D
daestrom
Guest
"Jed Checketts" <jedcheck@yahoo.com> wrote in message
news:e98177f2.0407212044.35090f5d@posting.google.com...
For 90 kg of reactants (54kg of NaAlH4 and 36kg of H2O), you get 8kg of H2.
For each 1kg of H2 you can expect about 141.9 MJ of energy. That works out
to about 12.6 MJ per kg of reactants. If you don't carry the 2H2O, then it
would be 21 MJ per kg of NaAlH4.
And gasoline carries about 43.8 MJ/kg when reacted with air.
So, explain again how 12.6 MJ per kg is so competitive with 43.8 MJ/kg????
(7+27+4*1). But add on the 36kg of water and we have 74kg of reactants for
8kg of H. That works out to about 15.3 MJ per kg of reactants. Excluding
the water, we get about 29.87 MJ per kg of LiAlH4. Better, but not
tremendously so.
And you seem to be forgetting about carrying the water needed. Gasoline at
least has the advantage that the other reactant can be taken directly from
the atmosphere. Getting these amounts of H2O directly from the atmosphere
is *not* as simple.
that hydrides still carry less energy per kg than gasoline.
liberates 8kg of H for an energy of 8*141.9 = 1135.2 MJ from 38kg of 'fuel'.
And that is 1135.2/38 = 29.87MJ/kg. While gasoline contains ~43.8MJ/kg.
And that is *assuming* the water reactant doesn't have to be carried.
daestrom
P.S. Energy values for hydrogen and gasoline taken from...
http://www.uvi.edu/Physics/SCI3xxWeb/Energy/GasolineFAQ.html
news:e98177f2.0407212044.35090f5d@posting.google.com...
Okay, so check my math here....Don Lancaster <don@tinaja.com> wrote in message
news:<40FE87F6.549B6C6@tinaja.com>...
"Fred B. McGalliard" wrote:
"Don Lancaster" <don@tinaja.com> wrote in message
news:40FDC08C.CDEE8A96@tinaja.com...
Jed Checketts wrote:
...
HYDROGEN WILL ALWAYS CONTAIN MORE ENERGY BY MASS THAN GASOLINE.
PERIOD. THIS IS SIMPLE SCIENTIFIC FACT.
...
CONTAINED TERESTRIAL HYDROGEN HAS MUCH --->LESS<--- ENERGY BY MASS
THAN
CONTAINED GASOLINE!
This is simple engineering fact.
Pay attention Don. He proposed storing the hydrogen in Sodium Aluminum
Hydride. The design of such a system may need work, but it is not the
same
as storing the gas. In principle, I expect it is possible to argue
that
NaAlH (and water) could be stored in thin walled tanks, and that the
converter and NaALOHx storage would not require that much additional
weight.
Not sure I believe that but it should be discussed and you didn't do
that.
It gets much worse when you throw heavy sodium and heavy aluminum into
the tank, of course.
Much worse than what?
Sodium aluminum hydride:
NaAlH4 + 2 H2O --> NaAlO2 + 4 H2
Note that you produce 8 Kg of hydrogen for each 54 Kg of Alanate.
For 90 kg of reactants (54kg of NaAlH4 and 36kg of H2O), you get 8kg of H2.
For each 1kg of H2 you can expect about 141.9 MJ of energy. That works out
to about 12.6 MJ per kg of reactants. If you don't carry the 2H2O, then it
would be 21 MJ per kg of NaAlH4.
And gasoline carries about 43.8 MJ/kg when reacted with air.
So, explain again how 12.6 MJ per kg is so competitive with 43.8 MJ/kg????
Re-working for LiAlH4, I get 38kg for every 8kg of H produced, not 23kgFor the above example, 8 Kg of hydrogen are produced from each 23 Kg
of Lithium Borohydride.
(7+27+4*1). But add on the 36kg of water and we have 74kg of reactants for
8kg of H. That works out to about 15.3 MJ per kg of reactants. Excluding
the water, we get about 29.87 MJ per kg of LiAlH4. Better, but not
tremendously so.
Hmm, the above shows that LiAlH4 carries *less* energy per kg than gasoline.Don often points out how how energy dense gasoline is as if it is the
ultimate energy storage medium. It isn't. He may be a proponent of
gasoline but the SCIENCE is straightforward. Lithium Borohydride and
other hydrides contain more energy by mass AND VOLUME than gasoline.
And you seem to be forgetting about carrying the water needed. Gasoline at
least has the advantage that the other reactant can be taken directly from
the atmosphere. Getting these amounts of H2O directly from the atmosphere
is *not* as simple.
Unless I made an error in my calculations, the 'scientific fact' would beThis is verifiable scientific fact.
that hydrides still carry less energy per kg than gasoline.
Oh? Please show me the error in my calculations that shows 38kg LiAlH4Claiming that gasoline contains more energy than hydrides like lithium
aluminum hydride are contradictory to scientific fact.
liberates 8kg of H for an energy of 8*141.9 = 1135.2 MJ from 38kg of 'fuel'.
And that is 1135.2/38 = 29.87MJ/kg. While gasoline contains ~43.8MJ/kg.
And that is *assuming* the water reactant doesn't have to be carried.
daestrom
P.S. Energy values for hydrogen and gasoline taken from...
http://www.uvi.edu/Physics/SCI3xxWeb/Energy/GasolineFAQ.html