[Stoves] [biochar] [biochar-stoves] A review of chronological development in cookstove assessment methods: Challenges and way forward
Frank Shields
franke at cruzio.com
Wed Nov 25 16:22:05 CST 2015
OK - I agree there are places where the efficiency is reduced. BUT IMO we have not even begin to address the Starting Energy of the fuel and the energy distribution of its components. We can’t even begin to determine efficiencies of whatever TASK it is we are doing until we do that.
You say:
> not everyone applies a “value" to the char ~ or at least not to the Energy (equivalency) of the char that is produced [whether or not it could be considered valuable "biochar" or "fuel for producing additional biochar... or energy").
sounds like a ‘percentage of importance’ type of answer : )
Regards
Frank
Frank Shields
> On Nov 25, 2015, at 2:09 PM, Lloyd Helferty <lhelferty at sympatico.ca> wrote:
>
> Ahhh, but you can go wrong....
>
> What if one "quenches" the end-of-batch char with a sound dousing of H2O, and that sopping wet (DAF) carbon is found to "still have hydrogen and lots of oxygen left indicating not a good biochar" (due to some volatiles)? This (DAF) carbon might not be very suitable for char cookin' anymore, which could bring us back down to a lower "efficiency" -- 0% in the case where one does not "use the pyrolysis gases for something" (cooking, heating [CHC, CHB, CHP, CHPB]), ...or, at least to a value that would be something approaching the "heat transfer efficiency" of flame --> pot --> water/food/load due to the use of the pyrolysis gases that were liberated during the pyrolysis process (expressed as a ratio of the initial total energy of the biomass fuel (dry weight)).
>
> I suppose this is where the confusion / debate comes, since not everyone applies a "value" to the char ~ or at least not to the Energy (equivalency) of the char that is produced [whether or not it could be considered valuable "biochar" or "fuel for producing additional biochar... or energy").
>
> Regards,
> Lloyd Helferty, Engineering Technologist
> Principal, Biochar Consulting (Canada)
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> On 2015-11-25 3:49 PM, Frank Shields wrote:
>> Dear Ron and Stovers,
>>
>> My interest is controlling the fuel. This done by 1) collecting fuel like that being used in real World and 2) normalizing the energy value going to the secondary by using pyrolyze gases + (CO -> CO2) values.
>>
>> I cannot determine any energy efficiency values because this is just one side of the equation. And you do not supply me with the values of this one side as I need them.
>>
>> The value I am proposing is only useful for energy traveling to another location - secondary. Making char does not require energy, in fact it waste energy. And (bio-)char does not have useful energy, in fact the energy is locked up and cannot be used by soil microbes for 1000 years. So what I propose is not applicatable to what you are talking about and not intended to be so.
>>
>> Your (bio-)char (not charcoal used for cooking) is not ‘energy’ locked up but should be referred to as carbon. Following the total carbon in the feedstock; separating it into available carbon and non-available carbon (TGA) for optimum then determining the amount actually made from your char-maker is more to what you want. And that being your efficiency values.
>>
>> But in a World that is connecting fuel energy producing non-available carbon (biochar) and that biochar is made >90% carbon (DAF) I guess it would be ok to assign non-available carbon with an energy value and use in calculations. Lets see if we can do that:
>> 1) we need total energy of the biomass fuel (dry weight)
>> 2) using TGA we need energy of the total char (DAF)
>> We assume the char (DAF) is 90+% carbon and assign that an energy value.
>> 3) We determine energy of the pyrolysis gases (total - char)
>> 4) So thats the total maximum amount of energy assigned to biochar that should be produced in your devise.
>> 5) You run YOUR device and produce biochar. Ash a subsample to determine the weight of biochar (DAF). Assign an energy value to it based on biochar (DAF) being >90% carbon.
>>
>> Now you can calculate the efficiency of your device at producing biochar.
>>
>> Note: If you have wood (dry) and you use the pyrolysis gases for something, you use the CO->CO2 gases for something and use the (Bio-)char left over for something then 100% of the energy in the wood is always used. You are left with efficiency determinations found (compared to that determined by TGA) for making biochar. But if making biochar is found less than expected so to be not very efficient then the non-biochar gases (CO -> CO2) went to join the pyrolysis gases and it still always = all adds up to 100%. You can’t go wrong!
>>
>> Where you can go wrong is if after making the biochar you test it to see if it still has hydrogen and lots of oxygen left indicating not a good biochar and it is then wasted. This is bad.
>> But if still good for char cooking (due to some volatiles) you are now back to 100% efficiency. You can’t go wrong!
