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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It’s the best way to turn a turbine that can be wherever you want it to be. Hydroelectric dams are more efficient, but suitable locations aren’t always conveniently placed.
Water is pretty amazing, as a gas (steam) you can pump a huge amount of energy into it and it doesn’t come apart into individual atoms. It decomposes at 2,000˚C (3,632˚F). It’s also so cheap it might as well be free, so using huge quantities is very affordable.
There are two parts to why that is: Water is actually extremely good for a wide variety of applications, including this one.
And generally speaking, we have ready access to a *lot* of water. There are maybe some applications where you could devise a custom-designed substance to eek out marginally better efficiency, and there may be some situations where that is worth it.
But for most things we use water for most of the time, it has the major advantages of being clean, cheap and extremely easy to get your hands on relative to anything else you might want to use.
For now it’s the best method we have.
Water is plentiful, doesn’t inherently pollute (by itself), and can convert a lot of energy into steam without breaking apart.
But it’s also not super efficient, there’s a lot of energy lost in the process.
The next miracle in terms of energy production might be the magneto-hydrodynamic process. Where plasma from a Fusion reactor can be passed through a closed loop and electrons from the plasma can pass or excite electrons in a wire directly to generate electricity
It really depends on what the actual source of energy driving the turbine is. In this case of those driven by stream, that steam comes from heat, either by burning fuel or a nuclear reactor. Turbines driven by water are usually found in dams, where gravity is the driving force pushing the water through the turbine. When energy changes state there’s generally some loss due to inefficiency, so fewer steps along the way means more efficiency.
It really is the best option, in part because it is widely available.
You can use almost any fluid, but something with a relatively low boiling point and high specific heat and heat of vaporization is helpful. Water has that.
While some material out there may have better numbers, water also benefits from being easy to work with and common. Very few materials have a higher heat of vaporization, and of those that do, fewer still have a higher specific heat.
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.
“Is steam the best way to turn turbines” — Yes
“or is it just the best thing we are most familiar with?” — Yes
Sorry, I’m being a little snide here, but “best” is such a general term. I feel obligated to argue that the dominance of the steam turbine in thermal power production indicates it is clearly the best solution. 😈
OK, so I suspect you are asking if steam is the most efficient working fluid we can have. In this case, the answer is no. But there are big problems with some of the others: Helium – expensive, limited supply, likes to leak; Mercury — need I say more?
The 100 deg C boiling point of water also allows us to use a condensing gas turbine system at atmospheric temperatures. The condensing system produces low outlet pressures (lower than atmospheric) for the turbines, improving efficiency without the need for extremely high inlet temperatures.
The efficiency of GAS turbines tends to be limited by the maximum temperature that the turbine blades can handle. This is just one example of how it’s never just a simple question of what working fluid could be the most efficient. There are all kinds of practical considerations that effect the achievable efficiency.
You might be interest in the comments by BadAndy and Nicky McLean here:
https://arstechnica.com/civis/viewtopic.php?f=26&t=1124663
At the end of the day, the generator stage is very efficient at turning rotary motion into electricity (98%+) and turbines are pretty efficient at extracting energy from a hot fluid and turning it into rotary motion, their efficiency is limited by physics not our design. The reason we use it is because it is legitimately the best way to extract energy from a hot fuel
The fact that its water is largely irrelevant to the actual generation of the power
All you need is a working fluid that you can heat up and ram through a turbine which cools it down and extracts the energy from it. The efficiency is defined by the ratio between the temperature of the hot side and the temperature of the cold side but since you can’t cool it below outside your cold side is almost always 300 K and up so you’ll lose efficiency there regardless of the material. The best way to boost the efficiency of your turbine is to heat up the hotside more(because you can’t cool the cold side) so many modern plants run their steam at 550-600C
Water is nice in that it sticks together at 2000C so you can heat it wayyyy up and you don’t just end up with hydrogen and oxygen. Its also non-corrosive which makes everything a lot nicer to work with. Molten salt has been used some places but you have to select your materials carefully because most salts have two halves that are each corrosive and if you heat them up they’ll try to eat through whatever you have them in.
Many of the gas turbines used for power plants are similar to jet engines; the use the hot exhaust gases to drive a turbine directly.
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