Dear Crispin,
Crispin Pemberton-Pigott wrote:
Dear Frank
"The starting fuel and, especially, the ending fuel has a lot of room for
error. If we ran a cord of wood through Paul's TLUD without stopping the
error percent at the ends would be much smaller than when we just run a few
Kg of fuel. That's my point."
Hmmm....well my point is that if you do that with a cord of wood, you will
not get anything lie a representative emissions profile.
Measurement one: What you get with a long continuous run is a good
representation of emissions during the run. You do not get this with
short runs.
Measurement two: But, as you say, the start and end of the runs are also
important. As that happens in a short span of time we need many Start /
Stop events so to get an average. We need to not try to be careful (that
doesn't happen the real world) but we need to stir the fuel when adding
and try to get the maximum emissions possible the stove can produce. I
suggest, designing a stove -fuel combination that produces the lowest
maximum emission possible (along with efficiency -measure three)
should be the goal when comparing stoves.
After reading the rest I see we agree with each other. But I also want
to add the importance of the fuel type and characteristics can not be
ignored.
So we have our homework:
Start Runs (emission)
Long runs (emission)
Ending (emission)
Thermal efficiency
Fuel characteristic range.
All measured for each stove.
Goal is to develop methods that make this as direct, simple, quick and
cheap as possible.
Thanks
Frank
The greater part of PM and CO do not come from the long term burn. This is
an important consideration. Have a look at the two charts I sent yesterday.
The vast majority is emitted when starting. After a while there are nearly
no particles emitted if the fuel is a batch process. If it is continuous,
like pushed sticks, or continuously added pellets, that is a different
story.
So how you set up the test can give very different results from the same
stove. Running stove for a very long time that will, in use, not be run for
a long time, means very incorrect evaluations. You get my drift?
There is a strong belief in European testing circles that the emissions from
fuel are inherent in the material being burned - that when it is burned they
are 'released'. This is obviously incorrect. The black smoke belching from a
poorly adjusted diesel engine has nothing to do with the diesel.
So testing should represent actual use especially in terms of the starting
cycle and the operating parameters such as cooking a pot of beans or frying
in a wok. For space heating that means (in most cases) an ignition cycle, a
refuelling cycle and a dying fire phase. It is easy to add sections together
afterwards in any combination such as 1 ignition, 3 refuelling and 1 drying
fire. That is typical of some cities in winter months.
During spring the cycle might be 1 ignition and 1 dying fire. Running the
stove for 16 or 20 hours only tells us something when a change is made (like
adding fuel).
It is all about profiles and capturing the emissions and performance during
each repeatable segment.
Regards
Crispin
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