Green hydrogen will be an essential part of the future 100% sustainable energy and industry system. Up to one-third of the required solar and wind electricity would eventually be used for water electrolysis to produce hydrogen, increasing the cumulative electrolyzer capacity to about 17 TWel by 2050. The key method applied in this research is a learning curve approach for the key technologies, i.e., solar photovoltaics (PV) and water electrolyzers, and levelized cost of hydrogen (LCOH). Sensitivities for the hydrogen demand and various input parameters are considered. Electrolyzer capital expenditure (CAPEX) for a large utility-scale system is expected to decrease from the current 400 euro/kW(el) to 240 euro/kW(el) by 2030 and to 80 euro/kW(el) by 2050. With the continuing solar PV cost decrease, this will lead to an LCOH decrease from the current 31-81 euro/MWh(H2,LHV) (1.0-2.7 euro/kg(H2)) to 20-54 euro/MWh(H2,LHV) (0.7-1.8 euro/kg(H2)) by 2030 and 10-27 euro/MWh(H2,LHV) (0.3-0.9 euro/kg(H2)) by 2050, depending on the location. The share of PV electricity cost in the LCOH will increase from the current 63% to 74% by 2050.