the procedures
> that Crispin is questioning.   Please send to me the full details.   Could
> be off-list, but this is sufficiently important that we will want the full
> results known.
>
> I have a specific case of official testing of one of my stoves with
> unfavorable results for Low-Heat Efficiency (simmering).   I will add that
> into the list of examples and provide the details very soon.
>
> I invite anyone else who has something to report about simmering
> efficiency to also send details of their experiences, either favorable or
> unfavorable or neutral.
>
> The examination of the questionable methods about simmer efficiency might
> take some days, maybe weeks.   But not the months or years that this debate
> has been "simmering".
>
> Remember:  A testing center that properly conducts testing using an
> endorsed but possibly flawed procedure is NOT a culprit.  The culprit is
> the testing protocols, *IF found to be faulty.   *And we hope that the
> testing center people (employees and leaders) who understand the technical
> aspects of the calculations will be among those who can help resolve these
> serious issues.
>
> Even those who developed protocols that are eventually shown to be faulty
> are not culprits.   Mistakes can be made.    However, the culprits can
> include those who advocate a protocol that he or she knows (or reasonably
> suspects) to be faulty.
>
> 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
>
>
>
>
>
>
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