[Stoves] Advocacy action: ask the GACC to stop promoting the WBT

[Crispin Pemberton-Pigott]

Dear Ron

Nearly everything you ask is answered in the message to Paul

“This is a 2013 EPA webinar (achieved by GACC) devoted to batch stoves - principally char-making.”

The presentations makes a fundamental mistake of making two calculations and calling them both ‘thermal efficiency’. You can’t just go subtracting and adding things willy-nilly and assume that the result has meaning.

The presentation from the EPA takes the incomplete WBT heat transfer efficiency formula (defective because it does not include all the necessary variables) and extends the application of it to claim it is considering the benefit of the energy in the char. It is not.

It is also stated that the energy in the pot cannot be added to the energy in the char! Rubbish! They are both forms of energy, one sensible and the other stored chemical energy. I can added them without even using a calculator. They are both benefits of the operation of the stove, benefits derived from the consumption of the fuel. So is space heating, or operating a TEG to generate electricity. I can easily add all the energy in those benefits and arrive at an overall efficiency for the stove. Or, I can report them individually as if the other benefits were not needed or wanted.

What I cannot do is subtract anything from the denominator, unless I am trying to determine the heat transfer efficiency, which so far no one has claimed to be trying to do. Were I to subtract numbers correctly, I could get the heat transfer efficiency to the TEG, the heat exchange, or the pot. But no one asked for that. They asked for the fuel consumption, the cooking efficiency and Paul want the char energy retention efficiency. No problem. Please see the response to Paul.

Explain to me why you would want the cooking+char production efficiency of 37.5% reported as 16.66%. I look forward to that.

Regards
Crispin

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