You mean black holes as a power source?

Will technically in Balance of Terror in ToS they were using fusion drives still. They vented excess plasma and wraponized it.

I don't know why you made me laugh so much, thanks for that post.

I think it's because it turns the concept into something so low tech and banal

There could be a whole industry of Dyson Dudes that run back and forth with the tubes

3.6M Scoville. Not great, not terrible

Entropy is maximized by turning heat into electricity, so electricity appears on the device, as it gets cooler (by a tiny amount).

EDIT: I just noticed that you may be asking about the "reverse electro-dialysis" part :)

It's a process where fresh and salty water enter a machine, and they get mixed while generating electricity. It's the reverse of this:

https://en.wikipedia.org/wiki/Electrodialysis

That runs on the same conceptual machine.

(And oh, looks like it's written together.)

why the salinity gradient provides energy?

It doesn't. It's the thermal energy that is converted to electricity.

The salinity gradient provides an entropy dump. The dialysis machine is built in a way that the only possible way for that entropy to increase is by generating some electricity.

when you dissolve salt in water, then salt splits into ions and each can hold up specific number of water molecules, which means that this water can't do water things. so on top of salt's physical presence, there's a fraction of water that can't water, or salt water is less watery in a sense than fresh water. now it turns out, if you put a membrane between these two that allows water through but not salt, water goes to higher salinity on its own, because it's less watery there. how hard it happens is quantified as osmotic pressure and it can be in tens of atmospheres. reverse electrodialysis is just a clever arrangement that avoids energy recovery from low volume of high pressure liquid, like how reverse of reverse osmosis would work