This review evaluates solar- and wind-powered green hydrogen pathways for decarbonizing energy systems, focusing on system design, electrolyser operation, storage, economics, environmental footprints, and policy alignment. A structured evidence map compiles input ranges for renewable generation, batteries, electrolysers, and storage and reconciles reported cost outcomes across case studies. Electrolyser efficiency spans 60–80%, water demand spans 9–15 L kgH₂⁻ 1, and salt-cavern storage costs fall less than 1 kWh⁻ 1. Hybrid photovoltaic–wind systems with battery buffering report curtailed renewable energy less than 15% in high-utilization designs. Across reviewed studies, the levelized cost of hydrogen commonly ranges from 3 to 13 kg⁻ 1 under present-day capital costs, financing, and capacity factors. Policy instruments such as tax credits, carbon contracts for difference, and concessional finance are reported to reduce costs by up to 3 kg⁻ 1 when paired with certification and procurement commitments. An integrated 2030–2040 roadmap aligns technical targets (electrolyser CAPEX 400–600 kW⁻ 1, lifetime more than 80 000 h) with phased policy milestones to support a cost pathway toward less than 2. 0 kg⁻ 1 by 2040 while managing land and water trade-offs. • Global hydrogen exceeds 95 Mt yearly, 96% fossil-based with 900 Mt CO₂ emissions. • PV-only systems face 30–40% curtailment, cut to less than 15% with storage. • Electrolyzers operate at 60–80% efficiency, CAPEX ranges 500–1400 kW⁻¹. • Green hydrogen LCA shows 0. 6–2. 5 kg CO₂e kgH₂⁻¹, grey reaches 12–14 kg CO₂e. • Roadmap targets 2 kgH₂⁻¹ cost, 15 GW scale, and 80% efficiency by 2040.
Alkhawlani et al. (Fri,) studied this question.