The Tata AirPod: a car that runs on compressed air w/150-200km range

http://stoweboyd.com/post/29621528557/the-tata-airpod-is-a-city-car-running-on

by masnick • 14 years ago

126 77 14 years ago

That's pretty awesome, though I wonder how they achieved that efficiency from simple compressed air (surely a pack of Li-Ion batteries of the same volume would do better?).

Regardless, you can compress air yourself all day long using solar panels and/or wind turbines, and even if you use the grid, it'll still come out a lot cheaper...

_delirium• 14 years ago

The proposed benefits seem to mainly be in the ease of deploying the recharging infrastructure, not greater efficiency. Here's a paper that's skeptical of the overall efficiency: http://iopscience.iop.org/1748-9326/4/4/044011/fulltext/

podperson4• 14 years ago

Interesting paper, and it suggests some other possibilities, including a Pneumatic/Combustion hybrid (i.e. using a compressed air "flywheel") which seems to have greater benefits than an Electric/Combustion hybrid (a tank of compressed air is lighter than batteries).

Perhaps Tata is experimenting with an electric/pneumatic hybrid (so electric, but compresses air when braking, and consumes it when accelerating). This might work, but doesn't help with infrastructure rollout.

nsxwolf• 14 years ago

Mechanical simplicity and no expensive batteries are pluses.

typicalrunt3• 14 years ago

I agree with you, to a point. I wonder about the mechanical simplicity of having air drive pistons in the engine. It's yet another point of failure and, while similar to combustion engines, is there no other way to have compressed air drive a car other than with a piston engine?

I'm probably being naive here...I have no knowledge on this subject.

ajcarpy20052• 14 years ago

You could use a Quasi-Turbine. http://www.howstuffworks.com/quasiturbine.htm

kragen2• 14 years ago

There are a lot of different ways to have high-pressure gas push solid objects around. Piston engines, turbines, and rockets are the three most common, but there are also Wankel engines, rotary vane motors, and more exotic designs like the Quasiturbine and the dozen or so other kinds of positive-displacement pumps.

debacle• 14 years ago

It looks like this is getting completely owned by HN. Does anyone have a mirror?

andypants• 14 years ago

I doubt it, it's hosted on tumblr. It handles far more traffic than HN.

typicalrunt3• 14 years ago

I love this idea, especially for short city-style commutes. The price ($10k) is good enough that it's under my impulse buying threshold for cars.

My only worry (confusion?) is if I brought this car into a small town and the car runs out of air, where can I fill it up? Can I just go to any car-repair shop that has a compressed air line (e.g. for hydraulics) and use their equipment?

arethuza2• 14 years ago

What would be interesting is if it could carry a small electrically powered compressor that you could plug in for emergencies.

ajcarpy20052• 14 years ago

I think this is exactly what the electric motor does: compress the air if you run low.

jherdman• 14 years ago

> The price ($10k) is good enough that it's under my impulse buying threshold for cars.

I'm not even sure where to start with this.

qq66• 14 years ago

Not really that weird at all. Cars maintain a healthy resale market so if you buy a car with a couple of owners and a lot of miles for $8,000 and drive it for a few months, you can often sell it for the same, or just a little less, than you paid for it. It's not an $8,000 gamble, it's more like a $500 gamble.

typicalrunt3• 14 years ago

I hope it's just my wording that is throwing you off.

