No. 19: On photovoltaic generation in Japan (November 12, 2011)

Photovoltaic generation is expected to grow widespread as a generation technology because it is environmentally friendly. All Japanese companies involved are exerting lots of energy to develop the Japanese photovoltaic generation technology to be highly competitive in the world market. It is urgent for them to increase the energy exchange efficiency to higher than 18%. The photovoltaic generation roadmap published in 2009, it is scheduled to be increased to 20% in 2020 and 40% in 2050.

According to the estimated by New Energy and Industrial Technology DevelopmentOrganization (NEDO), it is expected that the exchange efficiency will be 20%, generation cost will be less than 14 yen per kW, and national annual output of photovoltaic generation will be 2-3 million kW in 2020, and the three figures are expected to be 40%, 7 yen per kW, and 25-35 million kW in 2050. If these targets are achieved, the area necessary for photovoltaic generation per kW will decrease drastically, making it possible to install a system in a small space.

Theoretically, the maximum exchange efficiency of silicon semiconductor prevailing most in photovoltaic generation is 27%. Accordingly, researchers are developing photovoltaic cells made of other chemical compounds. In addition, they are trying the tandem type that layers multiple materials, quantum dot type that uses fine particles, and light focusing type that collects light using lens. Currently, a new residential house can introduce a photovoltaic generation system with a generation capacity of 3 kW for about 900,000 yen (about 750,000 with subsidy). In view of the current technological progress, it may not be a dream that most houses in Japan will have a photovoltaic generation system in the future.

The large-scale photovoltaic power plant called mega solar has also been increasing presence because it can intensively control the unstable distribution grids caused by the output fluctuations. However, it creates transmission loss between the plant and households. In addition, maintenance does not create constant employment in the region. A vast land is required to build a large-scale photovoltaic power plant.