[Stoves] Differences in stove testing

[Ronal W. Larson]

Dr.  Bond:

	Thanks for repeating your important question today.

	I have been working on this problem since the 8th (and earlier) - and hope to have a better answer than the following for you soon.  

	As you and I discussed at the ETHOS meeting,  I am defending the equation in principle - as telling us a lot about each stove.  I think it should be viewed as a useful metric for establishing tiers.   I don’t view it as giving a useful overall efficiency value - or needing to do so.  That is, if it were an efficiency, its complement should be an inefficiency - and that equation certainly overestimates the inefficiency of any stove.

	For this reason,  I wouldn’t worry if we can’t find a similar situation with a subtraction in the denominator.   I have come up with a different (and defensible) means of specifying (the exact same) tiers from (the exact same) efficiencies in heat transfer and charring (already being determined and reported quite accurately) — that does not involve a subtraction in the denominator.

	I have been discussing this with several knowledgeable stove/other experts - and should have something soon for a larger audience. 

	 But I will take up your challenge as well;  I will be looking for metrics - not efficiencies - although efficiencies won’t be excluded.

	There is no need for the Tier structure to be based on an efficiency.  And I consider the Tier structure to be absolutely essential - as was shown in the unanimous (!) vote of 90 persons in the Netherlands in 2012.   I wasn’t there, but would have also voted for Tiers.   We can give up most hope of seeing stove improvement if we discard the Tier structure.  

	To repeat - the tier structure does NOT depend on that equation (which can be thought of as giving full credit to heat transfer and partial credit to char-making).  In my opinion, the equation (or its alternative derivation) does reflect (as a defensible metric) a reasonable allocation of values between heat transfer and charcoal-making - both very valuable to society.

	Anyone disagree that a non-efficiency (but useful) metric for tier determination is justifiable?

Ron
	

> On Feb 13, 2017, at 3:26 AM, Bond, Tami C <yark at illinois.edu> wrote:
> 
> Hello friends,
> 
> Gosh, it’s been awfully quiet! Anyone have anything for me? (see below). I’m putting together a document for our WG and I would really like to have an example of precedent to go with the char-subtraction formula.
> 
> Tami
> 
> 
>> On Feb 8, 2017, at 6:14 AM, Bond, Tami C <yark at illinois.edu> wrote: <…>
> 
>> Let us suppose that we have ANY device that does two things: giving heat and light, refrigerating food and making ice, producing heat and electricity, producing cooking heat and char. 
>> 
>> **If you know of ANY example in engineering practice, OTHER than the WBT, in which the efficiency is calculated by subtracting one of the services from the denominator rather than by putting both outputs in the numerator, can you please make it known to me?** 
> 
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