[Stoves] A call to stop using the WBT

[Andrew Heggie]

On 28 January 2018 at 12:26, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

>
>>> Ron doesn't really want to preserve the WBT, he wants to rate stoves
>>> that have a fuel efficiency of 20% to be reported to be 40%.
>
>>Not so he just wants the portion of fuel used to be accounted, in the same way the lpg used is calculated from what is left in the canister. You appear to want all the energy available in the initial fuel to be attributed to the cooking task.
>
> You have that exactly backwards.  It is I who am insisting on the "LPG Tank Equivalent."
>
> The mass of fuel drained from the pressure used to complete some task is the fuel consumed. The energy in that fuel is the energy consumed. I want the fuel mass consumed to be reported as "the fuel consumption and energy contained in that fuel to serve as the denominator when rating the cooking performance.

You again wilfully  misrepresent my statement: your method is
analogous to weighing the tank and its contents, subtracting the empty
weight of the tank and attributing all of the energy in the lpg to the
cooking task in hand despite there still being energy left in the lpg
remaining in the tank.

In a similar vein: were I to cook by biogas you would have me
calculate the mass of all the vegetation that went into the digester
and say that was the mass of fuel used whereas only the few cubic
metres of gas produced was actually used in the cooking task.
>
> Ron, on the other hand, wants to scrape the soot off the stove and pot, calculate the energy contained in it,

Again this is a gross misinterpretation, we are saying the TLUD is a
gas generator and the flame is doing the cooking, only the char
remaining in the stove at the end of cooking  that has an alternative
use is to be allowed for, soot on a pot is clearly a waste product of
the combustion.

<snipped drivel>

>
> The WBT agrees and deducts the energy in the sooty carbonaceous remnant, deducting it from the energy that might have been released from the fuel, and indeed, reports the cooking efficiency is higher than it actually is.

As soon as you mention sooty it is a waste product of incomplete
combustion and distinct from char.

> To repeat:
>>You appear to want all the energy available in the initial fuel to be attributed to the cooking task.
>
> Of course I do

My point proven then

> The difference of opinion on this has to do with a hot topic in WG1 and WG4 at the moment: defining the system boundaries. I am surprised at the lack of clarity on where the system boundaries. Defining cooking performance involves the new fuel required to replicate a task for any in a series of identical replications save the first. (The first may provide partially burned fuel carried forward to the next test).

Pass on this one but we are not even in agreement here as  the TLUD
char is not partially burnt fuel, it has become an intended part of
the production of a pyrolysis offgas which in turn is the fuel used in
the stove.
>
> If you define the system as one for char production, then the metrics are similar, but they are not the same. If you define the system as cooking-and-char-making, again, different metrics are appropriate. One cannot claim to be rating cooking performance but include something lies outside the cooking system, and inside the char production system.

Why not? The char production part produces the gas for the flame that
does the cooking, we can say, within the bounds of measurement, that
the char contains a percentage of the  initial energy and the gas has
the rest. The gas flame then has an efficiency  in which it heats the
pot.

>
>>I think this is the nub, this testing is about attracting funding and char making stoves feature in that, whether wood  harvesting is sustainable or not is a separate matter. It's a simple matter to calculate the costs in using a char making stove in that the wood input results in managing the cooking task and producing the char which may or may not have a value, this is separate from the  energy consideration.
>
> Excellent. I am curious as to why you have been confused about the calculation of such a simple pair of systems. The wood input is the input mass. It is not reduced by the energy content of the char produced. Full stop.

I'm not confused, the wood input is to the TLUD, the energy to the
cooking pot is from the burning of the offgas and just because you
talk loudest doen't give you any right to put a full stop on people
that disagree with you.


>
>>Char making stoves are sui generis, it's up to the cook to decide whether they prefer to use them for their low particulate pollution, the residual char for its value or both. I don't think this argument on testing protocols should be used  to persuade some quango or charity to foist one sort of stove or the other on users.
>
> Excellent. The main channel for foisting has been the unsupportable claims made for stoves that are being promoted. A Rocket Stove from Aprovecho, for example, produces an above average mass of char, compared with, for example, a Rocketworks Stove from Durban. Because the remnant char from a Rocket Stove was used to inflate the claimed cooking efficiency, it looks as if it uses about as much fuel as a Rocketworks stove. But when rated correctly, the Rocketworks stove is quite a bit better because - big surprise - it consumes less fuel.

Again a non sequitur of which I know nothing, I don't promote any
stove, you on the other hand do.

>
> Any reasonable protocol will report which uses less fuel, which is to say, has the higher cooking efficiency. The WBT doesn't because of its defective concepts.

> I am dwelling on correcting bad math.

No you are intent on disadvantaging char making stoves. You are
manipulating your preferred spreadsheet in order to do so.

Andrew