We can hope, at least. Renewables (which on a global scale are really limited to solar, offshore wind, and wave) certainly can provide all of the energy that is needed for terrestrial applications, provided that it can be collected, stored, and transferred from where it is collected to the end user. We have a lot of challenges in that today but none that really require great technological advances; it is mostly a problem of infrastructure and logistics. The ultimate renewable energy source would be a glucose-based economy where solar is converted to the carbohydrate that can be used in biologically-based or biomemetic industrial infrastructure but that is certainly a future development. Regardless, we shouldn’t be expecting nuclear fusion as any kind of replacement for fossil fuels to mitigate climate change or depletion of known energy supplies.
Where fusion is actually needed is as an energy source for exploration of the outer solar system (and likely for permanent habitation on Mars or the Moon, if you think that’s a good idea) where insolation levels are too low for solar power to be practical. Right now we use radioisotope thermoelectric generators (RTG) for small, low power probes, and will probably use compact nuclear fission for advanced propulsion and energy for larger probes, but for any kind of crewed exploration beyond Mars the use of nuclear fusion for both propulsion and the energy required to sustain habitation is a sine qua non technology. There is no particular need for this capability in the foreseeable future and so no reason to pour enormous amounts of money into crash programs to develop it even if it was practicable to overcome the known issues with extensions of current technology.
It would be better to continue to develop high temperature superconductors, radiation-resistant materials, ‘alternative’ nuclear fission technologies that provide better utilization of fissionable materials and full burnup of actinide products to reduce the waste issues, et cetera than to focus on trying to make fusion power production work. The much delayed and problematic ITER has been a case study in trying to bring a capability to fruition before the technology really exists, and while there will probably be a lot learned from operating ITER whenever it finally comes on line, as a ‘Big Science’ project it has consumed the lion’s share of funding in plasma and fusion physics that could have gone to other high energy physics projects in its member nations.
Stranger