[Stoves] Analysis of a two-stove cooking system

[Paul Anderson]

Crispin,

> A very important comment! Stove1 did not "produce fuel". That is a 
> misconception. The fuel was produced by the forest. Stove1 extracted 
> some of the energy available from the fuel and changed its appearance.
> .....
>
> No "fuel" was "produced". It was was always "fuel" and some of the 
> energy was extracted - leaving half un-released. There is nothing to 
> "credit". ‎
The wood comes from the forest and it is fuel.   If fuel is not 
produced, then the charcoal (left over from the wood) also came from the 
forest.   If it has value as fuel, charcoal should not be penalized or 
discounted because it no longer has the same characteristics as wood.

**********
This discussion might never end.   And certainly the debate about 
crediting stoves with production of BIOCHAR will assure debate for a 
very long time.   "Beauty is in the eye of the beholder." "Efficiency is 
in the calculations of whoever finalizes the definition of 
efficiency."     But in the end, the stove user at the household level 
will have a lot to say about what stove is or is not acceptable, with 
efficiencies (plural) being just some fraction of the full consideration.

Moving on.

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 11/28/2015 1:34 PM, Crispin Pemberton-Pigott wrote:
> Dear Paul
>
> >Typographical errors:
>
> Noted. Thanks.
>
> >Content:
> >Good exercise.   Well done.   Helpful for further discussion.  Yes, 
> there can be cooking systems with 2 stoves such as you describe.
>
> >But there is one issue concerning first paragraph of Item 2.5 (page 2):
>
> >The first 2 lines are fine.   But it seems that the final two lines 
> are trying to say that fuel efficiency is the same as energy 
> efficiency.   I read this at least 6 times.   How about some 
> re-wording to clarify what you are saying.
>
> I was attempting to describe the efficiency with which the energy 
> supplied to the stove is delivered to the pot up to the time the flame 
> goes out.
>
> >You and I have agreed in the past that fuel efficiency and energy 
> efficiency are not the same.
>
> I cannot think of a better term at the moment. Yes it is a change in 
> my choice of words. While I could have chosen 'cooking efficiency' the 
> heat might not be applied to cooking, it could be something else. I am 
> open to suggestions. One might consider ‎the space heating efficiency. 
> The main point of the exercise it to show that one cannot count some 
> portion of the energy twice. Nothing can be more than 100% efficient 
> without invoking magic.
>
> >For Stove1 the fuel efficiency is based on wood fuel.   Then for 
> Stove2 you switch to have the fuel efficiency based on charcoal.
>
> That is correct. My major point has been communicated it appears. The 
> fact that the appearance of the fuel changed does not change the 
> energy ‎content.
>
> >But you are not giving any credit to Stove1 for having produced the 
> fuel for Stove2.
>
> A very important comment! Stove1 did not "produce fuel". That is a 
> misconception. The fuel was produced by the forest. Stove1 extracted 
> some of the energy available from the fuel and changed its appearance.
>
> While doing so it did some cooking. At flame-out the remaining matter, 
> charcoal, was no longer useful to Stove1. It only extracted 1/2 the 
> energy available to it and only 1/4 of the fuel's energy was delivered 
> to the pot.
>
> No "fuel" was "produced". It was was always "fuel" and some of the 
> energy was extracted - leaving half un-released. There is nothing to 
> "credit". ‎ If Stove1 was the only product you had, 1/2 the energy was 
> left at the end in an unusable form (for that stove) so the next meal 
> requires more fuel from the forest. It is that requirement that is 
> consuming the forest, often unsustainably. Buying a second stove to 
> burn the charcoal does not increase the performance rating of Stove1.
>
> >And that is where Ron and I and others have been disagreeing with you.
>
> So this is your chance to show how the energy in the fuel consumed 
> should be counted.
>
> It is important that you demonstrate how the two are assessed 
> together, as I did, and then to analyse them separately using the same 
> approach. Follow the energy. If the cooking efficiency is correctly 
> assessed, then the combination of two stoves will be correct as well.
>
> If a different, single stove that has the fuel input of Stove1 and the 
> remnant ash content of Stove2, and further, delivers the same cooking 
> energy into a pot as the combined performance of Stoves 1+2, then the 
> performance rating of that single stove will be exactly the same 
> rating as the two stove combination, as it should be, because it did 
> the same amount of work with the same quantity of fuel.
>
> ‎A chain of three stoves can be imagined. No correct method of 
> analysis can have as a result an efficiency that is greater than all 
> the work done divided by all the energy available. The term 'energy 
> efficiency' can correctly be applied to any part of that system, or 
> the sum of all parts. It's a pretty good name.
>
> I hope a clear distinction between the energy efficiency (or cooking 
> efficiency) and the thermal efficiency ‎has been demonstrated. The 
> thermal efficiency does not take cognisance of the total energy 
> available in the fuel consumed, just the energy in the missing fuel. 
> Thus it can't be used as a proxy for fuel consumption as has been done 
> for years by the WBT. Notably, the Indian, Chinese and SeTAR test 
> methods do not make that mistake. There was a pre-WBT 1 test method 
> from 'Feu de Bois' and another from the University of Eindhoven that 
> reported the fuel consumption correctly.
>
> While it would be nice to validate the WBT results as 'fuel 
> consumption', it instead reports the thermal efficiency which is a 
> different metric. That difference is the main reason why WBT lab tests 
> do not match field observations of fuel use. ‎A second reason for the 
> mismatch in results is the differences in testing context but we can 
> leave that for another discussion.
>
> Regards
> Crispin
>
>
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