Key Findings
Operating hours reported in durability data typically indicate how long a stack was tested, not its total lifespan. A number such as 2,000, 5,000, or 10,000 hours does not inherently reveal if a cell remained healthy or reached its limit. To determine actual lifetime, an end-of-life criterion—the maximum allowable voltage rise—must be established, though this is often not documented by suppliers.
Technical Details
Degradation rate, measured in microvolts per hour (µV/h) per cell, allows for the comparison of runs with different lengths. When analyzing these rates, three factors are critical:
- Unit Scale: Rates can be expressed per cell or per stack; for a 23-cell stack, 20 µV/h per cell equals 0.46 mV/h for the whole stack.
- Fitting Window: Including the initial settling period increases the calculated rate compared to fitting only the later, stable part of the run.
- Current Stability: Rates are normally calculated at a fixed current; changing loads cannot be reduced to a rate in the same manner.
Furthermore, hours may be continuous or cumulative, with the latter including shutdowns and restarts that add specific loads to the cell.
Background & Context
Durability is heavily influenced by current density, temperature, electrolyte concentration, and outlet pressure. For example, a published AEM run reached 8,900 hours at 0.2 A/cm², starting at 1.92 V with a rise of 18 µV/h. In contrast, a two-cell, 16 cm² short stack using an HXP-an anode and a PiperION 80 µm membrane ran for 6,358 hours at a higher current density of 0.625 A/cm², with voltage rising from 1.893 V to 1.979 V.
Significance & Outlook
Component synergy is vital; the same anode in the aforementioned short-stack test yielded only 1,234 hours when paired with a different membrane. This demonstrates that durability figures for a single electrode cannot be transferred to different cell configurations. Currently, the HXS-2 2 kW stack has achieved over 3,000 hours of cumulative operation at 0.3 M KOH, 40 °C, and 50 A.
Source: https://hydroxpand.com/en/blog/2026-10-08-reading-electrolyzer-durability-data/
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