Green Hydrogen Production

Green hydrogen is hydrogen made by using renewable electricity to split water, so its production causes very low greenhouse-gas emissions. The splitting process, called electrolysis, occurs in an electrolyser and produces hydrogen and oxygen.

Production through electrolysis

Renewable electricity from sources such as solar, wind or hydropower supplies direct current to an electrolyser. Inside it, an electrolyte or membrane conducts ions and helps keep the product gases separate.

• Purified water enters the electrolyser, where electrical energy drives the overall reaction: 2H2O → 2H2 + O2.
• Reduction at the cathode forms hydrogen, while oxidation at the anode forms oxygen.
• The hydrogen is purified and dried, then compressed or converted into a derivative such as ammonia for storage, transport or use.
• Oxygen is obtained as a co-product and may be captured for industrial use.

What makes the hydrogen green

Electrolysis itself does not automatically make hydrogen green; the electricity must come from renewable sources and the associated production emissions must remain low. Under the Indian Green Hydrogen Standard, green hydrogen must have well-to-gate emissions of no more than 2 kg CO2 equivalent per kg of hydrogen, averaged over 12 months.

Significance and production constraints

Green hydrogen can support decarbonisation where direct electrification is difficult, including fertiliser production, refining, steelmaking and energy storage. Its viability depends on inexpensive renewable power, electrolyser cost and utilisation, water availability, and infrastructure for safe compression, storage and transport.

• Variable renewable generation may reduce electrolyser utilisation unless supported by storage, grid supply or flexible operation.
• Hydrogen's low volumetric energy density makes storage and transport more demanding than for many conventional fuels.