Balloons for solar energy?

Only about 10% of 1370 watts per square meter reaches the surface (as sunlight) on the average. A few rare locations, average about 300 watts per square meter, at 1 pm on the longest day of the year. These locations are practical for harvesting solar energy. Unfortunately few humans live close by, with rare exceptions and about 200 kilometers is about the farthest we can send electricity, before losses become prohibitive. We could harvest the energy and build model cities around the solar receiving sites.
I suggest very large free flying, hot air and/or hydrogen balloons (we don't have enough helium for a million very large balloons) with a large steerable mirror to beam sun light through holes in the clouds to solar sites on the surface. These would serve all the northern hemisphere, except very close to the North pole. These would be launched near the Equator when winds will carry them North to be recovered months later near the Arctic Circle, late summer and early fall. At present recovery would be too costly in Antarctica, so this is a Northern Hemisphere solution. The balloons would fly at up to 30 kilometers, altitude late afternoon, sinking to perhaps 15 kilometers (hydrogen has negligible fire and explosion hazard that high) about sunrise. This would allow them to beam sun light to solar sites on the surface, up to 200 kilometers away in some directions.
SPS = solar power satellites are impractical, until we have cheap access to space, perhaps not then. Neil