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'[EE]:: [TECHO] The Air Car - zero pollution and ve'
2007\03\20@083803 by

Matthew McMahon says -

Subject: The Air Car - zero pollution and very low running costs -
gizmag Article

> http://gizmag.com/go/7000/

300 km range claimed.
Approx 10% of petrol running costs claimed.
E1.5 per 300 km fill.
68 mph toppppp speed.
Lessee.
E1.5 ~~= \$US2? ~= \$NZ3.
Approx 2 litres petrol at NZ prices.
So 150 km/litre or about 375 mpg-US or 425 mpg imperial.

No mention of pressure used.
90 m^3 of gas said to be stored.
You'd be (very) lucky to get 1 m^3 of storage in a small car so that's
90+ atmosphere =~~ 1500 psi or 9 MPa.
Probably double that.
Would need a very many stage expansion motor to handle that
efficiently.

Very very (very ...) roughly using expanded energy equivalent, 90 m^3
at 1 atmosphere = 90 m^3 x 100 kPa  = 9 MPa energy.
9 E6  /1000 kW/W  /3600 hr/sec = 2.5 kWH = about 10% of what I
calculate the cost would buy in energy equivalent electricity. And 2.5
kWh is utterly insufficient for the task as 20 kWH (see below) is
rather skimpy. Possibly a missed decimal somewhere in my figures but
... .

>From an electricity point of view. \$NZ3 buys about 20 kWH of
electricity or the same energy content as 2 litre of petrol.
150 km on a litre of petrol given equivalent energy content is "rather
good".

I very strongly suspect that their energy costing claims are
fallacious.
I'd be happy to be proven wrong.

E&OE as always

Russell

>-----Original Message-----
>From: piclist-bouncesmit.edu [piclist-bouncesmit.edu]
>On Behalf Of Russell McMahon
>Sent: 20 March 2007 12:38
>To: PIC List
>Subject: [EE]:: [TECHO] The Air Car - zero pollution and very
>low running costs- gizmag Article
>
>Very very (very ...) roughly using expanded energy equivalent, 90 m^3
>at 1 atmosphere = 90 m^3 x 100 kPa  = 9 MPa energy.
>9 E6  /1000 kW/W  /3600 hr/sec = 2.5 kWH = about 10% of what I
>calculate the cost would buy in energy equivalent electricity. And 2.5
>kWh is utterly insufficient for the task as 20 kWH (see below) is
>rather skimpy. Possibly a missed decimal somewhere in my figures but
>... .

http://www.theaircar.com/faq.html#p7 suggests a pressure of 300bar in the tanks.  Then they emphasise safety by saying it's the same type of tank used for LPG storage in busses.  Hmm, IIRC LPG vapour pressure is about 12bar at nominal 25C temperature...

Some interesting stuff on the engine on that website however, especialy the atriculated con rod linkage.  It's only a two stage engine though.

Regards

Mike

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In the '70s, '80s maybe lots of airplane modellers used compressed CO2
engines. The biggest problem was that the pipes had frozen up very often. I
suppose when the weather is nice and warm it is not a problem, but what car
would they use in Iceland? :-)

In the other hand I can use the air compressor at the petrol station free of
charge, so it's not so bad idea to use them until they found out what's
going on :-)

Tamas

On 3/20/07, Russell McMahon <apptechparadise.net.nz> wrote:
{Quote hidden}

> -
> http://www.theaircar.com/faq.html#p7 suggests a pressure of
>300bar in the tanks.  Then they emphasise safety by saying it's
>the same type of tank used for LPG storage in busses.  Hmm,
>IIRC LPG vapour pressure is about 12bar at nominal 25C temperature...

300 bar is probably similar to that run in compressed air locos used in
hazardous environments around factories and in mines. Don't know if they are
still used now diesel and battery locos are available, but they were
certainly a viable alternative to steam locos.

See http://www.internationalsteam.co.uk/trains/fireless01.htm for examples -
essentially a steam loco with compressed air tank instead of boiler.

On 3/20/07, Alan B. Pearce <A.B.Pearcerl.ac.uk> wrote:

> > http://www.theaircar.com/faq.html#p7 suggests a pressure of
> >300bar in the tanks.  Then they emphasise safety by saying it's
> >the same type of tank used for LPG storage in busses.  Hmm,
> >IIRC LPG vapour pressure is about 12bar at nominal 25C temperature...
>
> 300 bar is probably similar to that run in compressed air locos used in
> hazardous environments around factories and in mines. Don't know if they are
> still used now diesel and battery locos are available, but they were
> certainly a viable alternative to steam locos.
>
> See http://www.internationalsteam.co.uk/trains/fireless01.htm for examples -
> essentially a steam loco with compressed air tank instead of boiler.

300 bar is about 4,350 PSI (pounds per square inch).  Scuba divers routinely
use 3,000 PSI (roughly 200 bar).

