[Stoves] Shields E450c as a way to test char-making stoves (attn: GACC testers)

[Frank Shields]

Dear Crispin,

 

See below:

 

<snip>

 

 

What exactly is the problem that you see that requires a (very) different
type of solution? 

[Frank >] Is that the variables are so many and such that getting accurate,
repeatable results difficult. And the only time we know what the accurate
energy value of a fuel is is before we use it. Once it had gone through any
heating process the only way to know the energy of that left over fuel
remaining is to determine moisture, then dry and grind and test for energy.
So I suggest energy is only determined on the fuel as being used. Left over
is discarded resulting in lower efficiency or used in the next run reporting
higher efficiency or averaged to report what's expected.  We need a simple
method using lab equipment that can be calibrated and common around the
world. Like TGA (or pipe) and calorimeter (or calculating from COHNS, ash).


The proposal is, ultimately, mass-based. Mass-based calculations of fuel
energy are plagued with problems because while you can get an answer for one
type of wood (with a certain error bar) as soon as you move to another fuel
like palm leaves or shells or rice hull then comparisons are not fair.

[Frank >] That's why you need to report in Box 1 (6 box system) a
description of the fuel used including moisture, shape, type etc. That
because that variable needs to be controlled and sometimes just describing
it is the only way. I suspect a stove will operate differently with fuels of
the same energy value but having different shapes or amount of lignin or
carbon densities etc. So many variables in fuel make-up we just describe
what we use and the E450c value. We then have a collection of stoves that
are tested using the fuel of choice at a location to see how well they do.
Not usable data for another location using a different fuel. 

So perhaps the reason why stoves that make charcoal need special treatment
should be clarified. All biomass stoves make some char and there are fair
methods of dealing with it.

[Frank >] Charcoal stove are treated no differently than rocket stoves. Like
rocket stoves that also have a secondary burner to do the task we just use
the Shields450c as the amount of energy used. I am not sure about coal or
charcoal fueled stoves because they have no secondary (?) and I have no idea
how they work.   

I suspect the root question being asked is 'What is the heat transfer
efficiency?"

[Frank >] The root question is How much energy did we use for the task(s).
And the energy value can be re-calculated to how many trees used, how many
trips to collect biomass etc.   

If you want to know that, then there are ways to find out.

[Frank >] Heat transfer, soot produced, particles, safety etc. are all
completely separate tests. 

If you want to know how much fuel a stove consumes, either in mass of
energy, there are also ways, and it gives an answer different answer from
the heat transfer efficiency question.

[Frank >] Perhaps I am confused by what you mean 'Heat Transfer Efficiency'.
I see the question is (Energy used) by (heat that made it through the
Cooking Utensil and into the water) for the WBT.  The problem is Energy
Used. A method of taking the ((energy IN) - (the energy OUT) = (energy
used)) is valid BUT the procedure is a nightmare and prone to so much error.
And then get different labs to get the same values..  Somehow we need to
improve on this and that is what I am trying to come up with. 

Calculating the mass of dry fuel equivalent that is the equivalent of the
energy used to cook is not helpful. We already would know the energy
involved. Dividing by the energy in that type of fuel just renders the final
number incomparable with stoves that use another fuel. [Frank >]  Agree
Leave it is Joules.[Frank >]  The Shields450c is reported in Joules. Total
energy of the fuel - energy of the char remaining at E450c in nitrogen.
Using this percentage of the fuel used and amount of fuel used we know the
E450c energy used for the task when the secondary flame goes out.   

Is the intention to find the heat transfer efficiency?[Frank >] ? 

Thanks
Crispin

[Frank >] Thanks

[Frank >] 

Frank Shields

Control Laboratories; Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

frank at biocharlab.com

www.controllabs.com

 

 

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