Dear Frank Your initial reply stimulates a number of things so I will respond later on more of them. The thermal eff one is worth commenting on right awat.
++++++++ Now we are starting to mix things up. I agree that different fuels will give different results in the same stove. We get different results with tests around the world using that specific stove and charted for each fuel selected for testing. Several charts for that same stove based on each of several fuels. But you throw in "thermal efficiency" (TE) as another variable. We are not ready to do that yet. Only after we test many different stoves and compare to the charts of the same fuel used in the tests do we look at TE to determine how long a stove must operate to get the same job done. And calculate the PM 2.5 released. ++++++++ I think you are mixing the units in a sort of a way that means I did not explain myself clearly. In the US many of the regulations state ' xx many g/hr of particles can be emitted per hour'. This is classic EPA-speak. It is intended to limit the _concentration_ of a pollutant in the environment. A more direct one is to limit the ppm in the chimney, something the power stations initially had to meet. After meeting the ppm requirement by pumping in air to dilute it, the EPA said wait, you are not emitting any less, you are just spreading it around. So they came up with total emissions per power plant, per stove and per anything else. But stoves amd power plants are very different in size so little ones could emit huge amounts of PM and still boil water and pass inspection. This happened with cars too. So the next obvious step is to specify the emissions per kg burned because for any fuel, the total heat is related to the mass burned. Then people pointed out that the fuel moisture varies so they made it per _dry_ kg of fuel. Then the coal people said there is far more ash in coal than wood so they said emissions per kg of dry, ash-free fuel (DAF). As fuels have completely different moisture, heat and ash contents, (witness for furore over Roger Samson's rice hull stove test) the the emissions per MJ gives a much more meaningful answer and avoids several of the implications above. The moisture issue drops away as it is automatically catered for iñ the LHV as is the kg. There is heat and there are emissions for each quantity of heat. Now I am saying the thermal efficiency of the stove when used for heating is as relevant. There is little point in saying this stove emits xx g of PM per MJ of heat generated if two stoves have very different thermal efficiencies. This is because one will have to burn much more fuel to deliver the quantity of heat needed. The result is xx g of PM and gases per MJ of useful heat. The moisture, density, carbon content, ash level, emissions per kg or hour matter not at all. To 'do anything' the emitted PM can be calculated, which means the emissions per hour can be calculated, and so on. Re the building: for years in Ulaanbaatar they tested the performance of the buuilding (insulation) and attributed it to the stove. Silly, really. It can rate the stove's ability to heat a building at all, but tou can calculate that easily from the thermal efficiency and burn rate of a known fuel. Thanks for thinking and responding. Crispin _______________________________________________ Stoves mailing list [email protected] http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org http://stoves.bioenergylists.org http://info.bioenergylists.org
