The world of energy is big. Really big. It is by far the single largest economical sector in the world.
We have written a story  in a book with a bunch of essays that has been created by Shell at its 100 years.
In this essay, the growth characteristics of various new energy technologies are compared, especially solar photovoltaics and nuclear fusion. The big difference between the two is the unit size of an energy generating device. As a fusion reactor is so much larger than a PV panel, this gives fusion more uncertainty in climbing the growth ladder.
The other essays are worth the read as well.
 essay Shell - search for: "The cradle of new energy technologies"