>>
>> 100% efficiency every time!
>>
>> Love it!
>>
>> Frank
>>
>>
>>
>>> On Nov 25, 2015, at 8:52 AM, Ronal W. Larson wrote:
>>>
>>> Paul, Brian, and lists:
>>>
>>> 1. Thanks to both Paul and Brian (their messages below). Brian’s is a nice comparison to CHP. The efficiency for CHP is always taken as the sum of the separate power and heat. Using the waste heat is clearly to everyone’s advantage (save companies selling less fuel). Biochar literature has tacked on a B to discuss combined heat, power and biochar as CHPB. There is a considerable difference from CHP in that the B = biochar competes with the H and P. More B means less of both H and P. But the terms are all (necessarily) measured in energy terms. What other units could be used?
>>>
>>> The same seems true for what Brian is calling CHC. No reason not to use this, but an alternative is obviously CHB. If one was producing char only for further combustion, then CHC would certainly be preferred. The stoves list will probably use both CHC and CHB interchangeably. Biochar (three sites receiving this) and climate (on which this first started) lists will presumably mostly prefer CHB.
>>>
>>> I cannot accept Frank Shield’s arguments below. He is trying to force a false preference between char-making or not - when such a choice is not needed. Both are wanted by many if not most stove users. I again ask Frank to express an opinion on which efficiency and inefficiency (presumably always inversely related exactly) is best. His reply to me was not used by Brian - so readers will have to go back to a message close to mine on the 22nd.
>>>
>>> I similarly reject the arguments by Kevin Chisholm against the use of both the third and fourth efficiencies. Like Frank, he offers no answers to my two basic ending questions, and (I find) no valid reasons for those two rejections.
>>>
>>> I have added Prof. Jain again - as it was his comment (below) that I quoted in moving this climate thread to the stoves and biochar arenas:
>>>
>>>>>>>>>>> the energy stored in the charcoal should be considered as a useful energy.
>>>>>>>>>>>
>>>
>>>
>>> I again urge readers new to this thread to read his lengthy scholarly (free) article relating climate issues to stoves in numerous ways.
>>>
>>> To all - I hope we can hear more on especially the inefficiency computations; forget efficiencies. Also on what is the physics or chemistry which causes char-making stoves to be more efficient? Is the fuel composition of either/both H2 and O2 important? Another possibility is that it is where the flame appears. Burning char in a TLUD is obviously inefficient because the main flame and energy release is as far from the cook pot as possible - below the char, not above it.
>>>
>>> To Paul - I hope this is what you wanted.
>>>
>>> Ron
>>>
>>>
>>>> On Nov 25, 2015, at 6:52 AM, Paul Anderson wrote:
>>>>
>>>> Stovers,
>>>>
>>>> The comment below from Brian to one Listserv merits being sent to the Stoves Listserv and Biocharstoves Listserv. Brian's comments make a lot of sense. Let's discuss further and see if some "implementation" can result.
>>>>
>>>> I hope that Ron will filter and coordinate any such discussions because there are numerous listservs to which the messages need to be circulated at least occasionally. There should be assistance from the rest of us, especially if implementation is to occur.
>>>>
>>>> Paul
>>>> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
>>>> Email: psanders at ilstu.edu <mailto:psanders at ilstu.edu>
>>>> Skype: paultlud Phone: +1-309-452-7072
>>>> Website: www.drtlud.com <http://www.drtlud.com/>
>>>> On 11/24/2015 8:54 PM, 'Brian Dougherty' [biochar] wrote:
>>>>>
>>>>> Ron,
>>>>>
>>>>> I don’t see a problem with reporting the higher efficiency values as long as it’s made clear what is included in that number. As an example, combined heat and power (CHP) plants typically report high efficiencies because they are factoring in the energy from the heat plus the energy from the electricity, but the name implies they are capturing both. A char making stove that is also heating water is essentially a miniature CHP plant if you think of the char as the “power’' output, but it would need to be labeled as such. It’s a matter of semantics, but if a unit is marketed as a char maker or a stove then the higher efficiency numbers might be misleading. If it’s marketed as or intended to be a combined heat and char maker (CHC stove?) then the higher number makes sense.
