[Stoves] Saving the WBT

[Ronal W. Larson]

Frank and list:

    see below.
On Aug 19, 2013, at 4:08 PM, "Frank Shields" <frank at compostlab.com> wrote:

> Dear Crispin, Ron, and all,
>  
> When I now think about all this it all seems so simple and obvious as the way to do it. Not sure if others are following me in my thinking.
     [RWL1.  I still am not.

> All we need to do is have all start with the same Energy from a biomass and use that as a baseline when comparing stoves. Oven dry weight energy value minus the char in the pipe. When burning wet (real) biomass we just report that in the 6 Box reporting sheet so a lower (or higher if the water reaction) results can be explained.   
    [RWL:  I see no way testing can start with "same energy", unless this means some average energy density (such as 18 MJ/kg).  But this varies with moisture content and the variation with different fuels is all over the place.  I gave a cite for a paper on this last week where Tom Miles was a co-author.  Huge variations and complexities.
>  
> When the fuel is wet we have all that FREE energy from the catalyst that will evaporate it IN the stove body.
     [RWL:  Sorry.  I mistrust the idea of free energy - and especially with the words "catalyst" and "evaporate in".  Can you give an example or a cite?

> In fact, if one puts a cup of water in a stove the evaporated steam hitting the pot will increase the water temperature in the pot. Unless the steam lowers the temperature of the secondary, or otherwise interferes with the secondary combustion,
     [RWL:  Both seem likely]
> it will add to the energy heating the water. It cost nothing to evaporate the water.  
     [RWL:  I think it WILL cost something.  If not, we would see a lot more of it than we do.  I know of only one stove with an added water supply - and don't think it is commercial.  Anyone?
>  
> As for coal: I have not thought how this would work and know little about burning coal. I would think it much like adding char to a rocket stove? There being little secondary combustion and the stove body getting very hot(?)
     [RWL:  Cooking with coal is a horrible idea - and China has the environment to prove it.  Yes - using a rocket stove to combust char is as bad an idea as in a TLUD.   Jikos aren't all that great but they are infinitely better than a rocket.
>  
> In my own mind I think this is what really happens in the real world and it seems clear to me this is the direction we should go.
     [RWL:  I presume the two words "this" refer to different topics.  But the whole point of the stoves list is to find better ways to go than todays "real world".  This is a subject that badly needs new ideas and expertise.   I would avoid following the "real world" like the plague.  In the "real world", the forest will be gone in a few decades.

> And if we can make it work it would simplify stove testing immensely.  
    [RWL:     Big "if".  Your being in a testing lane  should make it easier than for most of us.

     Please review what I wrote last time.  I think it great you are offering other approaches, but I can't see any way your testing one (?) small sample of anything in a pipe helps anything in stove analysis.  If others understand this, please let me know what I am missing. 

   Jim Jefford is already getting the energy content of every sample (wood blocks, pellets, rice husks, whatever) used in testing stoves.  He is in a webinar at 10 AM Eastern, 7AM Pacific tomorrow - possibly talking on this topic.  His having been doing this full time for many years, you (anyone) can pop any question in you wish to a world expert.

Ron
>  
> Regards
>  
> 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 Crispin Pemberton-Pigott
> Sent: Monday, August 19, 2013 1:45 PM
> To: 'Discussion of biomass cooking stoves'
> Subject: Re: [Stoves] Saving the WBT
>  
> Dear Frank
>  
> It is a difficult question to answer. Do you want the actual energy available from a particular piece of wood or the heat theoretically available, or what it would be if it was dry?
>  
> If the fuel is moist, then the gasification or the volatiles energy has to evaporate that moisture to get it out of the way. Unfortunately the amount of gas you can make from a bit of wood literally changes with the moisture level because the moisture is involved in the chemistry of what happens in the processes.
>  
> With respect to coal, I was not even about to get a carbon content of the ‘volatiles’ let alone an energy figure.
>  
> I suspect you are not going to get a good answer, and whatever answer you get is not going to be very useful in a real world problem.
>  
> Regards
> Crispin
>  
>  
>  
> Dear Stovers,
>  
>  
> I am trying to determine the best way to calculate the energy in the Natural Volatiles. The sample we place in the iron pipe of the oven dried biomass we can test or ‘look up’ the energy value. In the char remaining after 450c deg. (char-ash) we can give that a value of 34.78 kJ/g. Then for the total NV in the fuel we just subtract the total biomass from the char energy remaining. All done in the pipe. Then use the energy calculated from the increase temperature of the water to determine efficiency.
>  
> I am still wondering what to do with the moisture in the fuel. Any suggestions?
> It is like the NV fraction but with possible varying results. As Alex reminded me in his writings there is the water-reaction that can increase the energy output or the LHV stealing energy from the NV. So depending on the stove and operator working the catalyst to control the internal body temperature the water can be a plus or minus.  My thinking now is to just use the dry NV value as the total energy of the biomass. Like playing golf. You have a par 5 and you can go above or below depending on your day. The dry NV value is the value we use and we go above or below 100% efficiency depending on how good the stove and operator controls the catalyst and if water is included in with the biomass.
>  
> From the replies it’s a bit hard to tell but it seems we are mostly all in agreement. : )
>  
> Regards
>  
> Frank
>  
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