No. 16: On photovoltaic generation in Japan (November 9, 2011)

A module of photovoltaic generation is installed on a roof with a power conditioner, a power monitor, and electric wiring. In the early stage, the price of silicon thin film used as the semiconductor accounted for the largest part of a unit price. Thanks to technological innovation, the price of silicon thin film has been decreasing. However, as silicon materials are growing higher in price because of speculation, the development of silicon-free photovoltaic generation invites a wide attention lately.

Output of photovoltaic generation depends on the generation efficiency and amount of sunlight. The lower the temperature is, the higher efficiency a semiconductor exhibits. This is why the cold area is suitable for photovoltaic generation. However, photovoltaic generation cannot generate power when snow covers the generation module in the cold area. Naturally, photovoltaic generation generates power only in daytime, and its output peaks at 12:00 noon. Therefore, a household has surplus power in daytime and shortage in nighttime. It is totally impossible to adjust power supply and power demand in photovoltaic generation. Electric power companies purchase surplus power created in daytime and provide the shortage to households in nighttime to adjust the gap.

The present purchase system works well because photovoltaic generation accounts for merely 0.5% of all power supply at present. However, as photovoltaic generation is expected to increase the share to 20-30% in the future, the system to store power by dint of a storage battery is critical. It is not too much to say that the future of photovoltaic generation depends on the development of a high performance and highly efficient storage battery.