You can make liquid N2, though very inefficiently. So yeah, power is an issue although we are still making gains on cooling efficiency so it's not inconceivable the equation could swing towards super low temperature coolants.
I was curious, so I googled around a bit — please excuse the weird units.
- about 0.375kWh to produce 1kg of LN2
- about 0.056kWh to boil 1kg of LN2
So you get 15% efficiency; though you have “waste cold” in the exhaust you could recover if you wanted, eg, to run a Sterling engine. You still have a 220K temperature differential after boiling to gas versus ambient.
- about 0.375kWh to produce 1kg of LN2
- about 0.056kWh to boil 1kg of LN2
So you get 15% efficiency; though you have “waste cold” in the exhaust you could recover if you wanted, eg, to run a Sterling engine. You still have a 220K temperature differential after boiling to gas versus ambient.