AutoblogGreen

I firmly believe that this should be THE solution to all our transportation needs. I have no doubt that the engine can be scaled to any type of application. 2 bucks for 200km sounds like the bee`s knee`s to me. Increase the tank size and the range extends accordingly. A compressing station could be matted to a solar panel for free fill-ups with no emmisions.

Air in a tank vs. Flammable fuel in a fuel tank
Air in a tank tank vs. chemical-laden batteries

Air tank wins.

Reply

yep, brings a whole new meaning to car bomb. I'd really like to see mythbusters get there hands on one and simulate a bad crash to see that thing blow sky high in a million pieces. I'm afraid poor buster wouldn't survive the explosion though.

Reply

It's another example of an Indian company "just doing it" while the major players from other countries make excuses to stick to the technologies that they have invested heavily in and don't want to let go. When I was in India, I was surprised to see all the rickshaws in major cities in Gujarat converted to CNG. The government provided loans for conversions and then made it mandatory. The air quality improved drastically, (especially since some drivers were running on kerosene), and there are filling stations everywhere.

Atul
http://www.thingsivenoticed.com

Reply

ronEbear said:
Air in a tank vs. Flammable fuel in a fuel tank
Air in a tank tank vs. chemical-laden batteries

Air tank wins.

I have concerns about the ability to build a large/safe compressed air tank in the vehicle without dipping into expensive things like carbon fiber.

But the bigger problem is the overall efficiency of the system. Compressing/expanding air brings all kinds of thermodynamic losses into play. A significant portion of the energy used to compress air is transferred into heat rather than into pressure. That heat is then lost to the atmosphere. When transferring from a compressed tank at a filling station to an initially lower pressure tank in the car, the gas will be agian expanded then compressed, pumping more energy into and out of the system, and again some will be lost. Once in the tank, expanding the compressed air will cool it, reducing the energy you can extract from it. I've heard it theorized that such a system only works in hot climates where 1) you can more easily prevent your air motors from literally freezing as the expanding/cooling air flows through them and 2) you can extract some heat from the environment to counteract the cooling effects (think themal fins all over everything).

For anything other than free solar energy, the efficiency will probably be terrible. And then there is the fact that the longevity of a high pressure tank that is frequently pressurized/depressurized could be questionable. And the fact that the infrastructure to support this new fuel source isn't there - don't try to think you can charge the tank on a standard gas station compressor in 2 mins - you'd need a high pressure reservoir to accomplish that, with specialized connections and safety systems.

And even for that free solar energy - don't count on a full system with high pressure tank and large solar array being able to fill up more than a handful of cars each day at best.

I'm a pessimist on this technology. Prove me wrong Tata/MDI! Please!!!!!

Reply

That's a fine explosion scenario you paint there, MarkR, but it is far from reality. A ruptured air tank would discharge rapidly and noisily, but tank design engineers would see that the shrapnel is kept to a bare minimum. So no million pieces, no cloud of ignitable vapor, no hazardous liquid spills. If the range of an air car can be made adequate, what's not to like?

Reply

@MarkR - I saw this car a couple years ago on some TV show, and as far as I remember the tanks are made from carbon fiber. When they rupture, they don't explode, they split.

This technology is fantastic IMO. I'd like to see a rotary type design instead of a piston engine.

Reply

I want a air car now..., but wait what will happen with the cold air exhaust that the MDI gives off?
Global Chilling? Just kidding, the MDI might be the perfect EV, without the E.

Phil

Reply

There is no danger of tank ruptures. We have decennia of experience of transporting safely any gas in high pressure containers... why should it be a problem all of a sudden?
And about the whole refilling.. what about a quick tank swap? If the car is designed the right way, it could be done in seconds. Much faster than filling up with gas... The tanks are refilled at the same station for the next customer.

Reply

There's some video on the web of demonstrations of these air cars. The efficiency and infrastructure concerns are valid, but this is an interesting technology that sidesteps a lot of issues holding other alternative fuels back. No exotic and expensive energy storage methods have to be perfected and paid for, and it's as clean as electric vehicles ~could~ be since the primary energy source is an electric power plant which could be renewable and clean. Given how the fiber based tanks are engineered to fail by splitting rather than exploding, it doesn't appear to have any safety concerns other than its diminutive size.
I don't know how well this energy source would scale up, it may never be suitable for vehicles larger than the tiny example demonstrated, but that might well be enough for a lot of potential Nano owners. Plus, I the engines make a very cool putt putt noise as they work.

Reply

bolhuijo: You are certainly right that there would be "no million pieces, no cloud of ignitable vapor, no hazardous liquid spills", but if the tank is charged to 10,000 psi (for instance), and gets a hole in it with 1 square inch of area, then the car would take off quite literally like a BB out of an air rifle. Remember the Mythbusters where they knocked the neck off a tank of compressed air?

