Why do we still use steam as a primary means of producing electricity?

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It’s been more than 200 years since the widespread implementation of the steam engine.

Why is this still the most prevalent means of producing electricity? With things like fusion reactors, why is it so hard to convert the thermal energy into electrical energy?

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Aside from solar cells, the primary way of generating electricity is through rotating magnetic fields. It’s simple and effective. All you need is a magnet and some way of turning it.

Water is an ideal way of doing this. It’s plentiful and can go from liquid to gas and back within a range of easily achievable temperatures. So all you need to worry about is how to make water do this.

Steam Rankine cycle (vs other heat engine cycles) is very good up to about 550 C which is near the creep strength limit of steel. Going higher requires exotic materials or power cycles (gas Brayton or sCO2) and only gives marginal gains. Capital costs outweigh efficiency gains.

It’s better than other options for iron based materials. More expensive materials aren’t worth the gains.

> It’s been more than 200 years since the widespread implementation of the steam engine. Why is this still the most prevalent means of producing electricity? With things like fusion reactors, why is it so hard to convert the thermal energy into electrical energy?

Steam is used in most fission reactors and unless there is some fundamental discovery it will be used in fusion reactors as well. When something is cheap and efficient why change it?

Imagine 100 or 200 years from now you somehow are still alive and able to think rationally and someone asks you “why are we still using electricity and electronic devices, …?” How might you answer their question? Can you see how you question today is similar?

It is efficient, cheap and easy to scale.

For generating power your options are:

1. __Steam turbine, 30-40% efficient__. Used by coal/fossil fuels, nuclear, concentrated solar power, geothermal, etc.

2. __Combined cycle, 60% efficient__. This works for natural gas has 2 turbines one is NG burning the second is a steam turbine using the heat from the NG turbine so you get about double the efficiency. This is part of why NG is cleaner than coal (but still not very clean). Its generally more expensive to build and more complex though.

3. __Diesel generator, 30-40% efficient__. But also much more maintenance, costs more to build, needs specific fuel, can be very expensive at electric grid scale.

4. __Thermocouple, 5-10% efficient__. These are both expensive and inefficient. They produce electricity when heat is transferred through them via the [thermoelectric effect](https://en.m.wikipedia.org/wiki/Thermoelectric_effect). They are mainly used by NASA to power rovers and probes with the heat of nuclear decay (on the hot side and cold space/mars on the cold side).

5. __Solar PV, ~20% efficient__, but very cheap and who cares it’s not like we are wasting sunlight.

So for fusion 2 and 3 are not options, 5 would be vaporized instantly, leaving steam and thermocouple. I’d take cheap and efficient steam turbine over a thermocouple any day.

Also, Hydroelectric is ~90% efficient which is awesome for pumped hydro grid storage.

After thousands of years , we’re still boiling water to make electricity. We just need to find a safe, cheap way to do it. I’m not here to debate nuke plants. I think they can work.