Reliability of the balance of plant components in a unitized reversible fuel cell system with a bipolar membrane

The shift towards renewable energy sources has heightened the need for efficient, long-term energy storage solutions. This study assesses the reliability and safety of the Balance of Plant (BOP) components in a reversible Bipolar Membrane Fuel Cell - a unitized system capable of operating in both fuel cell and electrolyzer mode. Fault Tree Analysis is used to identify potential failures and their probabilities, and Failure Mode and Effects Analysis to evaluate failure consequences and propose mitigation strategies. Results indicate a mean time to failure (MTTF) of 1700 h in fuel cell mode, while electrolyzer mode shows a slightly lower mean time to failure of 1540 h. Hydrogen compressors emerge as the most failure-prone components, primarily due to hydrogen embrittlement. Introducing redundancy - particularly for hydrogen compressors - increases the MTTF by about 8 %. However, this does not only come with higher cost, but also a greater system complexity. As a consequence, the positive effect of redundancy on reliability is not very pronounced and can even become negative for certain system configurations. The FMEA revealed that maintenance should be prioritized for components critical to preserving the integrity of the membrane electrode assembly, particularly those protecting the membrane and catalyst, to prevent major damage.