[Digestion] Biogas conversation rates
David Fulford
davidf at kingdombio.com
Mon Jan 17 05:43:47 CST 2011
Loe, Hello,
The key to the problem is efficiencies (or more to the point:
inefficiencies). Getting light from burning kerosene or biogas is very
inefficient, as most of the energy is turned into heat. The temperature
of a wick lamp burning kerosene is about 290 deg.C = 563 K. The energy
at different frequencies is defined by Planck's law, which is can be
simplified using Wein's displacement law (see Wikipedia pages
<http://en.wikipedia.org/wiki/Planck%27s_law>). This suggests that less
than 0.01% of the total radiation from a flame at this temperature is in
the visible spectrum.
A gas lamp burns at a higher temperature (at least 1200 K). The heat is
used with a mantle that uses a rare earth that generates light when
heated. The overall efficiency is still fairly low (perhaps 1 to 3%),
but it is much higher (100 times) than for a kerosene wick lamp.
If you comparing like with like, it would be better to compare a
kerosene pressure lamp with a biogas lamp, as pressure lamps also use
mantles. I do not know how much kerosene a kerosene pressure lamp uses,
but it provides a much better light than a wick lamp.
So your figures are not at all surprising; you need to include overall
efficiency figures when comparing the light from fuels using calorific
values.
Regards,
David
On 16/01/2011 12:34, Franssen, Loe (Alumni) wrote:
> Hey Duncan (and the others),
> thanks for your elaborate answer ! I'm sorry for being unspecific. Let
> me be a bit more specific and take the kerosene conversion rate
> because the information on this one is the most inconsistent.
> Assumptions
> Consumption rate simple wick kerosene lamp; 0,01 liter kerosene per hour
> Biogas lamp; 70 liters of gas per hour
> (specifications of the lamp that will be supplied:
> http://kingoni.en.ec21.com/Biogas_Lamp--3003470_3352352.html)
> Lumen output of a simple wick kerosene lamp 7,8 lumen
> biogas lamp; 50 lumen (not sure on this
> number as there is a large range for it right?!)
> Calculation
> so 1 liter of kerosene is equivalent to 7000 liter gas. After
> correcting for lumen output, 1 liter of kerosene is equal to *1,077*
> liter of gas
> If i use calorific values i get the following result
>
> 1kilo kerosene = 46 mj/kg with a density of 0,95 kg/l so
>
> 1 liter kerosene = 43,7 mj/l
>
> 1m3 biogas is 22.5mJ
>
> 1 liter biogas = 0,0225 mJ
>
> 1L kerosene = (43.7/0.0225) = *1942,22L* biogas
>
> Quite a difference hm probably because of the lumen i took for the
> biogas lamp and the consumption rates?! do you have recommendations on
> these numbers?
> Then another small question.. for anthracite charcoal i found a
> calorific value of 27mJ/kg, for lignite charcoal 15 mj/kg. I'm talking
> about charcoal that these rural african farmers simply make in their
> backyard. i assume i should take 15 mj/kg then right?! or even less?
> Thanks again!
> ------------------------------------------------------------------------
> *Van:* digestion-bounces at lists.bioenergylists.org
> [digestion-bounces at lists.bioenergylists.org] namens Duncan Martin
> [duncanjmartin at gmail.com]
> *Verzonden:* zaterdag 15 januari 2011 10:51
> *Aan:* For Discussion of Anaerobic Digestion
> *Onderwerp:* Re: [Digestion] Biogas conversation rates
>
> Hi Loe
>
> A few quick comments:
>
> 1. You can check equivalences yourself by looking up the calorific
> values (heating values) of the three reference fuels. Go back to the
> raw data, rather than relying on the interpretations of others - who
> may well be biased. The data is readily available and it needs no more
> specialized knowledge to calculate equivalences than it does to
> calculate a currency conversion - which I am sure you could do in your
> sleep! *
>
> 2. Some of these fuels (eg biogas, firewood) are q variable so all
> equivalences would be best expressed as ranges. That might be one
> reason for the inconsistencies you mention. Make sure your source
> isn't based on biomethane - ie purified biogas.
