Dear Crispin and all, Yes, we need to discuss such topics.
No, the quantification of "when 95% of the combustion portion of the fuel has burned" leaves unanswered questions. In the TLUDs, we run them until about 100% (maybe 98.9% ;-) ) of the pyrolytic gases are released and consumed. But there is about 20% by weight (or about 30% by energy) remaining in the form of charcoal created.
Any testing protocols need to allow for such characteristics. Why stop at 95% and/or why require combustion all the way to 95% ash??
It will be great seeing you in DC in January (and at ETHOS also, I suspect.) Paul Quoting Crispin Pemberton-Pigott <[email protected]>:
Dear Friends Of the age-old questions I when to end a stove test in order to calculate the CO and PM emissions (which are the things usually legislated). There has been little agreement in different US states and few other countries outside Europe have anything at all. Stoves have very different burning times, heat generating capacities, fuel loads, burning properties, refuelling capabilities and purposes. What can we do that will make comparisons fair and possible? So, here follows a proposal which seems to work in practise. The test is started at the time of ignition. The test ends when 95% of the combustion portion of the fuel has burned, leaving 5%. The combustible portion is the non-moisture, non-ash portion of the fuel as received (meaning as it is used in the stove). When the fuel is weighed, say 5 kg, and either set aside or loaded into the stove, the total amount is noted and the moisture content calculated, for example at 15% = 750 g. That means there is 4250 g of dry fuel there. Then subtract the ash portion, say it was 3% of the initial mass = 30 g. Final number is 4250-30 = 4220. That is the mass of 'things which can burn'. 95% of that is 4220 x .95 = 4009 g. All the moisture is expected to be gone. So if the whole stove is mounted on a scale the mass change will be burnables + moisture = 4009+750 = 4759. One the scaled mass has dropped 4759 g the test is over. Then the emissions are calculated based on the MJ of heat theoretically generated (using LHV as received). If a scale is not used, then the mass burned can be determined by weighing the fuel as it is use, fuel remaining or anything else that shows when 95% of the fuel is gone. Typically this is late in the dying fire stage so it is a bit easier then it perhaps sounds. When do test a stove that includes refuelling or a number of refuellings, the same calculation applies. It seems to work very well, gives results representative of real life and normally has a test time that is less than a working day. It is offered a test method for rating the emissions of any type of testing from water boiling to 24/7 space heating. Regards Crispin
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