[Stoves] stoves and credits again

[Crispin Pemberton-Pigott]

Dear Paul

>Thank you for the message and for calling attention to the spreadsheet dated July 2008.   I am sure that it is useful.   To someone.   This is not in my realm of activities.

>What I (we) can hope for is that someone will  use your message and spreadsheet and then help me  understand its significance to the topic.

The usefulness of the sheet for you is that you can get the energy content of the char, whatever its state of char-ness, showing that indeed the energy retained in the char is about half of that available in the original fuel.

There was some doubt expressed about what fraction of energy is available in what portion of the fuel. Let there be no further doubt.

Charcoal is never going to be pure carbon because it will always contain some ash. The highest practical value for a charcoal product is going to be somewhere near 30 MJ/kg.  Wood, on the other hand, can be as low as 12 MJ/kg, dung 9 or even less.

So instead of people guessing, there is a tool to get the actual values. I put two common fuels: a hardwood and a pinus species in so comparisons can be made using normal moisture contents like 12%.

Enter 12% moisture in the Eucalyptus line and you can see the LHV.

Then see the char value (which will be dry), and calculate the fraction of energy based on the mass of char. The values on the right are per kg so you should factor them for the initial and remaining masses.

If you start with 1000g of wood at 20% moisture and end up with 200 g of high temperature char at 0% moisture, you have an energy value comparison, in that case 49% of the original value in the char.

Regards
Crispin

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