Solar Tanker

The Sun puts out an incredible amount of energy, but thanks to the inverse-square law a relatively small amount actually reaches us. If we could somehow get closer to the Sun, we should be able to harvest substantially more energy. But how?

What if we constructed a massive solar-powered battery, then sent it to the Sun to collect energy before returning to Earth? We could launch the tanker so that it follows a secant line to Earth's orbit. In essence, we would be throwing the tanker towards the sun, then moving around to the spot where we could catch it. It wouldn't even need to be in the same orbital period—we could plan on catching the tanker, say, one and one third years after launching it.

Once we have extracted the energy from the tanker, it could perform a gravity assist maneuver around the Earth to continue its next journey past the Sun, and so on indefinitely. It should be able to perform most of its course-correction maneuvers during the charging period, so as little energy as possible would be siphoned from the stored power. Ideally, the tanker should be near empty as it gets close to the Sun, and as full as possible by the time it approaches Earth. Ensuring that the course towards the Sun is accurate is thus less important than the course away from it. Just aim for the big glowing thing, and once you get there you have effectively unlimited energy to precisely adjust your course towards Earth.

Of course, we don't quite have the technology for this to be practical yet, and a single tanker might not provide much usable energy. But a constant stream of such tankers could conceivably produce enough energy to make this a viable power source in the future. And apart from the initial construction and launch costs, the ongoing operational cost should be virtually nil, as any energy needed could simply be acquired from the Sun.

Certain things we will have to handwave away at present— battery technology, for one. Currently batteries don't last indefinitely, though research into supercapacitors may ameliorate this issue. Also, the question of how to return the power to Earth from space once the tanker has arrived remains unanswered, but that is beyond the scope of this idea. Once we get the power into Earth's orbit, getting it down to the surface is somebody else's problem. And of course, the whole issue of creating propulsion without ejecting mass is still something that has yet to be worked out, but a quick perusal of Wikipedia leads me to believe that significant progress is being made in that area. So while this idea may seem far-fetched today, it should be technologically feasible (if perhaps not entirely practical) at some point in the future.