edit and update: the assumption here is that necessary batteries for storing solar energy simply aren't available on a global scale (without intending to get into the veracity of such a statement).)
In relation to the question from James, who's moving to the moon, I'm just surprised at the small-scale approaches to solar energy collection prevalent with the space agencies. Particularly in consideration of peak oil, etc, there seems almost a dearth of large scale thinking on energy production.
I suppose the question is: what will it take to generate the grass-roots pressure to effect the political will to seriously look at large-scale solar energy in relation not just to colonization but survival?
I only mean this in the context of total available output of the sun for a dyson sphere, as:
A spherical shell Dyson sphere in the Solar System with a radius of one astronomical unit, so that the interior surface would receive the same amount of sunlight as Earth does per unit solid angle, would have a surface area of approximately 2.8×1017 km2 (1.1×1017 sq mi), or about 550 million times the surface area of Earth. This would intercept the full 384.6 yottawatts (3.846 × 1026 watts) of the Sun's output. Non-shell designs would intercept less, but the shell variant represents the maximum possible energy captured for the Solar System at this point of the Sun's evolution. This is approximately 33 trillion times the power consumption of humanity in 1998, which was 12 terawatts.
of which a small fraction would have tremendous utility both on earth or, as above, on the moon (or mars, etc).
Of course such technology is well beyond current capabilities -- at that scale.
Put another way, what's the break-even point for collecting solar energy in space at scale?