[Stoves] The need to continue the discussion: simmer efficiency
Paul Anderson
psanders at ilstu.edu
Thu Feb 19 17:40:37 CST 2015
To all,
If you are going to reply to Teddy's OTHER issues, please change the
Subject line. We want this thread to be very focused on the issues of
the testing procedures.
Thanks.
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 2/19/2015 5:26 PM, Cookswell Jikos wrote:
> Dear Dean and Paul and everyone else who has kindly contributed to
> this discussion. I personally have never been more fascinated by any
> other biomass stoveslist emails as much as this recent discourse and I
> would like to thank all of you who have contributed.
>
> From my perspective as the owner of a small but growing family
> business oriented around cookstoves and the provision of sustainable
> woodfuel for the 'seed-to-ash cycle' of biomass household energy in
> East Africa, and more recently the EU, these emails have been of great
> interest to me and my business partners.
>
> I heartily encourage you both, and everyone else, to please share more
> of your thoughts and reflections on these very pertinent physical and
> social science aspects of these testing issues.
>
> If it is not out of line to suggest, I would also be very keen to hear
> anyones inputs on the potential negative/positive externalities and
> life cycle analysis observations of the current and projected trends
> of biomass cookstove designers, manufacturers, testers and marketers.
> To further clarify my question - does anyone know of any studies,
> reports or papers of what the overall impacts and resource use
> implications by our industry from a cradle to grave cycle are?
>
> Does anyone know of anyone studying and/or certifying ''green''
> cookstove manufacturing, testing and distribution processes and
> generally how to improve our overall efficiencies? i.e. use of
> renewable energy in production, use of recycled materials, LEED
> certified factories, woodfuel security programs vis-a-vis
> afforestation advocacy etc.
>
> I feel that a part of this testing discussion could also be geared to
> also studying the factors involved in the study of stoves, the
> manufacture of stoves, the distribution of stoves and the final
> decommissioning and recycling of our products because after all, if we
> collectively aim to make a few billion of the things, I think it will
> be a helpful thing to know. :)
>
> Kind regards and again, many thanks,
>
> Teddy Kinyanjui
>
>
> *
> *
> *
> *
> *Cookswell Jikos*
> www.cookswell.co.ke <http://www.cookswell.co.ke>
> www.facebook.com/CookswellJikos <http://www.facebook.com/CookswellJikos>
> www.kenyacharcoal.blogspot.com <http://www.kenyacharcoal.blogspot.com>
> Mobile: +254 700 380 009
> Mobile: +254 700 905 913
> P.O. Box 1433, Nairobi 00606, Kenya
>
> Save trees - think twice before printing.
>
>
>
>
>
>
> On Fri, Feb 20, 2015 at 12:31 AM, Dean Still <deankstill at gmail.com
> <mailto:deankstill at gmail.com>> wrote:
>
> Dear Paul,
>
> I'll try once again.
>
> The WBT was designed to be a lab tool.
>
> The CCT and KPT are used to make stoves that please cooks, meet
> requirements in use.
>
> The instructions in the WBT, CCT, KPT plainly state the intentions.
>
> Aprovecho uses the CCT when we want to design a stove with the
> local cooks using their foods, pots. They operate the stoves. The
> cooks should design the stove.
>
> The WBT teaches how to improve stove technology. Two very
> different uses.
>
> All Best,
>
> Dean
>
> On Thu, Feb 19, 2015 at 1:06 PM, Paul Anderson <psanders at ilstu.edu
> <mailto:psanders at ilstu.edu>> wrote:
>
> Dear Jiddu, and to all who share the concerns about errors in
> testing of stoves.
>
> Your comments are greatly appreciated. Well said. As we
> make progress on these topics, the comments will be
> continually refined for clarity of expression, and will be the
> composite work of too many people to be individually named.
> Thank you.
>
> To know of your credentials as a theoretical physicist is
> appreciated. There could be people with credentials on both
> or all sides of the discussion. But you can talk to other
> physicists much better than I can. In debates (and
> courtrooms) both sides like to have their expert witnesses.
> Thanks for stepping forward.
>
> I especially like your comment that shows your convictions:
>> I find myself in the position where I have to tell my company
>> to produce stoves with lower rating because it will be better
>> for women that we build them for.
> That is worth re-reading and repeating!!!
>
> As I get further into this topic, I am realizing that invalid
> metrics must be STOPPED. I do not yet know how much they have
> hurt various stove designs, but I can see no way that such
> metrics have been of any positive value. ------
>
> ----- Oh, and if some stoves are benefited by such
> inaccurate metrics, and if the manufacturers know that they
> have made claims based on faulty testing, THAT would be truly
> reprehensible.
>
> It is fast becoming (in my opinion) the time when the
> defenders of the status quo about the three Low Power
> measurements in the WBT will need to speak up with some quite
> convincing arguments.
>
> Paul
>
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email:psanders at ilstu.edu <mailto:psanders at ilstu.edu>
> Skype: paultlud Phone:+1-309-452-7072 <tel:%2B1-309-452-7072>
> Website:www.drtlud.com <http://www.drtlud.com>
>
> On 2/19/2015 1:56 AM, Jiddu Broersma wrote:
>> Dear All,
>>
>> First,
>> Paul, thank you for keeping the conversation going with great
>> intentions. Much appreciated.
