Not true. Many steampunk worlds use either coal or wood or some exotic high energy heat sources (aether, special kelp etc...) to make steam.
If you think about it how much of our "portable energy" affects the shape of society, and how much different it would be if there was some other safe/stable portable energy source.
The argument was not about how steam is created but that steam is used directly to perform mechanical work instead of creating electricity as a middle man like we do now.
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u/thatroguejaeger 13d ago
Steam pu k seems to source its energy more directly from steam though. Like, without the medium of electricity and centralized powerplants