Stirling engine combined within car engine

[simoncowley]

Hi, I am interested in the Stirling engine and its applications. i
was wondering whether it would be possible to apply this within a
normal car engine to run ancillary components (air con/power steering
pump etc) and whether this would have a positive effect on MPG
achieved? Would it be possible to use the heat from the exhaust or
hot water before the radiator to provide the heat, then the cooler
water after the radiator for the cool side?

thanks

Simon

[stan.hornbaker]

This would be a marvelous way to power the air conditioning, power steering, etc. IF it could provide the power needed for them.
There simply isn't a sufficient temperature difference and quantity of heat available to run a practical Stirling engine.

[simoncowley]

Hi, thanks for your response. out of interest what amount of heat and heat difference do you feel it would require to run these kind of components? i would imagine they would need to be run at 1500-2000 rpm. would a use of a heat exchanger on the exhaust be any good? or maybe using the a/c indeed to cool as well to further the difference?

thanks

simon

[stan.hornbaker]

Power producing Stirling engines run at well over 1,000 deg F. on the hot side and as cold as possible on the cool side.
A heat exchanger is usually a necessary evil used to separate counterflowing streams of liquids/gasses. It would be better to apply the exhaust gas directly to the hot cap of the Stirling rather than via a heat exchanger.
Using the Stirling to cool its self would be self defeating and verges on perpetual motion IF it were possible.
You would need 1 to 2 HP or approx. 3/4 to 1.5 KW output.

[cdematas]

I actually think this is a good idea. The exhaust gases should have a sufficient temperature difference. While the power generated would be low it would save some fuel. For cooling maybe a Stirling/Stirling combination of engine and heat pump would work. The Stirling machine may not provide all the power needed but could be a part of the cooling system.
Another alternative is to generate electricity to help recharge the battery.

[stan.hornbaker]

A rather bizarre set of suggestion. The waste heat from the ICE would not be adequate to provide much if any power to charge the battery. What do you think the alternator is for?

Using a Stirling engine to drive a Stirling cooler results is a loss of energy and gains nothing.

And as above why complicate the system by taking a circuitous route to charge the battery?

In other words you eschew simplicity if favor of making everything complex and wonderful in order to somehow use a Stirling engine.

Don't forget the 2nd Law of Thermodynamics hasn't been repealed.

[dplconsulting]

A huge amount of the energy used to do work in an ICE is lost, either through cooling or out the tailpipe. Obviously, if one could economically recover a portion of that energy, what was a net gain to the oil companies and a loss to the consumer becomes the opposite.

The key here is, "economically" which is related to, but not the same as "efficiently." As long as there is an energy recovery that can b put to net beneficial use, and the value of that recovered resource exceeds the cost of doing so, the laws of economics trump the laws of thermodynamics.

Remember, it's about the conservation of capital, not the conservation of energy. Otherwise, we would all be burning coal.