Renewable electricity splits water via electrolysis into hydrogen and oxygen (2H2O -> 2H2 + O2). Hydrogen is compressed into storage, then recombined with atmospheric oxygen in a fuel cell to regenerate electricity and water — a chemical "battery" for long-duration or transportable energy storage.
Electrolyzer: 2H2O + electricity -> 2H2 + O2
Fuel cell: 2H2 + O2 -> 2H2O + electricity
round_trip_eff = eff_electrolyzer * eff_fuelcell (~35-50% typical)
- Input power — renewable electricity fed to the electrolyzer stack; more power drives faster bubble production.
- Electrolyzer efficiency — fraction of input energy converted to hydrogen's chemical energy (rest is heat loss).
- Storage tank size — capacity multiplier for the compressed H2 buffer between production and use.
- Fuel-cell draw — how much stored hydrogen is drawn per second to generate electricity on demand.
Because both conversion steps lose energy as heat, the hydrogen economy's round-trip efficiency is inherently lower than direct battery storage — its advantage is energy density and long-duration/seasonal storage, not round-trip efficiency.