Compressed air engine

Hans_de_Vries

The design of a conventionally powered car precludes regenerative braking.
By braking regeneratively a substantial amount of kinetic energy may be recycled.

Hans_de_Vries

There may be other factors at work but I'm not qualified to express an opinion.

Hans_de_Vries

Test data and results of calculations are published on the English version of the website of the MDI company: https://www.theaircar.com

redux

According to a graph on the website, it has about a quarter of the power and torque of the engine in my car.

- which isn't actually bad, but won't power anything other than a small car nipping around town.

Is there any info on the volume of the compressed air tank, or how hot it gets while being filled? The thermodynamics and mileage page is not on the server at the moment

tomstickland

The website really needs some work on it. Spelling mistakes and rather random layout.
Why are there no efficiency estimates?

tomstickland

The website needs some basic information to be taken seriously.

I like the idea, but I need some basic information on the efficiency, because I suspect that it might not be very good.

What is the approximate efficiency of the engine?
ie: output power divided by input power in the air.
Output power being the produce of brake torque and shaft rpm, input power being the pressure multiplied by the air flow rate.
This should be presented as efficiency versus rpm, as for a conventional engine.

What is the approximate efficiency of the charging process?
ie: how much energy is stored in the tank divided by the amount of energy needed to charge it up.

300L tank with 300 bar.

I'm just looking at this compressor site: http://www.abac.co.uk/diving-compressors.htm#highlights
and a 300L tank would take 90 minutes running a 15KW motor. That's 81MW of energy, for a tank to then contain 46MJ (http://www.theaircar.com/ficha.html)
So we might be looking at around 50% charging efficiency.



http://auto.howstuffworks.com/air-car1.htm

French Revolution - Negre Air-Powered vehicles (120 miles per charge / 68.75mph*) are to go on sale around the world from the beginning of next year - 2002. After many contradictory and conflicting reports, Moteur Developpement International (email: cqfd.ad@mdi.lu ) have announced that Frenchman Guy Negre's compressed-air powered vehicles are at last to go into full-scale production at the start of 2002. The vehicles will appear in four different flavours - family car, van, small pick-up, and taxi and are to be manufactured and built in over 60 different countries worldwide (Think global, act local....).

These Zero Emission Vehicles can be 'recharged' in three and a half hours by means of the onboard plug-in compressor. However, the vehicles can also be recharged in just 3 minutes from an external 'industrial strength' external compressor compressor. Selling price: from £6,250(+ vat). Running costs: around a penny a mile...

http://www.evuk.co.uk/hotwires/jim/art25.html

Better site than aircar
http://www.mdi.lu/

redux

I can't see why they are still using steel bottles, when they suggest that they will eventually use carbon-fibre reinforced plastic ones weighing about a quarter of the amount, which will help towards saving about a third of the kerb weight.

Hans_de_Vries

The source of information that says it all is the article 'air engine' in wikipedia.com. Engineering efforts are going on in four countries - each with their concept of how to put compressed air to work in a moving vehicle. There is no question about the viability of this. The sticky problem is how to attract investment in order to put these vehicles on the roads and highways of the world without relying on hydrocarbons or hydrogen and providing virtually free transport for billions of people.
I have had my say on this website. I hope that it will get some way towards ridding us of the con of fast and powerful cars.
Bye all. I wish you God's speed!
Hans de Vries

Generali

According to the University of Oregon ( http://zebu.uoregon.edu/2001/ph162/l10.html ), compressed air can store 2kWH of energy per cubic meter (1000 litres). The capacity of a Toyota Corolla's fuel tank is 60l and so could store 0.12kWH.

According to Wikipedia, a modern battery powered car uses 0.2-0.3 kWH per mile ( http://en.wikipedia.org/wiki/Battery_electric_vehicle ). That means that, assuming the same efficiency, 60l of compressed air would take you up to 0.6km.

Another way to look at it is a litre of petrol contains 8kWH of energy (UofO), over 65 times more than a litre of air!

Yet another way to look at it would be that the gentleman that went to all the trouble of writing all that tosh about compressed air driven cars clearly hopes that the readers of his website can't count!

If in the next 5 years anyone produces a car retailing at less than £20k that can travel for more than 100 miles at 30mph powered solely by compressed air plus any energy that can be regained by braking, I will give £100 to the Alzheimers Society.

tomstickland

There is no question about the viability of this.

Well, give us some decent numbers then. The websites promoting air powered vehicles all skirt round the basic performance data. If they can't be bothered to put together a decent presentation then why should anyone bother to invest in the technology or support it?