Clarifying the Butler–Volmer equation and related approximations for calculating activation losses in solid oxide fuel cell models

This paper shows the importance of including the activation losses in a model designed to accurately predict the voltage–current relationship of a modern solid oxide fuel cell. The governing equation for voltage drop due to activation losses, the Butler–Volmer equation, is discussed and the derivation and applicability of several approximations is investigated. Finally, the assumptions required to combine the separate anode and cathode activation loss calculations into a single-term equation are clarified.