Green Hydrogen Production: From Water Electrolysis to Industrial Scale
Green hydrogen is hydrogen gas (H2) produced from renewable energy sources such as solar, wind, or hydropower through water electrolysis. Unlike grey hydrogen (from natural gas via steam reforming) and blue hydrogen (with carbon capture), green hydrogen offers zero direct CO2 emissions, making it a critical enabler of net-zero pathways across refineries, fertilizer production, steelmaking, and mobility.
Core Concepts
Water Electrolysis: The process splits water (H2O) using electricity: 2H2O + electricity → 2H2 + O2. Electrolyzer types include Polymer Electrolyte Membrane (PEM), Alkaline, and Solid Oxide Electrolyzers (SOEC), each with different efficiency and operational characteristics.
Current Cost vs. Targets: Green hydrogen currently costs $4-8 per kg; targets by 2030 are $2-3/kg to achieve cost parity with grey hydrogen in energy-intensive applications.
Electrolyzer Technology & Efficiency: PEM electrolyzers operate at 55-65% electrical efficiency and support dynamic operation aligned with variable renewable supply. Alkaline electrolyzers (65-75% efficiency) are more mature and cost-effective but less flexible. SOEC technology (up to 80-90% at higher temperatures) is in demonstration phase.
Renewable-to-H2 Systems: Integration requires co-locating electrolysers with renewable power plants (solar/wind) or connecting to grids with high renewable penetration. Power-to-Hydrogen (P2H) concepts are emerging in Europe, India, and the Middle East.
Demand Pull: Industrial hydrogen demand is ~75 million tonnes annually; replacing grey hydrogen in refineries (40% of use) and ammonia synthesis (50% of use) represents ~60 million tonnes of potential green H2 displacement.
Policy & Investment: India's National Green Hydrogen Mission (2022) targets 5 MMT of green hydrogen and 125 GW dedicated renewable capacity by 2030. EU, Japan, South Korea also announced ambitious targets.
Research Frontiers
Anode & Cathode Materials: Novel catalysts (e.g., non-precious metal catalysts) and electrode architectures to reduce capital costs of electrolysers by 50-70%.
Thermochemical Water Splitting: High-temperature solar concentrators paired with cyclic redox reactions to produce hydrogen directly without intermediate electricity; efficiency potential of 25-50%.
Proton Exchange Membrane (PEM) Durability: Operating lifetimes of 50,000+ hours under cycling conditions require advances in ionomer and catalyst layer stability.
Hybrid Systems: Coupling electrolysis with algae or biomass gasification for consolidated green hydrogen + biochar or bio-products.
Conclusion
Green hydrogen represents a pivotal decarbonisation lever for heavy industry, with PEM and alkaline technologies mature enough for commercial deployment. Cost reduction and renewable-to-hydrogen integration will define the transition trajectory.
Keywords: Green hydrogen, water electrolysis, renewable energy, PEM electrolyzer, alkaline electrolyzer, net-zero hydrogen, decarbonisation, industrial hydrogen