Powering cars by hot air
Surly it's just a small step to convert these into a flying car.
Paris, because it's a French invention
French inventor Guy Negre, who has promoted his plan for air-powered cars for decades without significant success, says he has finally secured backing from a major motor manufacturer. Negre's small family design firm MDI has announced a partnership agreement with Indian car giant Tata, and excited reports have it that air-driven …
I seem to recall there were plans to trial a fleet of liquid nitrogen powered cars in Mexico City where the thin air is a stew of ozone, nitrogen oxides and finely powdered human sewage. A zero emission car running on cheap as dirt liquid nitrogen would have helped a little tiny bit.
Anyone know if anything happened with this?
I disagree. I can see it going into production in France, where they have a terrific tradition of small, light, 'sans permis' microcars. But I find the predicted price a little hard to believe: the lack of mass production over the years has ensured that French microcars are anything but cheap for what you get. If they *did* manage to produce one for around the £3000 mark, I'd be over there like a shot with my cheque book at the ready.
Petrol stations already with big tanks, so big tanks of air, perchance?
Infrastructure ready, flat roofs on filling stations for solar assist, plus wind stuff on the roof or surrounding grounds??
Cars parking next to outlets, with hoses already in place so no major upheaval??
Oh, and the heat can be recovered during fill up to add power, if they get it right.
Does it use the engine to fill the tank again when going downhill?
It's a neat idea if it works, but will still suffer from the usual problem of such vehicles: the energy required to heat/cool the interior. Round here we go from -18C on a winter morning, to +40C on a summer day...
If I was to cover my house with solar panels, it would generate power during the day whilst I needed it most at night. Now to store up the power, currently I have to have a bank of chemical batteries. Not very environmentally friendly and so defeats the point. But could I instead just store the energy as compressed air using whatever super-strong tank they are using? I would have thought the energy needed to power a 350kg for 100km would happily cover my domestic needs for a while.
Aren't nicknamed "coffins on wheels" for nothing... The only thing more frightening than seeing one of those rolling down a main road flat out at 90kph is knowing that the only reason the driver is driving one is that (s)he hasn't got a licence for a real car!
As to prices, Renault's Romanian subsidiary Dacia sells the Logan for €8000 in France, which is about £5000, so £3000 for a compressed-air toycar isn't impossible. More of an issue is how many extra kilos the mandatory safety features will add.
Not only will filling the tank heat it up but the expanding exhaust will be very very cold. This is essentially a lightweight alternative to aircon. For heating there is the burner mentioned in the article or regenerative braking which will compress gas in the engine cylinders creating heat a la 1st law of thermodynamics.
While compressing the air makes it become hot, be sure that decompressing it (inside the engine) will make it become freezing cold!
It will surely need some heath/cold distribution system with liquid and a radiator.
In the summer this shouldn't be too much of a problem (in France, at least), as can absorb enough heath energy from the air. It could also used the heat inside the car, doubling as a natural airconditioning.
But in winter time it will freeze your nuts off!
Combine your gym's step machine with a foot-powered tire pump, and you'd have it made. Charge your car and get fit at the same time. (Provided you didn't have to take more steps to charge it than you'd take walking wherever you're planning to drive.) And, if you keep a foot pump in the car, you'd never run out of "fuel"!
Not a single person has stated the obvious source of unlimited fuel for such a vehicle. One's wife or girlfriend. Surely when you factor in the copious amounts of hot air generated by those graced with marriage or long term relationships, the potential for unlimited, clean fuel means the search for alternative energy to power our vehicles is all but over.
Personally I reckon my wife could power one of these things for 1000km (625m) at least - from a single phone call to one of her friends, and I would assume most chaps more aesthetically pleasing halves could match our mpp with ease (miles per phone call).
The other problem with air cars is they have a reduction in power output as the air reserve is drawn down. At the end of the 100km the response will be somewhat less than sprightly.
