A net-zero world would require 306 million tonnes of green hydrogen to be produced annually by 2050, according to the International Energy Agency (IEA). That would require something in the region of 3,000GW of electrolysers and 6,000GW of renewable energy, based on current technology.

Considering the world had only installed 3,371GW of renewables by the end of last year (according to the International Renewable Energy Agency [Irena]) — and that the planet will need about 30,000GW of renewable energy to decarbonise the global electricity supply, that’s a fairly tall order.

Based on the notion that economies of scale would reduce the cost of green hydrogen production, several developers have announced massive and extremely ambitious projects that aim to meet much of the world's future demand for clean H₂. <Read more: Impossible dreams? The 11 biggest green hydrogen projects announced around the world so far.>