<ul><li>Explain how a fuel cell generates electricity. </li></ul><ul><li>Discuss the advantages and disadvantages of fuel cells. </li></ul><ul><li>List the types of fuel cells. </li></ul><ul><li>Explain how ultracapacitors work. </li></ul><ul><li>Discuss alternative energy sources. </li></ul>OBJECTIVES: After studying Chapter 66, the reader should be able to:
<ul><li>double-layer technology • electrolysis • electrolyte • energy carrier • energy density </li></ul><ul><li>farads • fuel cell • fuel cell hybrid vehicle (FCHV) • fuel-cell stack • fuel cell vehicle (FCV) </li></ul><ul><li>homogeneous charge compression ignition (HCCI) • hydraulic power assist (HPA) • inverter </li></ul><ul><li>low-grade heat </li></ul>KEY TERMS: Continued
<ul><li>membrane electrode assembly (MEA) • NEDRA </li></ul><ul><li>plug-in hybrid electric vehicle (PHEV) • polymer electrolyte fuel cell (PEFC) • proton exchange </li></ul><ul><li>membrane (PEM) • range • specific energy ultracapacitor • wheel motors • wind farms </li></ul>KEY TERMS:
FUEL CELL TECHNOLOGY <ul><li>What 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, discovered in 1839 by Sir William Grove, a Welsh physician. In the 1950s, NASA put this principle to work in building devices for powering space exploration vehicles. In the present day, fuel cells are being developed to power homes and vehicles while producing low or zero emissions. </li></ul>Continued Figure 66–1 Ford Motor Company has produced a number of demonstration fuel-cell vehicles based on the Ford Focus.
<ul><li>The chemical reaction in a fuel cell is the opposite of electrolysis , in which electrical current is passed through water in order to break it into its components, hydrogen and oxygen. Energy can be retrieved by allowing hydrogen and oxygen to reunite in a fuel cell. It is important to note that while hydrogen can be used as a fuel, it is not an energy source. Instead, hydrogen is only an energy carrier , as energy must be expended to generate the hydrogen and store it so it can be used as a fuel. Hydrogen is an excellent fuel because it has a very high specific energy when compared to an equivalent amount of fossil fuel. One kilogram (kg) of hydrogen has three times the energy content as one kilogram of gasoline. Hydrogen is the most abundant element on earth, but it does not exist by itself in nature. </li></ul>Continued
<ul><li>Hydrogen is also found in many other compounds, most notably hydrocarbons, such as natural gas or crude oil. In order to store hydrogen for use as a fuel, processes must be undertaken to separate it from these materials. </li></ul>Figure 66–2 Hydrogen does not exist by itself in nature. Energy must be expended to separate it from other, more complex materials. Continued
Figure 66–3 The Mercedes-Benz B-Class fuel-cell car was introduced in 2005. <ul><li>Benefits of a Fuel Cell A fuel cell can be used to move a vehicle by generating electricity to power electric drive motors. Fuel cells by themselves do not generate carbon emissions such as CO 2 . The only emissions are water vapor and heat, and this makes the fuel cell an ideal candidate for a ZEV (zero-emission vehicle). Another benefit of fuel cells is they have very few moving parts and potential to be very reliable. A number of OEMs have spent many years and millions of dollars in order to develop a low-cost, durable, and compact fuel cell that will operate satisfactorily under all driving conditions. </li></ul>Continued
<ul><li>A fuel-cell vehicle ( FCV ) uses the fuel cell as its only source of power, where a fuel - cell hybrid vehicle ( FCHV ) would also have an electrical storage device that can be used to power the vehicle. Most new designs of fuel-cell vehicles are now based on a hybrid configuration due to the significant increase in efficiency and driveability that can be achieved with this approach. </li></ul>Figure 66–4 The Toyota FCHV is based on the Highlander platform and uses much of Toyota’s Hybrid Synergy Drive (HSD) technology in its design. Continued
<ul><li>Fuel-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: </li></ul>Continued <ul><li>High cost </li></ul><ul><li>Insufficient power density </li></ul><ul><li>Insufficient vehicle range; lack of refueling infrastructure </li></ul><ul><li>Safety perception ; l ack of durability </li></ul><ul><li>Freeze starting problem </li></ul>All of these problems are being actively addressed by researchers, and significant improvements are being made. Once cost and performance levels meet that of current vehicles, fuel cells will be adopted as a mainstream technology.