I'm not particularly saying that one form of energy storage is more safe than another. Any time you have millions of Joules of potential energy confined in a vehicle there is certainly the potential for trouble, and compressed air is NOT an exception.

And the well-to-wheels efficiency stinks.

Reply

s10 -

>> There is no danger of tank ruptures.

Huh? Try Googling "air tank explosion", and you'll see several recent examples of fatal air tank explosions.

That said, we can certainly make high-energy air tanks that are acceptably safe for road transit.

Reply

@ MarkR -

CNG tanks at 200 bar should be even more dangerous, yet those vehicles have passed crash tests and are in series production. Fire safety is no worse than for gasoline cars, for pressurized air that is not even an issue.

http://video.google.com/videoplay?docid=2671799355409334448&q=erdgasfahrzeug&total=3&start=0&num=10&so=0&type=search&plindex=1
http://video.google.com/videoplay?docid=4578020292507366544&q=ngv+safety&total=1&start=0&num=10&so=0&type=search&plindex=0

@ Jason -

google the DiPietro engine.

@ evolknuj, GoodCheer -

well-to-wheels efficiency is almost certainly worse than for BEVs and possibly no better than regular ICEs. I haven't seen a good side-by-side analysis yet. However, batteries and electric motors are seriously expensive and apart from the noise of the air motor, there are no tailpipe emissions except air and possibly, liquid water (see below).

Note that the exhaust temperature from the air motor may be adjustable via valve timing, I don't know the details of the MDI design. In tropical countries, it may be significantly below the ambient temeperature, which means cabin air conditioning is free. That is a major consideration in e.g. India, where A/C load may account for as much as 20% of total fuel consumed by an ICE engine in stop-and-go traffic.

Ice formation must of course be avoided, but condensation should not be a serious issue provided gravity drains it out of the engine and the exhaust system is not subject to corrosion (note: it may even be made from plastic).

Reply

A company called "Zero Pollution Motors" is going to bring the AirCar to the US. They are not yet taking orders, but you can sign up to be on a miling list :-)

http://zeropollutionmotors.us/

Also, Zero Pollution Motors plans to take the air car into the Automotive X Prize, which should be interesting.

http://xprizecars.com/2007/12/mdi-inc-and-zero-pollution-mot.php

Reply

Yep, the real problem is efficiency. The best industrial compressors which use the heat regeneratively get about 60% efficient. A small compressor like you'd get onboard a vehicle or put in your garage will get 10-15% efficiency at best. Then factor in power generation efficiency (typically 40-50% for modern plants), transmission efficiency (~92%), and drivetrain efficiency (~80%?), and you're left with barely over 4% efficiency. Compare to ~20% efficiency for a gasoline engine.

In short, drive an aircar powered by a home or onboard compressor if you want to *destroy* the environment. Drive one filled by big industrial compressors if you want to make no difference to the environment.

As for safety, yes, gasoline, batteries, and air tanks all contain a tremendous amount of energy. A burning pool of gasoline will take half an hour to consume itself. "Safe" li-ion batteries (for example, A123's "Nanophosphate" or AltairNano's "Nanosafe") don't burn at all in an accident, unlike LiCoO2/graphite "laptop batteries"; their energy is in ion energy states, so you can discharge a lot of energy all at once if there's a short in an accident, but that'd only be an internal short (external shorts would blow out the fuses on the terminals). In an air car, if air escapes, it's going to *really escape, and fast*.

Even if there's no shrapnel, which is very iffy, it's still a tremendous amount of concussion and thrust. 10,000 PSI is three times the PSI of a scuba tank, and the tanks in this car are far bigger than scuba tanks, too. Anyone who's watched Mythbusters has seen what happens when you sever the neck of a "mere" scuba tank (it shot straight through a cinder block wall leaving a scuba tank-shaped hole in the wall)

Lastly, for cost, the only reason it's so cheap is that it's made by Tata. It costs several times what an equivalent size gasoline car by Tata would cost. Personally, I wouldn't even drive a *gasoline* car made by Tata, let alone an air car made by them.

This is not a solution.

Reply

Oh, and I forgot to mention the other dirty little secret of air cars: they lose horsepower the closer they get to empty. So, if the *initial* top speed is 68mph, how fast do you think you'll be going when you're running on an empty tank?

Also, they lose the inherent benefits of electrics (low maintenance (assuming long-life batteries) due to having almost no moving parts, efficient regenerative braking, etc). Oh, and also they often don't make clear when the numbers they give are relying on range extenders, which are often used on the shorter-range air cars (the range extenders basically being fuel burners that heat the air that comes out before it gets to the pistons).

