[Stoves] Fuel consumption vs Energy consumption in WBT Re: Updating your WBT and PEMS/LEMS Spreadsheet

[Paul Anderson]

Stovers,

I appreciate Crispin's detailed message about corrections to the WBT 
spreadsheet.  I suspect that Crispin has it correct, but I leave it to 
the technical experts about what is right or wrong in each cell of the 
spreadsheet.   (His full message is below, in case you missed it.)

There is one specific issue that needs discussion, so I have changed the 
Subject line (so that we can stick to that single topic). Crispin wrote:
> For stoves that produce a lot of charcoal, it will give a large 
> difference in the performance rating for ‘fuel consumption’, something 
> much closer to its actual consumption.   ...
> For TLUD pyrolysers that SFC number will increase more than 200%. 
> Don’t be shocked. It is now reporting “Fuel Consumed”, not “Energy 
> Theoretically Released turned into a dry fuel mass equivalent”.
I agree with Crispin about "fuel" and "energy" consumptions being 
different if charcoal is produced.   Wood that is changed to charcoal 
that is not burned is no longer wood, thus his suggested corrections 
about _fuel _consumed are correct.

But equally true is that the energy consumed should recognize that 
charcoal is energy that still remains, and therefore should be credited 
against the total energy of the fuel consumed.

The question for the Stove Testing Community is whether what is 
important is the fuel consumption or the energy consumption for a 
specific task.

Actually BOTH are important, and BOTH should be reported.

Then the persons evaluating stoves can see both values and make 
appropriate decisions, such as in the case of communities where wood is 
in short supply and deforestation is a concern.   For example:
A.  If the energy to accomplish the cooking task is the same, and one 
stove does it with 1 kg of wood and another stove with 1.2 kg of wood 
but leaving behind charcoal worth the energy in 0.2 kg of wood, then the 
char-making stove consumed more wood (that is, more fuel).

B.  But if in that same situation one stove uses 1 kg of wood and 
another uses (is able to use) 1.5 kg of agricultural residue (such as 
stems or cobs) and leaves behind some appropriate quantity of charcoal, 
then the first stove consumed 1 kg of wood and the char-making stove 
consumed ZERO kg of wood (but it did use a fuel that did not relate to 
the deforestation issue).

Clearly, the fuel consumption (including knowing the type of fuel) is 
important, but so is the energy consumption.

By the way, the created charcoal STILL has its value, whether as a fuel 
in a charcoal burning stove or as a soil amendment as biochar.

Concerning the WBT as it currently is established, the WBT fails to 
provide sufficient information to the evaluators of the stoves. The full 
data exist in the detailed records of each test, but only a selection is 
reported, and that selection is BIASED.   Not intentionally biased.   
Simply biased by not informing enough about the realities of stoves, in 
this case about stoves that produce charcoal.   It is not only about the 
making of charcoal, it is also about the ability of TLUDs (and some 
related stoves) to nicely utilize non-woody biomass.

This issue was of minor concern before TLUD stoves were seriously 
considered to be viable for households.  The WBT has links back many 
decades and to early WBT spreadsheets in the mid 2000s.   Even in 2010 
there was minimal recognition of TLUDs and their char-making 
characteristics, certainly not enough recognition for cause concern in 
the WBT calculations.   But things have changed, micro-gasifier 
cookstoves were highly evident at the recent ETHOS meeting.   And there 
is no going back.

Therefore, the WBT and other aspects of the evaluation of stoves 
(including the Tier system that simplistically yields only a few 
evaluative numbers) need to be brought up to date.

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 2/26/2015 12:00 PM, Crispin Pemberton-Pigott wrote:
> For TLUD pyrolysers that SFC number will increase more than 200%. 
> Don’t be shocked. It is now reporting “Fuel Consumed”, not “Energy 
> Theoretically Released turned into a dry fuel mass equivalent”.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20150226/e9fa1656/attachment.html>