Shown are the cost-optimal ranges (green) as well as ranges under green hydrogen minimization (blue) and maximization (red). For the minimization and maximization, the ranges are shown for 2%, 5%, and 10% total system cost slack levels. For each category, we use a letter-value plot44to visualize the distribution of green hydrogen production levels in the 216 different scenarios. The lines in the middle indicate the median and successive boxes mark the 0.25–0.75 quartiles (containing 50% of the data points), the 0.125–0.875 quartiles (containing 25% of the data), and so on. Although we give hydrogen production figures in Mt/a and TWh/a,Figure S1shows the relationship with installed electrolyzer capacity, which reaches about 750–1,000 GW or more for 80 Mt of annual green hydrogen production. The peak in hydrogen production in 2040 is primarily caused by remaining internal combustion engine cars in combination with the 90% emissions reduction target causing significant demand for synthetic liquid fuels, which subsequently drops with further land transport electrification.
