Indian billionaire Mukesh Ambani unveiled an ambitious push into clean energy involving 750 billion rupees ($13 billion) of investment over three years, heralding another crucial transformation of his oil-to-petrochemicals empire.

Reliance Industries, which operates the world’s largest crude-oil refining complex, plans to spend 600 billion rupees on four “giga factories” to produce solar cells, modules, hydrogen, fuel cells and build a battery grid to store electricity. An additional 150 billion rupees will be invested in value chain and other partnerships, Asia’s richest man told shareholders on Thursday.

Bloomberg