Understanding Hydrogen Fuel Cells
Hydrogen has the highest energy density per mass of any fuel at 33.3 kWh/kg (120 MJ/kg). Fuel cells convert hydrogen to electricity at 40-60% efficiency, producing only water. One kg of H2 equals about 1 gallon of gasoline in energy. Green hydrogen from renewable electrolysis produces near-zero CO₂, while grey hydrogen from natural gas reforming emits about 10 kg CO₂ per kg H2.