[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.  

>    [RWL1:   So is the word "stove" used -  and is so used by GACC.  They use the term "stove", not "appliance"  in 4.2.2.

 

I am not influenced by the contents of any particular test protocol. National Standards have their own peculiar way fo referring to things that is much more informed by the wording use in patents. There are good reasons for this. Something failing a national standard may end up in court over definitions. “Stove” is a word that would not stand up well in court. Even the stove makers cannot agree on its meaning!

 

>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.

>     [RWL2:  So you are confirming my guess that you are trying to separate the words "charcoal-making" and "stoves".  

 

Why on earth would I try to conjoin the words ‘charcoal making’ and ‘stove’? This is not a game.

 

>That is not the case now and I ask why you want to not call a CMS (Charcoal Making Stove) a stove, but rather (I gather) a CMA?

 

Because all biomass burners make charcoal so the definition would fail if it was supposed to define a certain class of char-makers. That is why I have defined a carbon retention rate. You can’t easily weasel around the definition. Biomass goes in. I what comes out has more than 15% of the original carbon in the fuel and that remaining fuel would otherwise be considered ‘wasted’ (because it cannot serve as fuel in the same device) the submitting manufacturer can choose to have the appliance rated on the basis of its heat transfer efficiency rather than its fuel efficiency. This correct a very big problem with the WBT’s which only rate the heat transfer efficiency. If you do not consider this issue to be a big problem, you have not been keeping up.

 

>     [RWL3:   Does the tsotso make 15% char?    

It usually make char because it has a terrible air supply. IF the fire is small it makes almost none. If it is large, it makes so much it renders the stove unusable.

>Whether any particular stove does or doesn't perform well shouldn't be part of this discussion.  

Excuse me? We are talking about rating the performance of the stoves!

>If the Tsotso is a critcal example of bad testing of charcoal-making stoves (CMSs),  I hope you will explain why.] 

It was not designed to produce charcoal it was supposed to be a stove with preheated under-air but the holes through which it must pass are far too small. That’s all. Design defect. Nothing more. It wastes a lot of fuel.

>      [RWL4:   I think you probably can get the carbon content from the bomb calorimetry tests on all (?) input and output wood/biomass and char quantities.  The important point  is that they (Jetter, Still  etal) already do calculate and use the energy in the char  (which includes the important impact of hydrogen).   

That is not for sue in determining the char making or carbon retention capability. That is for calculating the heat transfer efficiency (THE). The reason for doing it is to provide a more accurate HTE. An mentioned above, this is a misleading number. Classically people thought a higher heat transfer efficiency means fuel saving. This is no longer true because of the introduction of char making stoves that use less energy (total) but consume even more fuel.

>I am only asking that they also report that ENERGY number separately - since many people are interested in that number.  

Why do you think they are interested in that number?

>Weights and carbon content are important - but not as important as energy, when the IWA group divisions depend so strongly on energy, not carbon contents, etc.

It will help if you understand why they want the energy calculation to be done so accurately. They intend to report the heat transfer efficiency as a proxy for fuel consumption which clearly it is not. This discrepancy was accepted by Jim J and me and lots of other people more than a year ago. We are interested in reporting the heat transfer efficiency to people who design stoves. We are interested in reporting the fuel efficiency to people who are concerned with the environment and work about the total fuel offtake from the available supply. Until now, stoves that used as much or more fuel than the open fire baselines have been credited with using less, often much less. That is cheating. It must stop.

>    [RWL5:  I guess you are suggesting that test 4.2.2  reporting is too loose.  I don't see that at all.

WBT 4.2.1 was not written to be a Standard, it is a test protocol. Standards usually refer to protocols or have them written into the standard (which is usually a bad idea).

 

>       My understanding is that the efficiency number has been and still is the ratio of  pot energy divided by (input fuel energy minus char energy).   

That is the heat transfer efficiency. If you are processing a lot of raw fuel into char , the difference in heat transfer efficiency is not the same and their different in fuel efficiency. 

>I only want to also let people know how much energy is in the char.  That number is already being calculated.

It can be reported. It is not helpful to projects that are primarily concerned with fuel consumption (which is most programmes). While it can be argued that char can be used as fuel, it is already banned in those countries where it would have the most positive impact. This will take a while to sort out. You can’t regulate the use of fuels that are not allowed to be used or sold.

>    In your description above, you seem to be using 20% char by weight directly in an equation for energy ratios.  Makes no sense.]

I made no reference to the energy content – you did.

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

   [RWL7:  I need it - given to the whole list.  With the specific equation numbers from the 4.2.2 procedures with which you disagree.   Example faulty calculations are needed,  We want to be sure we punish where appropriate.       Ron]

It does not require a change in the WBT4.2.1 formula which correctly calculates the heat transfer efficiency (or a reasonable proxy for it). The problem with the WBT 4.2.1 is that it assumes (or did) that the heat transfer efficiency tells you the fuel efficiency. In fact in old documents from VITA and Aprovecho and others the terms are used interchangeably. The UNFCCC current regulations for CDM projects also reflect this thinking. It is a conceptual error, not a mathematical error. As we are not holding talks on conceptual errors it may, I fear, continue to be a problem – one of several.

Regards

Crispin

 

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