Hydrogen EconomyHydrogen EconomyFuel CellsFuel Cells

PGCC Honors Program ProjectPGCC Honors Program ProjectPresented byPresented by

Queenet IbekwehQueenet Ibekweh7 December 20077 December 2007

Academic Advisor:Academic Advisor:

Prof. William Antonio Boyle, PhDProf. William Antonio Boyle, PhD

What Is A Fuel Cell?What Is A Fuel Cell?A fuel cell, also known as a flow battery, is A fuel cell, also known as a flow battery, is

an electrochemical device that combines a an electrochemical device that combines a fuel and an oxidizer such hydrogen and fuel and an oxidizer such hydrogen and oxygen to produce electricity.oxygen to produce electricity.

Purpose of a Fuel CellPurpose of a Fuel Cell

It is used to produce electrical current that It is used to produce electrical current that can be directed outside the cell to perform can be directed outside the cell to perform work, such as powering an electric motor work, such as powering an electric motor or illuminating a light bulb or a city.or illuminating a light bulb or a city.

Due to the way electricity behaves, this Due to the way electricity behaves, this current returns to the fuel cell, completing current returns to the fuel cell, completing an electric circuit.an electric circuit.

How the Fuel Cell WorksHow the Fuel Cell Works

Hydrogen molecules enter the fuel cell at the anode and Hydrogen molecules enter the fuel cell at the anode and are stripped of their electrons.are stripped of their electrons.

Hydrogen atoms become “ionized” and carry positive Hydrogen atoms become “ionized” and carry positive charges.charges.

Negative charged electrons provide current through the Negative charged electrons provide current through the electrical circuit to perform work.electrical circuit to perform work.

Oxygen enters at the cathode and combines with the Oxygen enters at the cathode and combines with the electrons returning from the electric circuit and the electrons returning from the electric circuit and the hydrogen ions that have traveled through the electrolyte hydrogen ions that have traveled through the electrolyte to the anode.to the anode.

Types of Fuel CellsTypes of Fuel CellsProton exchange membrane fuel Proton exchange membrane fuel

cell (PEMFC)cell (PEMFC)Solid oxide fuel cell (SOFC)Solid oxide fuel cell (SOFC) Alkali fuel cell (AFC)Alkali fuel cell (AFC)Molten-carbonate fuel cell (MCFC)Molten-carbonate fuel cell (MCFC) Phosphoric-acid fuel cell (PAFC)Phosphoric-acid fuel cell (PAFC)Direct-methanol fuel cell (DMFC)Direct-methanol fuel cell (DMFC)

Alkali Fuel CellAlkali Fuel Cell Reactants: Pure hydrogen and oxygen (compressed)Reactants: Pure hydrogen and oxygen (compressed) Electrolyte: Potassium hydroxide (KOH) in water.Electrolyte: Potassium hydroxide (KOH) in water.

Its operating temperature is 150 to 200 degrees C. Its operating temperature is 150 to 200 degrees C.

Alkali cells were used in the Apollo spacecraft to provide both electricity and Alkali cells were used in the Apollo spacecraft to provide both electricity and

drinking water. It has an efficiency of about 70%.drinking water. It has an efficiency of about 70%. It It is very susceptible to is very susceptible to contamination, so it requires very pure hydrogen and oxygen. It is also very contamination, so it requires very pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized. expensive, so this type of fuel cell is unlikely to be commercialized.

Solid Oxide Fuel CellSolid Oxide Fuel Cell

These fuel cells are best suited for large-scale These fuel cells are best suited for large-scale stationary power generators that could provide stationary power generators that could provide electricity for factories or towns. They operate at a electricity for factories or towns. They operate at a temperature of about 700-1000 degrees C. The high temperature of about 700-1000 degrees C. The high temperature also has an advantage: the steam temperature also has an advantage: the steam produced by the fuel cell can be channeled into produced by the fuel cell can be channeled into turbines to generate more electricity. turbines to generate more electricity.

