Thanks for that, John; I wasn't aware of the Peugeot project
. I must look into it in more detail.
There was a Tata 'runs on air' car which was going to revolutionise the auto scene a few years back, but it was a very unconvincing scam by a mad inventor. Tata clammed up totally when they realised they'd been had.
It's just not thermodynamically feasible to use an air compressor
and an air motor
and get any sort of range, which is what "runs on air" suggests, and any engineer
could do some sums on the back of a fag packet and prove that in short order.
It's a shame the guff your link goes through to was written by an ad agency hack. Some of it makes about as much sense as astrology*. The best sense I could make of the video is that it's coincidentally almost the same idea as my proposal: there's a hydraulic pump driven by the engine
, and a hydraulic motor
which can assist the direct drive, or take over from it. (In my case, however, there's no direct drive; it's all through the latter mode). And there's a hydraulic accumulator.
The "compressed air" of which they speak is on one side of a bladder in the long accumulator, which lies lengthwise under the passenger compartment. The other side of the bladder has the pressurised hydraulic oil
, provided by the pump, and kept under pressure by the fact that the air is highly compressed from the get-go. The oil
comes and goes from the accumulator, but (in their case) the air is constantly there, just getting squashed up when the oil arrives.
I'm guessing the 'low pressure" tanks
under the cargo compartment are for oil.
In my case, as well as tanks
for hydraulic oil, I'll have three or four nitrogen bottles, each about the size of the accumulators, because (low down and central) their weight is actually beneficial for a shallow draft hull
, which would otherwise require internal ballast.
They will prevent the pressure decaying significantly (like a battery
voltage sagging) when the accumulators empty out, and furthermore one bottle can be left isolated for emergency
Whereas for a car they will be trying to minimise weight, so I guess that's a benefit they can't cash in on.
The Peugeot accumulator looks about the size of each of mine, (except I'll have two - one like theirs, the other like a hydraulic cylinder with a free piston and no rod)
And my fallback "get me home" position would be to use air on the other side of the membrane and piston, as they apparently do. But normally I will use nitrogen, unless and until it leaks
away far from civilisation, because I'm concerned about the corrosion
potential of air gathered in a salty environment
, and because nitrogen is less prone to leakage.
* eg <<Motorists never run the risk of running out of compressed air late at night on a deserted country road because the car will be fitted with a sophisticated artificial brain that ensures it replenishes itself automatically.>>
That sounds like bollocks to me. Even if it does replenish the air (which would be necessary only in the case of a leak) the 'artificial brain' to oversee this would have to be about as sophisticated as that fitted to a security
And the range on what they call air, but I would call oil, won't be enough to matter, with a single
accumulator and no extra store for compressed air. It's reliant on fossil fuel
, as far as I can see, and that's what the motorist will have to worry about running out of on a deserted country road, IMO.
I'm guessing they're plugging the "Air" rather than the more appropriate "Oil" is that oil, even hydraulic oil, is derived from fossil sources.