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Fuel cell

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agney1995

This document provides an overview of fuel cells, including: 1. Fuel cells convert chemical energy directly into electricity through electrochemical reactions. They can produce electricity continuously as long as fuel and oxygen are supplied. 2. Fuel cells are classified based on fuel/oxidizer type and electrolyte. Common types include hydrogen-oxygen, hydrocarbon, alkaline, phosphoric acid, and molten carbonate fuel cells. 3. Proton exchange membrane fuel cells (PEMFCs) operate at lower temperatures (50-100°C) and use a proton-conducting polymer membrane. They are being developed for transport and portable power applications.

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Fuel Cell B.TECH MECHANICAL ENGINEERING, VJTI MUSTAFA KAPADIA- 141010057 AGNEY BHAKARE – 141020040 ANKET TELKAPALLIWAR- 141020039 MUSTAFA POONAWALA- 131020047
Outline 1. Review of Electrochemistry. 2. Fuel Cell Introduction 3. History 4. Design and working principle 5. Classification of fuel cells. 6. Fuel cell analysis and efficiency 7. Proton exchange membrane Fuel Cell (PEMFC) 8. Applications and operating challenges
Electrochemistry: Review Oxidation State (or Oxidation Number): The oxidation state, sometimes referred to as oxidation number, describes degree of oxidation (loss of electrons) of an atom in a chemical compound. Oxidation: A reaction that results in the addition of oxygen or elimination of hydrogen from the element. Electrochemically, oxidation results in the increase in the oxidation state (loss of electrons) from the element. 𝐶𝑢 300 −800 ℃ 𝐶𝑢2+ + 2𝑒− Reduction: A reaction that results in the elimination of oxygen or addition of hydrogen from the element. Electrochemically, reduction results in the decrease in the oxidation state (absorption of electrons) by the element. 𝐶𝑙2 + 2𝑒− 2𝐶𝑙− Anode: The electrode where oxidation occurs. Cathode: The electrode where reduction occurs.
What is Fuel Cell? A fuel cell is an electrochemical cell that converts the chemical energy from a fuel into electricity through an electrochemical reaction of hydrogen fuel with oxygen or another oxidizing agent. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. A related technology is flow batteries, in which the fuel can be regenerated by recharging. The fuel cell market is growing, and in 2013 Pike Research estimated that the stationary fuel cell market will reach 50 GW by 2020.
History October 1838- William Grove : First references to hydrogen fuel cells. 1842- Grove: development of modern Phosphoric-acid fuel cell. 1939- Francis Thomas Bacon: Developed a 5kW stationary fuel cell. 1955- W. Thomas Grubb: modified the original fuel cell design by using a sulphonated polystyrene ion-exchange membrane. Use of platinum as catalyst. 1955-1959: GE developed the technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini. 1960’s: Pratt and Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water 1991- Roger Billings: developed the first hydrogen fuel cell automobile.
Fuel cell: Design Features Fuel cells come in many varieties; however, they all work in the same general manner. Three components: i. Anode ii. Cathode iii. Electrolyte. A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load. Voltage decreases as current increases. To deliver the desired amount of energy, the fuel cells can be combined in series to yield higher voltage, and in parallel to allow a higher current to be supplied. Heat and water generated as byproducts from the cell (CO2 is also produced in some cells).
Fuel cell: Working Principle At the anode a catalyst (platinum) oxidizes the fuel, usually hydrogen, turning the fuel into a positively charged ion and a negatively charged electron. The electrolyte is a substance specifically designed so ions can pass through it, but the electrons cannot. The freed electrons travel through a wire creating the electric current. Ions travel to the cathode. Once reaching the cathode, the ions are reunited with the electrons and the two react with a third chemical, usually oxygen, in presence of a catalyst (nickel), to create water or carbon dioxide.
Classification of Fuel Cells BASED ON FUEL AND OXIDIZER 1. Hydrogen and Oxygen Fuel cell 2. Hydrocarbon and Oxygen Fuel cell 3. Regenerative Fuel cell. BASED ON ELECTROLYTE 1. Alkaline fuel cell 2. Molten Carbonate fuel cell 3. Phosphoric acid Fuel cell
Based on types of Fuel and Oxidant: Hydrogen and Oxygen Fuel Cell: Anode Reaction: 2𝐻2 + 4𝑂𝐻− 4𝐻2 𝑂 + 4𝑒− Cathode Reaction: 𝑂2 + 2𝐻2 𝑂 + 4𝑒− 4𝑂𝐻−
Hydrocarbon and Oxygen Fuel Cell
Regenerative Fuel Cell Cathode: 𝐻2 𝑂 + 2𝑒− 𝐻2 + 𝑂2− Anode: 𝑂2− 1 2 𝑂2 + 𝐻2 Overall: 𝐻2 𝑂 1 2 𝑂2 + 𝐻2
Based on Electrolyte: Alkaline Fuel Cell: • Operates at low temperature 100-220 C • Efficiency 70% • require platinum electrodes therefore expensive. • Require pure Oxygen or air and pure hydrogen. • Used in Apollo spacecraft to provide electricity and water. • Also give heat which can give extra power. • Susceptible to co2 poisoning (formation of K2CO3, blocking of the pores in the cathode by k2co3) therefore air needs to be purified before using.