Say, for instance, you need a car. For me, if a car costs more than $10k, I really have to think about how reliable it is, what features it has, and generally if I am getting value for my money. This is all because anything over $10k is going to take longer for me to recoup. This is what I'm defining as my impulse buying threshold.

ams61102• 14 years ago

Your impulse threshold is about 3x my ceiling price for a car.

davidarkemp2• 14 years ago

Most petrol stations in the UK have an air compressor that you can use to top up your tyres. I wonder if these could be re-purposed.

masklinn5• 14 years ago

I'm pretty sure you don't top up your tyres to 20MPa (~200 bar)

aakil• 14 years ago

These would be great for city travel. The two main issues would be safety and parking. They'd have to make a strong case for the vehicle being safe in the case of an accident, not unlike the challenge the Smart Car had. For the issue of parking it would be unlikely that a city would set aside real estate just for these cars as they'd have to do it all over the city and it would be relatively expensive. I think a better solution would be a car-sharing one like Zip Cars. I can pay a monthly fee to have access to the cars at certain spots and if I want to leave in rush hour, I'd pay a premium, or something to that extent. It's a really interesting idea, I live in NYC and I'd love it here.

evan_• 14 years ago

Did I miss something, why can't they use normal parking spaces?

ta12121• 14 years ago

I assume because the cars need to be charged while parked so you can get home.

GFischer• 14 years ago

I hope this works - a compressed-air bike design from here (Uruguay) from 2005 failed to be funded, probably because the inventor was a bit of the crackpot type, but it did work.

http://www.practicalenvironmentalist.com/eco-gadgets/air-bik...

http://www.youtube.com/watch?v=05kQHmXfcQw

mrspandex• 14 years ago

> a city car running on compressed air (as well as a battery-powered electric motor)

The range sounds implausible to me at any reasonable speed on compressed air alone. How is the electric motor involved? Is the air a backup for the battery or vice-versa?

anovikov3• 14 years ago

this is a scam which has been explained a lot of time. energy storage density of compressed air is extremely small and will be enough for only a few miles of range, no way for improvement here, and efficiency is very, very low, way lower than batteries because of the energy inevitably lost when the gas heats due to compression, then dissipates heat. forget it.

peteretep• 14 years ago

And yet Tata are a huge, well-known international.

If they say they have an air-powered car, they have an air-powered car. This isn't just some dude in their garage.

rglovejoy• 14 years ago

So what if it's Tata? They may be a huge, well-known multinational, but the laws of thermodynamics apply to them too.

masklinn5• 14 years ago

The car apparently also has an electric engine. Did tata actually say the car ran on compressed air for the range specified in TFA, or is it just TFAA bullshitting?

Because AFAIK the effective energy density of CAES (Compressed Air Energy Storage) is 40~100kJ/kg depending on the tank material, with variable pressure. The upper range is roughly that of a standard lead-acid battery (except the battery has roughly constant voltage) and it gets completely blown away by e.g. li-ion (360~900kJ/kg)

shortlived• 14 years ago

Do you have any sources for the technical arguments to why this is not feasible?

Someone• 14 years ago

http://www.combro.co.uk/nigelh/diver/tank.html claims about 1/3 kWH in a 230 bar 12l scuba tank. http://www.tinaja.com/glib/energfun.pdf claims 17 Wh/l for compressed air (without mentioning pressure, but that is in the same ballpark if is 150 bar, as I guess from the text).

Let's be very, very generous and put a cubic meter of compressed air in that car. That would be, rounding up at every step, 30 kWh of energy in the air. If you manage to transfer all of it to your wheels, a small engine might run for an hour on that (http://en.wikipedia.org/wiki/Tata_Nano has a 28 kWh engine) at full speed.

So, with lots of hand waiving, this seems doable, if you are willing to build a 1000 liter tank for this thing, and manage to keep the car and its tank within the Nano's weight. With a more realistic but still IMO very generous 250 liter (about twice the Nano's trunk), you already are at least a factor three of (rounding generously as in every step before). Oh, and did I mention that that Nano will drive about 50 miles in that hour, if driven at full speed, not the 125 claimed?

CamperBob2• 14 years ago

If for no other reason, consider the amount of energy that would be released if a tank with enough compressed air to propel an automobile for 50 miles were released in a collision over the course of a few hundred milliseconds.

