Renewable energy has expanded significantly especially wind and solar energy in both Japan and overseas in order to preserving global environment by reducing CO2. However, since solar and wind energy are unstable power sources whose power generation fluctuates greatly depending on conditions, thus effect the power system and it becomes a major issue. Therefore, the necessity of large capacity storage batteries is increasing.
The changes (looks like a duck) represents the net load, equal to the normal load minus PV generation called duck curve phenomenon. The huge penetration of PV generation in the world cause a big problem to electric power supply.
Until now, suppression of short cycle fluctuation (frequency adjustment in a short time) has been the dominant for storage batteries, and output factor has been emphasized. However, based on the future trend for the adjustment of power demand, the number of large capacity batteries that can store electric power for a long period is expected to increase.