The Air Car

[Charlie99]

Only 6 miles of paved roadway on our little island, and that encompasses 99% of the places I drive (I'd just ride a bike if the weather were better...). Perfect location for an alternative energy vehicle...maybe I should just convert my minivan to battery power.

-B

But what generates your electricity? If you are on a remote island that gets its electric power from a diesel generator, then going to battery power doesn't gain you much, if anything. OTOH, if your local electrical grid is wind or hydro power, then going electric is a nice green solution. Another possibility is a conversion to propane or CNG. Internal combustion engines can be converted over to propane without outrageous expense, and the emissions are lower than with gasoline.

The base problem with air powered vehicles is that the energy storage/weight is about the same as what you can get out of electric batteries and the the compressor has lower efficiency and more complexity than charging batteries.

 

[ronbeau]

Much better info here, the site for the US group:

Zero Pollution Motors - Air Car

-B

I would wonder how well it would work with the "mild" winter temperatuires in your home town.

 

[Charlie99]

The air car has been getting good press for several years now. Typical articles are like this January 2004 CNN article: Fresh air driving

MDI was going to be selling the MiniCat version of the air car starting late 2004, with a price tag of $6,500. Never happened.

That is typical of other articles, where MDI claimed that everything was set and production would start anywhere from 6 months to 24 months from when the interview was taking place. It doesn't matter which year the interview was --- production was always in the next year or two.

I've been trying to get an idea of the energy efficiency of the energy storage cycle of compressing the air and then later using it to power an air motor; and also to get some good numbers on energy storage density (watt-hours/kg and watt-hrs/liter) to compare to electric vehicles. So far, particularly with the need to dump the heat of compression since the composite tanks can't be used at high temp, both the efficiency and energy density look to be inferior to even old lead-acid version of the General Motors EV1 electric car of the late 90's..

 

[Speargirl]

Well I for one would love to have one of those cars, but like you said they have been working on this forever so my chances are slim to none at this point I would think.

 

[The Anchor]

It seems to me like they are trying to invent the wheel a little bit. Air powered motors look to be very similar to steam poered motors. Insrtead of using heat to generate steam, they are using air stored in bottles to do the same job. A nice green alternative would be to use diesel (cleaner to refine than gas/petrol) in a boiler system to heat water and run steam cars.

Back when the car was first produces, before the assembly line took over, there were a number of steam powered cars as opposed to the internal EXPLOSION engine. The problems with them were not mechanical, but rather safety and technological. The reason not just anyone could drive a loco was because it requires precise monitoring of water levels in the boiler, pressure, and heat to make the engine run. You cant just "floor" it or the pistons will lock open.

THe other problem is that boilers can pose a very serious explosion hazard. While a safety valve does keep the pressure manageable, you still need 2-300 pis to be effective at driving a vehicle, and that 200-300 psi can be quite leathal if it were ruptured in an accident.

Then there is the problem of the diver beeing "cooked alive" before any rescuers could pull him out. On the other hand, it could serve to make drivers more safe...

 

[Charlie99]

To put the MDI Air Car system into perspective, the storage system is 330 liters internal volume, 300bar which is about about 90 cubic meters (90,000 liters) free gas volume. In imperial terms, thats about 3200 cubic feet at 4500psi. In the promotional literature they say that a fill at a service station will take only 3 or 4 minutes. The ultimate "hot fill".

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Air-powered locomotives were used in many mines in the 1920's and 1930's. They had the advantage of being less likely to set off a mine explosion. Google "H.K. Porter locomotives" for more info. They were typically 2 stage engines, with a heat exchanger between the stages to bring back up the air temp of the air (kind of like the reverse of the interstage coolers of multistage compressors). Relatively short range, but they were typically designed for a very specific run length and load -- usually just a couple of miles.

Interestingly, Rix shows up as another designer and manufacturer of air-powered mine locomotives --- the same Edward Rix that designed some of the compressors popular for filling scuba tanks.

There were some European mine locomotives also. Designed in the 1930's they expanded on the HK Porter designs by adding a 3rd stage -- increasing the efficiency a bit.

MDI has gone a bit beyond just re-inventing the wheel. Their engine does a neat trick of having one chamber that compresses air, thereby heating it, and then they blast in a bit of air from the storage tank, which will be quite cold from expanding. This trick recovers a bit of the energy lost in the interstage coolers of the compressors when first compressing that air. The DiPietro rotrary air engine appears to be the equivalent of a 6 stage engine, which is why it has better efficiency than other air powered engines.

 

[Charlie99]

Well I for one would love to have one of those cars, but like you said they have been working on this forever so my chances are slim to none at this point I would think.

I've done quite well investing in several startup companies, so I don't reject things out of hand. Unfortunately, in this case my due diligence investigation keeps showing up false/inflated claims, more puff than substance, the sort of secretiveness that is associated with most perpetual motion inventors, and lots of missed deadlines and targets.

The air car seems to be a bust, but it has led me into finding some interesting stuff on micro co-generation systems or micro CHP. Basically a Honda stirling engine is powered by the waste heat from a residential gas heating system. Nowhere near as sexy as an air car, but it is the sort of thing that has the potential of becoming very common as there is a solid economic benefit behind it.

Welcome to freewatt — the future of home energy is a prepackaged micro CHP system that uses the Honda stirling engine.

 

[Brandon]

I had a similar idea for heating a greenhouse - wrap copper tubing around the exhaust stacks for our fuel oil boiler and propane hot water heater, then circulate the liquid with a small pump to a radiator in the greenhouse. Energy is expensive, no sense wasting it!

This month's electricity bill was .52 cents a kWh... I'm starting to wonder if I can just buy my own diesel generator and generate power cheaper than the city can...

-B

 

[justleesa]

would solar energy be worth having in the Summer in AK?

Our water heater is solar....works pretty good (just the tank is a bit small for such a big house hold)

 

[Brandon]

Solar might be worth it in some parts, I really don't know for sure. The northern latitudes are usually worst for solar energy, and we just don't have that much of it. Certainly not with any regularity out here in the Aleutians...