<ul><li>Types of Fuel Cells There are a number of different types of fuel cells, differentiated by type of electrolyte used in their design. Some operate at room temperature; others at up to 1800°F. </li></ul>See the chart on Page 798 of your textbook. The design best suited for automotive applications is the Proton Exchange Membrane ( PEM ). It must have hydrogen to operate, and this may be stored on the vehicle or generated as needed.
PEM FUEL CELLS <ul><li>Description and Operation The Proton Exchange Membrane fuel cell is also known as a Polymer Electrolyte Fuel Cell ( PEFC ). It is known for lightweight and compact design, and ability to operate at ambient temperatures. The PEM is a simple design based on a membrane that is coated on both sides with a catalyst such as platinum or palladium. Two electrodes, one each side of the membrane, are responsible for distributing hydrogen and oxygen over the membrane surface, removing waste heat, and providing a path for electrical current. The part of the PEM fuel cell that contains the membrane, catalyst coatings, and electrodes is known as the Membrane Electrode Assembly ( MEA ). </li></ul>Continued
<ul><li>The negative electrode ( anode ) has hydrogen gas directed to it, oxygen is sent to the positive electrode ( cathode ). Hydrogen is sent to the negative electrode as H 2 molecules, which break apart into H + ions (protons) in the presence of the catalyst. The electrons (e - ) from the hydrogen atoms are sent through the external circuit, generating electricity to perform work. These same electrons are then sent to the positive electrode where they rejoin the H + ions that have passed through the membrane and have reacted with oxygen in the presence of the catalyst. This creates H 2 O and waste heat, the only emissions from a PEM cell. </li></ul>Continued NOTE: Remember a fuel cell generates direct current (DC) electricity as electrons only flow in one direction (from the anode to the cathode).
Figure 66–5 The polymer electrolyte membrane only allows H ions (protons) to pass through it. This means electrons follow the external circuit and pass through the load to perform work. Continued
<ul><li>Fuel-Cell Stacks A single fuel cell is not particularly useful, as it will generate less than 1 volt of electrical potential. It is common for hundreds of fuel cells to be built together in a fuel - cell stack . </li></ul>Figure 66–6 A fuel-cell stack is made of hundreds of individual cells connected in series. Continued The fuel cells are connected in series so total voltage of the stack is the sum of the individual cell voltages. The fuel cells are placed end-to-end in the stack, much like slices in a loaf of bread. Automotive fuel-cell stacks contain upwards of 400 cells in their construction.
<ul><li>Total voltage of the fuel-cell stack is determined by the number of individual cells incorporated into the assembly. Current-producing ability of the stack is dependent on the surface area of the electrodes. Since output of the fuel-cell stack is related to both voltage and current ( voltage x current = power ), increasing the number of cells or increasing the surface area of the cells will increase power output. Some fuel-cell vehicles will use more than one stack, depending on power output requirements and space limitations. </li></ul>Continued
<ul><li>Purity of the fuel gas is critical with PEM fuel cells. If more than 10 parts per million (ppm) of carbon monoxide is present in the hydrogen stream being fed to the PEM anode, the catalyst will be gradually poisoned and the fuel cell will eventually be disabled. This means that the purity must be “five nines” (99.999% pure). This is a major concern in vehicles where hydrogen is generated by reforming hydrocarbons such as gasoline, because it is difficult to remove all CO from the hydrogen during the reforming process. In these applications, some means of hydrogen purification must be used to prevent CO poisoning of the catalyst. </li></ul>CO Poisons the PEM Fuel Cell Catalyst Continued
<ul><li>Direct Methanol Fuel Cells High-pressure cylinders are one method simple and lightweight storage method onboard a vehicle for use in a fuel cell, but often does not provide sufficient range. </li></ul>Figure 66–7 A direct methanol fuel cell uses a methanol/water solution for fuel instead of hydrogen gas. Continued Another approach has been to fuel a modified PEM fuel cell with liquid methanol instead of hydrogen gas.
