Hydrogen fuel advantages and disadvantages

Hydrogen fuel is hydrogen (H₂) used as an energy carrier: it is burnt in engines and turbines or used in fuel cells to produce electricity with water as the only product. Hydrogen is not found free in nature in large amounts, so it must be produced from water (electrolysis), natural gas (steam reforming), biomass or coal. It is an energy carrier, not a primary source.

2H₂ + O₂ → 2H₂O + energy

Calorific value: about 120–142 MJ/kg (higher than any other fuel; about 2.5 times that of petrol per kg), but its volume energy density is very low.

Advantages

• Burns cleanly: only water vapour, no CO₂ at the point of use (and no SO₂, soot).
• High energy per kilogram (about 120 MJ/kg).
• Can be produced from water using renewable electricity (green hydrogen), and so supports a clean energy system.
• Fuel cells have high efficiency (40–60%, up to 80% with combined heat) and quiet operation.
• Can store surplus renewable electricity, and can be used in transport, industry and power.
• Can be transported by pipelines and stored for long periods.

Disadvantages

• Does not exist free; production needs energy, and today most hydrogen (grey hydrogen) comes from natural gas and emits CO₂.
• Low volumetric energy density, so needs high-pressure tanks (350–700 bar), liquefaction (−253 °C) or hydrides: costly and heavy.
• Highly flammable and explosive (wide flammability range 4–75% in air), and leaks easily, so safety is a concern.
• Infrastructure (production, pipelines, filling stations) is missing and expensive.
• Fuel cells and electrolysers are costly, and round-trip efficiency is low (about 30–40%).
• Embrittlement of metals.