Anode Cathode Reactions 𝐻2 + 2𝑂𝐻− 2𝐻2 𝑂 + 2𝑒− 𝑂2 + 2𝐻2 𝑂 + 4𝑒− 4𝑂𝐻−
Molten Carbonate Fuel Cell.
Molten Carbonate fuel cell. MCFC’s use a liquid electrolyte (molten carbonate) which consists of a sodium(Na) and potassium(K) carbonate. Molten-carbonate fuel cells (MCFCs) are high-temperature fuel cells that operate at temperatures of 600 °C and above. Since they operate at extremely high temperatures of 650 °C and above, non-precious metals can be used as catalysts at the anode and cathode, reducing costs. When the waste heat is captured and used, overall fuel efficiencies can be as high as 85% The higher temperature also makes the cell less prone to carbon monoxide poisoning than lower temperature systems.
Molten Carbonate Fuel Cell. can be used with a variety of fuels. Disadvantage -- High temperature corrosion and the corrosive nature of the electrolyte
Phosphoric Acid Fuel Cell.
Phosphoric Acid Fuel Cell. At an operating range of 150 to 200 °C, the expelled water can be converted to steam for air and water heating. This potentially allows efficiency increases of up to 70%. PAFCs are CO2-tolerant and even can tolerate a CO concentration of about 1.5%, which broadens the choice of fuels they can use. At lower temperatures phosphoric acid is a poor ionic conductor, and CO poisoning of the platinum electro-catalyst in the anode becomes severe. Disadvantages include rather low power density and aggressive electrolyte.
Phosphoric Acid Fuel Cell. Anode Reaction: 2𝐻2 𝑔 4𝐻+ + 4𝑒− Cathode Reaction: 𝑂2 𝑔 + 4𝐻+ + 4𝑒− 2𝐻2 𝑂 Overall Reaction: 2𝐻2 + 𝑂2 2𝐻20
FUEL CELL PERFORMANCE Electric Work= V*i Charge= Current * time Fuel cell---Q=number of electron*F F= 96500 C ( Faraday’s Constant) W=nFE ( E is no load voltage)
Thermodynamic analysis Here work done will ne nFE nFE=-(dH-TdS)=-dG 1st law dQ=dU+dW dU dH Assumption Reversible Process: If no changes take place in the cell except during the passage of current, and all changes which accompany the current can be reversed by reversing the current, the cell may be called a perfect electrochemical apparatus 2nd LAW: dQ=TdS G- GIBBS FREE ENERGY (MEASURE OF SPONTAINITY) dG<0 : spontaneous (exergonic reaction) dG>0 : endergonic reaction
Efficiency= W/Q • Work=-dG • Q=Change in enthalpy Theoretical Efficiency=-dG/-dH • Actual Efficiency= 𝐴𝑐𝑡𝑢𝑎𝑙 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 • Theoretical voltage(E)= 𝐺 𝑛𝐹 Thermodynamic analysis
EFFICIENCY Cogeneration : The use of the byproducts from Fuel Cell to improve its efficiency. Heat: Can be used as a source of heat to produce electricity or for heating. Cogeneration can give efficiency as high as 90% Efficiency 40% To 60% Note on efficiency: Doesn’t depend on the operating temperature Direct conversion of chemical to electrical energy, so minimum losses Not limited by Carnot efficiency
LOSSES IN ACTUAL FUEL CELL
LOSSES IN ACTUAL FUEL CELL
Proton Exchange Membrane Fuel Cell (PEMFC) Proton-exchange membrane fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges (50 to 100 °C) and a special proton-conducting polymer electrolyte membrane. They are a leading candidate to replace the aging alkaline fuel- cell technology, which was used in the Space Shuttle.
