Table 3.
Comparison of two chosen electrochemical devices for study.
| Reversible PEM Fuel Cells | Redox Flow Batteries | |
|---|---|---|
| Reactants | Gas | Liquid |
| Operational temperature | <120 °C [91] | −20 °C to 50 °C [147] |
| Toxicity | No toxic gas emission | Sometimes include toxic materials |
| Flammability | Yes | No |
| Components needed | Power cells; water and gas tubes; hydrogen containers; wires; pumps | Power cells; tubes; electrolyte solution containers; wires; pumps |
| Roundtrip efficiency | 50% [148] | 70–80% [149] |
| Life cycle and life time | >5000 cycles [148] | 1500–15,000 cycles [149] |
| Energy density (Wh/kg) | 400 Wh/kg [150] | 10–35 Wh/kg [151,152] |
| Power density | 10–500 W/kg [153] | 100–166 W/kg [152] |