Re: Why Willie's ideas for hydrogen fuelled aircraft are BONKERs !
- From: Monkey Clumps <spacebrain71@xxxxxxxxx>
- Date: Sun, 30 Dec 2007 07:59:54 -0800 (PST)
On Dec 30, 3:52 am, Eeyore <rabbitsfriendsandrelati...@xxxxxxxxxxx>
wrote:
Aside from the very considerable extra space required for H2 fuel which
makes any hydrogen fuelling of an existing aircraft design utterly
impractical without extensive rebuilding/conversion and 'megastretching'
with attendant weight increases that lose the very benefit of hydrogen's
lower weight in the first place, we did not pursue the added weight of
the hydrogen tank.
Willie has asserted that the tank will weight a fraction of the weight
of the hydrogen contained.
THIS IS PURE NONSENSE like most of his ramblings.
I looked for sources of info about H2 tanks and it's apparent that the
tank weights VASTLY more than the H2 fuel ! Current benchmarks figures
seem to hover around 4.5 - 6.5% for the weight of the contained hydrogen
!
This was the very best advance I could find ....
"QUANTUM Fuel Systems Technologies.......... announced today that it
demonstrated a hydrogen storage tank with a world record 13% hydrogen
weight efficiency. This breakthrough
offers a dramatic weight reduction in hydrogen storage technology and
will
significantly improve on-board energy storage in aircraft and spacecraft
applications where weight is critical."http://www.prnewswire.com/cgi-bin/stories.pl?ACCT=104&STORY=/www/stor...
So the hydrogen is 13% of the weight and the tank is the other 87%.
That's a ratio of 1:6.7
And this is supposed to be a BREAKTHROUGH !
Instantly all Willie's plans for H2 aircarft can be dismissed as pure
pipe dreams. The weight of their fuel tanks would mean they'd never get
off the ground.
Even if that great breakthrough could be 'doubled' in hydrogen storage
efficiency, there would still be no net weight advantage and of course
the space required and attendant extra fuselage will increase weight to
the point where it's STILL a dead loss.
Maybe if H2 tanks could be made no heavier than the fuel inside there
might be a long odds chance of viability. I don't see how that could
ever be acheived if the best materials we have today are seven times off
that target.
Graham
The ratio of structural weight to hydrogen weight is going to be very
dependent on size and shape. Obviously the larger the tank the better
your ratio since the structure weight should increase with the surface
area (square function) while the fuel weight will increase in
proportion to the volume (cubic function). The 13% figure in the
article would improve dramatically if they just scaled the tank up in
size. Of course they did not mention the size of the tank but given
that it was intended for spacecraft it is probably pretty tiny. Also
a shape that maximizes volume and minimizes surface area will be
best. A sphere is the most efficient shape, but not very good for
storage in an airplane fuselage or wing. Narrow wing tanks would have
a particularly poor ratio of structure to fuel. A streamlined nacelle
shape might have a decent ratio, although it is hard to imagine a
modern airliner design having external fuel nacelles given the
significant drag penalty they would impose.
.
- References:
- Prev by Date: Re: Storing H2 at high pressure or cryogenically.
- Next by Date: Re: Why Willie's ideas for hydrogen fuelled aircraft are BONKERs !
- Previous by thread: Why Willie's ideas for hydrogen fuelled aircraft are BONKERs !
- Next by thread: Re: Why Willie's ideas for hydrogen fuelled aircraft are BONKERs !
- Index(es):
Relevant Pages
|
