Frank and list:
see below.
On Aug 19, 2013, at 4:08 PM, "Frank Shields" <[email protected]> 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
> [email protected]
> www.controllabs.com
>
>
>
>
> From: Stoves [mailto:[email protected]] 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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