Unlike a heat engine, fuel cells are not limited by the Carnot efficiency. cite:shell
High-temperature fuel cells such as the solid-oxide fuel cell can make use a combined heat and power process (CHP), leading to higher efficiencies.
stacks :: Multiple fuel cells are combined into fuel cell stacks
Types of fuel cells
In general as the operating temperature of the fuel cell increases, the purity of hydrogen required decreases cite:shell.
Proton-exchange membrane fuel cell cite:shell
- Are the most applicable to the transportation sector,
- Expensive due to a platinum catalyst.
- Operates with air rather than pure oxygen.
- Highest potential for cost reduction. Expected to achieve 30 $/kWel (kilowatt electric), which is comparable to ICEs.
Solid oxide fuel cell cite:shell
- The second most important type of fuel cell.
- More efficient than the PEMFC, but hindered due to high start-up times.
- Applicable to power plants and home energy.