On another sort of related topic, people may be interested in the worlds first rapid fire, breech loading assault rifle. This little baby was approx 50 cal and had a 22 round capacity. It could deliver 20+ accurate aimed rounds per minute from its single barrel. Effective range was 100 metres+
It was so deadly compared to the other weapons of the day that possession of a unit was deemed an automatic death penalty in some regions.
I'm referring of course to the brilliant Girandoni repeating air rifle - http://www.beemans.net/images/Austrian%20airguns.htm
Even today, US SEALS use 9mm air rifles for sniping in Iraq.
I filled a few thousand scuba tanks back in my diving days, so I have the badge of authority here.
The scuba tanks do get warm and need cooling, but that is only because you're filling them fast (complete fill in 5 minutes or so). If you fill then very slowly, as planned with the onboard comressor, then the tanks won't get hot.
There are two other very good reasons to use slow filling with a small conpressor. Firstly compressor cost/weight/noise and maintenance - pretty obvious. Less obvious is that high output compressors are pretty power hungry and need 3 phase power. Most Indian (and presumably French) houses don't have industrial spec three phase power sockets. Thus, small is beautiful.
Many countries require you to pass an industrial compressor operator's license to fill scuba because high pressure air is as deadly as explosive if handled incorrectly. Would every air car owner need to do the same?
In fact, words cannot begin to express how completely and utterly moronic the very concept of this vehicle is.
Compressed air is by FAR the most expensive and least efficient form of motive power currently in existence.
Manufacturers of large fan compressors currently claim efficiencies of up to 95% when running at maximum capacity at 100PSI - this only applies to the very large compressors when they are actually running above 85% capacity.
These same large compressors drop to well below 50% efficiency when operating at lower outputs.
If the pressure is increased (which is essential for reasonable range and sensible size of pressure vessel), then efficiency also drops through the floor, as then screw compressors (mid-range efficiency) or reciprocating engines (extremely low efficiency) become the only possible techniques.
Add to that the very large losses involved in the transport of compressed air through small diameter nozzles, plus the inevitable leakage, this whole concept can be shown to be exactly the reverse of "Green" motoring.
Once again, a so-called "Green" system has completely ignored the issue of the Prime Mover.
Where do you get the original power from, and can that system be efficient and low-emissions?
One dirty little secret about industrial hydrogen is that most of it comes from electrolysis of hydrocarbons... producing the same carbon monoxide and carbon dioxide that would have been produced if it had simply been burnt.
However, I have much more confidence that sustainable ways of generating free hydrogen can be found compared to the idea of generating huge amounts of compressed air!
Not really new. The use of compressed air as motive power was widely used in Paris between 1880 and 1910 for powering tramcars in a system attributed to Mekarski. The trams used to weigh about 11 tonnes and carried up to 9 high and low pressure air bottles. They used a bouillotte containing water at 155C at 200atmospheres to warm the air as it was released into the pistons and extend the range. Gawd help us if they use that on board these little cars - should go like a bomb!!!
Mine's the anorak with the notepad and pencil ..............
Compressors really had 85% efficiency (from the energy production to compressed air delivery, that is), it would be by very very far MORE efficient than pretty much any other power source.
Anyway, just have to get the kids on the backseat (and possibly the missus) to pump, here is your free, green energy. Plus the driver's stress level is bound to decrease, too...
One of the problems with something like a compressed air car is similar to the problems you have with ideas like massive spinning flywheels to recover energy while braking - what happens when you get into an accident?
Let's say you fill some carbon-fiber tanks with enough very high pressure air to power this vehicle up to 100km. Five miles out onto the road you get rear-ended hard and burst the air tank.
Well, we've all seen the videos of dry ice bombs made in soft drink bottles, haven't we? Magnify that effect by hundreds of times and put it a few feet away from passengers and drivers in a car accident, and you've got an awful mess.
So, Pintos used to burst into flames from time to time when hit in the rear. And this new air car? It just blows the car and everyone in it into a billion pieces.
