SEOUL -- South Korea's SK Group has said it will invest 18 trillion won ($16 billion) over the next five years to develop the domestic hydrogen energy industry. The country's third-largest conglomerate aims to become a leader in the emerging clean-energy source, which is attracting attention from businesses and policymakers around the world, most notably in Japan, but also in China and Europe.
Here are five things to know about SK's ambitious project.
