Lecture 8 Fuel cells revisited
Lecture #8 Fuel Cells Revisited
Fuel cells Load Chemical Rxn> Electricity HO Net:H2+1/202=H2O A: H2-2e=2H+ Ov C:2H++2e+1/202=H2O1.23 Desired voltage achieved by anode k cathode stacking cells(in series) 击00 Fuel reformer Natural gas, alcohol hydrocarbons→H2+CO H2(fuel 02(oxidant)
Fuel Cells Chemical Rxn → Electricity: Net: H2 + 1/2O2 = H2O A: H2 - 2e- = 2H+ OV C: 2H+ + 2e- + 1/2O2 = H2O 1.23 V Desired voltage achieved by stacking cells (in series) Fuel reformer Natural gas, alcohol, hydrocarbons → H2 + CO anode cathode H2 (fuel) H2O O2 (oxidant) Separator (porous) Load
Choice of fuels orogen Hydrazine toxic expensive Natural gas/petroleum catalytic stream reforming(900C) remove co by shift reaction
Choice of Fuels Hydrogen Hydrazine toxic expensive Natural gas/petroleum catalytic stream reforming (900oC) remove CO by shift reaction
How Different from Battery? Battery internal supply of fuel and oxidizer Significance: must be replenished/ recharged EX: Alkaline cell(primary battery discharge and discard Car battery(primary and secondary) discharge(primary and recharge(secondary)
How Different from Battery? Battery internal supply of fuel and oxidizer Significance: must be replenished/recharged EX: Alkaline cell (primary battery) • discharge and discard Car battery (primary and secondary) • discharge (primary) and recharge (secondary)
Fuel Cells Why? No moving parts Long lifetime /reliability High efficiency(40-70%) No Carnot cycle limitations(efficiency independent of size) heat available for cogeneration ow emissions PAFC: 1 ppm Nox, 4 ppm cO,< 1 ppm non-methane reactive organic gases
Fuel Cells - Why? No moving parts Long lifetime/reliability High efficiency (40 - 70%) No Carnot cycle limitations (efficiency independent of size) heat available for cogeneration Low emissions PAFC: < 1 ppm Nox, 4 ppm CO, < 1 ppm non-methane reactive organic gases