[Stoves] Radical ideas from Paul and Philip {re: stoves and credits again}

Nikhil Desai pienergy2008 at gmail.com
Thu Sep 28 12:24:13 CDT 2017


Paul:

@ Philip's calculations: I am not used to kJ calculations, so this is how I
understand: (100-15) refers to raising the water temperature from 15C to
100C and 4.186 is the conversion factor kJ/kCal. Wood LHVs are contextual
and I imagine so too charcoal LHV, depending on the input and operating
conditions. am not sure about his Case 2; a little confusing.

Anyway, Philip is introducing the concept of "system efficiency". This is
radically different from "stove efficiency" whose computations there seem
to be allocating different inputs to different outputs.

And you wrote of "FUEL efficiency measured by communities, not by single
stoves."

Together, you two seem to suggest that whatever the lab tests and ISO TC
285 ratings, project design must be informed by appropriate contexts of
fuel availability and relative costs, and a collective measure of "before"
and "after" service requirements and community-level performance.

I may add that "communities" also include users of wood and charcoal other
than household stoves.

It is ridiculous under CDM rules to have to destroy "old" cookstoves, or
under Kirk Smith's rule to not permit "stacking". Projects with large
enough % of users in a particular context, finding new cookstoves
acceptable, cleaner, and usable enough to do many or most of the tasks from
"old" cookstoves, are likely to yield measurable benefits promised. (Except
climate benefits and aDALYs which are fictional.)

Boiling water for coffee this morning as the weather is turning cooler
around here, I realized that even boiling water is a multi-purpose
activity, the steam warming up the kitchen. A cookstove will often be used
for multiple products and "single stove" efficiency ratings for just
boiling water have no practical counterpart. Or meaningful application.

But we are on to the search for savior stoves. Let's pray.

Nikhil

------------------------------------------------------------------------
Nikhil Desai
(US +1) 202 568 5831 <(202)%20568-5831>
*Skype: nikhildesai888*


On Mon, Sep 25, 2017 at 8:41 AM, Paul Anderson <psanders at ilstu.edu> wrote:

> Philip
>
> I suspect something is not correct,
>
> 1.  In your example, the 0.395 kg wood contains 5930 kJ of total energy.
> 2.  You calculate that the char produced would contain3163 kJ.   That
> would be 53.3% of the total energy is maintained in the char.
> 3.  Later you write that "the efficiency of char production would have
> been ... 36.4%.
>
> I leave it for you and others check this out.
>
> 3.  At the end you say
>
> this would have been statistically indistinguishable from the efficiency
> with no char production – i.e. it would have shown no benefit to char
> production.
>
> That statement could also be written "it would have shown no benefit to
> cooking the regular, full-combustion way, without char production."
>


> And since produced char can be stored for later use, is essentially
> smokeless cooking for ventilated "indoor" cooking, and can be used for
> other purposes, cooking with char-producing stoves could be viewed as
> having some benefits.
>
> I respect those of you who are good number crunchers and know the
> formulae.   Please comment on the above.   I am here to learn.
>
> Paul
>
>
> Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
> Email:  psanders at ilstu.edu
> Skype:   paultlud    Phone: +1-309-452-7072 <(309)%20452-7072>
> Website:  www.drtlud.com
>
> On 9/25/2017 4:29 AM, Philip Lloyd wrote:
>
> I carried out a thought experiment.
>
>
>
> In case 1, a cookstove burning wood boiled 5 litres of water at an energy
> efficiency of 30%.  The useful energy provided was 5*4.186*(100-15) =
> 1779kJ. This required 5*4.186*(100-15)/0.3 = 5930kJ.  If the as-fired wood
> had a LHV of 15MJ/kg, it would have needed 5930/15000 = 0.395kg wood
>
>
>
> In case 2, the same stove was operated to produce charcoal while also
> boiling 5litres of water.  More wood would be needed, because not all the
> wood would be combusted – some would be left as char. If you fed 0.395kg
> wood to be turned into char at 29% efficiency, and the char had an LHV of
> 28MJ/kg, then the char would have an energy of 0.395*28000*0.29=3163kJ. The
> wood from which it was prepared had an energy content of 5930kJ, which was
> what was needed to boil the water in the absence of char production. So
> 5930-3163 = 2768kJ of additional energy* would be needed to boil the water
> if there was char production. At 15MJ/kg, this is 2768/15000 = 0.185kg
> extra wood, or an increase of 47% in the wood supply. The total energy
> supplied would then be 5930+2768 = 8698kJ.  The energy efficiency of
> cooking would therefore fall to 1779/8698*100 = 20.5%, while the efficiency
> of char production would have been 3163/8698*100 = 36.4%.  The system
> efficiency would have been 20.5+36.4 = 56.9%
>
>
>
> If you used the WBT formula, the efficiency of boiling with char
> production would have been 1779/(8968-3163)*100 = 32.1%.  Given the
> measurement errors inherent in the WBT method, this would have been
> statistically indistinguishable from the efficiency with no char production
> – i.e. it would have shown no benefit to char production.
>
>
>
> Prof Philip Lloyd
>
> Energy Institute, CPUT
>
> PO Box 1906
>
> Bellville 7535
>
> Tel 021 959 4323
>
> Cell 083 441 5247
>
> PA Nadia 021 959 4330
>
>
>
> *This assumes that there is no endotherm in the pyrolysis of wood in the
> presence of air, and that all the pyrolysis products except the char burn
> to provide heat. There is evidence in the literature of no endotherm in the
> presence of air.
>
>
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org
> <stoves-bounces at lists.bioenergylists.org>] *On Behalf Of *Paul Anderson
> *Sent:* Sunday, September 24, 2017 11:27 PM
> *To:* Discussion of biomass cooking stoves
> *Cc:* ndesai at alum.mit.edu; Andrew Heggie; Crispin Pemberton-Pigott
> *Subject:* Re: [Stoves] stoves and credits again
>
>
>
> Philip, Tom and all,
>
> Philip is mostly correct.  Actually wood takes up (has) too much WEIGHT.
> Wood has 3 times (or more, if the char is poorly made) the ENERGY value of
> charcoal that could come from that char.   But it has about 5 times the DRY
> weight of the char, plus there can be 20 to 50% moisture  content to make
> the wood even heavier.
>
> And the charcoal has  almost double (30 vs. 16) the energy content by
> weight, but char is so much lighter per unit of volume.  So the trucks are
> buldging upward and sideways with the sacks of charcoal strapped to them.
> Weight of charcoal is not a problem for most transport.
>
> Apart from the transportation issue, I believe that the appeal of charcoal
> is that it does not smoke (not much).   CO is invisible and deadly, but the
> people learn to cook on the balcony or keep some  air flowing.  And it does
> not turn the bottom of the pots black.
>
> Charcoal is an attractive fuel.   Too bad it is made by processes that
> throw away 2/3rds of the energy.    (So, let's promote TLUD stroves and
> collect the char for sale to the urban folks.  Only one third of the
> cutting of wood/forest.)
>
>  So, if 100,000 households (mainly in rural or peri-urban areas) would use
> TLUDs, the resultant char would equal to the energy needed for an
> approximately equal number of households (mainly urban) that would want to
> burn charcoal.
>
> Now that would be FUEL efficiency measured by communities, not by single
> stoves.
>
> Paul
>
>
> Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
>
> Email:  psanders at ilstu.edu
>
> Skype:   paultlud    Phone: +1-309-452-7072 <(309)%20452-7072>
>
> Website:  www.drtlud.com
>
>
>
>
>
>
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