<ul><li>Methanol, most often produced from natural gas, has a chemical symbol of CH 3 OH and a higher energy density than gaseous hydrogen. It exists in a liquid state at normal temperatures, and no compressors or other high-pressure equipment is needed. </li></ul>Figure 66–8 A direct methanol fuel cell can be refueled similar to a gasoline-powered vehicle. Continued This means a fuel-cell vehicle can be refueled with a liquid instead of high-pressure gas. This makes refueling simpler and produces greater vehicle driving range.
<ul><li>Direct methanol fuel cells suffer from a number of problems, including the corrosive nature of methanol itself. Methanol cannot be stored in existing tanks and requires a separate infrastructure for handling and storage. Another problem is “fuel crossover,” in which methanol makes its way across the membrane assembly and diminishes performance of the cell. Direct methanol fuel cells also require much greater amounts of catalyst in their construction, which leads to higher costs. These challenges are leading researchers to look for alternative electrolyte materials and catalysts to lower cost and improve cell performance. </li></ul>Continued
<ul><li>Most of the methanol in the world is produced by reforming natural gas. Natural gas is a hydrocarbon, but does not increase the carbon content of our atmosphere as long as it remains in reservoirs below the earth’s surface. However, natural gas that is used as a fuel causes extra carbon to be released into the atmosphere, which is said to contribute to global warming. Natural gas is not a carbon-neutral fuel, and neither is methanol that is made from natural gas. Fortunately, it is possible to generate methanol from biomass and wood waste. Methanol made from renewable resources is carbon neutral, because no extra carbon is being released into the earth’s atmosphere than what was originally absorbed by the plants used to make methanol. </li></ul>When is Methanol Considered to be a “Carbon-Neutral” Fuel?
FUEL CELL VEHICLE SYSTEMS <ul><li>Humidifiers Water management in PEM fuel cell is critical. Too much can prevent oxygen making contact with the positive electrode; too little allows the electrolyte to dry out and lower its conductivity. Amount of water and where it resides is critical in determining at how low a temperature the fuel cell will start; water freezing in the fuel cell can prevent it from starting. The humidifier achieves balance, providing sufficient moisture to the fuel cell by recycling water evaporating at the cathode. It is located in the air line leading to the cathode of the fuel-cell stack. See Figure 66–9. </li></ul>Continued
Figure 66–9 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. Continued
<ul><li>The polymer electrolyte membrane assembly in a PEM fuel cell acts as conductor of positive ions and as a gas separator. However, it can only perform these functions effectively if it is kept moist. A fuel-cell vehicle uses an air compressor to supply air to the positive electrodes of each cell, and this air is sometimes sent through a humidifier first to increase its moisture content. The humid air then comes in contact with the membrane assembly and keeps the electrolyte damp and functioning correctly. </li></ul>What is the Role of the Humidifier in a PEM Fuel Cell?
<ul><li>Fuel-Cell Cooling Systems Excess heat generated by the fuel cell during normal operation can lead to a breakdown of the polymer electrolyte membrane. A liquid cooling system must be utilized to remove waste heat from the fuel-cell stack. </li></ul>Figure 66–10 The Honda FCX uses one large radiator for cooling the fuel cell, and two smaller ones on either side for cooling drive train components. Continued The heat generated by a fuel cell is classified as low - grade heat . This means that there is only a small difference between the temperature of the coolant and that of the ambient air. Heat exchangers with a larger surface area must be utilized.
<ul><li>In some cases, heat exchangers may be placed in other areas of the vehicle when available space at the front of the engine compartment is insufficient. </li></ul>Figure 66–11 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. Continued An electric water pump and a fan drive motor are used to enable operation of the fuel cell’s cooling system. In the Toyota FCHV, an auxiliary heat exchanger is underneath the vehicle to increase the cooling system heat-rejection capacity. These and other support devices use electrical power generated by the fuel cell, and decrease overall efficiency of the vehicle.
