[Stoves] Selecting stoves based on data... was Re: kgharris stove test

[Paul Anderson]

Crispin, Kirk and all,

Subject Line changed to reflect the change in the Subject.  This is NOT 
about Kirk's stove, but about DATA about stoves being used for stove 
selection.

Crispin's message (below) raises TOO MANY questions about the SPECIFICS 
OF stove test data.  Instead, this message/topic is about what is 
actually done when selecting stoves that would be put into the market in 
a project.   It is not about the household or cook selecting a stove 
from the several choices in the market or project.   It is about project 
leaders and scientists examining stove characteristics when making 
selections.

My contention is that the numbers (data) do not matter all that much.   
There are simply too many variables, so "perceptual averages" (or 
generalities) come into the process.  One example is from (IMO = in my 
opinion) one of the best selection efforts that use data, the large 
project in Indonesia.  It created a 3-star qualitative system to examine 
(I believe) 3 major characteristics (like emissions, 
efficiency......).   Really great implementation of a rating system 
linked to financial assistance for stove purchases. [[[ The much 
discussed Tier 0-to-4 system has not been used in a similar way, as far 
as I know, even though there is a stove database that gathers such data. ]]]

But even with those stars, in the end the factors of cost and 
attractiveness and convience of use and fuel issues can simply overwhelm 
the "data" approach.

So I say (mainly to Crispin, but to all), the three numbers for 
fire-power can be used as indicators, if used at all.   The "devil in 
the details" (such as moisture content of the fuel, and including or 
excluding time and fuel during ignition time, etc.) simply blow away the 
data themselves.  In other words, even with all of the fullest 
calculations possible, words such as "6 kW firepower" simply mean that 
this combustion arrangement "can really put out some heat."   From that 
generality, stove designers work with pot placement, skirts, plancha vs 
direct flame to pot, size changes, etc etc etc.

For some readers (and project leaders, etc.), this message is terrible 
because it diminishes the importance of data (and some related 
employment and budgets).   Others see it as "that's what I do."   Others 
say "so what?  Not interested.  Already have too much invested in my 
stove and factory, so I ignore the data evaluations."

For stove INNOVATORS like Kirk Harris who are making experimental units, 
getting test results are extremely important to fine-tune the 
improvements so that we do (and should) pay attention to new developments.

But in the end, the data do not mean acceptance or rejection of a 
manufactured line of stoves.  Marketing overwhelms stove science. So do 
cost and conveinece, etc.

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 6/9/2016 7:01 AM, Crispin Pemberton-Pigott wrote:
>
> Dear Kirk and Paul
>
> There were three numbers provided for power, the low the high and the 
> test-high.
>
> It was mentioned that there was a scale under the stove (which is a 
> very good idea) and that readings were taken per 5 minutes (which is a 
> pretty long interval).
>
> Was the high power a maximum during the test phase, or the average 
> over the phase? If it was the average then it should be presented like 
> that because the phase includes an ignition. If it is the maximum 
> firepower, that would not be the average including ignition.
>
> If I say an electric stove has a 5 kW element, that is the maximum 
> input power.  The cooking power is the input power times the heat 
> transfer efficiency.  That is pretty straightforward.
>
> So I wondered if the scale readings were used to determine the maximum 
> power by using the burn rate, or if the power was determined in some 
> other way. If it was scale-based, it means it is the average of the 5 
> minute intervals. If it was based on the scale, what energy content 
> was applied? Was it the WBT sheet LHV (compensated for moisture? Was 
> it the As Received, Ash-Free heating value? Was that value 
> char-remaining-compensated to correct for the energy not released?
>
> The determination of the firepower of a stove is not nearly as easy as 
> getting the cooking power, which in any case is what people experience 
> when they use it.
>
> At the moment I do not have a clear picture of what that 6 kW refers 
> to, and as mentioned already, we don’t know the cooking power 
> (delivered energy). Planning to introduce a design to a certain area 
> will require taking a pretty good guess that the product is in the 
> right cooking power range.
>
> Because we don’t’ have the test spreadsheet with all the input numbers 
> it is hard to know these answers, hence all the questions.
>
> Dr Nurhuda provided a photo of a pot as proof that the PM is low for 
> his latest stove. That is not a ‘test result’ in the numerical sense, 
> but we can assume it must be pretty good.
>
> Kirk provided some numbers from a WBT conducted at Aprovecho, which 
> have emissions per MJ and per unit time etc. But we don’t have the 
> numbers for the total MJ or the total time so we can’t tell a whole 
> bunch of things we need to know to evaluate the performance or 
> suitability.
>
> The best we could do is to share the official test spreadsheet so the 
> missing metrics are available to those who need them. I cannot select 
> a stove design based on an emissions per MJ if I don’t know how many 
> MJ it is capable of delivering. I can /rate/ a stove I have already 
> selected using that metric.
>
> I can’t select a stove design based on a heat transfer efficiency if I 
> don’t know how much heat was involved. Similarly, the firepower 
> combined with other metrics could be used to determine cooking 
> capabilities but only if I am quite sure what that firepower number 
> refers to: peak, average, smoothed 3-minute peak, and so on.
>
> What do we want to know?
> Cooking power total.
>
> Cooking power per sq cm.
>
> System efficiency for some known and relevant task, expressed as the 
> “Energy Efficiency”
>
> Fuel flexibility.
>
> Cost.
>
> Durability.
>
> Pot holding capacity.
>
> Pot stability (when stirring).
>
> Tilt stability.
>
> PM mass per delivered MJ (used together with the cooking power)
>
> CO mass per delivered MJ (ditto)
>
> Note: the Energy efficiency is used as a proxy for relative fuel 
> consumption to compare stoves. Very importantly, it must not refer to 
> the heat transfer efficiency or any proxy of it. That is an internal 
> relationship, and we want the black box version of the fuel consumption.
>
> Most of these numbers can be calculated from the information recorded 
> in a WBT spreadsheet.
>
> Regards
>
> Crispin
>
>

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