>>
>> I have been a quiet follower of the stovelist and I just
>> caught up on the simmering discussion. I believe it is a
>> necessary discussion.
>>
>> I would like to share my opinion. It is one from the
>> perspective of a stove manufacturer and a theoretical physicist.
>> I do this purely to contribute to the discussion. Although I
>> will formulate my opinion direct with strong language, I want
>> to assure you all that I value everyone's opinion equally.
>> Now, I will jump straight into the low power metrics.
>>
>> *Simmering*
>> As has been explained, simmering is a 'zero work' task, it
>> does not have an efficiency. Evaporating water and overcoming
>> heat losses require work, they can have an efficiency.
>> However, is anyone interested in knowing the efficiency of
>> evaporating water? Or is anyone calculating how much energy
>> is lost from the pot?
>>
>> Either way, simmering is only a term that we will hopefully
>> agree on. Most important is to understand the meaning of the
>> metrics that are calculated: Low power specific fuel
>> consumption, Low power CO and Low power PM.
>>
>> *Low Power Specific Fuel Consumption*
>> From the WBT sheet I find that (equation)
>> Low power specific fuel consumption = (weight fuel consumed *
>> calorific value of fuel ) / (weight of water remaining *
>> minutes of simmering * 1000)
>> To explain in steps:
>>
>> 1. Weight of fuel consumed divided by minutes simmering is
>> the burn rate.
>> 2. If we multiply this by calorific value we get the energy
>> released by the combustion per minute. Let's call this
>> the 'energy rate'.
>> 3. If we divide this weight of water remaining we just
>> divide it by a random number that has no meaning. Keeping
>> more food/water hot does not require more energy. (I
>> believe it does the contrary, because volume grows faster
>> than surface when you increase quantities)
>>
>> -> We have the energy released by the combustion divided by a
>> random number.
>>
>> If we wish to calculate some kind of efficiency number we
>> require useful energy (into pot) divided by used energy (from
>> combustion). What we have calculated is nothing close to this.
>>
>> We could possibly calculate the energy into evaporation and
>> heat loss from the pot, but we have no interest in this.
>> Hence, a simmering task can't give us a useful efficiency
>> type of number!
>>
>> That was me as a physicist, as a employee of a manufacturer I
>> am concerned that stoves are unfairly compared. Because the
>> system can be manipulated to gain better results by using a
>> pot with larger volume capacity and higher insulating
>> properties.
>> Also another big issue is that more efficient stoves can have
>> lower rating at the same power output. I'll explain by
>> example (as others have done before me):
>> /Two stoves are equal except that one has better heat
>> transfer efficiency. When they both run at the lowest power
>> possible (which is the same power for both), the one with the
>> better heat transfer efficiency will have likely evaporated
>> more water because more energy went into the pot. Do to more
>> evaporation it will end up with a rating that is worse!/
>>
>> *Low power Emissions*
>> Both PM and CO are given in
>> weight / (minute * liters of water)
>>
>> Similar breakdown:
>> Weight of emissions per minute is straightforward.
>> Dividing this by number of liters in the pot is simply
>> dividing the emissions by a number of your choice (the liters
>> you fill in the pot). It has no value to stove rating.
>>
>> Generally I think that weight of emissions per minute is not
>> a bad metric. However, simmering is not a task that can be
>> compared fairly between two stoves because it is not a
>> specific task! If we can't compare the way two stoves simmer
>> because we know nothing about the useful energy that went
>> into the pot we are not allowed to compare the results
>> because it means nothing without enough information.
>>
>> *Wrap-up*
>> The list of complications that result from these invalid
>> simmering metrics goes on. Please read again Crispin's and
>> Philip Lloyd's comments for a more comprehensive list.
>>
>> Worst is that many manufacturers are optimizing their
>> products using the WBT and that stoves are not actually
>> improving in the field. The WBT can result into the
>> production of bad stoves for millions of already suffering
>> women!
>> I find myself in the position where I have to tell my company
>> to produce stoves with lower rating because it will be better
>> for women that we build them for.
>>
>> It is not a matter of right or wrong, it is a matter of how
>> we stimulate the production of stoves that are really
>> improving lives.
>> My opinion is that we need to review the meaning of metrics
>> at fundamental level. (Ie. Boiling and simmering are not
>> scientific ways of describing a state of cooking for stoves).
>>
>> Due to the differences in opinion in the stove world, I
>> believe an external review (scientific: engineers,
>> physicists, mathematicians) would be the most suitable
>> option. The review could simply explain the physical meaning
>> of all calculated results.
>>
>> Best regards,
>> Jiddu
>>
>> *Jiddu Broersma*
>> *Technology and Organization Officer*
>>
>>
>> www.praktidesign.com <http://www.praktidesign.com/>
>>
>> Spirit Sense, Old Auroville Road
>> Bommiyarpalayam
>> 605104 Tamil Nadu
>> INDIA
>> stoves at lists.bioenergylists.org
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>>
>>
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>
>
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