Bill

--
Psst...  Hey, you... Buddy...  Want a kitten?  straycatblues.petfinder.org

>-----Original Message-----
>From: piclist-bouncesmit.edu [piclist-bouncesmit.edu]
>On Behalf Of William Couture
>Sent: 20 March 2007 13:58
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE]:: [TECHO] The Air Car - zero pollution and
>very lowrunningcosts- gizmag Article
>
>300 bar is about 4,350 PSI (pounds per square inch).  Scuba
>divers routinely use 3,000 PSI (roughly 200 bar).
>

How often do scuba divers have trucks crash into them though :D

Regards

Mike

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> http://www.theaircar.com/faq.html#p7 suggests a pressure of 300bar
> in the tanks.  Then they emphasise safety by saying it's the same
> type of tank used for LPG storage in busses.  Hmm, IIRC LPG vapour
> pressure is about 12bar at nominal 25C temperature...
>
> Some interesting stuff on the engine on that website however,
> especialy the atriculated con rod linkage.  It's only a two stage
> engine though.

300 bar ~~= 4500 psi / 30 MPa - that's VERY high by almost any
standards. And it would take rather specialist compression equipment
I'd imagine. Plus, only two stage expansion seems rather too little
for such extremes of pressure. That's about 17:1 per stage at full
pressure, declining markedly as pressure drops. The large change in
pressure ratio is also liable to provide interesting challenges.

Overall, a good trick if they can really accomplish it.

Russell.

2001. War was beginning ...

Note that the site was last updated in December 2005 :-(.
Most website references are to 2002 or 2001 with the odd one to 2003.
A 2002 page referes to a rollout in the next few months.
It would seem that they haven't achieved their goals.

September 2003 Press release re a London demo

http://www.motordeaire.com/ing/UKPressrelease.html#Eng

Investors meeting, Nice, April 2005.
Video clips provided of power module and "the prototypes" in
operation.
"The prototypes" in 2005 sounds ominous.

http://www.theaircar.com/niza05uk.html

Hopefully they are still progressing.

Maybe CATS didn't win after all and all their base actually belong to
somebody else?

Russell

Tamas Rudnai <tamas.rudnai <at> gmail.com> writes:

> In the '70s, '80s maybe lots of airplane modellers used compressed CO2
> engines. The biggest problem was that the pipes had frozen up very often. I
> suppose when the weather is nice and warm it is not a problem, but what car
> would they use in Iceland?
>
> In the other hand I can use the air compressor at the petrol station free of
> charge, so it's not so bad idea to use them until they found out what's
> going on

The air compressor at the gas station gives at most 12bar. You want 300. A scuba
cylinder filling compressor will do the job but it will have to run for the
whole night to fill a car's tanks.

Peter

Once upon a time torpedos were powered exactly like that afaik. The first lesson
after that was to add alcohool or kerosene and water and to burn it so the heat
of expansion was supplied. And not at 300bars. Afaik to avoid losses one expands
the gas through a machine, not through a simple nozzle, and uses reheating (from
ambient air at least, but better with fuel). I don't know how they calculated
the efficiency on that thing because storing compressed air is quite wasteful
(by losing the heat of compression among other things). However I think that
driving a car that uses torpedo propulsion principles is cool (probably in the
same class as turbine karts - and it could race them too).

Peter P.

>
>  Afaik to avoid losses one expands
> the gas through a machine, not through a simple nozzle, and uses reheating
> (from
> ambient air at least, but better with fuel). I don't know how they
> calculated
> the efficiency on that thing because storing compressed air is quite
> wasteful
> (by losing the heat of compression among other things).

Subs usually have a fair amount of compressed air handy, if they want to
come back up :)
David VanHorn <dvanhorn <at> microbrix.com> writes:

> >  Afaik to avoid losses one expands
> > the gas through a machine, not through a simple nozzle, and uses reheating
> > (from
> > ambient air at least, but better with fuel). I don't know how they
> > calculated
> > the efficiency on that thing because storing compressed air is quite
> > wasteful
> > (by losing the heat of compression among other things).
>
> Subs usually have a fair amount of compressed air handy, if they want to
> come back up :)

Yes but torpedoes have more burning constraints. Also compressed air plants
waste a lot of heat, unless it is used to heat water or buildings or such. The
higher the pressure the more heat is lost. When the air is expanded then the
heat must be put back in or else everything will freeze solid and efficiency
will be very poor (cold expanded air has significantly lower volume than the
same heated - two to five times less). Worse, the efficiency of making
compressed air is only 12.5%. See here:

http://www.mntap.umn.edu/energy/82-CompAir.htm

I'm not saying that that car can't do what it says it can do, but if it does
what it says then there is likely a little more to it than 'just' compressed air.

Peter P.

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