Electrolysis
Diagnosing Degradation in PEM Electrolyzers
Dynamic operation with renewable energy causes accelerated aging. EIS helps distinguish between membrane thinning and mass transport issues.
- Ohmic Resistance (R_ohm): Increases due to membrane chemical decomposition (fluoride release).
- Mass Transport (R_mt): Increases at high current densities due to bubble accumulation blocking the PTL.
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Equivalent Circuit Model
L -- R_ohm -- (R_act || CPE) -- (R_mt || CPE)
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Equivalent Circuit Model
L -- R_s -- (R_sei || C) -- (R_ct || C) -- W
Energy Storage
Li-Ion Battery State of Health (SOH)
Rapidly grading retired EV batteries for second-life applications without full cycling.
- SEI Growth (High Freq Arc): Expands significantly as the battery ages and consumes cyclable lithium.
- Charge Transfer (Mid Freq Arc): Increases but is also sensitive to State of Charge (SOC).
Fuel Cells
Flooding vs. Drying in PEM Fuel Cells
Distinguishing between too much water (flooding) and too little (drying) to optimize stack performance.
- Drying: High-Frequency Resistance (HFR) increases as the membrane dries out.
- Flooding: Low-Frequency Arc expands dramatically as liquid water blocks gas diffusion.
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Equivalent Circuit Model
R_mem -- (R_ct || C) -- (R_mt || C)