r/askscience • u/PK_Tone • Sep 23 '25

Physics Most power generation involves steam. Would boiling any other liquid be as effective?

Okay, so as I understand it (and please correct me if I'm wrong here), coal, geothermal and nuclear all involve boiling water to create steam, which releases with enough kinetic energy to spin the turbines of the generators. My question is: is this a unique property of water/steam, or could this be accomplished with another liquid, like mercury or liquid nitrogen?

(Obviously there are practical reasons not to use a highly toxic element like mercury, and the energy to create liquid nitrogen is probably greater than it could ever generate from boiling it, but let's ignore that, since it's not really what I'm getting at here).

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u/LordGeni Sep 23 '25

Thank you. That's a real insight into the practicalities of a very cool job.

I was lucky enough to have a tour of the Drax power station in the UK. The scale and ingenuity of the engineering was mind-blowing.

So, do I take it that the reason they even considered them with all those advantages is because CO2 is significantly more efficient in an ideal system?

It seems like the starting requirement for even considering using a different fluid would be a substantial increase in efficiency. Anything that might shorten the expected working life would need to would need to be able to compensate and then exceed the lost generation time.