Well that's a neat twist on hybrid. I like it. I also wonder if it'll ever be available in Canada.

Compressed air is hugely inefficient!!

To be precise, the efficiency from compressor to wheel of the AIRCAR is calculated to be ~40% according to the following report: http://www.efcf.com/reports/E14.pdf

Whereas the efficiency of BEV from battery to wheel is 80%.

Let's say the air compressor is powered by an ICE with efficiency of about 40%, then overall efficiency of the AIRCAR from fuel to wheel is 40% x 40%= 16%. No improvement at all from the ICE, and a lot worse than the Prius at 37% tank to wheel efficiency.

Regenerative braking is part of the design and they also have some interesting patents for stationary generating of compressed air using renewable, non-polluting resources. The range of the air-only car was the biggest hurdle to overcome, but with the hybrid combustion / air model that problem is solved, altho pollution is re-introduced.

In a hydrogen vehicle the same amount of energy is used compressing the gas, but that energy is completely wasted because the pressure is not exploited in the vehicle, the gas just gets burned. I think many people ignore that energy sink in their calculations of hydrogen powered vehicles.

Compressed-air car concept is DOA in term of range and cargo room and load capacity. Here's why:
1) A carbon-fiber Quantum H2 storage tank for 5000psi of 160 liter weighs 170-200 lbs can contain 4kg of H2, costing ~$2000. 300 liters' worth of air tanks of the same pressure will weigh almost 400 lbs and costing >$4000.

2) 300 liters of H2 in those tanks will weigh 8 kg (17.6 lbs). Air weighs 17 times as much as H2, so multiply 17.6 lbs by 17 = 299 lbs. Adding the weight of air and the weight of the tanks will give you almost 700 lbs! Didn't realize "light as air" can weigh that much, did you?

3) Range: Look into this pdf report, page 9, (http://www.efcf.com/reports/E13.pdf) will give you the fact that the compressed energy of H2 is but 5% of the total heating value of H2. According to ideal gas law, air and H2 when compressed to the same pressure will have nearly the same mechanical energy. The Ford Airstream hybrid FCV can travel 280 mi using 4.5 kg of H2 at an estimated 50% efficiency. If this car uses only the compression energy of the H2 at 80% efficiency, the calculation will be 280 mi /50% x 5% x 8%= 22.4 mi. That is for a tank of 180 liter. For 300 liter compress air storage as in the original AIRCAR, the total travel distance will be 22.4/180 x 300= 37 miles for the Ford Airstream. This is assuming slow speed travel wherein the expanded cold air from each stage of airmotor has the chance to warm up to nearly ambient temperature (near isothermal expansion) At normal highway cruising speed, expect a range of about 1/2 as much, or ~20 miles. Look in theaircar.com for further details, but beware that the number you see there for the AIRCAR's range is for a much smaller and lighter car of plastic construction, weighing but ~1600lbs, and the number is still very much hype!

Now, can anyone justify having an energy storage weighing ~700 lbs costing ~$4000 and can give you a range of only ~20 miles in a typical compact 5-seat family car, with a fuel-to-wheel efficiency of 16%?

Roger -- Thanks for all those numbers and analysis.
I wish that the numbers were not so discourageing because I love the air-car concept. The only hope that I now see is for some breakthrough to greatly lower the cost of the tank. A twenty mile range on a $400. tank would look great to me.

There's certainly a serious efficiency and range concern, but compressed air cars do have some potential areas of advantage over BEVs. The compressed air tanks are simpler and cheaper than batteries and likely have much longer cycle lifetimes and lower self discharge rates. The tanks can also be refilled very quickly compared to most batteries. These could be advantages in very cost conscious markets, like India.

Pure compressed-air vehicles suffer from five problems:

1 - low well-to-wheels efficiency
2 - very limited range
3 - large, expensive pneumatic accumulators
4 - high risk of uncontrolled energy release in a crash
5 - high noise levels

For these reasons, they are probably a dead end as prime mover technology.

The one area where pneumatics could prove useful in a passenger car is in reducing the lag characteristic of turbocharged gasoline engines at low RPM. In that scenario, a compressor (e.g. two-stage centrifugal) attached to the transmission via a wet clutch and planetary gears would recuperate kinetic energy during braking and hill descents. The engine clutch should be disengaged while the tank is filled up. The already present intercooler would be "hijacked" using a set of bypass valves, to increase the air mass stored and, to reduce process temperature levels. When the vehicle needs to accelerate again, it initially receives its fresh charges from this already pressurized tank until it is empty.

The required size of this tank would still be significant, e.g. 40 liters, at 10 bar absolute and 200 degC, since only the first compression stage would be cooled. At this intermediate pressure level, there would be no need to resort to expensive composite constructions. Also, since we're just talking about air not combustible fuel, it might be acceptable to regulators to integrate the tank directly into the chassis to save weight.

With the parameters given, the full tank would contain about 0.3 kg of air. Note that the engine must be fed air at e.g. 2 bar absolute, so a regulated throttle is needed, which cools the air back down. To prevent excessive condensation or ice formation between the throttle and compressor wheel of the turbocharger, the storage tank would have to be insulated and the air stored inside used in short order or else blown off. In other words, the tank will be empty immediately after a cold engine start.

After the first braking maneuver from ~60 kph, the stored air mass would be enough to operate a 2L inline 4 at 1800 RPM and wide open throttle at a boost pressure of 1 bar for ~4.5 seconds. This would permit a lot of low-end torque even as the turboshaft spins up, so the vehicle dynamics would approximate those of a supercharged engine as the driver accelerates quickly up to urban cruise speed. Turbo lag is the primary reason for low customer acceptance of fuel-saving downsizing concepts for gasoline engines.

You could reasonably argue that the same effect, with much higher efficiency, could be obtained with a mild hybrid setup comprising a motor-generator, power converter and traction battery or ultracapacitor bank. However, the pneumatic one outlined above could be a lot cheaper.

Actually this looks like an application of the scuderi Patent which is an internal combustion compressed air engine with phenomenal implications for efficiency see: http://www.theautochannel.com/link.html?http://www.scuderigroup.com/technology/animations/split_sideview.html
for more details on the actual engine. It has the design possibilities to double engine efficiency be it gasoline or diesel and reduce air pollution by 80%.

Compressed air locomotive engines were used in the past, most recently in coal mines, where they were safer then electric due to absence of electric sparks. Nice site for the history (including compressed air bicycle):

http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/comprair/comprair.htm

Hi, does any one know any additional information on the Massive Yet Tiney engine from Angel Labs? Would it fall into the Green Car or engine catagory? It is an engine that is supposed to be able to replace truck and automobile engines but it is many times smaller. The size of the engine that replaces a car engine will be the size of a coffee can. The engine is supposed to run best on soybean oil but it can run on comressed air as well. They have a video showing the engine running on compressed air. The engine supposedly will get some where between 100 to 150 mpg on the soybean oil. Here is a link to one of the sites it can be found on:

http://www.angellabsllc.com/index.html

Is this an engine that could hold lots of possibilities or would it be bought out by big business and then shelved in some big warehouse?

marck

price

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