                            Drawing of a solid oxide cell

Molten CarbonateMolten Carbonate Fuel Cells Fuel Cells

This type of fuel cells use high temperature compounds of This type of fuel cells use high temperature compounds of salts such as sodium or magnesium carbonate. Its salts such as sodium or magnesium carbonate. Its efficiency ranges from 60-80% and it operates at a efficiency ranges from 60-80% and it operates at a temperature of about 650 degrees C.temperature of about 650 degrees C.

                                             

Drawing of a molten carbonate cell

PEM Fuel CellsPEM Fuel Cells The Proton Exchange Membrane Fuel Cell (PEMFC) is The Proton Exchange Membrane Fuel Cell (PEMFC) is

the most likely candidate for transportation applications the most likely candidate for transportation applications due to its high power density and low operating due to its high power density and low operating temperature which ranges from 60-80 degrees Celsius. temperature which ranges from 60-80 degrees Celsius. With its low operating temperature, it does not take a With its low operating temperature, it does not take a long time for the fuel cell to warm up and start generating long time for the fuel cell to warm up and start generating energy. The solid, flexible electrolyte will not leak or energy. The solid, flexible electrolyte will not leak or crack, and these cells operate at a low enough crack, and these cells operate at a low enough temperature to make them suitable for homes and cars.temperature to make them suitable for homes and cars.

Hydrogen Fuel CellHydrogen Fuel Cell

Purpose of ElectrolytePurpose of Electrolyte

Electrolyte permits the appropriate ions to Electrolyte permits the appropriate ions to pass between the anode and the cathode.pass between the anode and the cathode.

It acts as the proton exchange membrane It acts as the proton exchange membrane which only conducts positively charged which only conducts positively charged ions and blocks the electrons.ions and blocks the electrons.

Fuel Cell Problems Fuel Cell Problems

Cost Cost

Durability Durability

Infrastructure Infrastructure

Why Use Fuel Cells?Why Use Fuel Cells?

The efficiency of a gasoline-powered car is surprisingly low The efficiency of a gasoline-powered car is surprisingly low and all the heat that comes out in the exhaust or goes and all the heat that comes out in the exhaust or goes into the radiator is wasted energy. The overall efficiency into the radiator is wasted energy. The overall efficiency of a gas engine is around 20% which refers to the of a gas engine is around 20% which refers to the thermal-energy content of the gasoline converted into thermal-energy content of the gasoline converted into mechanical work. mechanical work.

Fuel-cell vehicles are potentially as efficient as a battery-Fuel-cell vehicles are potentially as efficient as a battery-powered car that relies on a non-fuel-burning power powered car that relies on a non-fuel-burning power plant, therefore, decreasing our dependency on oil and plant, therefore, decreasing our dependency on oil and atmospheric deterioration (“pollution”) due to the atmospheric deterioration (“pollution”) due to the combustion of fossil fuels.combustion of fossil fuels.

Gas prices from 1990-2004Gas prices from 1990-2004

Literature CitedLiterature CitedCBC News, Technology and Science CBC News, Technology and Science Research boosts potential of Research boosts potential of

hydrogen fuel.hydrogen fuel.

http://www.cbc.ca/technology/story/2007/11/13/hydrogen.html#skip300x250http://www.cbc.ca/technology/story/2007/11/13/hydrogen.html#skip300x250

The Lugar Energy Initiative. The Lugar Energy Initiative.

http://lugar.senate.gov/.../fuel/electricity.htmhttp://lugar.senate.gov/.../fuel/electricity.htm

The Time to Care. The Time to Care.

http://thetimetocare.blogspot.com/http://thetimetocare.blogspot.com/

How Stuff Works. It’s good to know.How Stuff Works. It’s good to know.

http://auto.howstuffworks.com/fuel-cell2.htm http://auto.howstuffworks.com/fuel-cell2.htm

Fuell Cells: Fuel Cell BasicsFuell Cells: Fuel Cell Basics

http://americanhistory.si.edu/fuelcells/basics.htm http://americanhistory.si.edu/fuelcells/basics.htm