eli5 Is steam the best way to turn turbines, or is it just the best thing we are most familiar with?

Question

Water seems to just be the right tool for the job in many applications. It always seemed funny to me that we have not found a better option to generate electricity over the years. Most large scale generators, no matter how complex, is just using something to heat up water and spin a really big fan in order to spin a really big magnet.

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Answer 1

Moving liquid water is if I am not mistaken efficient that moves water as a gas ie steam.

But is is quite irrelevant because you can use heat in a simple way to get liquid water moving but you can use heat to create high-pressure steam. Water expands in volume by around 1000x when it changes from a liquid to a gas and if you do that in an enclosed space you get high-pressure steam that will flow to a lower pressure area.

Using heat to boild a liquid and create a high pressure that can be used to spin a turbine is the simple and quite efficient way we know of to generate electricity from just heat. For coal power planes the efficiency is around 33%

There is another way with some fuels and that is gas turbines where the exhaust is used do drive a turbine direct and then you can use the heat in the exhaust to heat up water and run a steam turbine the efficiency can no reach 64% heat to electricity, this is 84% of the max theoretical efficiency of a Carnot cycle

Gas turbine works with fuel like natural, fuel oil but not with coal. It alos is not a possibility for nuclear reactors.

Moving liquid water is alos used for electricity generation with turbines. This is what hydroelectric power is, the way you get water moving is with gravity.

You can use another liquid that builds to instead of water but why would you? Water if practically free and it does not have a nasty reaction with metal and if released just water is not a pollutant. So water is safe and cheap.

So just steam to drive turbine is not the most energy-efficient way, it is more efficient to use both hot exhaust and then use it to make steam, the problem it is not possible with all fule you burn or with nuclear reactors.