

The Tata AirPod: a car that runs on compressed air w/150-200km range - masnick
http://stoweboyd.com/post/29621528557/the-tata-airpod-is-a-city-car-running-on

======
jgrahamc
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.

~~~
ChuckMcM
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.

~~~
ars
> 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.

~~~
ChuckMcM
You are pedantically correct sir, but there is a larger context. So in that
larger context I was working on this plan when working for a company that had
a data center near the Columbia River and 'industry leading' PUE numbers.

Generally when the wind was blowing (and it blows a lot along the Columbia
River Gorge) there is no need for additional cooling. When there is no air
movement and the outside temperature is high, the demand for cooling increases
requiring a more 'active' engagement (sorry but I can't be more specific than
that).

So realistically I was looking to time shift the excess cooling capacity that
was available during windy times to the times when there was little wind and
excess heat. Compressing air has some advantages in that the amount of energy
you can get out vs the amount you put in is comparatively efficient to battery
power, and using / exploiting the cooling effect of the expanding air, and the
kinetic energy of its expansion to generate electricity, was actually more
efficient than other methods. Maintenance burdens were also lower and
municipal permitting was made easier by the lack of 'dangerous' chemicals or
catalysts.

These advantages are perhaps uniquely suited to data centers. Of course I
didn't get to actually build it because MDI wouldn't participate. That was too
bad but certainly well within their rights.

~~~
ars
Essentially what you are saying is that your want to (also) store cold rather
than store just energy.

I'm not convinced it was worth it. You anyway are collecting energy from the
wind, and instead of storing it as energy you stored (part of) it as
(potential) cold.

But in order to do that you threw some of the energy away - I suspect that if
you stored all the energy directly, and then created the cold on the spot as
needed you would have higher efficiency.

If I did want to store cold I would not do it using compressed air, I would
use a water tank - cool the water to ambient (no active cooling, just some
pumping) then dump heat into the water when necessary.

~~~
ChuckMcM
Perhaps when I get a chance to build my own data center for Blekko I'll be
able to actually run the experiment [1]. Then I'll have a better answer. But
would like to share a bit my reasoning.

You are correct that my concept 'threw away' the heat generated by compressing
the air. However, since any energy stored at all was collected from a
previously unharnessed source (the wind blowing past the data center) it might
be more accurate to say that it would not collect all that it 'could'. But
here is a very important distinction, the heat from air compression is 'low
grade' heat, which is to say the delta between it and ambient is small enough
that harvesting it in meaningful amounts is quite difficult. You also need to
consider that this thing is operating next to a data center which is running
an evaporative cooler 24/7 to pull excess heat from inside the box and dump it
into the air outside the box. Basically spending energy to move the heat
outside.

So from this side of the screen, to accept you point that not capturing the
heat generated from compression was 'throwing it away' I would need to have
some credible way of utilizing the captured heat.

Looking at it from the overall energy exchange picture, you've got the kinetic
energy of the wind, with is 1/2mv^2 where m is the mass of the wind moving
pass the windmill. Some percentage of that you convert to mechanical energy
which runs the air pumps and some of that becomes heat in the bearings and
linkages. The mechanical energy then compresses the air which by the ideal gas
law goes up in temperature proportional to the change in volume. Just sitting
there, the tanks holding the air cool off, losing this heat to the surrounding
atmosphere. We could insulate the tanks to keep it inside (and pressures up)
but it turns out that we'd like to harvest heat energy out of the data center
later so we let this heat leave by convection. The tanks then go down in
pressure thanks to that same ideal gas law.

So when we use this air, we decompress it inside our data center. This allows
heat in the data center to be absorbed by the expanding air, which saves us
the energy we would have been using to run the evaporative coolers to pull it
out and increases this energy available in the air as it increases that static
pressure differential between ambient and the decompressed air. So we 'get it
back' as it were, in a positive way. Running it through the engines allows us
to then harness the pressure differential, and if it comes out of the engines
still 'colder' than the data center air we can inject it right into the
regular atmosphere of the data center to offset warm air that is already
there.

[1] Facebook also has a data center up there in the region and if someone
there wants to pick up the ball and run with it that would be pretty cool to.
You could write it up for the open compute stuff. Of course you still have to
figure out how to get an MDI engine. If Tata ever shipped I considered buying
cars, throwing away the body and just pulling out the engines. That would work
but requires Tata to actually have a product you can buy.

