a car powered by compressed air:
news.bbc.co.uk/2/hi/science/nature/7241909.stm
Edited by Pugugly {P} on 13/02/2008 at 16:30
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"The biggest risk is to the ears."
risk to the ears...........
Considering the the compressed air tanks are in the chassis, its the body parts nearest to it that would concern me rather than the ears.
Of course, seemingly it could mean the ears could be deafened before being modified by the upwardly mobile posterior, or a central jet of compressed air could rise internally and exit via the ears.....
Perhaps safest to drive with the mouth open and wearing leather underpants
Regards
Edited by oilrag on 13/02/2008 at 14:56
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Perhaps safest to drive with the mouth open and wearing leather underpants
It must be well known too, since so many are already doing it.
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Before discussing this, it is probably worth reading
en.wikipedia.org/wiki/Compressed_air_vehicle
Many of the so called authorative sites are those seeking investment, so maybe the Wiki may (or maynot) be regarded as accurate. The most telling single 'fact' is
300l air at 300 MPa only amounts to about 12kWh (the equivalent of 1.4 liter (0.37 gallons) of gasoline) but then you see 30 MPa = (4500 psi or 300 bar).
Assuming electricity is used to to do the compressing, the efficiency of the compressed air storage/drive cannot be any better than than an electric car with storage batteries (heat loss energy inc friction must be significant worse in a mechanical process). Recharcharging the car in 3 mins as in the original article must have a rather large compressor! (or a very short/long? duty cycle).
NC any quantative comments on range and operating costs, - presumably slightly higher than electric storage?
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So which would you prefer, a piece of shrapnel in your backside or being burned to death by 50litres of petrol?
I don't think the compressed air is any more or less dangerous than any other method of storing energy. Even batteries can be danergous, just look at how the dell laptop batteries burst into flames.
As for recharging them the piece on the news last night showed it being filled from what looked like a row of scuba diving tanks, rather than plugging into a compressor.
I quite like the idea of it, anyone know what sort range they reckon it will get?
I also like the idea that you could run it for 'free' if you had solar panels or wind turbine to power the compressor.
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Surely this is just (another) way of moving the polution around.. and I'm not sure I like being involved in the learning curve of making these high pressure systems safe.
If you look back at some of the silly things we did because it was considered safe at the time, how do you think we'll look back on this?
The list is so long, I'm not really sure where to start...
How about encouraging civilians to watch nuclear explosions in Nevada - the "up and Atom city - Las Vegas"
tinyurl.com/3988gf
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An interesting concept, probably comparable to battery electric - presumably the air tanks are ligher than the equivalent batteries.
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That's how I read it; that this design requires less energy input to achieve the same performance as a battery car and that the energy consumption during manufacture (which is a huge proportion of a car's whole life energy footprint) is significantly less than a battery car and much much less than a trad car.
Ultimately we are not going to achieve a step change unless people stick their neck out and try something new so on the face of it, hats off to him and to TATA for funding it. If GM or Ford or Toyota etc see there is money to be made here, then the technology will leap ahead.
But don't hold your breath a report from Accenture of 500 major businesses suggests that private investment may be a long time coming:
The survey, carried out by the consulting firm Accenture, found that only 5 per cent of the companies questioned ? and not one in China ? regarded global warming as their top priority. And only 11 per cent put it in second or third place.
Overall it ranked eighth in business leaders' concerns, below increasing sales, reducing costs, developing new products and services, competing for talented staff, securing growth in emerging markets, innovation and technology. Although most are taking limited action to reduce their own emissions, almost one in five had done nothing.
From the Indy this week
Edited by Nsar on 13/02/2008 at 21:35
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There's an unsurprising wooliness of detail surrounding this concept.
If the air is supposed to be stored in receivers that form the stressed chassis rails; then that must limit it to around 100 litres and for that quantity to have a range measured in more than yards, they must be charged to around 4000lbf/sq/ft.
That quantity/pressure would give it a lethal blast radius of around 50 yards - enough to take out an entire street - and for such a flimsy vehicle, the high probability of receiver rupture in almost any serious accident. I can't see such a mobile bomb being welcomed in many towns.
Nice in theory - shame about the practicalities...
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Correct about the air pressure being around 4000psi.
Wrong about it being able to destroy a whole street...
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Sorry; not precise enough.... "to take out an entire street - of people."
I've seen the photos of a big machine-shop when a similar receiver went bang - nothing left of the building at all - just rows of big lathes.
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When hydrogen peroxide is passed over brass it produces steam at a very high pressure, some submarine engines used this principle before the advent of nuclear power.
Compressed gas car engines could use a similar fuel source - the only thing coming out of the back would be steam.
It would be a lot safer and more compact to carry hydrogen peroxide liquid around than compressed air. I'm surprised somebody hasn't built a motor vehicle like this already.
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I think you might be comparing apples to oranges.
I would of thought that the tank in the machine shop was made of steel. The tanks on the air car are carbon fibre, they would both go bang, but in very different ways. Steel tank would make a load noise and send pieces of steel flying around. Carbon fibre would just make a loud noise.
Found from a google search:
One of the most frequently asked questions is about the safety of the compressed air storage tanks. These tanks hold 90 cubic metres of air compressed to 300 bars. Many people ask whether this system is dangerous in case of an accident and if there is a risk of explosion. The answer is NO. Why? Because these are the same tanks used to carry the liquid gas used by buses for public transport. The tanks enjoy the same technology developed to contain natural gas. They are designed and officially approved to carry an explosive product: methane gas.
In the case of a major accident, where the tanks are ruptured, they would not explode since they are not metal. Instead they would crack, as they are made of carbon fibre. An elongated crack would appear in the tank, without exploding, and the air would simply escape, producing a loud but harmless noise. Of course, since this technology is licenced to transport an inflammable and explosive gas (Natural gas), it is perfectly capable inoffensive and non-flammable air.
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Wouldnt it be a load of "cold" air according to boyles law?
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Regardless of the nature of failure; I still can't see how highly-stressed receivers/chassis rails can be engineered to a safe level when the whole car only weighs 350kg. The risk of catastrophic failure in an impact must be unacceptable.
Tanks on buses are far less weight-critical and can be carefully located to be at less risk of impact.
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I think pmh raises the fundamental objections very well - the energy density just isn't appropriate for use in a car.
Where compressed air can be useful as an energy storage method is where you have a huge volume available - like the people in the US, using a dis-used mine to store lots of air at relatively low pressure to then convert back into electricity when there are peaks in demand.
The issue of tank explosions is effectively a distraction, which could be overcome with some good design - appropriate containment, allowing a gradual release - but, the fundamental physics isn't avoidable by good design. I hope none of you have money invested in the scheme!
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Some interested reading..
Link not made clickable due to site policy on rival publications (I think?).
news.bbc.co.uk/1/hi/sci/tech/7243247.stm
{Alternate link found. All links to that particular publication you posted (and it's sister publications) aren't allowed here, whether clickable or otherwise}
{Also moved to a previous discussion on the subject}
Edited by Dynamic Dave on 21/02/2008 at 12:33
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We had this thread las week - perhaps HJ could merge the threads?
{Too late, I've already done it}
Edited by Dynamic Dave on 21/02/2008 at 12:34
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Damn, didn't see that.
Last week!
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what are they powering the compressor with? a petrol or deisel engine or an even bigger compressor?
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According to an unmentionable source, the air tanks are filled by plugging an onboard compressor into the mains.
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