<ul><li>Air Supply Pumps Air must be supplied to the fuel-cell stack at the proper pressure and flow rate to enable proper performance under all driving conditions. This function is performed by an onboard air supply pump that compresses atmospheric air and supplies it to the fuel cell’s positive electrode (cathode). This pump is often driven by a high-voltage electric drive motor. </li></ul>Continued
<ul><li>Fuel - Cell Hybrid Vehicles Hybridization increases efficiency in vehicles with conventional drive trains, as energy that was once lost during braking and otherwise normal operation is instead stored for later use in a high-voltage battery or ultracapacitor . This same advantage can be gained by applying hybrid design concepts to fuel-cell vehicles. The fuel cell is the only power source in a fuel-cell vehicle; the fuel-cell hybrid vehicle (FCHV) relies on both the fuel cell and an electrical storage device for motive power. Driveability also enhanced with this design, as the electrical storage device is able to supply energy immediately to drive motors and overcome “throttle lag” on the part of the fuel cell. </li></ul>Continued
<ul><li>Secondary Batteries All hybrid vehicle designs require a means of storing electrical energy generated during regenerative braking and other applications. </li></ul>Figure 66–12 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. Continued The secondary battery is built similar to a fuel-cell stack. It is many low-voltage cells connected in series to build a high-voltage battery. In most FCHV designs, a high-voltage nickel-metal hydride (NiMH) battery pack is used as a secondary battery. This is most often located near the back of the vehicle, either under or behind the rear passenger seat.
<ul><li>Ultracapacitors An alternative to storing electrical energy in batteries is to use ultracapacitors, which are built very different from conventional capacitors. </li></ul>Figure 66–13 The Honda ultracapacitor module and construction of the individual cells. Ultracapacitor cells are based on double - layer technology , in which two activated-carbon electrodes are immersed in an organic electrolyte. The electrodes have a very large surface area and are separated by a membrane that allows ions to migrate but prevents the electrodes from touching. Continued
<ul><li>Charging and discharging occurs as ions move in the electrolyte, but no chemical reaction takes place. Ultracapacitors can charge and discharge quickly and efficiently, making them especially suited for electric assist applications in fuel-cell hybrid vehicles. </li></ul>Figure 66–14 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. Total capacitance = sum of individual cells Ultracapacitors that are used in fuel-cell hybrid vehicles are made up of multiple cylindrical cells connected in parallel. Greater capacitance means greater storage ability, and contributes to greater assist for the electric motors in a fuel-cell hybrid vehicle. Continued
<ul><li>Fuel-Cell Traction Motors Electric traction motors used in fuel-cell hybrid vehicles are very similar to those being used in current hybrid electric vehicles. The typical drive motor is based on an AC synchronous design, referred to as a DC brushless motor. </li></ul>Figure 66–15 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. Continued This design is very reliable as it does not use a commutator or brushes, but has a three-phase stator and permanent magnet rotor. An electronic controller (inverter) is used to generate the three-phase high-voltage AC current required by the motor.
