[Stoves] Request for technology proposals - Clean Stove Initiative, Indonesia

Mon Feb 24 19:31:28 CST 2014

Crispin ( And AGAIN adding back the stove list).

     1.  I may be able to get to this in three days  (conference coming up).  But I think the stove list deserves to see your responses sooner. 

     2.   You are not understanding about half of what I am saying - but no time to try again.   But you have made it very that a char-making stove will receive no credit at all for making char.  I sure hope you have not started a trend in stove testing.  

      3.   I point out to others that not only will a char-making stove receive no credit, but it is not clear what amount of wood can be used as you go through the three successive replicating tests. I base this on this  exchange below

RWL saying:
.I look forward to hearing whether you have changed your mind on a)  wanting to keep the input wood quantity and wood energy the same as you test char-making stoves,
>  
> I am not changing my mind at all. The mass of fuel consumed per test replication will be accurately determined by observations. Unburnable char remaining, whatever its energy content, is not considered ‘unburned fuel’. End of short story. Any test that pretends it is, will not be used. We have suffered enough in Africa from stoves selected on that basis using UCB-WBT 3.1. Those days are gone.

    4.   I also quote Crispin from below, for anyone who has seen merit in the normal testing:
> We have suffered enough in Africa from stoves selected on that basis using UCB-WBT 3.1. Those days are gone.

   5.   I repeat my conclusion that only dismal test results await any char-making stove going through this new Crispin procedure.

Ron

On Feb 24, 2014, at 4:20 PM, Crispin Pembert-Pigott <crispinpigott at outlook.com> wrote:

