In 2010–2030, the annual growing rate of power demand is expected as around 1%/year in Japan, and the amount of renewable and dispersed generation (DG: distribution generation) will considerably increase in the future electric power supply system. Also, the following factors are the accelerant for increasing the ratio of the distribution generation in the whole supply power.

✓ Pressure to the fossil fuel plant as CO₂ exhausting plant.

✓ Political strategy for utilizing the natural resource plant like a wind plant, a photo-voltaic (PV) plant or a biomass plant.

✓ Future innovation of hydrogen technology such as an economical...