[Stoves] Definition of char-making appliance

[Crispin Pemberton-Pigott]

Dear Ron

 

Stove testers are not carriers of opinions on social benefits, that is for regulators. This definition is for an ‘appliance’ because that is the correct term for a ‘device’ used for cooking.  They are in fact domestic appliances in this case. A toaster is not a stove. A kettle is not a stove. They are cooking appliances and will be regulated.

 

>The number 15 % could be useful.  I can't think of a better number, if we need this, since 15% is easy to achieve.

I chose the number because it is easy to achieve and I want to eliminate stoves that are just ‘lousy burners of the fuel’ like the so-called Namibian Tsotso. They may or may not produce copious amounts of partly burned wood. That is not a char making stove, in my view.

>    I would make NO or LITTLE distinctions in the way 4.2.2 tests are performed and reported for char production above or below 15%.  

I sense you angling for some additional ‘benefit’ to accrue to a stove that produces biochar. The test only reports what happens, it does not have opinions on what the products are. The mass of char is already recorded (has been for ages) but it was not reported. The only difference is to report it. At the moment the WBT uses the mass of char, not the carbon content.

I am tightening that definition a little to counter the possibility that ‘cheating’ may be seen with respect to high ash fuels like palm fronds and rice hulls. If it is being ‘rewarded’ as a biochar or charcoal fuel producer, ash can’t be slipped in as a qualifying product.

The reason I am being careful is that the formula for fuel efficiency is tilted slightly towards char making stoves in that they are not ‘fully punished’ for using slightly more fuel provided the char production rate is high enough. The mechanism is to give a fuel efficiency (heat energy in the fuel to heat in the pot) then require that char making stoves achieve that % plus the rate of char produced. For example if the target is 30% fuel efficiency, and a stove makes 20% char by dry mass calculation, it will have to have a heat transfer efficiency (not a fuel efficiency) of 30+20 = 50% in order to be accepted. This is slightly advantageous to the char maker in terms of fuel consumption. At a 25% char production rate it is an advantage (a forgiveness) of 10% of the fuel consumed.

If anyone needs a more stringent explanation of this I can provide it.

Regards

Crispin

 

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