Say the energy output is equivalent to running a 50-horsepower engine for an hour. 50 HP-hours = about 35000 watt-hours, or 250 megawatt-seconds (MJ).

A stick of dynamite produces about 2 MJ. So that tank of compressed air, if it ever ruptures, will yield the equivalent explosive power of more than 100 sticks of dynamite.

Gasoline is a safe way to store this much energy because a tankful of gas can't be oxidized rapidly enough to do much damage, at least not by accident. Same is true for hydrogen. But compressed air, where the released energy is purely mechanical, is a bit more interesting.

Never mind the extremely high thermodynamic losses associated with compressing (and expanding) that much gas. They're probably on the same order as internal-combustion efficiency, or lack thereof.

Sorry, but the physics just don't work as far as I can see. It really does smell like a scam.

forgottenpaswrd• 14 years ago

It looks lame, like the Segway.

This seems to be the official teletubbie's car.

People wants something more akin a kiss ass compress air-electric kart to move in the city. Something simple, that does its job well, and fast when you need to accelerate in a hurry.

Cars are empty in the cities most of the time, make them unipersonal.

codegeek• 14 years ago

"Something simple, that does its job well"

Exactly. And isnt it what this thing is trying to do ?

jgrahamc• 14 years ago

The company behind this invention has been talking about the roll out of these cars for many, many years (http://en.wikipedia.org/wiki/Motor_Development_International). And this particular blog post doesn't give any details of when Tata is going to actually produce a car. I recall a long time ago that these cars were going to be introduced in Mexico (that was one of many things that didn't happen).

Wikipedia has good articles on compressed-air engines and cars. Here: http://en.wikipedia.org/wiki/Air_engine#Automotive and http://en.wikipedia.org/wiki/Compressed-air_vehicle

Tata has been a licensee of the technology since 2007 (http://www.gizmag.com/tata-motors-air-car-mdi/22447/). When they go into production it will be interesting news.

ChuckMcM5• 14 years ago

This.

So back in 2007 I saw that Tata had licensed the technology for using the air-motor in its cars. As an infrastructure guy I thought "Hmmm, if this stuff works, I could use it in a data center." So I tried to do that.

Here was the plan, using a windmill you could compress air, it's a pretty simple mechanical linkage, run a pump off the rotating vanes, has been done for hundreds if not thousands of years. But instead of water, you pump air into tanks. This generates heat because you are compressing the air of course but its windy so you've got heat sink vanes in the air flow being cooled by convection. Now at some point your data center wants a bit more juice, so you dump air through these MDI engines, which are running electrical generators. But here is the thing, when you dump the air it gets colder, a lot colder and the pipes can freeze up, but this is a datacenter and you run the pipes through the data center and cool it epic win! Power and cooling for free, the more power you use the more cooling you get, how neat is that?!

Except there was no amount of money I could give MDI in exchange for engines. They don't make the engines, they don't have a plan to make the engines, they won't let someone build the engines and sell them at a profit because they won't license them to do so. I was a classic case of an inventor being so unrealistic about what the value of their invention is, they prohibit the creation of a market around it.

The trick is that markets have choices, and an air engine would be a good choice, but not if it is not cost competitive with high efficiency diesel, or cheap (and dirty) two stroke gas engines. After I gave up (by mid 2008) trying to get them to see the error of their ways I figured it would be 20 years until we saw a credible use of this technology because all the patents would finally expire, and people would start to make them, and probably curse the folks at MDI for their short sightedness.

Moto7451• 14 years ago

Taking your idea a step further... When I did an internship at an architecture studio, the design of the central plants that provide hot/cold water/air to their surrounding buildings would use the exhaust heat of say, a water chiller for the air conditioning unit, to help heat the hot water flow, taking load off of the water heaters. In one case, they had enough "excess" heat available from doing this that a school got a heated pool for "free."

You could do the same thing with the exhaust heat from the compressor to heat the restroom water for the data center's bathrooms.

