How much renewables expansion is needed for a global green hydrogen economy?

Hydrogen is increasingly being touted as the molecule of choice for the energy systems of the future. It has a vast range of potential applications, from heating to long-distance transportation to steel production, and “green hydrogen” can be produced with renewable energy. But using solar or wind power to split water into hydrogen and oxygen is not exactly energy efficient. So how much renewable energy would we need to meet hydrogen projections for 2050 with green hydrogen? The answer, based on a Canary Media analysis of data provided by Siemens Gamesa Renewable Energy and other sources, is a lot — but probably not so much as to make the whole concept unviable.