The picture above illustrates what is claimed to be by this website the amount of Earth's surface that would have to be covered in current (2014) generation solar panels in order to provide electricity for the World, the European Union and Germany, from largest to smallest box.
While the distribution network would be logistically complicated, and there would be some loss from resistance in the power lines necessitating some increase in the area of the boxes, this is pretty impressive. I have not studied the science behind this assertion, but I am assuming that it is reasonably correct.
In an earlier post I discussed why food would be the big trading commodity in the Far Future instead of energy. If the above assertion is correct, then the problem of powering a stellar tech society becomes trivial.
The average population of the 260+ planets in my TU is roughly 44 million, or about half the population of Germany in 2014. The tiny box on the right, probably less than 50 km on a side, would certainly suffice for the worlds on the lower side of that average. Even my highest population worlds, with people in the hundreds of millions would not need a box bigger than the large one - and they also have a whole world surface to choose from in siting it. There's no necessity for all the solar panels to be in one place, so break the box up into smaller boxes and scatter them about on all the less-enticing bits of land.
This doesn't even bring into the equation the potential for Space-based Solar Power, which takes the real estate issue even further out of the picture. This concept has been in the theory/development stage since the late 1960's, and one of the major issues is cost of boosting the equipment into space to begin with.
Imagine what another few levels of tech development would do for the cost & technical difficulties. The introduction of contra-gravity technology for space & orbital transportation at TL 9 alone should greatly reduce the barrier of cost.
You get major Sci-Fi cred if you know (Before reading the Wikipedia article) what major science fiction writer proposed this method of power generation in a short story in the 1940's!
As solar power, particularly from orbit, is both free and inexhaustible, a world that uses it as the sole or primary source of electrical power will not be dependent on either hydrocarbons to burn or water for hydrogen fusion. There could be interstellar trading in electrical power (superbatteries) much like trading in hydrocarbons today.
These solar collection farms, whether on the ground or in space, will be strategically vulnerable points. Travellers can interact with them in a number of ways, including:
- commando raids to cripple planetary power grids as part of a planetary invasion
- repair missions working in hazardous conditions vacuum or atmospheric
- an unusual location to visit and have a 'space station' adventure
- accidental or intentional impending collisions with ships or space debris (watch out for near-C rocks!)
- illegal tapping into the power grid for private purposes
- delivery/installation of space based collectors
- terrorists attempting to redirect the microwave beam onto a populated area
- ground-based facilities run entirely by robots could be a great hideout location for the PCs or for the baddies.
- Exploration work on the ground, surveying new regions of the planet for potential siting of solar collectors.
- New trade item - large-scale batteries. imagine the potential danger of a cargo bay hit in space combat while carrying Terawatt level capacitors. Wait, then you could build one-shot spinal mount weapons in smaller ships. Oh dear, what have I done?