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Author Topic: Air car revisited  (Read 3569 times)
Woodenstop
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« on: February 13, 2008, 08:31:14 PM »

For those interested in the air car project here is the "fan page" of MDI who are making the Air car.

http://www.cyber-media.com/aircar/

Andy
« Last Edit: February 14, 2008, 09:31:16 PM by Woodenstop » Logged
energybob
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« Reply #1 on: June 08, 2008, 11:59:04 PM »

Fantastic idea! I'd have one and the more the merrier  bike  bike  bike  bike  bike
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martin
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« Reply #2 on: June 09, 2008, 12:25:42 AM »

sorry, acute dose of the Meldrews on air cars "I just don't believe it" - there is more than one lot trying to market this idea - lots of unsubstantiated claims, and offering "investment opportunities" - I strongly suspect they would require a similar rewriting of the laws of physics as roof-mounted chocolate teapots! chocolateteapot
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Unpaid volunteer administrator and moderator (not employed by Navitron) - Views expressed are my own - curmudgeonly babyboomer! - http://www.farmco.co.uk
Ivan
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« Reply #3 on: June 09, 2008, 01:03:15 AM »

In the spec it suggests you can recharge it at home in 4hours. However, it has 300litres of storage tank at 300bar.

A few years ago, we looked at the feasibility of converting Cardiff's bus fleet to run on CNG. This requires compression to 200bar. I spent a considerable time looking at CNG compressors, including small-scale home compressors. We found that the restriction of single phase ring mains, the fastest you could refuel say 60litres of CNG tank at 200bar, was overnight. If you put a dedicated 32A ring main in, you could do this in around 5hours.

The air car has 5x more 'fuel' tank, and is pressurised to 50% higher pressure... So I can't see how it is possible to recharge at home in 4 hours (other than by having pre-charged air storage tanks at home). Incidentally, if you do manage to compress 90m3 of air to 300bar in 4hours, it will generate a lot of heat, and presumably be less efficient unless good quality charge-coolers are used.
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Alan
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« Reply #4 on: June 09, 2008, 08:12:27 AM »

From Ivans Data

32 Amp ring main over night ( assume 10 hours ) = 80 K.W. of leccey.

Times five ( 400 K.W.H. ) for the increase in capacity of the air cylinder on this one.

For a car that runs 125 miles on a flat surface on one charge.

How green is it if you donít own a wind farm.

If I had a wind farm Hydrogen cars would be the way to go.

Regards

Alan
« Last Edit: June 09, 2008, 08:16:22 AM by Alan » Logged
Woodenstop
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« Reply #5 on: June 19, 2008, 11:05:46 PM »

It probably is a  chocolateteapot but compressors for dive cylinders are readily available up to 300 bar operating on 230v witha 2.2 kw motor and it seems the charge time is feasable, plus if you took off the filters (output side) it might be quicker.
http://www.sailgb.com/p/diving_compressor_mch6_em__powder_coated_steel/ I can't imagine they would be designing a new compressor from scratch when these are close to the spec required.
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Ivan
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« Reply #6 on: June 20, 2008, 02:01:06 AM »

Useful to have some figures:

They quote :Filling time cylinder 10L 0/200 Bar: 25 min (for a 2.2kW compressor)

So for the aircar (300litres), you'd need 300/10 x 25minutes = 12.5hours....and that's only to 200bar. If you want to go to 300bar, then you're doing 50% more work, so assuming no loss of efficiency (which you will definitely get, by going to 300bar), you'll need 18.75hours for a full charge.

Assuming the air car's claim of a 4hour recharge is true, you'll need to have 18.75/4 x as much power as the diving compressor - ie 10kW (or 43Amps at mains voltage!), however, you'll get significant heating, which will reduce the efficiency of the compressor considerably.
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KenB
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« Reply #7 on: June 20, 2008, 10:07:01 AM »

List,

The range that the Aircar achieves purely on compressed air is miserably low - but has been over-hyped and glossed over by the hybrid mode, where the energy in the compressed air is increased by heating it using fossil fuels.

Until AirCar/Tata  come clean about the true range of this vehicle in its different modes of running, it will be impossible to make real world calculations on the true range.

IMHO, we do not have sufficient excess electricity available to "waste" it is an inefficient air compression/expansion scheme - when even humble lead acid batteries have a much better turn around efficiency.

In August 1995, a friend an I drove from Hyde Park to Milton Keynes (62 miles) on a single charge in a self built electric car powered by lead acid batteries.   If this could be done 13 years ago using off the shelf parts, then surely newer battery chemistry would allow greater an improved  range/performance envelope.

I am very sceptical about the overall efficiency of the aircar.

Given a tonne of Chinese coal (or Australian coal), which yield approximately 2500kWh of electricity, there must be more energy efficient ways of providing transport for the masses.


Ken





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