[telchar]

Yes they are. An ideal stirling engine has the Carnot level efficiency, i.e. maximum theoretical efficiency for a heat engine.

https://blog.mide.com/thermodynamic-theory-of-the-ideal-stir...

[coryrc]

Except the ideal one doesn't exist and multistage stream turbines are more efficient in practice.

[hwillis]

Definitely not at that scale. Small turbines have low efficiency because tip speed increases quadratically as they get smaller.

[jacquesm]

And more reliable too. The Stirling does have one huge advantage which is that it is entirely self contained.

[Faaak]

But I suppose that having a multistage steam turbine in mars in not something will see at first

[rfrey]

You may be interested in reading Allan Organ’s books. He claims that aspirations to Carnot efficiency are a red herring and claims (with Much Math) that the peak efficiency is closer to 50% of The Carnot cycle.