[Stoves] Differences in stove testing ---- was Re: ETHOS 2017 agenda and logistics

[Andrew Heggie]

On 7 February 2017 at 11:54, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:
> Dear Andrew
>
> I think it is time you and Ron take a break from putting words in my mouth.
>
> "Ronal sees that as an attribute you don't and see it as a waste
> without value in energy or cash terms."
>
> I have NO problem with recognising the value of the char and if you will recall, I am the one who posted years ago how to correctly credit the various energy destinations and also how to correctly rate the performance of a pair of stoves. Now we have a stove available from Nurhuda that has two distinct burning phases.

Okay I may well have missed the point

>
> I do not accept saying that a stove that uses ten kg of wood to cook uses less than ten kg. That is my objection.
>
> Paul's objection to this is calling the char 'waste' as far as the char making stove is concerned. ‎Yet from a fuel consumption point of view it is.

I disagree  because the TLUD is co generating wood gas for cooking and
a char residue, the cooking effort is from the  (already hot) gases.
>
> Ron's objection is calling the energy in the char a 'loss'. Yet is is as far as the firs stove in a putative chain of stoves is concerned.
>
> You can call the char whatever you like. But it's mass and it's energy do not reduce the amount of fuel needed fromm the source.
>
> Prof Lloyd has just explained, clearly, twice, that to rate these additional 'benefits' all of which involve energy that originates from the fuel fed, is done by putting them in the numerator, over the total energy in the fuel fed, the 10 kg.

But he also  said that efficiencies from co generation of  products
are additive.

> It would be helpful is the char making stoves were evaluated as part of a larger system so that all the co-benefits could be ‎seen in the larger context.

Agreed they are not simple  cook stoves unless they continue through
the char burning  phase, even then they lose some of their low
particulate attributes don't they.
>
> Here are some ideas:
>
> Fuel is consumed.
> Energy is released
> Cooking is accomplished
> Energy needed to convert the food into cooked food is an energy gain

This is a dubious proposition

> Heat past the pot is a cooking energy loss

Yes

> Char is produced
> Char energy is thereby retained

Yes

> Cooling the char is an energy loss

Yes but is that attributed to the cooking or the char making

> Unrecovered ‎char in the ash is a char loss

Maybe for further  combustion tasks but...

> Cooling the ash in an energy loss
> Cooling the stove after cooking is an energy loss

Yes both


>
> If you want to know how much of the heat released gets transferred to the pot, you are asking for the heat transfer efficiency. Perfectly reasonable request. You have to determine all the energy in the residual solids, not just 'a major portion' of the char or the answer won't be accurate.

On that basis I am probably interested in the heat transfer efficiency
then as I am talking about the energy released from the fuel rather
than the raw energy of the fuel. Smoke and char in the ash are the
unreleased energy losses in my usage.

I should be clear I use wood energy for space heating, very rarely
cooking, for which I use electricity.

Andrew