ECCS Exam 3 9 24

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EECS – Prof. A. Casalegno – 3rd September 2024 1 Standard EECS exam [duration 1 h 40 min] Students who passed TiP reduced number of questions marked with (TiP) [duration 1 h 10 min, remaining further means cancelling TiP mark] To upload https://forms.office.com/e/FtXDEZmsMC maximum 5 single-side A4 pages – “file name” = PERSON_CODE.pdf Basic Part (4.5 points per question, minimum score 12) (TiP: 7.5 points) 1. Draw the electrical potential in the double layer of a PEMFC for the ORR in equilibrium 2. Write the Nernst-Plank equation for mass transport in a solid electrolyte with fixed charges 3. (TiP) Depict the charge curve of a Lithium-ion battery including a period at constant voltage, indicating also reasonable values for State of Charge and voltage Exercise (TiP) A PEMFC stack with 320 cells supplies at low power 17.5 kW and 0.3 A cm-2(LHV=120 MJ/kg). Assuming that 3% of H2 is wasted and its performance follows the reported polarization curve, estimate the efficiency and the power values at 1.8 A cm-2 (high power). Intermediate Part (3 points for each question) (TiP: 5 points) 1. Is the anode overpotential of a PEM electrolyzer positive or negative when O2 evolution reaction (OER) occurs? Demonstrate analyzing 𝐺" 2. (TiP) Voltage limits of batteries can reduce their actual available capacity during discharge: show how this effect is influenced by C-rate. ∆𝑉 0 𝑗 0.78 V 0.67 V 0.3 A cm-2 1.8 A cm-2 EECS – Prof. A. Casalegno – 3rd September 2024 2 Exercise (TiP) A Li-ion battery with nominal capacity of 50 Ah operates at ambient pressure and temperature, supplying 3.35 V during discharge at SoC=70% and C-rate=2 and requiring 3.9 V during charge at SoC=30% and C-rate=0.75. Assuming that: 1. Tafel kinetics is valid for both electrodes 2. ion and mass transport effects in…