[Stoves] Efficiencies for the rich and poor.

[Ronal W. Larson]

Frank and list:

   Sorry.  I am still not getting it.   Am I correct that your proposed new method (still with a pipe at some point) does NOT ever measure the amount of char produced?  But you are going to tell folks what the efficiency of the stove was?

Ron


On Oct 4, 2013, at 11:45 AM, "Frank Shields" <frank at compostlab.com> wrote:

> Greetings Ron, Stovers,
>  
> When a stove is used to do a variety of things like: cook, heat a home and make char for the garden we need just to make a larger circle around the stove to include the bundle of biomass stock piled in the corner of the home as the reference. When a forest is being removed at too fast a rate we need to extend the circle to the outside of the village. Back to the home; we use the pile of biomass to do lots of things so we keep track of how fast we are using up the pile. It’s not calculating the energy to cook the food AND how we are going to account for the char left over we put on the garden or how to account for heating the home when we are through with dinner. We can only account for all these uses by enlarging the circle and monitoring the bundle of biomass in the corner.
>  
> *This I think important*
> I’m thinking when we test stoves we should start with knowing the weight of a pile of biomass. Then test and determine the total energy450c (E450c) dry weight of the pile. Weigh the remaining pile after each test to determine the amount of E450c used for the task(s). Using this volatile fraction as the measured energy input (not total energy of the fuel) we can then determine the amount of E450c it took to cook a pot of rice without the need to subtract the energy in the char left over. Once the biomass pile has been used up the sum of the E450c used should add up to the total in the starting biomass. The char left over for the garden has no E450c so there is nothing to subtract from the total E450c value of the starting biomass. But if you want to know how much E450c was required to produce it just add up all the E450c used for the completed tasks that left the char behind. All we need to do is make sure the stove it at or above 450c when the task is completed so to make sure all E450c in the fuel has been used. So simple…..  (I think!).
>  
> 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
>  
>  
>  
>  
>  
>  
>  
>  
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Ronal W. Larson
> Sent: Thursday, October 03, 2013 8:57 PM
> To: Discussion of biomass cooking stoves
> Subject: Re: [Stoves] Efficiencies for the rich and poor.
>  
> Frank:
>  
>    The folks working with char-making stoves are not going to understand this sentence at all:     'We do not need to determine the char left in the stove. '
>  
>     That is as simple a measurement as you can find.   Granted that most of the weight loss is before 450 C,  the weight is NOT constant as you keep going higher in temperature   You will have a fair shot at the temperature achieved by measuring the weights in and out.  But temp is not the only variable, there is also the time at temperature, the size of the fuel etc.  See material in the Gaur-Reed Chapter 8.
>  
>    I know people are trying hard to determine the peak pyrolysis temperature from the characteristics of the char - besides weight differences, there is density, water-adsorbing properties, pH, and electrical conductivity in the "simple" (poor man) category.  Some big changes in conductivity can occur above a certain temp.   Many people would like to know the CEC characteristics, but I know nothing on that measurement.
>  
>    I guess I am saying that the stove itself might serve as the "pipe" you are describing.  If you have a good guess at the temperature of the produced char, you have a reasonable estimate of its remaining energy content, which is what I guess you are after.   I don't have much hope that any test with a "pipe" is going to tell you much about a particular stove.
>  
>    But mainly, I urge you to keep measuring the weight of the char.  You will not understand much about a char-making stove if you don't know the weight of the produced char.
>  
> Ron
>  
>  
>    
> On Oct 3, 2013, at 3:54 PM, Frank Shields <frank at compostlab.com> wrote:
> 
> 
> 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&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
>  
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