>
> 3. Rating biogas per so many hours of cooking is meaningless unless
> better defined - are you assuming an open gas ring, an enclosed oven
> or what**? Just one burning at a time? What kind of food is being
> cooked - because some foods need long, slow cooking? (Maybe a better
> yardstick would be a typical daily household consumption.)
>
> 4. Rating biogas per so many hours of lighting is equally meaningless.
> How many lights? What output? A reasonable assumption for this
> application might be a single ~40W-equivalent to light a single room
> - but state it.
>
> * If that sounds unhelpful, it comes from long experience of
> university teaching - and exposure to a lot of "/I am a student and I
> need someone to do my assignment for me/" requests! You'll learn more
> if you learn how to work it out for yourself.
>
> ** A well known problem here is that the poorest people often (though
> not always) use the least efficient cooking methods - eg an open fire.
> A common site in urban Zimbabwe a few years ago was a pot suspended
> above an electric fire laid on its back!!!
>
> Duncan Martin
> Cloughjordan Ecovillage
> Ireland
>
> On 12 January 2011 13:52, Franssen, Loe (Alumni)
> <LLC.Franssen at alumni.maastrichtuniversity.nl
> <mailto:LLC.Franssen at alumni.maastrichtuniversity.nl>> wrote:
>
> Dear biogas experts,
>
> I am a 22 year old student from the Maastricht University where I
> am doing a bachelor in International Business. I am currently
> doing an internship for a Dutch biogas company that is planning to
> sell systems in East Africa. I am developing a huge mathematical
> model that calculates - among other things - how big (m³) a
> digester should be for those households. I want to determine this
> on the basis of the kilo’s of charcoal and firewood and liters of
> kerosene they already use and also on the basis of cooking time
> and lighting hours. After studying several articles from GTZ, SNV,
> and master or Phd. students’ reports I came to the following
> conversion rates and I was hoping you guys could give your opinion
> on it.
>
>
>
>
>
>
>
> Source
>
>
>
>
> Charcoal (kg) >> Gas (l)
>
>
>
> 500
>
>
>
> GTZ article Biogas digest volume 1
> <http://www.gtz.de/de/dokumente/en-biogas-volume1.pdf>
>
> GTZ article Biogas digest volume 1
>
> firewood (kg) >> Gas (l)
>
>
>
> 200
>
> Kerosene (l) >> Gas (l)
>
>
>
> 1600
>
>
>
> _link 1
> <http://www.shvoong.com/humanities/1957301-biogas-making-technique-simplified/>_
>
>
>
> _link 2
> <http://www.inseda.org/Presentation/Biogas-the%20future%20Sustainable%20Energy-Fr%20Mathew.pdf>_
>
>
>
> _link 3
> <http://www.eplantscience.com/index_files/biotechnology/Biotechnology%20and%20environment/Biomass%20Energy%20%28Bio-energy%29/biotech_bio-energy_gaseous_fuels.php>_
>
>
>
>
>
>
>
> Cooking (hrs) >> Gas (l)
>
>
>
> 300
>
>
>
>
>
> Lighting (hrs) >> Gas (l)
>
>
>
> 70
>
>
>
> SNVworld.org link4
> <http://www.snvworld.org/en/Documents/Biogas_stoves_and_lamps_test_report_2009.pdf>
>
>
>
>
>
> I am particularly concerned about the conversion rate from liters
> of kerosene to liters of biogas. The results I found online don’t
> seem to be very constant. I tried to do some calculations myself
> but I have no idea how to calculate this (my background is
> (micro-) finance) so I was hoping you could shed some lights on
> these numbers!!
>
> Kind regards,
>
> Loe Franssen Maastricht University student
>
>
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> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>
>
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> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
--
********************************************************************
Dr David Fulford CEnv MEI, 15, Brandon Ave, Woodley, Reading RG5 4PU
d.j.fulford at btinternet.com <mailto:d.j.fulford at btinternet.com>, Tel:
+44(0)118 326 9779 Mob: +44(0)7746 806401
Kingdom Bioenergy Ltd, www.kingdombio.com <http://www.kingdombio.com>,
davidf at kindombio.com <mailto:davidf at kindombio.com>
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