Speaking at the convocation of Pandit Deendayal Energy University (PDEU), Mukesh Ambani, who heads the nation's most valuable company Reliance Industries Ltd, said the Indian economy will become a USD 40 trillion economy by 2047 from the current USD 3.5 trillion. "And to fuel this growth, the country will need enormous amounts of energy - clean, green energy that won't choke mother nature for the sake of human progress," he said. "In fact, India's energy requirement is set to double just by the end of this decade."