Not exactly super exciting to most, but for whatever reason I think stuff like this is the coolest thing ever.

ars7• 14 years ago

> Power and cooling for free

It's not in the slightest free. If you attached your windmill to a regular electrical generator, then used the electrical power as needed, plus a standard A/C you would come out ahead vs first compressing air, which is very wasteful.

The reason it's so wasteful is the "you've got heat sink vanes in the air flow being cooled by convection". You are throwing away energy there.

DaniFong3• 14 years ago

Hi Chuck,

If you're still interested in a real company that's building highly efficient air engines (compression and expansion) for this, and other purposes, send us a message. We have a legitimate approach and will, in fact, sell people things to work real applications. We've been in talks with the big guys to power their data centers. But you could be among the first.

dfong@LightSail.com

PonyGumbo• 14 years ago

These have been cooking for a long time. I was on the MDI mailing list back in 2000/2001 when they were supposedly coming to market the following year. It's cool to finally see them in production - I thought it might never happen.

fpp• 14 years ago

Great when they finally will start mass producing this technology - perfect for large cities in India, Argentina and Brazil e.a where already lots of small vehicles run on compressed natural gas (CNG).

BTW - This story has been all over the I-Net the last days (again). A link to the actual manufacturer / technology company behind that. http://www.mdi.lu/english/

If such energy storage technology becomes available at low prices lots of additional "synergies" can be envisioned - e.g decentralized & cheap storage for small solar power (e.g. 50KW) - seen some DYI solutions for that with compressed air - overall the issue with compressed air storage is the low energy density.

ars7• 14 years ago

CNG and compressed air are quite different. One burns to provide energy, the compression is just for storage. The other uses the compressed air as the power source.

They are not interchangeable, and having one doesn't help you with the other since the pressures are so different.

z922• 14 years ago

I wish they published energy storage capacity in KW-hr. Theoretically a car can run for infinite distance once it has been accelerated to its desired speed.

mpyne• 14 years ago

No, a car can't run for infinite distance even once at its final speed, unless you're talking about the kind of theory that doesn't involve friction, drivetrain losses, aerodynamic resistance, or even things as simple as having a radio turned on (not to mention headlights)

eavc• 14 years ago

You forgot to account for the ramjet.

z922• 14 years ago

Sure. These are practical things. And practically it can't.

starpilot• 14 years ago

Theoretically an electric circuit can operate with zero heat output using perfect conductors.

podperson4• 14 years ago

Leaving aside the laws of thermodynamics, well-to-wheel efficiency, etc.

Imagine getting stuck in traffic in such a car. What powers the A/C?

giardini• 14 years ago

That's easy - the expanding gas!

Releasing pressurized gas absorbs heat so simply running the released gas through a set of A/C coils would provide indirect A/C or you could merely vent the "exhaust" (it is air, after all) into the passenger compartment since that "exhaust" should be very cold.

podperson4• 14 years ago

It's a cute answer, but very inefficient. You're throwing away the mechanical energy. Also bear in mind that "refueling" with compressed air will heat up your car.

ams61102• 14 years ago

Releasing pressurized gas is cold when there is a phase change, i.e. from liquid to gas. Going from high pressure gas to low does involve a temperature drop but it's not going to be anything like a real air conditioner.

Refefer• 14 years ago

What happens in a car accident? I can't imagine the sudden expulsion of all that compressed air is going to act like anything other than a small bomb going off.

masklinn5• 14 years ago

Some sort of quick-release valve as with LPG?

Not sure it's sufficient considering the kind of pressure you'll need in the tank to store an amount of energy worth using.

ars7• 14 years ago

It's not hard to make a tank like that strong enough for a car accident. It already needs to be very strong just to handle the pressure.

jimgardener• 14 years ago

search http://www.tatamotors.com/search.php?query=airpod shows 0 results !!

The Tata AirPod: a car that runs on compressed air w/150-200km range

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