~~~
pyoung
This is an awesome idea by the way. I work in the energy industry and haven't
heard about anything like this.

Just curious, it seems like with prior art, MDI would not have exclusive
rights to the motor, right? Also their Wikipedia page says that they are
currently using a design that was patented in 1990. Did you abandon this idea
because of patent issues, or was it merely the lack of access to a
proven/tested motor that stopped you?

~~~
ChuckMcM
It was getting reasonably efficient compressed air motors of decent size. The
MDI docs claim they do about 50hp (or about 37kW). You'd probably want five or
ten 'units' at that level (assuming the data center is 10 or 20MW like the
ones Apple, Facebook, and Amazon have built).

You can of course run an existing steam engine on air pressure (I've done that
with models) but they are optimized for a higher static pressure than the MDI
engines target.

------
anovikov
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
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.

~~~
masklinn
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)

~~~
anovikov
worse than that, 'charge-discharge' efficiency is terrible compared to any
kind of battery. it won't save any energy vs conventional car as measured in
well-to-wheel efficiency.

~~~
masklinn
Yes absolutely, I wasn't putting that in because the case was damning enough
without involving the energy loss in charging the thing.

Though the comments suggesting the electric engine is a compressor to "refill"
the bottles on the go could need that reality check.

------
mrspandex
> 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?

------
fpp
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.

~~~
ars
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.

------
GFischer
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.practicalenvironmentalist.com/eco-gadgets/air-bike-shoots-
around-for-15-miles-per-penny-but-unfortunately-looks-kooky-and-dangerous.htm)

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

------
jakeonthemove
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
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/>

~~~
podperson
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.

~~~
masklinn
> a tank of compressed air is lighter than batteries

Joule for joule, it's not. The _best_ compressed air tanks you'll find roughly
reach lead/acid batteries in energy/weight (~100kJ/kg). Lithium-Ion batteries
have 4 to 9 times the energy density.

~~~
podperson
Indeed. Also the mechanism to capture compressed air when braking would be in
addition to the electric motor, which is needed in any event, and can charge
batteries when braking. So yeah, upon reflection, just a Bad Idea.

------
typicalrunt
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?

~~~
jherdman
> 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.

~~~
ams6110
Your impulse threshold is about 3x my ceiling price for a car.

~~~
rorrr
If your ceiling is $3333, maybe you should stick to riding a bus. Do you
realize how much it costs to run one car for a year? Gas, registration,
insurance, oil changes, maintenance, it adds up pretty quickly.

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

~~~
ta12121
I assume because the cars need to be charged while parked so you can get home.

------
nsxwolf
Mechanical simplicity and no expensive batteries are pluses.

~~~
typicalrunt
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.

~~~
ajcarpy2005
You could use a Quasi-Turbine. <http://www.howstuffworks.com/quasiturbine.htm>

------
Refefer
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.

~~~
masklinn
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.

------
PonyGumbo
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.

------
podperson
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
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.

~~~
podperson
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.

~~~
rfugger
The system overall may be inefficient, but using the cold exhaust from the
engine as A/C doesn't make it any more inefficient.

~~~
kragen
In fact, if the air conditioner coils are between the air tank and the engine,
the air conditioner could make it _more_ efficient, if you don't have some
other kind of regenerator-in-a-dewar trick going on.

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

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

------
z92
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
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)

~~~
z92
Sure. These are practical things. And practically it can't.

~~~
vibragiel
Friction forces have been core theoretical concepts since many centuries.

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

------
forgottenpaswrd
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
"Something simple, that does its job well"

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