As others have said its a wonderful idea until you crash.
To quote the BBC website:
Mr Negre says there's no issue with safety - if the air-car crashes the air tanks won't shatter - they will split with a very loud bang. "The biggest risk is to the ears."
Fixed air compressors and their tanks in an industrial setting are very tightly controlled for a reason, there is a hell of a lot of energy stored in there and it can do nasty things like blow walls out, not just give you ringing in the ears.
I've used full size gas cylinders in lab settings in the past, they have to be treated with respect. Even just opening the valve a fraction without a regulator attached can cause such delights as ruptured eardrums, or can kill you with a gas embolism if a high pressure jet impinges on the skin.
Its a good idea for stationary emergency power generation, but for vehicle use, I don't think so
Paris, because even she's not that stupid
Queue all the usual objections:
1. "Where do you get the original power from, and can that system be efficient and low-emissions?"
Asked and answered Richard. Repeatedly. But to save you the effort of looking it up:
* Internal Combustion engines are less efficient than Oil burning power stations
* Nuclear and alternative generators can be used too.
* Replacing stations with greener ones as time goes by is a lot easier than replacing a nations fleet of vehicles.
Internal Combusions engines give you no route forward to a green alternative. Those powered off the grid, whatever form the power is stored in, do.
As for you Lewis, for shame:
"wasting energy unnecessarily in electricity generation/transmission in all likelihood and at the compressor for certain. It would make more sense in terms of carbon emissions to just burn the fossil fuel on board in a conventional small car: you'd use less overall."
I'm sure you've got figures to back that up, don't you? Give me some frickin' numbers already.
"The first buyers will be people who care about the environment,"
Especially closed or explosive environments such as coal mines, but somehow I don't think that's what he had in mind! I want to see come complete energy chain calculations before I'll beleive this is environmentally freindly.
I do think that compressed air could be a useful storage medium when combined with some, yet to be developed, technology. Perhaps small, high efficiency air pumps on a windmill, or some clever direct from solar mechanism not involving a compressor as we know it. Surely there are alternative ways to pressurize a gas.
Unfortunately the problem with ALL cars is that it is inefficient to carry hundreds or thousands of pounds of metal (or whatever) around with you wherever you go.
It's a while since I filled a SCUBA bottle but I'm not sure that the air will heat up if you are charging the car from a precharged, ambient temperature bottle bank (rather than directly from a compressor) ? A further slight cooling all round (Joules Thomson) seems more likely.
In any event - airbank or direct compressor - some reasonably smart engineering should be able to press a heat pump into service, at least in colder weather (you could heat the house?).
Not sure what you do in hot places, say like the Middle East. But then again, maybe they don't really care about stuf that doesn't need oil..
Lol! I pretty much just choked on my breakfast :)
As for these cars.....100km on a single charge?? That'd be about as much use to me as a blow-up doll with no holes.
And as Dave says, compressed gas systems aren't exactly safe.....mind you, can't be much more dangerous than driving around sitting on top of a petrol "bomb".
"Away from France or Switzerland, the air car would be essentially a very inefficient fossil-fuelled one; wasting energy unnecessarily in electricity generation/transmission in all likelihood and at the compressor for certain. It would make more sense in terms of carbon emissions to just burn the fossil fuel on board in a conventional small car:"
Did you do any research for this Lewis, or just write what you imagined might possibly be something close to accurate?
Hydrocarbon based electricity generation and transfer is several times as efficient as an internal combustion engine. ICEs are generally in the region of 35% efficient, a modern gas turbine power plant is >85% efficient.
The compressor and the air driven engine will reduce that efficiency, but I'd be surprised if drops below 50% overall.
None of which means it's a good idea, but try to contain your rants against things to facts rather than imagination.
Sure the compressor will remove some efficiency from the process and grid transmission losses will knock a bit more off (although this is so trivial in comparison to other losses it is hardly worth mentioning). The key losses will be in the conversion of air to compressed air and back to work. The main question is the efficiency with which work is generated from the compressed gas.
