🔬 Module 2: PEM Technology
Performance Characteristics
Figure 2.1: Fuel cell voltage and power vs current density. The voltage curve (blue) shows cell voltage decreasing with load due to activation, ohmic, and mass transport losses. The power curve (red) shows peak power output occurring at moderate current densities.
Key Specifications
| Parameter | Typical Value | Notes |
|---|---|---|
| Single Cell Voltage | 0.6-0.8 V | Operating range (OCV: 0.95-1.0V) |
| Power Density | 0.4-1.0 W/cm² | At active area |
| System Efficiency | 40-60% | LHV basis, including BoP losses |
| Operating Temperature | 60-80°C | Optimal for PEM |
| Startup Time | < 30 seconds | From ambient temperature |
Membrane Electrode Assembly (MEA)
Key Components:
1. Proton Exchange Membrane: Nafion® polymer (15-50 μm thick) that conducts H⁺ ions
2. Catalyst Layers: Platinum nanoparticles on carbon (0.2-0.4 mg Pt/cm² total)
3. Gas Diffusion Layers: Carbon fiber paper with PTFE coating (200-250 μm)
4. Bipolar Plates: Coated stainless steel or graphite composite with flow channels
Water Management Challenge
Too Dry: Membrane resistance increases (poor conductivity)
Too Wet: Water floods gas channels (mass transport limitations)
Solution: Control humidity (60-100% RH), temperature, and air stoichiometry