I think 1) and 3) are the only ones that do not require advances in fundamental science to achieve.
Space based energy requires a way to send the energy to the surface for monetization. The three ways to do this would be
1) Wireless transmission -- infeasible with current level tech at the distances required.
2) Wired transmission -- requires materials with very high tensile strength in quantities never before produced.
3) Deorbit batteries -- You spend more energy launching/deorbiting and distributing batteries than you gain.
High speed transport (ground to orbit, and interplanetary) have huge problems in scaling, but it mostly can be solved with current level engineering.
Wireless transmission is perfectly feasible with current tech level and distances required. In fact, we do precisely the same thing with telecommunications.
It's just a difference in scale. To get high efficiency, low cost radio amplifiers, you need to operate at relatively low frequency (think microwave oven magnetron, but modified to follow a phase and frequency input). Rectification of this has also been done. But you're going to need an enormous aperture on both sides to make it happen. That means, to me, you need on the order of 10 Gigawatts to be feasible (rough, back-of-envelope calculations). And even then, you need an enormous plot of land, preferably in the desert. So you're basically competing with cheap solar power backed by cheap batteries. Both of those are improving in cost every year. So it's possible. Feasible, even, if we had no other options. But it's not going to be competitive from what I can tell.
So it's the same type of scaling problem as #3. Except the main issue with #3 is safety: passenger aviation is just so ridiculously safe it's extremely hard to compete with.
Space based energy requires a way to send the energy to the surface for monetization. The three ways to do this would be 1) Wireless transmission -- infeasible with current level tech at the distances required. 2) Wired transmission -- requires materials with very high tensile strength in quantities never before produced. 3) Deorbit batteries -- You spend more energy launching/deorbiting and distributing batteries than you gain.
High speed transport (ground to orbit, and interplanetary) have huge problems in scaling, but it mostly can be solved with current level engineering.