C4 Dispatches - Killer Diesel

forgotmyname

There are several manufacturers making air powered cars, But they tend to be small lightweight cars, the mileage is limited, But reliability is still an unknown.

I don't think they have one that will do 100,000+ miles reliably?

Arfa__

Just to stir the pot a little more, as a biker, I'd be happy to see less diesels about. Seen and heard of no end of fellow bikers hit the deck for no apparent reason on a bend and only when getting back on their feet (if lucky enough) do they spot the tell tail rainbow of split diesel on a wet road.

Though most instances are likely to be from trucks/buses etc, which ain't going to move away from diesel anytime soon.

shammyjack

I have a compressor with a 3Kw motor to power it for the occasions when I need to use air tools . To run a large air tool it runs nearly constant so costs more than the equivalent self powered electric tool .

Unless the compressed air is supplied by industrial charging stations then the cost of air power could be more than electric battery for the consumer !

Cornucopia

If it's about cost, then we're back to petrol.

However, just to be clear where people are coming from with the compressed air argument...

- The technology is inherently clean at the point of discharge of the stored energy (unlike fossil fuels).

- The storage technology is relatively clean and doesn't require unusual metals or minerals (unlike electric).

- The "refuelling" technology is already well known, and doesn't require unusual metals or minerals.

- The entire process avoids transport or storage of volatile substances.

- The refuelling technology is simple, safe and cheap enough to install on garage forecourts (unlike the vast infrastructure that would be required for hydrogen).

I hate to suggest it, because I hate conspiracy theories, but it does seem like the technology is not favoured by the industry because there is little opportunity to exploit exotic technology and materials for profit.

Weird_Nev

Where does this compressed air come from then? It's not a zero energy cost to put it in cans!

And personally, I thInk that a large container of air at a pressure sufficient to drive a car any significant distance classes as 'volstile'.

Ultimately, its less efficient than expanding air in the cylinder by adding heat to it, via the burning of a small amount of hydrocarbons. If it wasn't, we'd all be driving magic zero emission compressed air cars.

shammyjack

Weird_Nev wrote: »

Where does this compressed air come from then? It's not a zero energy cost to put it in cans!

And personally, I thInk that a large container of air at a pressure sufficient to drive a car any significant distance classes as 'volstile'.

Ultimately, its less efficient than expanding air in the cylinder by adding heat to it, via the burning of a small amount of hydrocarbons. If it wasn't, we'd all be driving magic zero emission compressed air cars.

The receiver on my compressor is approx 1 m x .3 m and runs at 120 lbs per square inch pressure . I think it unlikely that it could power a car for more than 100m even if the car was already rolling.

The cubic capacities and pressures to run a car for a few miles seem mind boggling to me .

Weird_Nev

shammyjack wrote: »

The receiver on my compressor is approx 1 m x .3 m and runs at 120 lbs per square inch pressure . I think it unlikely that it could power a car for more than 100m even if the car was already rolling.

The cubic capacities and pressures to run a car for a few miles seem mind boggling to me .

Exactly. You only have to read the Wiki page on compressed air cars to realise that they have significant (insurmountable?) problems:

• Compressed air at 4,500 Psi :eek: Has an energy density of 50Wh/L, Li-Ion batteries manage 500Wh/L, and Fossil fuels 2000Wh/L
• A compressor that can fill a compressed air tank in a car acceptably quickly draws a third of a megawatt! And you get a 10% conversion efficiency too.
• The heat management of compressing and then de-compressing gasses is non trivial, and means the air also has to be dried out adding to the energy cost.
• No compressed air car has managed to go more than 5 miles on a fill up (and they would take 4 hours to refill on a home compressor drawing only 30Kw)
• They are only 5% efficient overall, where internal combustion engines approach 14% efficient source to sink... Their greenhouse emissions are actually WORSE than a conventional car, petrol or diesel.
• Have you ever seen a 4,500Psi tank getting ruptured or overheated or being filled beyond capacity? A bomb is just rapidly expanding gases, after all...

It's clear they're not a viable technology. It's just a case of out of sight, out of mind because the point of energy consumption is taken out of the car and transmitted to some chunk of plant elsewhere.


But back on topic: We just ahd to choose between a 1.2 Turbo petrol, which was very nice, and a 2.0 Diesel turbo, which was also very nice to drive. We went for the Diesel, not because of fuel efficiency (it will trump the petrol there but we don't do enough miles to justify it) but because the manufacturer didn't offer the vehicle in AWD trim in the petrol version.

If they'd done the 1.8 PEtrol turbo in AWD, we'd have had it like a shot. I hope that there is a bit of a diesel backlash, if only to drive manufacturers towards further improving petrol engine technology.

arcon5

4500psi is tiny, at least compared to your diesels common rail running at typically 20k. Some as much as 50k

Cornucopia

One of the things I am complaining about (both with Dispatches and generally) is the lack of like-for-like comparison.

There is an intrinsic difference between say, electric and petrol - the energy density may be different, but nothing is lost from the battery other than charge which can easily be replaced. Whereas petrol and other combustible fuels are being carried to be burnt.

Hydrogen shares characteristics with both.

fred246

Pollution of course is a massive global killer. So yes, diesel fumes do kill. It's just you'll never be able to prove who it has killed on an individual basis.