[Stoves] Woodstove rules in western North Carolina amount to'jumping on the crazy train'

Mon May 30 16:50:40 CDT 2016

Dear Kirk

>It occurs to me that you may be fixating on your created negative here.  

I am really sure I did not create the 'negative' here. I am trying to save
you from spoiling a really good design in an attempt to 'get a better
number' on an invalid metric from which there is no physical foundation.  As
Jiddu noted here, it takes another wise good measurement and divides it by a
random number. In the case of your 'Tier 3 rating' for specific fuel
consumption, it mislead you, apparently, into thinking that you 'did not
achieve' what you should have.

>Did you notice the high power indoor PM2.5?  At 0.7345 mg/min it is very
low, and that is a positive.  

Yes this is a good value, but it is a measurement relevant to indoor air
quality. If I make your stove exactly half the capacity I would cut the
emissions rate in half by producing half the emission mass.  What does this
prove? For practical purposes, the emission rate should be per MJ delivered
into a pot so we know if we are getting somewhere with the performance.
Better heat transfer, better combustion efficiency, whatever, if the amount
of heat getting into the pot is more per unit of PM mass emitted, that is
'better'.

If you have a 10 kW stove that emits twice as much as your stove, then the
ventilation rate of the kitchen should/could be increased by a factor of
two. Then the exposure for the cook is the same. Thus it is not a useful
metric to report the emitted mass per minute only, you have to show what you
are getting accomplished for that result. If I made a stove that was half
the power and has the same mass emitted per minute, are those stoves equal?
It would take it twice as long to accomplish any task, but the 'per minute'
rating would be the same. What do we learn from that about stove
performance?

>Also, all other results are very good.  When your test methods are ready I
will be happy to test accordingly.  Until then I can only show the quality
of this stove by the current standards.  I am looking forward to also show
the quality of this stove by your standards, when available.

The method you refer to as 'mine' is widely available and used in multiple
projects and countries. It is used by the national standard for Mongolia. It
was developed by experts from about a dozen developing countries over a
period of three years. No one has to use it, of course. People can do what
they want. What is important is using metrics that are valid indicators of
something about the stove that is meaningful for some policy or purpose. 

PM mass emitted per minute assists air quality - either indoor or outdoor
depending on where it is emitted. Airshed modellers use mass per minute as
an input for either allocating an airshed's capacity or to predict air
quality under various weather regimes.

Engineering numbers for stove performance usually pertain to an efficiency
of accomplishing something, for example CO mas per MJ of energy delivered
into a cooking vessel or a living space. In a similar manner, the amount of
energy taken from the available source per MJ delivered into the pot of room
is relevant.

For user experience, the convenience of not working much to prepare the
fuel, fast lighting, controllability and heat per sq cm in the pot are all
important parts of the cooking experience. Cleaning, disposal of wastes and
ease of maintenance are also on that list - nothing to do with the
engineering numbers (except the heat flux).

In Mongolia the national standard includes a number of metrics which the
cooking stove market doesn't seem to notice. One is the kw/unit volume of
the combustion chamber which I though was pretty interesting. Basically it
is a measure of how hard the system and materials are pushed. 

>This stove or one like it will be at Aprovecho for Stove Camp in August.
You are all welcome to be there to examine and test it.  You will find a
good stove, described during testing as "rock solid".

I look forward to being about to build and or teste one this year. Thanks
for your efforts. And again thanks for putting new ideas into the public
domain. Not everyone is doing this. Some out of necessity (investors) some
out of a generosity of spirit.  

It will be great if someone takes it to market and demonstrates the benefits
it brings in a practical manner.

Best regards
Crispin

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