[Stoves] Heat Content of Ethanol Gel

[psanders at ilstu.edu]

Dear Crispin,

Your excellent reply seemed to come only to me, so I am sending it to 
the Stove
Listserv readers.  Good to know that the errors you are finding are in draft
documents, not those already in use for making decisions.

Separately I will post a comment about water in alcohol fuels.

Paul

Quoting Crispin Pemberton-Pigott <crispinpigott at gmail.com>:

> Dear Paul
>
> Actually it has not affected the calculations much because this was from a
> proposed (draft) standard for Ethanol Gel fuelled appliances.  I play a
> minor role on a technical committee and there are others who are not so good
> with spreadsheets so I like to just check things over.  It is probably a
> misprint and who knows where it came from?
>
> Instead of showing 1.05 KW in the example it gives something like 0.057 or
> some such. No matter.
>
> While researching the ethanol heat yield (as far as small stoves are
> concerned) I came across a message from me to you on the subject and I said
> that ethanol has 31.8 MJ/Kg.  This is only the total (HHV) heat and is not
> useful to us.  I am changing my mind!
>
> The LHV which does not include heat yielded by condensing the water in the
> smoke is realistic as the temp of the gases leaving the pot-side is still
> above 100 C.
>
> The value of 27 MJ-ish is OK.  There a surprising number of values for this
> fuel listed all over the place.
>
> The impact it has for ethanol stove designers is that most of the fuel is
> diluted with water (actually it was never removed as it costs more to do so)
> and the actual heating value is lowered because it has to evaporate that
> water.  The effective heat content of ethanol gel is about 24.89 MJ/Kg and
> 19.64 per litre.  The fuel is sold by the litre usually.
>
> That is for 5% water gel with 2% additives (I don't really know what the
> additive content is - I am guessing - and I also don't know what the heat
> contribution of the additives are.  I hope someone can comment on it.  I
> know it costs about one SA Rand to gel a litre of ethanol so it might be
> more than 2%.
>
> As people are finding out when putting ethanol into gasoline, there is a big
> loss of performance per litre. Gasoline is in the high 40's so for every 20%
> added there is a 10% increase in fuel consumption.
>
> What I really get bothered about is when people selling ethanol gel compare
> their fuel with paraffin, quoting heat content per litre of paraffin with
> HHV heat content of ethanol per Kg.  I have seen some sophisticated
> pamphlets with this kind of misleading info printed in it.
>
> In Swaziland it costs about 4.5 times more to cook with ethanol than
> paraffin, usually with 1.5 times the CO emitted to boot.  As Dr P Lloyd has
> commented after testing about 6 stoves earlier this year, none are really
> ready for the market and all needed burner development work.
>
> The setting of a compulsory standard for ethanol gel fuelled stoves in South
> Africa is going to take some of the 'wild west' features out of the ethanol
> cooking market - for the benefit of the producers and the public.
>
> Regards
> Crispin
>
> -----Original Message-----
> From: Paul S. Anderson [mailto:psanders at ilstu.edu]
> Sent: August 27, 2007 4:46 PM
> To: crispin at newdawn.sz; Discussion of biomass cooking stoves; Crispin
> Pemberton-Pigott
> Cc: 'Discussion of biomass cooking stoves'; Harry Stokes - alcohol -
> Pennsylvania
> Subject: Re: [Stoves] Heat Content of Ethanol Gel
>
> Quoting Crispin Pemberton-Pigott <crispinpigott at gmail.com>:  (snipped)
>
>>
>> I have been working on a formula to calculate the heat content (LHV) of
>> ethanol gel.
>
>> There are large differences in the claimed heat content of ethanol.
>
>> PO = (Mi-Mf)*16/18,000 = Kw       [what has been used]
>>
>> PO = (Mi-Mf)*16/1,157 to get the correct answer for 5% water,   [What
>> Crispin has calculated ]
>
>> It is out by a factor of more than 15
>
> Wow!!!!!!!!
>
> Sorry I cannot assist with the numbers.  And I am not even sure where
> the 18,000
> came from or the 1,157.
>
> Can you tell us how long this massive discrepency has been around, and what
> impact it has had on prior evaluations of ethanol gel projects and their
> funding?
>
> Do you know if this type of error has been around in relation to the LIQUID
> ethanol calculations?
>
> And thanks to Tom M. for putting this to the Internet at
> See http://www.bioenergylists.org/en/crispingelfuel
>
> I hope some of the ethanol enthusiasts can shed more light on this.
>
> Paul
>
>



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