Matthew Miller wrote:
>>>> Hydrogen looks even worse when you factor in the
>>>> efficiency of the internal
>>>> combustion engine that moves the vehicle.

Russell replied:
>>> Stirling engine?
>>> Fuel cell?

& Matthew
>> Russell, I'm going to bed and will respond more fully 
>> tomorrow, but
>> with
>> these two options, your fooling, right?

& CC
> Russell is not fooling around.  He always makes an effort 
> to be
> informative.  Thus it is tiring to see someone say "you 
> are
> fooling".

'Tis fine. I take that as rhetorical, or close enough to it. 
All such questions are grist to the mill. Some grist is 
tastier than other ... ;-).
_________

The two 'options' are somewhat independent. Not necessarily 
totally so.


Note that anyone who critiques Hydrogen for automotive use 
and assumes an electric motor at the end of the chain is 
tacitly assuming a Hydrogen to electrical convertor. If this 
is an electrochemical device - ie Hydrogen in, electricity 
out, no moving parts in the converter proper, then this will 
'probably' be a fuel cell or something functionally 
equivalent. While conversion efficincy is 'not as good as 
we'd like' [tm] the electric motor that follows it ias a far 
better proposition than an internal combustion engine. 
Further, the characteristics of electric motors make them 
suited in some vehicular applications to the use of in hub 
or near hub motors with high to very high mechanical 
conversion efficincies. Note that the (pipe-)dream Lotus 
electric car mentioned the other day used a gerabox and/ was 
being plagued with early gearbox failures due to the 
massivetorques involved. Providing a 0-60 mph performance of 
under 4 seconds encourages such problems. I should be so 
lucky :-).

Re Stirling engines. Their day is not yet. Their day will 
come. At present they have poor mass power density and 
poorer volumetric power density OR very high internal 
pressures and/or temperatures. They work best when filled 
with very hot very high pressure Hydrogen !!! :-) !!!. . 
Reliability is in many cases ' not scintillating' [tm]. BUT 
the Stirling Cycle (aka Carnot cycle) which they are based 
on has much to commend it (for starters it's the most 
efficienct thermodynamic cycle possible). But, probably best 
of all, they are EXTERNAL combustion engines and combustion 
can not only use a very wide range of fuels (suject to 
suitable burner designs) but also are inherently exempt from 
some of the evils of burning hydrocarbons in nitrogen rich 
air at high temperature and pressure in conditions as close 
to this side of detonation as can be managed. Various 
nitrous oxides are a direct consequence of such an approach. 
A Stirling engine can burn eg Hydrogen and air with minimal 
nitrous oxides produced. Needless to say, a Hydrogen powered 
Stirling engine also produces no "greenhouse gases" either - 
except the overwhelmingly most predominant greenhouse gas of 
all. But, as most people don't seem to mind water vapo(u)r, 
that doesn't seem to be a problem. Note that the "waste 
heat" is of potentially of use in some applications, 
although not overly so in most vehicular ones. The most 
successful firm of all time by volume sold or contracted to 
sell, NZ based Whispertech, has a deal (still?)(these things 
change) to sell $300M of Stirling cogeneration units for use 
in UK homes. Needless to say, they don't use super hot super 
high pressure Hydrogen inside. FWIW here's a performance 
analysis when used asa micro-CHP system. Natural gas firing.

    Performance of Whispergen micro CHP in UK homes - 
eonfieldtrial260606[1].pdf

        http://www.micropower.co.uk/publications/eonfieldtrial260606.pdf

The reason that THIS Stirling implementation is succeeding 
as perhaps the first true mass market application is related 
to the energy disparity between the consumer energy cost of 
UK 'North Sea gas' and UK electricity. That notwithstanding, 
it shows that the stirling engine is standing 'just outside 
the door' in more evenly assessed situations and that as 
practice is gained, SE prices drop and energy prices rise, 
the SE will strat to appear in real worls applications. 
[[Note that when run in reverse as a cooler the Stirling 
cooler is the device of choise in much of the ondustry 
including in NASA's deeps pace ultra long life 
applications.]]

Long ago the great and gian Philips Corporation bailed out 
of Stirling Engine development during a period of product 
rationalisation. Up until then they had spent at least 10's 
of millions thereon. Somewhere about then a spokesman stated 
that to be successful in the IC engine replacement market 
then the SE would probably need $X spent on it. AFAIR $X was 
in the low 10's of billions of dollars !!! ($40B? Maybe 
$4B)). The spokesman also noted that once success had been 
achieved the payback period would be about 4 months :-).




        Russell







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