OBJECTIVES

2. OBJECTIVES After studying Chapter 31, the reader will be able to: • Explain how a fuel cell generates electricity. • Discuss the advantages and disadvantages of fuel cells. • List the types of fuel cells. • Explain how ultracapacitors work. • Discuss alternative energy sources.

3. FUEL-CELL TECHNOLOGYWhat Is a Fuel Cell? • A fuel cell is an electrochemical device in which the chemical energy of hydrogen and oxygen is converted into electrical energy. FIGURE 31-1 Ford Motor Company has produced a number of demonstration fuel-cell vehicles based on the Ford Focus.

4. FUEL-CELL TECHNOLOGYWhat Is a Fuel Cell? FIGURE 31-2 Hydrogen does not exist by itself in nature. Energy must be expended to separate it from other, more complex materials.

5. FUEL-CELL TECHNOLOGYBenefits of a Fuel Cell • A fuel cell can be used to move a vehicle by generating electricity to power electric drive motors, as well as powering the remainder of the vehicle’s electrical system. FIGURE 31-3 The Mercedes-Benz B-Class fuel-cell car was introduced in 2005.

6. FUEL-CELL TECHNOLOGYBenefits of a Fuel Cell • A fuel-cell vehicle (FCV) uses the fuel cell as its only source of power, whereas a fuel-cell hybrid vehicle (FCHV) would also have an electrical storage device that can be used to power the vehicle. FIGURE 31-4 The Toyota FCHV is based on the Highlander platform and uses much of Toyota’s Hybrid Synergy Drive (HSD) technology in its design.

7. FUEL-CELL TECHNOLOGYFuel-Cell Challenges • While major automobile manufacturers continue to build demonstration vehicles and work on improving fuel-cell system design, no vehicle powered by a fuel cell has been placed into mass production. • There are a number of reasons for this, including: • High cost • Lack of refueling infrastructure • Safety perception • Insufficient vehicle range • Lack of durability • Freeze starting problems • Insufficient power density

8. FUEL-CELL TECHNOLOGYTypes of Fuel Cells

9. PEM FUEL CELLSDescription and Operation • The Proton Exchange Membrane fuel cell is also known as a Polymer Electrolyte Fuel Cell (PEFC). • The PEM fuel cell is known for its lightweight and compact design, as well as its ability to operate at ambient temperatures. • This means that a PEM fuel cell can start quickly and produce full power without an extensive warmup period.

10. PEM FUEL CELLSDescription and Operation FIGURE 31-5 The polymer electrolyte membrane only allows H+ ions (protons) to pass through it. This means that electrons must follow the external circuit and pass through the load to perform work.

11. PEM FUEL CELLSFuel-Cell Stacks • A single fuel cell by itself is not particularly useful, as it will generate less than 1 volt of electrical potential. • It is more common for hundreds of fuel cells to be built together in a fuel-cell stack. FIGURE 31-6 A fuel-cell stack is made up of hundreds of individual cells connected in series.

12. PEM FUEL CELLSDirect Methanol Fuel Cells • High-pressure cylinders are one method of storing hydrogen onboard a vehicle for use in a fuel cell. • This is a simple and lightweight storage method, but often does not provide sufficient vehicle driving range. • Another approach has been to fuel a modified PEM fuel cell with liquid methanol instead of hydrogen gas.

13. PEM FUEL CELLSDirect Methanol Fuel Cells FIGURE 31-7 A direct methanol fuel cell uses a methanol/water solution for fuel instead of hydrogen gas.

14. PEM FUEL CELLSDirect Methanol Fuel Cells FIGURE 31-8 A direct methanol fuel cell can be refueled similar to a gasoline-powered vehicle.

15. FUEL-CELL VEHICLE SYSTEMS • Humidifiers • Fuel-Cell Cooling Systems • Air Supply Pumps • Fuel-Cell Hybrid Vehicles • Secondary Batteries. • Ultracapacitors. • Fuel-Cell Traction Motors. • Transaxles. • Power Control Units. • Hydrogen Storage • High-Pressure Compressed Gas. • Liquid Hydrogen. • Solid Storage of Hydrogen.

16. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-9 Power train layout in a Honda FCX fuel-cell vehicle. Note the use of a humidifier behind the fuel-cell stack to maintain moisture levels in the membrane electrode assemblies.

17. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-10 The Honda FCX uses one large radiator for cooling the fuel cell, and two smaller ones on either side for cooling drivetrain components.

18. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-11 Space is limited at the front of the Toyota FCHV engine compartment, so an auxiliary heat exchanger is located under the vehicle to help cool the fuel-cell stack.

19. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-12 The secondary battery in a fuel-cell hybrid vehicle is made up of many individual cells connected in series, much like a fuel-cell stack.

20. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-13 The Honda ultracapacitor module and construction of the individual cells.

21. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-14 An ultracapacitor can be used in place of a high-voltage battery in a hybrid electric vehicle. This example is from the Honda FCX fuel-cell hybrid vehicle.

22. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-15 Drive motors in fuel-cell hybrid vehicles often use stator assemblies similar to ones found in Toyota hybrid electric vehicles. The rotor turns inside the stator and has permanent magnets on its outer circumference.

23. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-16 The General Motors “Skateboard” concept uses a fuel-cell propulsion system with wheel motors at all four corners.

24. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-17 The electric drive motor and transaxle assembly from a Toyota FCHV. Note the three orange cables, indicating that this motor is powered by high-voltage three-phase alternating current.

25. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-18 The power control unit (PCU) on a Honda FCX fuel-cell hybrid vehicle is located under the hood.

26. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-19 Toyota’s FCHV uses a power control unit that directs electrical energy flow between the fuel cell, battery, and drive motor.

27. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-20 This GM fuel-cell vehicle uses compressed hydrogen in three high-pressure storage tanks.

28. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-21 The Toyota FCHV uses high-pressure storage tanks that are rated at 350 bar. This is the equivalent of 5,000 pounds per square inch.

29. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-22 The high-pressure fitting used to refuel a fuel-cell hybrid vehicle.

30. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-23 Note that high-pressure hydrogen storage tanks must be replaced in 2020.

31. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-24 GM’s Hydrogen3 has a range of 249 miles when using liquid hydrogen.

32. FUEL-CELL VEHICLE SYSTEMS FIGURE 31-25 Refueling a vehicle with liquid hydrogen.

33. HYDROGEN FUEL = NO CARBON FIGURE 31-26 Carbon deposits, such as these, are created by incomplete combustion of a hydrocarbon fuel.

34. HYDRAULIC HYBRID STORAGE SYSTEM • Ford Motor Co. is experimenting with a system it calls Hydraulic Power Assist (HPA). • This system converts kinetic energy to hydraulic pressure, and then uses that pressure to help accelerate the vehicle. • It is currently being tested on a four-wheel-drive (4WD) Lincoln Navigator with a 4.0-L V-8 engine in place of the standard 5.4-L engine.

35. HCCI • Homogeneous Charge Compression Ignition (HCCI) is a combustion process. • HCCI is the combustion of a very lean gasoline air–fuel mixture without the use of a spark ignition. • It is a low-temperature, chemically controlled (flameless) combustion process.

36. HCCI FIGURE 31-27 Both diesel and conventional gasoline engines create exhaust emissions due to high peak temperatures created in the combustion chamber. The lower combustion temperatures during HCCI operation result in high efficiency with reduced emissions.

37. PLUG-IN HYBRID ELECTRIC VEHICLES • A plug-in hybrid electric vehicle (PHEV) is a hybrid electric vehicle that is designed to be plugged into an electrical outlet at night to charge the batteries. • By charging the batteries in the vehicle, it can operate using electric power alone (stealth mode) for a longer time, thereby reducing the use of the internal combustion engine (ICE).

38. THE FUTURE FOR ELECTRIC VEHICLES • The future of electric vehicles depends on many factors, including: • The legislative and environmental incentives to overcome the cost and research efforts to bring a usable electric vehicle to the market. • The cost of alternative energy. • Advancement in battery technology that would allow the use of lighter-weight and higher-energy batteries

39. THE FUTURE FOR ELECTRIC VEHICLES • Cold-Weather Concerns • Hot-Weather Concerns • Recharging Methods and Concerns • Charging Methods • Conductive Charging. • Inductive Charging.

40. THE FUTURE FOR ELECTRIC VEHICLES FIGURE 31-28 A typical electric vehicle charging station on the campus of a college in Southern California.

41. THE FUTURE FOR ELECTRIC VEHICLES FIGURE 31-29 A conductive-type charging connector. This type of battery charging connector is sometimes called an AVCON connector, named for the manufacturer.

42. THE FUTURE FOR ELECTRIC VEHICLES FIGURE 31-30 An inductive-type electric vehicle battery charger connector. This type of connector fits into a charging slot in the vehicle, but does not make electrical contact.

43. WHAT IS NEDRA? • NEDRA is the National Electric Drag Racing Association that holds drag races for electric-powered vehicles throughout the United States. FIGURE 31-31 (a) The motor in a compact electric drag car. This 8-inch-diameter motor is controlled by an electronic controller that limits the voltage to 170 volts to prevent commutator flash-over yet provides up to 2,000 amperes. This results in an amazing 340,000 watts or 455 Hp. (b) The batteries used for the compact drag car include twenty 12-volt absorbed glass mat (AGM) batteries connected in series to provide 240 volts.

44. WIND POWER • Wind power is used to help supplement electric power generation in many parts of the country. • Because AC electricity cannot be stored, this energy source is best used to reduce the use of natural gas and coal to help reduce CO2 emissions.

45. WIND POWER FIGURE 31-32 Wind power capacity by area. (Courtesy of U.S. Department of Energy)

46. WIND POWER FIGURE 31-33 A typical wind generator that is used to generate electricity.

47. HYDROELECTRIC POWER • Hydroelectric power is limited to locations where there are dammed rivers and hydroelectric plants. • However, electricity can and is transmitted long distances—so that electricity generated at the Hoover Dam can be used in California and other remote locations

48. HYDROELECTRIC POWER FIGURE 31-34 The Hoover Dam in Nevada/Arizona is used to create electricity for use in the southwest United States.

49. SUMMARY • The chemical reaction inside a fuel cell is the opposite of electrolysis in that electricity is created when hydrogen and oxygen are allowed to combine in the fuel cell. • A fuel cell produces electricity and releases heat and water as the only by-products. • The major disadvantages of fuel cells include: • High cost • Lack of hydrogen refueling stations • Short range • Freezing-temperature starting problems 4. Types of fuel cells include PEM (the most commonly used), PAFC, MCFC, and SOFC.

50. SUMMARY • Ultracapacitors are an alternative to batteries for the storage of electrical energy. • A gasoline-powered engine can be more efficient if it uses a homogeneous charge compression ignition (HCCI) combustion process. • Plug-in hybrid electric vehicles could expand the range of hybrid vehicles by operating on battery power alone. • Wind power and hydroelectric power are being used to recharge plug-in hybrids and provide electrical power for all uses, without harmful emissions.