<ul><li>While the motor itself simple, the electronics to power and control it are complex. Some fuel-cell hybrid vehicles use a single electric drive motor and a transaxle to direct power to the wheels. </li></ul>Figure 66–16 The General Motors “Skateboard” concept uses a fuel-cell propulsion system with wheel motors at all four corners. It is also possible to use wheel motors to drive individual wheels, which allows greater control of the torque being applied to each individual wheel. Continued
<ul><li>Transaxles Fuel-cell hybrid vehicles are effectively pure electric vehicles in that their drive train is electrically driven. Electric motors work very well for automotive applications because they produce high torque at low rpms and maintain a consistent power output throughout their entire rpm range. ICE-powered vehicles require complex transmissions with multiple speed ranges in order to accelerate the vehicle quickly and maximize efficiency. Fuel-cell hybrid vehicles use electric drive motors that require only a simple reduction in their final drive and a differential to send power to the drive wheels. </li></ul>Continued
Figure 66–17 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. <ul><li>No gear shifting is required, nor are mechanisms such as torque converters and clutches. A reverse gear is not required, as the electric drive motor is simply powered in the opposite direction. </li></ul>Transaxles used in fuel-cell hybrid vehicles are extremely simple with few moving parts. They are extremely durable, quiet, and reliable. Continued
<ul><li>Power Control Units The drive train of a fuel-cell hybrid vehicle is controlled by a power control unit (PCU), which controls fuel-cell output and directs the flow of electricity between components. One of the functions of the PCU is to act as an inverter , which changes direct current from the fuel-cell stack into three-phase alternating current for use in the vehicle drive motor(s). </li></ul>Figure 66–18 The power control unit (PCU) on a Honda FCX fuel-cell hybrid vehicle is located under the hood. Continued
Figure 66–19 Toyota’s FCHV uses a power control unit that directs electrical energy flow between the fuel cell, battery, and drive motor. <ul><li>Power to & from the secondary battery is directed through the power control unit. </li></ul>It is also responsible for maintaining the state of charge of the battery pack. Also for controlling and directing the output of the fuel-cell stack. Continued
<ul><li>During regenerative braking, the electric drive motor acts as a generator and converts kinetic energy of the vehicle into electricity for recharging the high-voltage battery pack. The PCU must take three-phase power from the motor (generator) and convert (or rectify ) this into DC voltage, sent to the battery. DC power from the fuel cell will also be processed through the PCU for recharging the battery pack. A DC-to-DC converter is for converting high voltage from the secondary battery pack into 12 volts required for the vehicle’s electrical system. 42 volts may also be required to operate accessories such as the electric-assist power steering. The DC converter function may be built into the power control unit. </li></ul>Continued
<ul><li>Hydrogen Storage Modern drivers have grown accustomed to having a minimum of 300 miles between refueling stops. Hydrogen has a very high energy content on a pound-for-pound basis, but density is less than that of conventional liquid fuels. This is because gaseous hydrogen, even at high pressure, has a very low physical density (mass per unit volume). </li></ul>Figure 66–20 This GM fuel-cell vehicle uses compressed hydrogen in three high-pressure storage tanks. Continued
<ul><li>A number of methods of hydrogen storage are considered for use in fuel-cell hybrid vehicles, including high-pressure compressed gas, liquefied hydrogen, and solid storage in metal hydrides. Much research is being conducted to solve the issue of onboard hydrogen storage. </li></ul>Continued High-Pressure Compressed Gas Most current fuel-cell hybrid vehicles use compressed hydrogen that is stored in tanks as a high-pressure gas. This approach is the least complex of all the storage possibilities, but also has the least energy density. Multiple small storage tanks are often used rather than one large one in order to fit them into unused areas of the vehicle.
<ul><li>It is common for a pressure of 5,000 psi (350 bar) to be used. Technology is available to store at up to 10,000 psi (700 bar). </li></ul>Figure 66–21 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. The tanks used for compressed hydrogen storage are typically made with an aluminum liner wrapped in several layers of carbon fiber and an external coating of fiberglass. There is also a special electrical connector that is used to enable communication between the vehicle and the filling station during the refueling process. Continued
