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Optimizing PEM Hydrogen Electrolyzer Efficiency with a Smart Balance of Plant (BoP)

🟦 1) PEM Hydrogen Electrolyzers:

- Proton exchange membrane (PEM) hydrogen electrolyzer replaces liquid electrolyte with a solid polymer electrolyte that conducts positive ions such as protons.

- PEM tech improves energy efficiency, current density, and dynamic operation by creating a locally acidic environment where protons split water.

- PEM hydrogen electrolyzer uses a solid polymer electrolyte, in contact with electrodes. Bipolar plates made of platinum for the cathode and iridium for the anode are added to resist corrosion caused by uncontrolled polarity and fluctuating charges.

- PEM hydrogen electrolyzers can operate at a current density of up to 2 A/cm2. This is made possible due to the polymer electrolyte membrane, which reduces gas crossover and allows the electrolyzers to function at a lower partial load range of 0-10%. The compact design of this technology enables high operating pressures of 30-40 bar, which is achieved through electrochemical compression.

🟦 2) PEM Hydrogen Electrolyzer efficiency calculation:

2.1 Estack =PH2 / Pelec
Estack = stack efficiency
PH2 = power produced as hydrogen (W)
Pelec = electrical power consumed by electrolyzer (W)

2.2 PH2 =.mH2_stack * HVH2
HVH2 = hydrogen heating value (J/kg)
.mH2_stack = stack hydrogen mass rate (kg/s)

2.3 .mH2_stack = MMH2 * .nH2_stack
MMH2 = hydrogen molar mass (2*10-3 kg/mol)
.nH2_stack = stack hydrogen molar rate (kg/s) 2.4 .nH2_stack = Ncells * Istack / 2F
F = Faraday constant (96485 A.s/mol)
Istack = stack current (A)
Ncells = stack cells number

2.5 Pelec = Vstack * Istack
Istack = stack current (A)
Vstack = stack voltage (V) 2.6 Vstack = Ncells * Vcell
Ncell = stack cells number
Vcell = cell voltage (V)

2.7 Estack = (MMH2 * HVH2)/ (2F * Vcell)

2.8 Esystem = PH2 / (Pelec + PAux)

Esystem = system efficiency
PAux = auxiliary power consumption

🟦 3) Parameter achieved of the developed PEM hydrogen electrolyzer:

- Stack power consumption Operating range = 10 kWe (at max. production), 11.8 kWe (experimental value), 0–100%.
- Auxiliary consumption = 1.25 kW
- Stack efficiency = 77–91%
- Electrolyzer efficiency = 52–61%
- Hydrogen production rate = 0–2.2 Nm3/h
- Pressurization time (at 20 bar) = 10:00 (mm:ss)
- Operating temperature range <68  °C (water flow), <72  °C (hydrogen flow)
- Water consumption = 1.8 l/h, 0.056 µScm -1 < conductivity < 1 µScm -1

🟦 4) Result:
One of the keys to achieving the best performance of PEM hydrogen electrolyzers is the optimal design of the BoP. This involves paying particular attention to its subsystems:
- stack power supply subsystem;
- water management subsystem;
- hydrogen production subsystem;
- cooling subsystem;
- control subsystem;
- control logic. ✅ Source: Check the post image and hyperlink in the comments. ✅ My posts reflect my personal knowledge, experience, and advice. 👇 Can the use of smart BoP improve PEM efficiency?