Air-Powered Cars

tata motors: AIRPOD air powered urban commuter vehicle
Something about compressed air powered cars doesn't make sense.

Agreed, I just tried a few figures based on the Tata site. Used their 175 litre. They don't give a figure for pressure, but assuming a generous 200 bar (3000 psi) which I wouldn't want to ride with, based on isothermal compression I get ~ 18 MJ stored energy. Assuming that gives shaft power at 60% effy and petrol engine is 30%, I make that eq to < 0.3 USgal. So even at 80 mpg it only gets you ~ 20 miles.

Air tank 0.4m dia x 1.4m gives 175 litre, and using ordinary steel at 170 MPa is ~ 25mm thick and at least 400kg. Might use stronger material, but it's still going to be heavy. Lighter if spherical but then it's 0.7m dia which is big to fit in a small car.

I might be a bit of a Luddite and flight was once thought impossible, but it doesn't look practical to me.

Compressed air car = blow it out your rear. It really isn't much more complicated than that. There might be weird "green money" to which Peugeot might suck up, in which case they might spend it better than the fools who provided it. Nice work if you can get it.

Yeah looks like it will be available in 2016...

"Compressed-Air Hybrid Tech: Peugeot To Offer In 2016 On Subcompacts

According to Autocar and Auto Express, the system is likely to make its debut in Peugeot's 2008 subcompact crossover in 2016. From there, it's likely to spread to other small Peugeot and Citroen models.

The system uses compressed air exactly as a regular hybrid would use its battery pack.

Under normal driving, air is compressed into a storage container sitting under the vehicle, just as driving a hybrid vehicle can feed charge into a battery pack.

Accelerate gently at low speeds, and compressed air can drive the car alone for a limited distance--and according to PSA, at speeds of up to 43 mph. Accelerate hard and the air can assist the regular gasoline engine sitting under the hood.

One of Hybrid Air's major benefits is cost: Peugeot says the technology is less expensive than a battery-based hybrid setup."

http://www.greencarreports.com/news/1090407_compressed-air-hybrid-tech-peugeot-to-offer-in-2016-on-subcompacts

43 mph. Excuse me if I can't have an orgasm over that.

You should rethink that. Thousands of orgasms at 23 mph would be a pretty good deal.

Some doofus apparently couldn't figure that out correctly.

43 mph, Scotty, we need more power!

I'm givin' it all she's got. If I push it any more she's gonna blow!

Apparently somebody doesn't want thousands of orgasms at 23 mph. I suppose we could offer our condolences. Or a raspberry.

Apparently somebody doesn't want thousands of orgasms at 23 mph

I would be happy with one at 0 mph

Excuse me but I very much like the concept of compressed air for a hybrid energy storage approach with an Internal Compression Engine.

For those who say nay, you are absolutely correct that the heat based energy lost in compressing an inelastic gas is always where this energy storage system looses power. However, an ICE works by compression in the first place. Storing kinetic energy to a compressed gas and returning compressed gas energy back to kinetic can use part of the existing ICE for both storage and release. Adding an electric motor/generator to an ICE to store and release energy seems like adding more complications for a reward of hybrid efficiency.

"loses" and "looses" are not the same thing.

Maybe the lose is caused by loose connections.

Or a sail?

Wind-powered car? Isn't that a sailboard?

Wind turbine replaces PV panel to drive the compressor. Like oxygen cylinders used in welding shops,compressed air cylinders could be charged & refilled.

I should have added - the earlier discussion was about compressed air only cars, which would be recharged at a fill point. Consensus was that range would be poor, and the energy still has to come from somewhere (as with battery, hydrogen or anything else).

This latest is if course a hybrid, but what surprises me is the high mpg achieved (or claimed, I've no personal experience) by petrol-electric hybrids. Energy to propel the car is same, or more with extra weight of battery etc. I can see there's some benefit in the engine running at constant power, with peaks and troughs of power at the wheels provided by the electrics, and regenerative braking, but it seems to give more improvement than I would expect, perhaps somebody can explain.

You mentioned the critical point: weight of batteries. If the compressor/air motor+ compressed air reservoir has a lower weight then the results can be better than for an electric hybrid car.

If the compressed air reservoir has a good thermal insulation losses are limited since the time between compression and usage is short. When the engine is connected to the compressor the heat from gas can be used to heat air at intake leading to a better efficiency.

We discussed ONLY NOT HYBRID pneumatic solutions this is a new solution which should be analysed. What I know is that hybrid cars with a pneumo-hydraulic accumulator as energy storage are build and hive quite good results. Peugeot solution is similar thus should also have good results.

A large portion of the mpg for a hybrid depends upon the control strategy coupled with the routine of the driver. A prime example is the Chevy Volt; if you can keep your daily commute to under 40-45 miles at speeds less than 55-60 mph on mostly level ground then the energy management system will run the vehicle exclusively on battery power.

So far my son has held to that strategy, as of yesterday he has almost 6,300 miles on his Volt with 22.6 of gasoline consumed. It takes about 10-12 kWh to charge a nearly flat battery; ambient and battery temperatures are used to determine the charge rate so the exact amount varies daily and seasonally.

It's hard to beat a buck a day for 45 miles of commuting, but then he doesn't pay any federal/state gasoline taxes either, but of course the powers to be are looking into ways of collecting that as well.

Interesting, but I assume the car is charged overnight from the mains, is this correct? I believe the new Peugeot only uses the petrol engine to charge the air tank.

The car doesn't have to be charged off the mains, unlike a Nissan Leaf, the Volt's petrol engine can power the car with a flat battery. At that point it's the same as any hybrid, petrol to go, regenerative braking to stop (and put some energy back into the battery).

