[Stoves] Efficiencies for the rich and poor.

[Frank Shields]

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

frank at biocharlab.com

www.controllabs.com

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20131003/73fd275e/attachment.html>