Why not spend $21 billion on solar power from space?

clipped from www.scientificamerican.com The Japanese government is prepared to spend some 2 trillion yen on a one-gigawatt orbiting solar power station—and this week Mitsubishi and other Japanese companies have signed on to boost the effort. Boasting some four kilometers of solar panels—maybe of the super-efficient Spectrolab variety but more likely domestically sourced from Mitsubishi or Sharp—the space solar power station would orbit some 36,000 kilometers above Earth and transmit power in a microwave or laser beam. The benefit? Constant solar energy production as the space-based power plant never passes out of sunlight. The downsides? Only enough power for roughly 300,000 Japanese homes at a price tag of $21 billion, according to Japan's science ministry (about 127 million people live in Japan in some 47 million households, according to Wikipedia and CIA Factbooks). The Japan Aerospace Exploration Agency (JAXA) aims to have a system in space by 2030.