Green Hydrogen is a zero-carbon hydrogen fuel produced by splitting water (H₂O) into hydrogen (H₂) and oxygen (O₂) through electrolysis powered entirely by renewable energy sources such as solar, wind, hydropower, or hybrid renewable systems.
Because renewable electricity is used and no fossil fuels are involved, the full production chain results in near-zero greenhouse gas emissions. Green Hydrogen is widely regarded as the cleanest and most sustainable hydrogen variant available today and a cornerstone of the global energy transition.
Green Hydrogen Production Technologies
1. Water Electrolysis (Core Process)
2H₂O → 2H₂ + O₂
Electrolysis uses electricity to split water molecules into hydrogen and oxygen. When powered by renewable energy, the process is completely carbon-free.
2. Types of Electrolyzers
a) Alkaline Electrolysis (AEL)
Most mature and widely deployed technology. Uses liquid alkaline electrolytes (KOH or NaOH). Efficiency ranges between 60–70%, with lower capital cost and suitability for large, steady operations.
b) Proton Exchange Membrane (PEM) Electrolysis
Uses a solid polymer electrolyte. Highly responsive to variable renewable power. Efficiency of 65–75%, compact footprint, and high-purity hydrogen output. Ideal for solar and wind integration.
c) Solid Oxide Electrolysis (SOEC)
Operates at high temperatures (700–850°C). Achieves very high efficiencies up to 85%. Can utilize industrial waste heat. Currently at early commercialization stage.
Key Characteristics
100% renewable and zero-carbon
No CO₂, NOx, or SOx emissions during production
Extremely high gravimetric energy density
Lightest and cleanest energy carrier
Highly versatile across sectors
Ideal for long-duration renewable energy storage
Physical & Chemical Properties
| Property | Value | Significance |
|---|---|---|
| Chemical Formula | H₂ | Pure hydrogen |
| Energy Content | 120–142 MJ/kg | Highest among fuels |
| Density (STP) | 0.0899 kg/m³ | Extremely light |
| Boiling Point | –252.9°C | Cryogenic storage |
| Auto-Ignition Temp. | ~585°C | Safety parameter |
| Flammability Range | 4–75% in air | Wide ignition window |
Storage & Available Forms
Compressed hydrogen gas (200–700 bar)
Liquid hydrogen (–253°C)
Metal hydride storage systems
Modular cartridges and portable tanks
Applications
Industrial: Green steel, cement, glass, petrochemicals
Chemicals: Green ammonia, green methanol, e-fuels
Power: Hydrogen turbines, grid storage, off-grid power
Transport: FCEVs, trucks, trains, marine, future aviation
Commercial: Backup power, distributed energy systems
R&D & Defense: Fuel cells, space propulsion
Green vs Other Hydrogen Types
| Parameter | Grey | Blue | Green |
|---|---|---|---|
| Feedstock | Fossil fuels | Fossil + CCUS | Water + Renewables |
| CO₂ Emissions | High | Low | Zero |
| Cost | Low | Medium | High (declining) |
| Sustainability | Poor | Moderate | Excellent |
| Role | Legacy | Transitional | Future standard |
Market Outlook
Green Hydrogen is expected to dominate global hydrogen production post-2035 as renewable energy costs decline, electrolyzer efficiency improves, and government incentives accelerate adoption. It is central to net-zero strategies, energy security, and long-term decarbonization.