However, if one is going to consider these losses then one must also benchmark ICE efficiency against the extraction, refining and distribution costs for hydrocarbon fuel. I suspect the air-car may compare favourably in this respect. It's the practicality and scalability aspects which are going to knacker it.
Actually gas power plant is only 55% efficient overall; the 85% refers to the maximum energy available from the cycle rather than the total energy put in I imagine.
ICEs may approach 35% efficiency at optimal running conditions but the true value is closer to 20%
Heating compressed gas by burning fuel:
Hey! My car does this. It's a turbo diesel.
If the air has to be heated, then this becomes an external combustion engine. Why not carry the gas as something that is liquid at room temperature, like water, to save on the compression losses, then heat that to its gaseous state and use that to drive the pistons, or a turbine. You can use anything to heat it, ethanol, methanol, diesel, even coal. You could call it a "steam engine"
Mine's the dirty blue overall next to the shovel and oil-can.
If this air car will only work efficiently if the air is heated, then let's get rid of the air altogether and use a Stirling engine. This uses pairs of cylinders, one heated and the other kept cooler. These are used in Africa for pumps, where a wood fire is lit under the hot cylinder and the cold cylinder is air cooled.
In a car you could use multicylinders, water cooling and any portable fuel - ethanol, methanol, LNG, Hydrogen, waste oil - even a fluidized bed coal burner. Unlike the air car these would run more efficiently in winter and the heat from the cold cylinder could be used for heating the car, though warm-up times might get a bit long.
Why aren't they already used? Long warm up times, (minutes rather than seconds) difficult changing the speed, so better suited to constant speed applications like pumps or generators. So, put a generator on one, a battery under the hood, and electric motors on the wheels, though then you introduce conversion losses, so back to square one.
Nuclear, etc - lovely. Where are we going to build them? Your back garden?
But anyway, please consider this:
The efficiency ratings given by air compressor manufacturers are for Electrical Energy to Compressed Air Energy.
Thus, a compressed-air driven motor has the following loss stages:
1) Electricity Generation and Transmission
2) Compressed Air Generation (needs large power machines for >50% efficiency)
3) Compressed Air Transmission (pressure differential losses through the hose)
4) Compressed Air Storage (leakage)
5) Compressed Air Engine (normal rules apply to expansion engines)
Compare this to a Hydrogen car (assuming electrolysis of water)
1) Electricity Generation and Transmission.
2) Hydrogen Generation (can be done slowly by low-power machines)
3) Hydrogen Storage
4) Hydrogen Combustion Engine
The difference is clear - not to mention that a hydrogen car could have considerably greater range than any reasonable compressed-air powered vehicle.
In the recent past I spent several months examining compressed air usage at a particular industrial site, and found possible cost savings in electricity bills alone of over £15,000 pa.
It's simply the most expensive motive power currently used in industry.
Compressed Air is only used in industry where no other motive force makes sense:
- High linear accelerations (rams are much faster than motors)
- High static torques (eg wheelnut drivers)
- Need to pressurise containers (eg food sterilisers)
- Sensitive atmospheres (eg explosive)
Internal combustion engine driven with compressed air is still internal combustion engine, sans combustion. Valve train alone takes significant portion of the energy used. 20-50% depending on the source, internal friction and transmission losses are most of the rest.
But the efficiency would be better as there's less cooling needed, let's be generous and use doubled efficiency, that is about 40%.
Compressing air is very lossy job, that 85% given holds to very large amounts of air to very low pressures, no or low need for cooling. Putting small amount of air to very high pressure needs more energy to cooling than is stored as potential energy in compressed air. So efficiency is much below 50% in that one stage. Let's use that 50% as an absolute maximum.
Unfortunately efficiency won't get any better if done in a long time, you just don't need external coolers.
So we got overall efficiency of 50%*40% = 20%, while combination of battery+ electric motor+gearbox reaches effortlessy 60% and the source is the same: electricity.
