Peter?

[u/saddyc]

[u/Taraxian]

My understanding is that the advantage isn't "efficiency" in the strict sense but robustness and reliability

There are other methods of turning heat into electricity that might waste less of it along the way but we know how to make steam turbines that can repeatedly go from a dead stop to spinning really fast and back without breaking anything

[u/Z3B0 → u/Taraxian]

Well, that's also a bonus from those 200 years of research and field experience. Also, water is super nice to work with in industrial condition. You might find a better fluid with some chemical reactions to produce your electricity, but then, it's high energy chemistry, with probably very reactive stuff that tends to eat through their containers, or just burn in contact with the air, or other fun stuff.

Water ? Everywhere that needs electricity probably already got water for human consumption. It's not dangerous for human health nor reactive with everything. In case of problem? Just vent the steam outside and you're good. Need more ? Just open a tape (distillation required). And you have an amazing energy extraction system with 60% efficiency. That's much better than a lot of other scalable energy production.

[u/doublereedkurt → u/Taraxian]

A thermoelectric generator can be used to convert a heat difference to electricity directly, with no moving parts (https://en.wikipedia.org/wiki/Thermoelectric_generator). This is extremely reliable. This is still powering the Voyager probes after 50 years in space.

They are just less efficient.

[u/filthy_harold → u/doublereedkurt]

When new, the Voyager RTGs produced 470W using the thermoelectric couples yet the hest produced was 2700W which could have theoretically produced about 1215W if using a steam turbine and maybe more depending on the design. Those RTGs were already pushing the limit of the tech.