2007 and No. 15 started up on October 30, 2008. [ 6 ] The sixth (No. 17) began operation on December 18, 2007, raising capacity to 14.1 GW, finally surpassing Itaipu (14.0 GW), to become the world's largest hydropower plant by capacity. [ 34 ] [ 35 ] [ 36 ] [ 37 ] The 6 underground