Could you use liguid nitrogen to freeze the cold side of the engine?

[kelly__mcdougall]

Or would the liquid nitrogen just break the metal

[stan.hornbaker]

Could you? Yes. What would be the point?
The cost of the ln2 would exceed the gain in improved operation of the Stirling engine. This is NOT a viable option.

If you used a Stirling engine to drive a Stirling cooler applied to the cold side of the engine you would have a PM machine. That won't work either.

[davdbarry]

Well the answer is yes of course. However the other respondent suggests that there would be
no advantage because of the energy cost of producing liquid nitrogen. That is only true if you
dont regard making liquid nitrogen as a way of STORING energy. Look up "liquid nitrogen
economy" in wikipedia. You could use liquid nitrogen to cool a Stirling engine that was
running off the ambiant temperature in the air. The liquid nitrogen would boil, turn into gas,
and expand through a microturbine.

The engine would then be recovering energy that had been used in making the liquid
nitrogen...

[stan.hornbaker]

To understand the viability of any system you must take into account all parts of the system and do an overall energy balance. Take into account all inputs, outputs, and losses.

[fvanicek]

Suggestion - instead of liquid N2, one could make liquid oxygen. That would be nice for submarines. You would have energy and oxygen, which you need both.

[dukejaz2002]

use the delta T between a cold creek,(5C) and,(at worst earth =13C, at next best passive solar = 85C) to produce the LN. Operating 24/7, storing the LN for a small (2Kw/h) motor that runs 2-3 hrs a day, or on demand. Fermi estimate only.

[stan.hornbaker]

Using LN2 or LO2(LOX) would only add unecessary complications by adding requirements for supplementary power input to the system to provide the LN2 and/or LOX.

You do not want to use external power input to a system if the object of the system is to create power output.

Do an overall energy balance of the entire system to realize the fallacy of the above suggested system.