Greetings Stovers,
Tom Reed coauthored a book tilted An Atlas of Thermal Data (link below) that explains the results of Thermogravimetric data on a wide variety of biomass under different conditions. The results show a rapid decrease in weight that then stabilizes around the 400c and mostly completed at 450c. Using Thermogravimetric analysis (TGA) on biomass can separate the fuel into two distinct and repeatable fractions. The one fraction between ambient temperature to 450c we know will be used during cooking as once this restively low temperature is reached it has volatilized. It needs no oxygen from outside and gets it all from the fuel to form a gas then secondary air to completely combust. The fraction of fuel left above 450c contains energy that may be used or left after cooking. To compare efficiencies of stoves it seems to me we just need to use the energy of the biomass fraction we know will be used and use that value as the energy provided. If a stove is designed to use some char as added energy all the better for that stove. We do not need to determine the char left in the stove. We need to decide to use HHV or LHV but since we are not testing for hydrogen and just using an agreed upon value it doesn't matter - as I see it. The Rich Man: Needs a (1) calorimeter to determine the total energy HHV of the fuel and then used to determine the energy of the char left (remaining in the TGA). The energy in the fraction volatilized below 450c. is then calculated. Rich people need a (2) TGA to get an accurate value of the weight fraction containing the energy used from the dry biomass. Very accurately heat to 450c in nitrogen then cool and char removed for calorimeter. The Poor Man: Needs a (1) look-up table of the total energy of the fuel and a (2) pipe of fuel to heat up to determine the weight of fraction in the char left. The energy of the char is looked up in the look up table to be able to determine the energy fraction of the fuel that is used in the stove comparison. Notice in Tom Reeds book that after 400c the weight stabilizes so as long as the pipe is heated to 450c or higher there will be little error. Error relative to other methods suggested and everyone can do the tests. Except for those where a look-up table will not work like Richard's briquettes or where mixed biomass is used will need the more expensive equipment. . www.nrel.gov/docs/legosti/old/7965.pdf www.tainstruments.com/product.aspx?siteid=11 <http://www.tainstruments.com/product.aspx?siteid=11&id=11&n=1> &id=11&n=1 Understanding the complete process of a stove and all the reactions taken place is well worth studying and should continue. But for the sake of comparing stoves we need a foolproof procedure - it seems to me. Thanks Frank Frank Shields Control Laboratories; Inc. 42 Hangar Way Watsonville, CA 95076 (831) 724-5422 tel (831) 724-3188 fax [email protected] www.controllabs.com
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