Hidden deep inside the Changlongshan mountain lies a mega project with a massive impact — powering 2 million homes and cutting 420,000 tons of carbon emissions every year. Erik Solheim, chairman of the Europe-Asia Center and former UN under-secretary-general, journeys to East China's Zhejiang to witness the giant "green power bank" there — a pumped-storage hydropower station harnessing the force of water to stabilize the grid and protect the planet. Why is it called a "green power bank"? Hit play to uncover the future of green energy.