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Since the 18th century, humankind relied on steam engines to convert heat into electricity on mass scale even in fission and fusion （in the future） power plants.

However, this process involves several energy transformations (i.e. heat energy to kinetic energy to electric energy) which severely decreases the efficiency and wastes a lot of energy.

Are there possible alternatives to convert heat energy to electric energy in the future?

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    $\begingroup$ I do not think this is the right place for that kind of question. Although, I may be wrong... $\endgroup$
    – RedGiant
    Jan 4 at 12:46
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    $\begingroup$ There was a lot of reasearch into MHD generators. But it turns out real ones are less efficient than traditional heat engines. $\endgroup$
    – Sebastian Riese
    Jan 4 at 14:23
  • $\begingroup$ It's only a severe efficiency problem when the temperature range is too narrow. When power plants make steam, let alone molten salt, it's often much hotter than what you get in a conventional steam engine. $\endgroup$
    – J.G.
    Jan 6 at 21:56

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Thermoelectric generators convert thermal energy directly into electricity, without using turbines or other moving parts. However, their low efficiency and high cost means they are only used in specialised applications such as the radioisotope thermoelectric generators used in space probes.

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Hydropower, PV, wind, etc. do not convert heat to electricity and thus do not suffer these losses. They are also mechanically simpler and cheaper to build, and because of this, are the fastest-growing energy sources.

As a result, it is unlikely we will have a new heat to electricity scheme because it is unlikely most electricity will come from heat in the future. There's simply no incentive to develop it. It is one of the many reasons it is extremely unlikely fusion will ever be economically useful en mass.

I should point out that this is not a theoretical claim, there are real-world examples. One that you see every so often is using supercritical gasses, normally CO2, as a transfer fluid instead of steam. There is an active CO2 development effort underway in the US now. But after 50 years of development, the largest testbed is still one that fits on a table. But we are assured they'll be in use any day now.

Those processes that are not ultimately electrical - chemical process heat, heating your home, etc. - are already extremely efficient and will likely remain in use for some time.

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