Fuel cell
An electrochemical device that converts the chemical energy of hydrogen or another fuel directly into electricity and heat, without combustion.
A fuel cell works like an electrolyser in reverse: hydrogen is oxidised at the anode, ions cross an electrolyte, and oxygen is reduced at the cathode, producing water. The theoretical cell voltage is 1.23 V; practical cells operate at 0.6–0.8 V under load.
Main types:
- PEMFC: 60–80°C, platinum catalyst, fast start; used in fuel cell electric vehicles and buses. System efficiency 50–60% at part load, lower at full power.
- SOFC: 600–1,000°C, can run on natural gas or biogas via internal reforming; 55–65% electrical efficiency, over 85% total with heat recovery in CHP.
- MCFC and PAFC: stationary power at hundreds of kW to MW scale.
- AFC: alkaline, historically used in spacecraft.
Hydrogen round-trip efficiency, from electricity to hydrogen and back through a fuel cell, is only 30–40%, compared with 85–90% for lithium-ion batteries, which limits hydrogen to long-duration and seasonal storage roles. PEM stacks for vehicles target 8,000 hours (cars) to 25,000–30,000 hours (heavy-duty). South Korea, Japan and the United States hold most installed stationary fuel cell capacity, with South Korea above 1 GW.
Related terms
All terms →- Electrolyser
An electrochemical device that uses electric current to split water into hydrogen and oxygen; the core equipment of green hydrogen production.
- Green hydrogen
Hydrogen produced by splitting water in an electrolyser powered by renewable electricity, with near-zero direct CO2 emissions.
- Fuel cell electric vehicle (FCEV)
An electric vehicle that generates its electricity on board from hydrogen in a fuel cell, emitting only water vapour at the tailpipe.
- Round-trip efficiency
The share of energy put into a storage system that can be recovered on discharge, measured at a defined boundary (cell, DC, or AC grid connection).
- CHP (Combined Heat and Power)
Simultaneous generation of electricity and useful heat from one fuel input, reaching total efficiencies of 75–90% versus about 35–60% for power-only plants.