The Peugeot sounds like any hybrid, except that the storage medium is compressed air. Compressing air with petrol still uses petrol, no savings from using alternative energy sources like solar, wind, etc.

I didn't mean the battery had to be charged from the mains, only that it could be, and if the car was mainly used for shortish journeys and charged every night, that would give a big reduction in petrol consumption.

What good is talking about economy per mile when you shell out $35,000 for the car?

So you now want to tell people how to spend their money?

No, but it does seems paradoxical when people spend huge sums of money for a car, then turn around touting how economical is.

Go tell Elon Musk about that! His Teslas are pushing 100G's around here.

I would buy a Tesla because it's a cool car, not because I need to save money.

I am pretty sure that all of his customers are of the same mind.

Thank an aggressive leasing plan and Gov't. subsidies for making the Volt lease within a few bucks of a hybrid. Now let's see, 36,000 miles at 50 mpg is 720 gallons of gas, at $3.50/gal that's $2,520; vs. 36,000 miles at $0.02/mile is $720, plus about 250 gals of gas or $875 equals $1,600. That's about the equivalent of a $25/mo offset against the lease cost.

I'm not getting into the politics of the $7,500 subsidy, obviously we all pay for that., but if we have another gas crisis his costs don't skyrocket, and if the grid goes down he just fires up his 12kW natural gas generator and charges the batteries (his electric costs triple but he's moving when no one else is). Too bad he doesn't have a gov't subsidized PV system!

If economy is really the goal, just buy a used car or even a new Kia or something.

I don't know what the lease actually is, but it's still money out the window on a per mile basis.

Now, there is nothing wrong with that if you have the disposable income and just want it for the fun/cool factor. However, calling it an economical purchase is not true.

Actually the only economic cars are the few, really rare vehicles that appreciate in value. Knowing which esoteric car will be the next "gem" featured in Hemming's Motor News or candidate for a trebuchet demonstration is nothing but gambling to me.

Yes, not many of them around. I actually may have one in my garage, but waiting 20 years for its value to escalate is silly compared to investing that same money into more traditional investments (i.e., mutual funds, etc.) - if your goal is to make money. I don't look at the car that way as it is a paid-for toy.

Most of us just need transportation that reliably gets us where we need to be and at a per mile cost that doesn't negatively impact our lives. That describes our family car (Saturn) and while it doesn't look very upscale, it's paid for and the cost of operation is far less than the payments of a new car or lease regardless of what may fuel it.

Same here, our family car is a 14 year old BMW 3-series sedan that gets 28MPG, runs like a top, is fun to drive, is worth about $4500, is very cheap to insure, and has been paid for for a long long time. Those Teslas sure are cool, though.

I have driven the Tesla sports car and it was an awesome drive.

One of the problems using compressed air is lubrication (ask Tata motors). As the compressed air expands there is a cooling effect which causes problems with the oil.

I recall seeing something about a US courier company (perhaps FedEx?) looking at a similar system but based on hydraulic accumulators, for this purpose.

The whole point of it was to recapture the energy wasted in frequent stops, and this seems to fulfil a similar purpose but with a much lighter system (I didn't read the article, but certainly hope they weren't using the engine to drive the compressor to.....!), and lighter and much less expensive than batteries. In other words, great idea for city commutes (if it works) but of very little value for long highway drives.

it all sounds like a lot of hot air to me!!

Interesting concept. Instead of charging a heavy and expendable battery, the braking system recharges a pneumatic tank which in turn will power the vehicle to some extent. I find it ok because I happen to have a small propeller model aircraft which works on compressed air. The air simply drives the very piston engine which burning fuel was supposed to drive.

How far can they push the pressure and all that is still to be confirmed.

Saw this a while back, not impressed, but would be more likely to be impressed by a hydraulic accumulator, and hydraulic motors on each wheel, with regenerative braking. See INGOCAR.l 167 mpg, 0-60 in 5.6 secs., 500+ bhp. The ICE on board is an opposing piston, computer controlled fuel injection (totally fuel flexible), and is less than 30 bhp. This means the power for acceleration, climbing hills, etc. mostly comes from the hydraulic system, with the ICE re-charging the system when on level terrain, or downhill.

Over all range of this vehicle is ~1000 miles. I think Peugeot Citroen would be better off as a snap on to fit on the standard INGOCAR chassis. (or whatever body style you want).

"I think Peugeot Citroen would be better off as a snap on to fit on the standard INGOCAR chassis."

Or perhaps just a large rubber band.

Every time you add another energy conversion stage, the overall efficiency decreases. In the end, more fuel will be consumed in order to power that extar energy conversion.

In reference to the INGOCAR: Well, if you consider there is no (1) transmission if motors are on each wheel, (and trust me that hydraulic has all the power needed at any initial speed to produce the required acceleration), (2) there is no differential, and (3) the ICE is a much smaller, but highly efficient engine, then you can see there exists a very significant weight savings over traditional road cars. Weight savings = transportation fuel economy, but this is factored against performance, but in such a case this car wins out on performance totally. It is possible for such a car to be made, with all the creature comforts, and still present unheard of fuel savings.

I don't know if that is true or not, but we are talking about pneumatics here, not hydraulics.

Quite. The fluid has to be compressible to store a significant amount of energy. That's why hydraulic testing of pressure vessels is much safer than pneumatic.

I think you meant the testing fluid must be incompressible (as hydraulic fluid or water) to avoid a rapid expansion when or if the vessel were to fail catastrophically during testing. A vessel that is "solid" with the fluid, i.e. no gas or vapor voids, will not have an explosive force behind the contents if rupture occurs. Thus testing of pressure with gas is simply verboten. Same reason why not to use PVC pipes to contain air pressure, although some who have received their marks for this yet, will still try it.

Yes of course. I didn't give all the reasons why as I assume anybody likely to read these posts would understand.