> Dear Ron
>  
>             I am going to confine myself only to the last few of your paragraphs, which was the only topic in last night’s message.  You said (from below):
>  
> Regarding the 85% efficient stoves:
>  
> A stove that has a very high combustion efficiency, burns all the fuel placed in it, and having a high heat transfer efficiency can put 85% of the energy theoretically available in the fuel consumed into the pot in the form of sensible heat. I have a water heater in my house that is 88% efficient calculated on this basis. I have a furnace that is 92% calculated on this basis. It is therefore possible to accomplish.  
>  
> [RWL:  I said last time that I agreed it is possible.   But we are starting at hundreds of dollars, I guess, for any wood burner with that possibility.
> 
> I don’t second-guess what people can do. Roger Samson was with me in my workshop when we made a pretty good TLUD stove that burned switchgrass pellets for $1.00 in stainless steel. You can do a lot with $10.
>  
> If the challenge is to provide a pellet burning, char-making stove with a rated fuel efficiency of 45% (also called the overall thermal efficiency), it would be a requirement to have a heat transfer efficiency that is above 45% in order to have char remaining as unburned fuel. If the heat transfer efficiency is 85% and the rated fuel efficiency is 45%, the difference of 40% can be delivered in the form of char remaining from the fuel consumed
>     RWL:  I am sorry that you have changed the problem from Tier two (55%) to Tier one (45%) - because now I have to do more work.  Clearly you were not happy with the conclusion I gave - that your numbers didn’t hold together.  I wish you would have acknowledged that they didn’t  in any reasonable test, (you can’t keep at either 85% reported efficiency or keep the same amount of wood).    Glad that you are now willing to report a 45% stove, because that gets closer to reality, but I am going to also keep the 55% Tier 2 results, because I feel a need to also correct what you did earlier.
>  
> I am not sure what you are on about. You can perform the same calculation at 55%, just make less char and you will have that. Do you following this I am speaking of a formula that allows you to set a performance target and a char result that together add up to a given heat transfer efficiency?
>  
> 
>             You earlier made a mistake, after you divided by 0.55 in the previous Tier-2 55% case in your lines that I repeated yesterday:
>    2 Stars means using up to 7/.55 = 12.727 MJ of heat   
>    Difference is 4.49 <J or 155 g of char   
>  
> Bu that was with a different example. Good grief. Rework the numbers for 55%. Be happy!
>  
> I don’t think you need to me put numbers on it to show this.
>             [RWL:  Wrong.  I hope you see why from looking below at my putting numbers in play.   Because of time pressures, I am going to just give results and not show equations - I will do for 85% (no char), 55% (Tier 2, your last example, some numbers above, after correction for handling lost energy in what I consider a proper manner) and 45% (Tier 1, the latest example)
>  
>       These are the 
>             useful energy (MJ): 7, 7, 7
>             Tier:                                         3, 2, 1
>             Desired “useful" %:  85, 55, 45
>             input wood energies (MJ): 8.235, 12.727, 15.555
>             Input fuels (gms):  484, 749, 914 
>             Lost energy (MJ):  1.235, 1.235, 1.235
>             Lost energy %:  15, 9.7, 7.9
>             Char energy(MJ):  0, 3.257, 6.095
>             Char energy  (%):  0,  25.6, 39.18
>             Char weights (gm):  0, 112, 210
>         Char weights (%):  0, 15.0, 23.0
>  
>    Note the third row from bottom is not what you predicted (because of your assumption on lost energies that I think is not likely - overly simplistic.   
>  
> So what? It was a worked example. Put in any numbers you like. I am demonstrating how to approach the problem.
>  
> The conclusion is that any TLUD exceeding 23% char by weight will not achieve Tier 1 standing.
>  
> Probably correct. So what? You are the one wants to make char and wrote words like, “a char making stove could not meet the requirements of the Indonesian programme and people should therefore not pay any attention to the opportunity”. I have worked an example showing this was not the case. You now provide an example showing there are good reasons to try to create char making stoves that meet the requirements. We are now in agreement that this opportunity for TLUD stoves is real and viable and we should proceed.
>  
> If you can make a controllable pyrolyser that makes char, the requirements are much less demanding.
>  
>  More than 23% is fairly likely.  There is no way most TLUDs could ever achieve Tier 2, since they would have to produce less than 15% char - which is hard to do,  
>  
> I disagree with this conclusion. The highest % char I have seen in a stove submitted so far was 18%. With slightly more primary air it would by 15%.
>  
> We find the perverse result that the better the char-making characteristics, the worse ranking the stove receives.  Exactly why I hope to see more than a single number for any stove test that involves char.
>  
> You can have as many numbers as you like, but the fuel consumption rating will be based on the fuel needed to perform any set task. You are going to have to deal with that because that is how the stove promotion programmes work. It is how the Gold Standard works, the CDM and above that the GEF.
>  
> [snip]…Since char-making stoves are usually reporting higher efficiencies  (less smoke, etc) than rockets, why should energy losses go up as one adds char-making.  
>  
> I agree that most TLUD’s make less smoke that Rocket Stoves. Not all, but most. It is not energy loss that goes up, it is fuel consumption that goes up as the mass of char remaining increases while the task remains the same. It is a zero sum game. There is no free lunch, nor any free energy nor any free char.
>  
> The same total energy is arriving at the pot, with or without char-making
> 
> Exactly my point. The work done remains the same. For any increase in char output, the raw fuel consumed has to rise. Char comes from raw fuel. More char, more raw fuel. Programme managers want to see that the total fuel drawn from the forest goes down, not up. You want to char everything to bury the char in the ground. When you fund a stove programme, make that a measure of performance. No problem. We will measure it and report.
>  
> To achieve this would require a fire heat (factored for combustion efficiency) to pot heat (net heat gained) efficiency of 85%.
>      [RWL:  That is what I think I am doing - and think you are not.  You are keeping the pot heat at 7MJ, but the lost energy (starting at 15%) keeps going up as one makes more and more char.  This assumption needs justification.
>  
> I am not all that sure what you are doing other than trying to get char remaining deducted from the raw fuel consumed in some clever manner so that people think means it uses less fuel, even if it uses more. I am definitely opposed to that proposition because it is cheating.
> 
> 
> The system efficiency is 45% (because for each unit of fuel consumed, 45% of the energy available is doing something useful in the pot).
>             [RWL:  Ditto - I think I am doing this, but the energy in the gas flow is the same for me in all three cases - not in yours.
>  
> You are citing the very same energy flow to the pot as I am, except you are not considering the energy in the pot material but that is a quibble. Don’t divert attention. The work done in the pot is always the same. Some energy is lost ‘past the pot’ in hot gases, some is lost to char, in the sense that the energy is not released.
> 
> 
> The char production efficiency would be the mass of char yielded divided by the mass of char potentially yieldable (I suppose) or the mass of char divided by the dry mass of fuel used.
>                 [RWL:  I don’t think we should introduce “potentially yieldable”;  sounds like a bag of worms that won’t help stove users or sellers.  Yes, we should report weights, but to really know what is going on, we also need a ratio of energies  - what I called eff2.
>  
> That is valuable to some people for design – knowing what the energy ratios are,. But there is NO WAY you are going to subtract char energy from the energy in the fuel consumed to pretend that the raw fuel was not consumed by the stove. You can call it eff2 or eff10 but you are not getting fuel consumption credit for producing char that can’t be burned in that same stove.
>  
> I look forward to hearing whether you have changed your mind on a)  wanting to keep the input wood quantity and wood energy the same as you test char-making stoves,
>  
> I am not changing my mind at all. The mass of fuel consumed per test replication will be accurately determined by observations. Unburnable char remaining, whatever its energy content, is not considered ‘unburned fuel’. End of short story. Any test that pretends it is, will not be used. We have suffered enough in Africa from stoves selected on that basis using UCB-WBT 3.1. Those days are gone.
>  
> b) whether lost energy percentage stays the same as one adds a char-making function,
>  
> Char remaining that cannot be burned in that same device is considered lost fuel. It is not considered ‘lost energy’ as the energy content is not determined if the question asked is ‘What is the fuel consumption’?’ Whether that fuel was burned or not is immaterial to the question. Whether it is char, torrefied wood, carbonates or condensed volatiles is also immaterial with respect to the mass of fuel consumed (as defined).
>  
> and c) whether you are providing appropriate information for the char-making stove community (and the country of Indonesia).
>  
> The information appropriate to the stove making community (there are no sub-categories of stove makers) is accurate, complete and fully explained in the Test Procedure document. Please refer to the Definitions in section 2 for a complete set of terms including synonyms where appropriate.
>  
> One might well consider questioning whether the proponents of char-making stoves are providing “appropriate information” to the prospective users of their technologies.  I have seen several stoves which produce char touted as consuming a very small amount of ‘dry fuel’ in order to conduct a 5 litre water boiling test – amounts so small as to be physically impossible. I have seen a claim that a TLUD char maker saves 50% of the fuel, and also delivers 45% of the available raw fuel energy in the form of char! Simultaneously! I believe in miracles, but not that one. That would mean the stove consumes 95% less fuel than the baseline product so the heat transfer efficiency would have to be 300%!  And you were worried about 85%. 
>  
> The problem is, Ron, you have for many years been converting the energy apparently released by the fire into a ‘dry fuel mass equivalent’ corrected for char energy remaining and claiming that the dry fuel mass equivalent represents in some manner, the amount of raw fuel needed to conduct the test.  It was never true.
>  
> Those days are gone. That chapter is closed. Those birds have flown the coop.  No more performance misrepresentation to stove selectors and users.  What a stove consumes, it consumes. If you cut another tree, I am counting it. No more jiggery-pokery-fiddle-fiddle-I-have-a-clever-formula. The jig is up. The past is past.
>  
> Get used to it.
> Crispin

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