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sci.PEM-electrolyzer-efficiency Calculator
Calculates PEM electrolyzer efficiency from hydrogen production rate, current density, and cell voltage versus thermoneutral voltage (1.48 V). PEM electrolyzers operate at 70–80% efficiency at current densities of 1–3 A/cm² — stack efficiency decreases at higher current density due to ohmic and kinetic overpotentials.
Inputs
P Kw
Rate of energy transfer (W). P = V×I (electrical). P = F×v (mechanical). 1 horsepower ≈ 746 W.
V Cell V
Electric potential difference (V). Drives current through a circuit. Household: 120 V (US) or 230 V (EU/UK).
I Density A Cm2
Mass per unit volume (kg/m³). Water: 1,000. Air: 1.225. Steel: 7,850. Affects buoyancy, flow, and structural loads.
N Cells
Count of items or occurrences.
Eta Faradaic Pct
Useful output divided by total input, as a percentage. 100% is impossible due to losses (heat, friction, resistance).
Results
H₂ production rate (Nm³/hr)
The result of multiplying all input values together.
system efficiency (HHV basis)
Useful output divided by total input, as a percentage. True 100% efficiency is impossible — losses appear as heat. LEDs: 30–50%. Electric motors: 85–97%. Switching supplies: 85–95%.
voltage efficiency η_V
Useful output divided by total input, as a percentage. True 100% efficiency is impossible — losses appear as heat. LEDs: 30–50%. Electric motors: 85–97%. Switching supplies: 85–95%.
molar H₂ production (mol/s)
The result of multiplying all input values together.
η_system = ṅ_H2 × HHV / P_input
Sample size or count used in the calculation.
levelized H₂ cost
The measured or computed level on the applicable scale.