100 MPG~Now we're talkin Mileage

[mickeyd]

Might be a good commute car.

Zero Pollution Motors is trying to bring a car to U.S. roads by early 2011 that's powered by a combination of compressed air and a small conventional engine.
ZPM Chief Executive Shiva Vencat said the ultimate goal is a price tag between $18,000 and $20,000, fuel economy equivalent to 100 miles per gallon and a tailpipe that emits nothing but air at low enough speeds.

Company looks to bring air-powered cars to US

 

[ziggy29]

The article raises what would have been my first point: How much energy is used to create the compressed air? That's one reason why I think corn-based ethanol was kind of a farce. Once you factor in the energy used to produce a gallon of ethanol from corn (which has like 2/3 the energy content of a gallon of gasoline), you haven't saved much fossil fuel with ethanol -- and you've jacked up the price of food because so much corn production was diverted to making fuel.

Ethanol from switchgrass, as they do in Brazil, is much more efficient per gallon of fuel produced.

That's why it's important to look not only at the ultimate "fuel" source itself, but how much conventional fuel was used to produce it.

 

[Zathras]

It is an awefully innefficient concept.
Directly from the article:

A look at some of ZPM's specifications illustrates the issue. With four hours of charging, the air car's 5.5-kilowatt compressor would eat up 22 kilowatt-hours of electricity. That means the same energy used to turn on 10 100-watt light bulbs for 22 hours would allow the car to travel 20 miles.

So from the wall, 22Kwh to go 20 miles. My EV which I will have in about a month will go about 110 miles on 33Kwh. Almost four times the efficiency (yes, they also claim further mileage as the air compressor will work as the engine runs, but I also get additional energy from regenerative braking).
For a commuter car, EVs using batteries is much more efficient.

 

[growing_older]

When I hear about these compressed air cars, I always think of the warnings from physics class about the cylinders of compressed gas in the lab. The TAs had a photo of a hole in the lab wall from an accident where the valves were knocked off a cylinder and the escaping gas turned the thing into a flying torpedo. I wonder what safety features are necessary to prevent flying compressed air tanks in a crash.

 

[samclem]

So from the wall, 22Kwh to go 20 miles. My EV which I will have in about a month will go about 110 miles on 33Kwh. Almost four times the efficiency (yes, they also claim further mileage as the air compressor will work as the engine runs, but I also get additional energy from regenerative braking).
For a commuter car, EVs using batteries is much more efficient.

I think the efficiency gained while it is burning fuel may be higher than you are estimating. If this is similar to their earlier concept, they claim that it will get 100 MPG when the car is burning fuel. Here's where we discussed this before, complete with some calculations.

It's getting very hard to say one technology is "more efficient" or "more green" than another. First, "green" and "efficient" are only loosely correlated. Then, one person's "green" is another person's "environmental disaster." Then, there's "mission profile:" there's no true "in use" MPG number for a car (plug-in electric hybrid or compressed-air hybrid) that goes the first 30 miles before it starts burning fuel.

For most folks with access to natural gas, it appears to be the cheapest source of energy (calculations at above link, though gasoline was $4 at that time--and probably will be again). But the devil is in the details--how far you'll typically drive every day, efficiencies of all the conversions that will be needed to move the car, etc.