Fuel to electricity efficiency in turbine isn't near 85%, even 50% would be a good achievement, but you could use the remaining energy for heating, thus raising the overall efficiency.
If you combine that with 20%, you'd get a 10% fuel to movement efficiency, compared to 20% of internal combustion engine.
Lesson learned: converting energy is almost every time a major loss in efficiency and should be avoided at (almost) any cost. Those losses cumulate and the chain fuel->heat-> electricity->movement->compressed air-> piston engine is losing 90% of the energy the fuel had, to conversions. "Environmentally friendly" means nothing with losses like that when said of the last phase.
You could use a windmill to run a mechanical compressor via gears to make the compressed air, that would be much more efficient, but very slow. On the other hand, losing 50% of something free and non-polluting isn't much of a loss.
"very inefficient fossil-fuelled one; wasting energy unnecessarily in electricity generation/transmission"
I wonder how this would compare to searching for, drilling, pumping, transporting over vast distances, refining and manufactuing, distrbuting and pumping feuls. As well as the many hazrards created and dealt with throughout these precesses. Not to mention having to deal with and supporting the terrorest underworld not to mention the whims of oil prodcing countries and governments. Plus having to deal with tree-hugging enviro-wackos trying to prevent the use of oil, coal and nuclear power generation.
I’ve wanted one of these since I first saw them on Beyond Tomorrow and year or two ago. The only reason I want one is because they’d be cheap to operate. I could fill the thing for free at work with our compressors. That would bring my cost per mile pretty close to zero. I rarely drive more than 100km per day and if I’m going farther than that I’m usually transporting stuff that weighs a ton or so, so I’ve got my pickup for that. So an air powered car would be perfect for someone like me assuming they aren’t too expensive to purchase once they become available.
I can't wait for one of the 'fully-sick' guys down the road to install some sub-woofers into one. I know in the past they have drilled through 2x car computers, and almost 1 LPG tank.
I figure a carbon-fiber tank won't give them a warning.
Aslo, when they figure out that the brake system can help create the heat needed to expand the air from the tank, it won't be an invertion, just them stealing the idea from the register posts.
*However i'm not so sure I'd ever want to be associated with the project.
Efficiency is a complicated subject - not least because different people mean different things by the word. Claiming internal combustion engines have an average of 35% efficiency is odd, given a four-stroke engine can't theoretically be more than 25% efficient (one out of four strokes produce energy, the other three use it). Unless you're trying to include 2-stroke engines in there .. but the numbers aren't there, especially for transport, and their efficiency suffers elsewhere anyway.
But I'm more concerned about this zinger:
"In France, to be sure, you can use grid power which comes mostly from nuclear generators and thus is nearly carbon-free"
From whoa to go (commissioning through mining through transport through decommissioning) your average fission nuclear power plant is about 75% of fossil fuel consumption, and consequently 'carbon emitting', as a coal-fired power plant. The myth that 'nuclear is nearly carbon-free' isn't one we should be perpetuating.
Anyhoo, what I really like about this (and similar) approaches is that it makes it possible for us little people to set up our own energy supply line - using home-scale wind or solar systems we can manage ourselves, incidentally removing us from the 'consumer' approach to energy.
The one thing no-one has mentioned is what happens if the valve comes off the cylinder in a prang. Would the thrust of the escaping gas be sufficient to transform the car into an aeroplane, I wonder? A few rough calculations suggest that the thrust from a large aperture in the tank would be well in excess of the vehicle weight, so probably yes it would, if the thrust were downward. Even if it didn't leave the ground, it would still be a dangerous and uncontrollable missile.
I got an air pump for my bike, will it be compatible? Think about it, instead of (1) pumping tires and (2) biking, you can glide effortlessly after step one. Now if I could find that generator plan using the earth magentic field to charge the batteries while driving ...
off to that underground laboratory again ...
Biting the hand that feeds IT © 1998–2021