The original question was: Is it possible that, when more efficient methods of harnessing light energy are established, light could be used as a means to transfer massive amounts of energy (for instance, enough to power a city) without physical wires? What are some of the obstacles that would prevent such energy transfer? Way back in the day Tesla did a whole bunch of research into exactly what you’re talking about: wireless transmission of power. There is some active research in using microwaves and magnetic coils to transfer energy, but so far the results have been pretty underwhelming. On the other hand, a beam would be the easiest way to transfer energy between the ground and space (not that it easy even then).