Energy storage systems are important for storing extra energy when the power grid has too much and releasing it when there's not enough. Traditional methods like pumped hydroelectric power plants are used for this, but now renewable energy sources like solar and wind are being used more. The problem with these sources is that they don't always produce a steady amount of power. Energy storage systems help balance this out by storing extra energy when there's too much and releasing it when there's not enough. They also help improve the stability of the power system and provide additional services like peak shaving and power quality enhancement.