Proton Exchange Membrane Fuel Cell (PEMFC)
PEMFC Design Issues Cost Water and Air Management Temperature Management Durability
Applications Long standing research and development in the following areas of application in being carried out. I. Automobiles (cars, scooters, buses, forklifts). II. Boats III. Submarines. IV. Space shuttle (Project Gemini, Apollo, and the Space Shuttle Programme). V. Airplanes.
Fuel cell

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Fuel cell

  • 1. Fuel Cell B.TECH MECHANICAL ENGINEERING, VJTI MUSTAFA KAPADIA- 141010057 AGNEY BHAKARE – 141020040 ANKET TELKAPALLIWAR- 141020039 MUSTAFA POONAWALA- 131020047
  • 2. Outline 1. Review of Electrochemistry. 2. Fuel Cell Introduction 3. History 4. Design and working principle 5. Classification of fuel cells. 6. Fuel cell analysis and efficiency 7. Proton exchange membrane Fuel Cell (PEMFC) 8. Applications and operating challenges
  • 3. Electrochemistry: Review Oxidation State (or Oxidation Number): The oxidation state, sometimes referred to as oxidation number, describes degree of oxidation (loss of electrons) of an atom in a chemical compound. Oxidation: A reaction that results in the addition of oxygen or elimination of hydrogen from the element. Electrochemically, oxidation results in the increase in the oxidation state (loss of electrons) from the element. 𝐶𝑢 300 −800 ℃ 𝐶𝑢2+ + 2𝑒− Reduction: A reaction that results in the elimination of oxygen or addition of hydrogen from the element. Electrochemically, reduction results in the decrease in the oxidation state (absorption of electrons) by the element. 𝐶𝑙2 + 2𝑒− 2𝐶𝑙− Anode: The electrode where oxidation occurs. Cathode: The electrode where reduction occurs.
  • 4. What is Fuel Cell? A fuel cell is an electrochemical cell that converts the chemical energy from a fuel into electricity through an electrochemical reaction of hydrogen fuel with oxygen or another oxidizing agent. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. A related technology is flow batteries, in which the fuel can be regenerated by recharging. The fuel cell market is growing, and in 2013 Pike Research estimated that the stationary fuel cell market will reach 50 GW by 2020.
  • 5. History October 1838- William Grove : First references to hydrogen fuel cells. 1842- Grove: development of modern Phosphoric-acid fuel cell. 1939- Francis Thomas Bacon: Developed a 5kW stationary fuel cell. 1955- W. Thomas Grubb: modified the original fuel cell design by using a sulphonated polystyrene ion-exchange membrane. Use of platinum as catalyst. 1955-1959: GE developed the technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini. 1960’s: Pratt and Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water 1991- Roger Billings: developed the first hydrogen fuel cell automobile.
  • 6. Fuel cell: Design Features Fuel cells come in many varieties; however, they all work in the same general manner. Three components: i. Anode ii. Cathode iii. Electrolyte. A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load. Voltage decreases as current increases. To deliver the desired amount of energy, the fuel cells can be combined in series to yield higher voltage, and in parallel to allow a higher current to be supplied. Heat and water generated as byproducts from the cell (CO2 is also produced in some cells).
  • 7. Fuel cell: Working Principle At the anode a catalyst (platinum) oxidizes the fuel, usually hydrogen, turning the fuel into a positively charged ion and a negatively charged electron. The electrolyte is a substance specifically designed so ions can pass through it, but the electrons cannot. The freed electrons travel through a wire creating the electric current. Ions travel to the cathode. Once reaching the cathode, the ions are reunited with the electrons and the two react with a third chemical, usually oxygen, in presence of a catalyst (nickel), to create water or carbon dioxide.
  • 8. Classification of Fuel Cells BASED ON FUEL AND OXIDIZER 1. Hydrogen and Oxygen Fuel cell 2. Hydrocarbon and Oxygen Fuel cell 3. Regenerative Fuel cell. BASED ON ELECTROLYTE 1. Alkaline fuel cell 2. Molten Carbonate fuel cell 3. Phosphoric acid Fuel cell
  • 9. Based on types of Fuel and Oxidant: Hydrogen and Oxygen Fuel Cell: Anode Reaction: 2𝐻2 + 4𝑂𝐻− 4𝐻2 𝑂 + 4𝑒− Cathode Reaction: 𝑂2 + 2𝐻2 𝑂 + 4𝑒− 4𝑂𝐻−
  • 11. Regenerative Fuel Cell Cathode: 𝐻2 𝑂 + 2𝑒− 𝐻2 + 𝑂2− Anode: 𝑂2− 1 2 𝑂2 + 𝐻2 Overall: 𝐻2 𝑂 1 2 𝑂2 + 𝐻2
  • 12. Based on Electrolyte: Alkaline Fuel Cell: • Operates at low temperature 100-220 C • Efficiency 70% • require platinum electrodes therefore expensive. • Require pure Oxygen or air and pure hydrogen. • Used in Apollo spacecraft to provide electricity and water. • Also give heat which can give extra power. • Susceptible to co2 poisoning (formation of K2CO3, blocking of the pores in the cathode by k2co3) therefore air needs to be purified before using.
