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
Fuel Cells- Why(cont'd) Quiet No moving parts Long device life Competitive price 1 g Pt/1 kW cell =$20-$50/kW Relatively low weight and small size 1 kg/kW
Fuel Cells - Why (cont’d) Quiet No moving parts Long device life Competitive price 1 g Pt/1 kW cell = $20-$50/kW) Relatively low weight and small size 1 kg/kW
Efficiency Heat engine Second Law-Carnot cycle Top efficiency 40% Higher temperatures, higher efficiency Fuel cell No such limitations
Efficiency Heat engine Second Law - Carnot cycle Top efficiency 40% Higher temperatures, higher efficiency Fuel Cell No such limitations
Fuel Cells why not? High initial cost-difficult to enter market Technology unfamiliar to power industry No existing infrastructure Regulatory
Fuel Cells - Why Not? High initial cost - difficult to enter market Technology unfamiliar to power industry No existing infrastructure Regulatory
History 1839 Sir William grove Electrolysis of water Fatherof the fuel Cell 1889 Ludwig Mond and charles Langer/ fuel cell First practical device based on pt Figure 6, 6. Ihe Bacon high pressure H, O, cell. (By courtesy of Mr. I 1932 Francis bacon Bacon Alkali=electrolyte Hart, A.B. Womack, G.J. Fuel Cells: Theory and Application Chapman and Hall: London, 1967 Nickel=electrodes
History 1839 Sir William Grove Electrolysis of water “Father” of the Fuel Cell 1889 Ludwig Mond and Charles Langer “fuel cell” First practical device based on Pt 1932 Francis Bacon Alkali=electrolyte Nickel=electrodes Hart, A.B.; Womack, G.J. Fuel Cells: Theory and Application Chapman and Hall: London, 1967
History (Cont'd 1912-1942 Bauer Molten alkali carbonate electrolyte, solid C anode@ 10000C 1945 davtyan Mixed carbonates and oxides with sand separator work basis for post-war fuel cell work 1950S NASA
History (Cont’d) 1912-1942 Bauer Molten alkali carbonate electrolyte, solid C anode @ 10000C 1945 Davtyan Mixed carbonates and oxides with sand separator work basis for post-war fuel cell work 1950’s NASA
