What are the other considerations for this? Is there any obvious flaw I haven't noticed?
Yes. First, there's plenty of solar energy at the Earth to be harvested with current technology. Second, there's much cheaper places to put space-based solar collectors than near the Sun. And third there's the small problem of creating an unstoppable weapon of mass destruction.
The amount of energy we receive from the Sun depends on where you measure it, at the surface or at the upper atmosphere, and if you measure total energy received vs energy we can likely utilize using today's technology.
The Earth currently consumes about 12 terawatts (TW). What do we get from the Sun?
At the upper bound, the Earth receives 174,000 TW at the upper atmosphere. That's what we'd get if we covered the whole planet in orbiting satellites with perfect efficiency. That's 14,500 times our energy consumption. No problem there! But obviously unrealistic.
More realistic is the potential energy we can harvest on the ground using today's technology. The UN World Energy Assessment in 2000 calculates that our realistically harvestable energy potential is anywhere from 50 TW to 1500 TW or 4 to 125 times our current consumption. See pages 162 and 163 (173 and 174 of the PDF). They conclude...
The solar energy potential in table 5.19 is more than sufficient to
meet current and projected energy uses well beyond 2100. Thus the
contribution of solar energy to global energy supplies will not be
limited by resource availability.
So we have plenty of solar energy right now on the Earth.
To paraphrase the What If hat guy, "what if we wanted more power?" Ok, let's just pretend we need more power. Where do we put our space-based solar collectors?
Sending satellites near the Sun is very expensive, more on that below, so before we considered that we'd first consider cheaper places to put solar collectors to increase our supply. This image illustrates the cost, in km/s delta-v, of going to various points in the solar system.
As you can see, just getting off the Earth and into Low Earth Orbit (LEO) is quite expensive. Getting to the Sun requires three times the delta-v, but because of the tyranny of the rocket equation the fuel cost increases by nine times (this changes depending on the propulsion method used, but point is it gets expensive fast). So we want to put our solar collectors in places with a low delta-V, and the Sun is the worst for that.
We'd start with the obvious choice: Low Earth Orbit or LEO. This would avoid solar energy absorption by the atmosphere, about 30%, and it doesn't require using land for solar farms. The increase in LEO launches would drive down the cost and allow funding of even cheaper launch technologies such as a space elevator or launch loop.
"What if we wanted more power?"
LEO is already a pretty crowded place, and we don't want to shade the whole Earth, so the next target for our energy hunger would be to expand the total area we're harvesting.
LEO is rather close to the Earth (just 100km up compared to the 6500km Earth) and doesn't significantly expand our collection area. Here is a to scale depiction of various orbits. We can significantly increase our collection area by putting satellites into higher and higher orbits. As we can see from the delta-V chart, getting all the way to Geosynchronous Earth Orbit 35,000km out only adds 4km/s to our delta-V budget but since surface area increases exponentially we've increased our collection area by about 25 times! Spendid!
"What if we wanted more power?"
The next target for our launch budget is the L4 and L5 Lagrange Points. These are points 60 degrees in front of and behind the Earth's orbit around the Sun around which a satellite can make a stable orbit, effectively parking them there. Getting there only requires about another 2km/s more than GEO.
"What if we wanted more power?"
At this point to further increase the surface area of sunlight we're collecting we'd get into things like Dyson swarms and Dyson bubbles which ring the Sun, at whatever orbit we like, with collectors.
The nice part about a swarm or bubble is it can be created gradually by adding more collectors to the swarm. As you add more collectors you increase your energy budget to build and launch more collectors. I covered this in another answer about peak sunlight.
"What if we wanted more power?"
Go away, hat guy.
Any sort of space-based solar collector means you need to beam that energy back to Earth. And yes, it probably would be a microwave laser. Unfortunately beaming that much energy back to Earth means you've just created a space weapon of mass destruction.
Accidentally, or deliberately, these solar collectors are capable of focusing terrawatts of energy, equivalent to a high yield nuclear explosion, at any point on the Earth. Whomever controlled the collectors could ransom the planet. Even if we trusted this organization to be good, there is a risk of them being taken over. Unlike a nuclear power plant or nuclear weapons which have humans to guard it, these collectors would be remote controlled. One hacker could vaporize a city.