  • 13. Anode Cathode Reactions 𝐻2 + 2𝑂𝐻− 2𝐻2 𝑂 + 2𝑒− 𝑂2 + 2𝐻2 𝑂 + 4𝑒− 4𝑂𝐻−
  • 15. Molten Carbonate fuel cell. MCFC’s use a liquid electrolyte (molten carbonate) which consists of a sodium(Na) and potassium(K) carbonate. Molten-carbonate fuel cells (MCFCs) are high-temperature fuel cells that operate at temperatures of 600 °C and above. Since they operate at extremely high temperatures of 650 °C and above, non-precious metals can be used as catalysts at the anode and cathode, reducing costs. When the waste heat is captured and used, overall fuel efficiencies can be as high as 85% The higher temperature also makes the cell less prone to carbon monoxide poisoning than lower temperature systems.
  • 16. Molten Carbonate Fuel Cell. can be used with a variety of fuels. Disadvantage -- High temperature corrosion and the corrosive nature of the electrolyte
  • 18. Phosphoric Acid Fuel Cell. At an operating range of 150 to 200 °C, the expelled water can be converted to steam for air and water heating. This potentially allows efficiency increases of up to 70%. PAFCs are CO2-tolerant and even can tolerate a CO concentration of about 1.5%, which broadens the choice of fuels they can use. At lower temperatures phosphoric acid is a poor ionic conductor, and CO poisoning of the platinum electro-catalyst in the anode becomes severe. Disadvantages include rather low power density and aggressive electrolyte.
  • 19. Phosphoric Acid Fuel Cell. Anode Reaction: 2𝐻2 𝑔 4𝐻+ + 4𝑒− Cathode Reaction: 𝑂2 𝑔 + 4𝐻+ + 4𝑒− 2𝐻2 𝑂 Overall Reaction: 2𝐻2 + 𝑂2 2𝐻20
  • 20. FUEL CELL PERFORMANCE Electric Work= V*i Charge= Current * time Fuel cell---Q=number of electron*F F= 96500 C ( Faraday’s Constant) W=nFE ( E is no load voltage)
  • 21. Thermodynamic analysis Here work done will ne nFE nFE=-(dH-TdS)=-dG 1st law dQ=dU+dW dU dH Assumption Reversible Process: If no changes take place in the cell except during the passage of current, and all changes which accompany the current can be reversed by reversing the current, the cell may be called a perfect electrochemical apparatus 2nd LAW: dQ=TdS G- GIBBS FREE ENERGY (MEASURE OF SPONTAINITY) dG<0 : spontaneous (exergonic reaction) dG>0 : endergonic reaction
  • 22. Efficiency= W/Q • Work=-dG • Q=Change in enthalpy Theoretical Efficiency=-dG/-dH • Actual Efficiency= 𝐴𝑐𝑡𝑢𝑎𝑙 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 • Theoretical voltage(E)= 𝐺 𝑛𝐹 Thermodynamic analysis
  • 23. EFFICIENCY Cogeneration : The use of the byproducts from Fuel Cell to improve its efficiency. Heat: Can be used as a source of heat to produce electricity or for heating. Cogeneration can give efficiency as high as 90% Efficiency 40% To 60% Note on efficiency: Doesn’t depend on the operating temperature Direct conversion of chemical to electrical energy, so minimum losses Not limited by Carnot efficiency
  • 24. LOSSES IN ACTUAL FUEL CELL
  • 25. LOSSES IN ACTUAL FUEL CELL
  • 26. Proton Exchange Membrane Fuel Cell (PEMFC) Proton-exchange membrane fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges (50 to 100 °C) and a special proton-conducting polymer electrolyte membrane. They are a leading candidate to replace the aging alkaline fuel- cell technology, which was used in the Space Shuttle.
  • 28. PEMFC Design Issues Cost Water and Air Management Temperature Management Durability
  • 29. Applications Long standing research and development in the following areas of application in being carried out. I. Automobiles (cars, scooters, buses, forklifts). II. Boats III. Submarines. IV. Space shuttle (Project Gemini, Apollo, and the Space Shuttle Programme). V. Airplanes.