>>>>>
>>>>> Brian
>>>>>
>>>>> From: <mailto:biochar at yahoogroups.com>mailto:biochar at yahoogroups.com <mailto:biochar at yahoogroups.com>
>>>>> Sent: Tuesday, November 24, 2015 5:38 AM
>>>>> To: Discussion of biomass <mailto:stoves at lists.bioenergylists.org>
>>>>> Cc: S. Jain (Env. Engg.) <mailto:sureshjiitd at gmail.com> ; Entire Group <mailto:biocharstoves-7xpll at wiggiomail.com> ; Biochar <mailto:biochar at yahoogroups.com>
>>>>> Subject: Re: [Stoves] [biochar] [biochar-stoves] A review of chronological development in cookstove assessment methods: Challenges and way forward
>>>>>
>>>>>
>>>>>
>>>>> Frank et al
>>>>>
>>>>> Those of us working on char-making stoves (a category bigger than TLUDs ) don’t have the “don’t know what to do with” problem. Even better is that they seem cleaner and are apt to save time and money (maybe make money). The issue is reporting - if you feel such a stove (stove not char-maker) has merit. What is your answer to my two questions?
>>>>>
>>>>> Ron
>>>>>
>>>>>> On Nov 23, 2015, at 12:36 AM, Frank Shields wrote:
>>>>>>
>>>>>> Dear Ron,
>>>>>>
>>>>>> If your task is to make char your calculations is dry weight of fuel IN and weight of char (DAF) OUT. Boiling water is just something to do so you can have a cup of tea while you wait.
>>>>>>
>>>>>> If your task is boiling water and you are left with char you have a byproduct to add to your garden.
>>>>>>
>>>>>> If you want both I suggest you place an importance on each (percentage of importance) for the span of a year or season. Then with each run you keep track of the char produced and water boiled and try to achieve your percentage ratio. At the end of the year you may need to just boil off some water to get more char or have left over char you don’t know what to do with.
>>>>>>
>>>>>> Regards
>>>>>>
>>>>>> Frank
>>>>>>
>>>>>> Frank Shields
>>>>>>
>>>>>>
>>>>>>
>>>>>>> On Nov 22, 2015, at 9:36 PM, Ronal W. Larson wrote:
>>>>>>>
>>>>>>> Lloyd et al: Adding “stoves - as that is where we have had a similar dialog in the past
>>>>>>>
>>>>>>> I promised an example. Use energy of wood and charcoal as measured to be 18 and 30 MJ/kg - both possible.)
>>>>>>>
>>>>>>> Assume 1 kg of wood into the stove - or 18 MJ.
>>>>>>>
>>>>>>> Assume water boiling away calculates to 6 MJ; Effic1 = 6/18 = 33% (Some say stop here; this is a typical number for many stoves including TLUDs)
>>>>>>>
>>>>>>> Assume (to get easy numbers) 26.7% (a little high but a possible number) by weight char production - gives .267* 30 = 8 MJ in the char. Effic2 = 8/18 = .444 = 44%,
>>>>>>>
>>>>>>> Using the pyrolysis gases in the denominator - Effic 3 = 6/(18-8) = 6/10 = 60% (This use of the char energy in the denominator is the most common way of handling char- added (60-33 =) 27% to the reported value of the stove - )
>>>>>>>
>>>>>>> But I think it more proper to add the first two efficiencies: Effic4 = Effic1+ Effic 2 = .333+.444 = .777 (17.7% bigger than the 60% value - and I think also an honest way to look at what is going on. Last I saw, EPA did not add these together, but they did report Effic 1 and Effic 2. Sales people for biochar and TLUDs are apt to add them of course. We obviously want both numbers to be as high as possible.
>>>>>>> The losses are 18-6-8 = 4 MJ or 4/18= 22.2% (mostly hot gases). This is what we should be concentrating on - not 100-60 = 40%. In inefficiency terms, I claim the losses we want to reduce are nowhere near 40% - if you want both char and water boiled away. 40% is the portion of energy in the pyrolysis gases that we failed to capture.
>>>>>>>
>>>>>>> If we burnt the wood (no resultant char) rather than pyrolyze it, we might expect to have a 60% efficient stove - but no-one measures any wood stove that high. Why not? I don’t have a good answer, but suspect it might relate to how hydrogen fits in. That is - with little hydrogen in the char, the hot gases are more hydrogen rich with a pyrolysis stove. Better heat transfer with more hydrogen? A hotter flame? Or is the effect due to oxygen - which also is a lower percentage in char than in wood? Or both?
>>>>>>>
>>>>>>>
>>>>>>> Comments appreciated when we are striving to make char in a stove:
>>>>>>> Q1: are the losses 22%, 40%, or 67%?
>>>>>>> Q2: Is the efficiency 78%, 60%, or 33%?
>>>>>>> Ron
> <snip>
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