Solar power could handle much of the non-commercial energy demands of the Japanese.
Commercial demand requires much more power than can be generated by panels.

JAXA (Japan Aerospace Exploration Agency), however, aims, by 2030, to put into geostationary orbit a solar-power generator that will transmit one gigawatt of energy to Earth, equivalent to the output of a nuclear power plant. Scientific American, July, 2008, "Farming Solar Energy in Space." The article is online- http://www.scientificamerican.com/article.cfm?id=farming-solar-energy-in-space.
The receiving end would have to be isolated, and plans are to put it at sea.
This plan would require support from th government and industry, but it might be a substitute for nuclear power. It also requires some 30 years lead-in time.

Windpower demand for land in a crowded country seems too large to be feasible.