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46 comments on The Air Car Part 2 - Q & A With Louis Arnoux of IT-MDI
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Gav,
Thanks for your interesting articles on the MDI Air Car.
Whilst there is a lot of criticism about the compressed air storage on the vehicle, and the limited range, when used in autonomous mode, I believe that Louis Arnoux is shifting the project emphasis towards the external combustion mode.
External combustion engines are not new, they include steam and hot air engines. They predate the internal combustion engine by centuries, but it was not until Newcomen's reciprocating atmospheric steam engine of 1712 before they really got moving.
Air engines include Stirling engines, Ericsson engines and engines that use the Brayton and Joule thermodynamic cycles. All of these predate the IC engine.
The MDI engine is best describes as an open cycle Ericsson engine, and relies on the fact that it takes less work to compress air at a low temperature, than is produced when the air is expanded at a higher temperature. The energy need to produce the higher temperature comes from burning a conventional hydrocarbon fuel.
The simplest Ericsson engine consists of an air compressor, a tubular heater - heated by a burner, and some sort of expansion device, which can be rotary expander or reciprocating piston in a cylinder. The output shaft of the expander is mechanically coupled to the compressor shaft. The exhaust is slightly heated fresh air at above atmospheric pressure - ideal for force-draughting the burner.
There is theoretically no need for the storage of the compressed air, compressor and expander can work as a heat engine without it.
It does however, offer an energy storage buffer and would allow the air engine to run more efficiently when powering a vehicle under widely varying load conditions. It also allows a certain amount of vehicle autonomy before you have to light the furnace heater.
The key advantage of air engines is that the source of heat can be derived from burning any available fuel - not restricted to common liquid or gaseous fuels, but solid fuels, biomass, firewood, woodchips, biogas etc.
Using a solar concentrator, an air engine can derive its power from focussed solar energy. Ericsson himself, demonstrated a solar driven water pump in the 1880s.
The efficiency of the air engine is questionable, however. It is likely to fall in the range of 10% to 20%. So it does not make good sense in a vehicle application, where you end up throwing away 80% of the energy contained in the fuel as waste heat.
A better application would be domestic combined heat and power or micro-CHP, where at least the energy rejected by the engine can be used for home heating.
Some European manufacturers are already developing CHP products based on external combustion engines.
This sort of technology would pair well with waste digestion or biomass gassification. Its likely you could have the engine in your garage and batteries in your car or bike. The engine would operate during peak times providing you with all the heat you needed, then the batteries would charge overnight from off peak electric / wind.
Using wind to power air compression directly without generating electricity is an interesting idea,
these guys http://www.generalcompression.com have a good idea, but I see a smaller domestic model. Would be cheaper than an electricity generating turbine, and the pressures/ volumes would be much reduced compared to the larger system.
I like this ericson engine -if it is real. That sort of efficiency would be a good match to a hybrid vehicle, which is what the descibed air-car strongly resembles. I too doubt the energy storage efficiency of compressed air, the stated 10-20% number seems to be in the right ball park. Of course if this "ericson engine" is real and practical it could be used to charge the batteries of an electric hybrid. This would likely be more costly, but would give outstanding fuel economy.
I'm pretty suspicious of this whole venture however. I could make arguments like if it is such a good idea, how has it been around so long without a product? That line about "advanced magneto-caloric quantum effect" strikes me as pure garbage (I have a degree in astrophysics) -if they actually made that statement, I would consider this to be almost certainly an investment fraud.
Yes they did use the phrase advanced magneto-caloric quantum effect. Look in the last paragraph of http://www.itmdi-energy.com/information/solutions.html
I received responses to my follow up questions from Louis :
Question:Tata have been reported as saying it will be at least 2 years before they produce an air car. Do you expect to get to the market before Tata ?
Question: Could you give me a "roadmap" outlining the dates of the product releases you are planning and a brief description of each product. I think some of the confusion generated by the press coverage is due to a range of different products being described without any clear differentiation between the different versions.
Question: Can you describe the target market for the power generators you plan to manufacture first - and the expected capabilities and price for these ?
Question: Can you describe how the external heat source is integrated into the design and how the multi-fuel version increases the range of the car?
Question:Can you describe how the engine is used in refilling the air tanks both in a stationary and mobile mode?