Reply

Meme.. I think you wil be proven very wrong on every point. If you like it or not, Tata will become a world leader very quickly, there is no doubt about it. We in the western world are so blocked in our visons of what and how a car should be that we just don't want to understand that cars can (and have to) be build in a different way as done up to now.
As with any new idea, there are problems and shortcomings, but instead of putting them down, we should learn from Tata and accept the challenge to make it work. But we can't, that's why they have the future and we don't.

Reply

Is absolute efficiency the end all be all we think it is? It seems pretty obvious to me that these vehicles will be cheap to run. How many people in North America have an air compressor in their garage? Nobody is going around and complaining how much these compressors cost to operate. When you go to the mechanic its not like you are hit with a "shop air" levy to run their tools. I don't see any hue and cry about the environmental damage being caused by the abundance of air compressors out there either. Correct me if I'm wrong, but I don't see an environmental case out there against this car that wouldn't also affect our general use of compressed air in all of society.

In terms of range, I would suggest this vehicle be treated much in the same manner as a plug in hybrid. If you charge it up every night, there should be plenty of range for most commutes. Hooking up your portable air compressor to the car for however long it takes to charge the car, likely only a few minutes would likely use no more energy than it would to top up a plug in hybrid.

What these air cars will likely fall short on is elegance. They won't be sporty and they won't be quiet or as refined as we're used to. They will be a good runabout that will be damn cheap to run, a great second car. I just don't see the environmental arguments against them. In my mind, a plug in hybrid for the main family car and an air car for the second runabout car would be the perfect combination....and maybe a nice motorcycle on the side when I feel the need for speed in the summer.

Reply

[quote]Meme.. I think you wil be proven very wrong on every point.[/quote]

Okay, let's start. Efficiency:

1) Prove me wrong that small compressors are 10-15% or less in efficiency
2) Prove me wrong that large industrial compressors generally don't get any better than 60% efficiency.
3) Prove me wrong that modern power plants are generally 40-50% efficient (older ones can get down to 30% efficient, and there are some new proposals that could potentially get up to 60%; we'll have to see).
4) Prove me wrong that transmission losses are generally around 92% in the US.
5) Prove me wrong that 80% isn't a realistic engine to wheel torque efficiency for a piston-driven motor (it's probably a bit kind).

Can't do it? Then deal with the fact that air cars are horrible for the environment.

6) Prove me wrong that air cars magically don't lose horsepower as the pressure in their tanks drops.
7) Prove me wrong that the Mythbusters demonstrated cutting the neck off a scuba tank and it went straight though a cinder block wall.
8) Prove me wrong that a scuba tank has only abouty 3,000 PSI, compared to the 10,000 PSI here.
9) Prove me wrong that a scuba tank is far smaller than the tanks on this car.
10) Prove me wrong that cheap import cars from poor countries are generally lousy. Anyone here remember the Yugo? Anyone here seen crash videos of Chery cars? Here's one for you:

http://www.youtube.com/watch?v=5kQGAK550LE

You think India has *higher* quality standards than China?

Reply

@ MEME
``Anyone who's watched Mythbusters has seen what happens when you sever the neck of a "mere" scuba tank (it shot straight through a cinder block wall leaving a scuba tank-shaped hole in the wall)``

The tank was launched from a long distance from that wall. Sure, the tank in this car will do the same thing if launched from a distance as well. But it`s not approx. 40 feet from the car when you`re driving , unless a trailer is required to haul the tank.

Numbers 7to 9 are now irrelevant to the topic.

`` 7) Prove me wrong that the Mythbusters demonstrated cutting the neck off a scuba tank and it went straight though a cinder block wall.
8) Prove me wrong that a scuba tank has only abouty 3,000 PSI, compared to the 10,000 PSI here.
9) Prove me wrong that a scuba tank is far smaller than the tanks on this car.``

I`m sure others will prove you wrong as well.

Reply

"The tank was launched from a long distance from that wall. Sure, the tank in this car will do the same thing if launched from a distance as well. But it`s not approx. 40 feet from the car when you`re driving , unless a trailer is required to haul the tank."

And it was one third the PSI and a tiny fraction the total mass of air stored, and it shot it across the room like a rocket.

"I`m sure others will prove you wrong as well."

Seing as you didn't "prove anything wrong", I'd love to see that. The mythbusters *did* cut the neck off a scuba tank, it *did* take off like a rocket, and it *did* plow straight through a cinder block wall.

Go on, why don't you. Show me how you think a single part of, for example, the efficiency numbers are in error. Basic googling would tell you as much for those numbers. This isn't some sort of esoteric trivia here.

Reply