> covered the earth's surface In any discussion of far-future considerations like this we need to remember that thermodynamics requires all energy used for wor

> covered the earth's surface In any discussion of far-future considerations like this we need to remember that thermodynamics requires all energy used for work to become heat. Covering the Earth's surface in solar panels is one thing, but by the time we're covering every inch in fusion power plants, we've turned the Earth's surface to lava from all the waste heat. There's a physical upper bound on energy usage within the Earth's biosphere that prevents useful energy production from scaling to infinity, and as a result we'll find ourselves optimizing for economics rather than being limited by energy production per unit of area. As for industry, yes, it seems likely that industry will still represent a large and relatively centralized consumer of power which may benefit from a large dedicated installation. But I'm not convinced that fusion will ever be more economical than even traditional nuclear fission energy (just because your fuel is relatively cheap doesn't mean a thing if the plant itself is essentially disposable because of the energies involved). As for space, maybe, though considerations of space exploration aren't driven by economics, so whether or not anybody ever figures out a viable fusion reactor design for a spaceship could have as little relevance to civilian power generation as your classic RTG did.