Figure 66–22 The high-pressure fitting used to refuel a fuel-cell hybrid vehicle. <ul><li>In order to refuel compressed hydrogen storage tanks, a special high- pressure fitting is installed in place of the filler neck for conventional vehicles. </li></ul>Figure 66–23 Note that high-pressure hydrogen storage tanks must be replaced in 2020. Continued
Figure 66–24 GM’s Hydrogen3 has a range of 249 miles when using liquid hydrogen. <ul><li>Liquid Hydrogen Hydrogen can be liquefied in an effort to increase its energy density, but this requires that it be stored in cryogenic tanks at -423°F (-253°C). </li></ul>This increases vehicle range, but impacts overall efficiency, as a great deal of energy is required to liquefy hydrogen and a certain amount of the liquid hydrogen will “boil off” while in storage. Continued
Figure 66–25 Refueling a vehicle with liquid hydrogen. Continued
<ul><li>Solid Storage of Hydrogen Solid form as a metal hydride, similar to how a nickel-metal hydride (NiMH) battery works. </li></ul><ul><li>A demonstration vehicle features a lightweight fiber-wrapped storage tank under the body storing 3 kg (about 6.6 pounds) of hydrogen as a metal hydride at low pressure. The vehicle can travel almost 200 miles with this amount of fuel. One kilogram of hydrogen is equal to 1 gallon of gasoline. Three gallons of water will generate 1 kilogram of hydrogen. A metal hydride is formed when gaseous hydrogen molecules disassociate into individual hydrogen atoms and bond with the metal atoms in the storage tank. This process uses powdered metallic alloys capable of rapidly absorbing hydrogen to make this occur. </li></ul>Continued
<ul><li>Most fuels contain hydrocarbons or molecules that contain both hydrogen and carbon. During combustion, the first element burned is the hydrogen. </li></ul>Hydrogen Fuel = No Carbon Figure 66–26 Carbon deposits, such as these, are created by incomplete combustion of a hydrocarbon fuel. If combustion is complete, then all the carbon is converted to carbon dioxide gas and exits the engine in the exhaust. However, if combustion is not complete, carbon monoxide is formed, plus leaving some unburned carbon to accumulate in the combustion chamber.
HYDRAULIC HYBRID STORAGE SYSTEM <ul><li>Ford is experimenting with a system it calls Hydraulic Power Assist ( HPA ), which converts kinetic energy to hydraulic pressure, and uses the pressure to help accelerate the vehicle. A variable-displacement hydraulic pump/motor is mounted on the transfer case and connected to the output shaft that powers the front drive shaft. HPA works with or without 4WD engaged. A valve block mounted on the pump contains solenoid valves to control the flow of hydraulic fluid. A high-pressure accumulator is mounted behind the rear axle, with a low-pressure accumulator behind it to store hydraulic fluid. </li></ul>Continued
<ul><li>The master cylinder has a “deadband,” meaning the first few fractions of an inch of travel do not pressurize the brake system. When the driver presses the brake pedal, a pedal movement sensor signals the control unit, which then operates solenoid valves to send hydraulic fluid from the low-pressure reservoir to the pump. The pumping action slows the vehicle, similar to compression braking, and the fluid is pumped into the high-pressure reservoir. </li></ul><ul><li>Releasing the brake and pressing on the accelerator signals the control unit to send that high-pressure fluid back to the pump, which then acts as a hydraulic motor and adds torque to the drive line. The system can be used to launch the vehicle from a stop and/or add torque for accelerating from any speed. </li></ul>Continued
<ul><li>While the concept is simple, the system itself is very complicated, and additional components include: </li></ul><ul><li>Pulse suppressors </li></ul><ul><li>Filters </li></ul><ul><li>An electric circulator pump for cooling the main pump/motor </li></ul>Potential problems with this system include leakage problems with seals and valves, getting air out of the system, and noise. A 23% improvement in fuel economy and improvements in emissions reduction were achieved using a dynamometer. The HPA system could be developed for any type of vehicle with any type of drive train, it does add weight and complexity, which would add to the cost.
<ul><li>Homogeneous Charge Compression Ignition ( 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. HCCI combustion is difficult to control and extremely sensitive to changes in temperature, pressure, and fuel type. Advantages include a gasoline engine able to deliver 80% of diesel efficiency (a 20% increase in fuel economy) for 50% of the cost. A diesel engine using HCCI can deliver gasoline-like emissions. Spark and injection timing are no longer a factor as they are in a conventional port-fuel injection system. </li></ul>HCCI Continued
Figure 66–27 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. <ul><li>Work is also being done on piston and combustion chamber shape to reduce combustion noise and vibration. </li></ul>Continued
PLUG-IN HYBRID ELECTRIC VEHICLES <ul><li>A plug-in hybrid electric vehicle ( PHEV ) is a hybrid electric vehicle 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, reducing the use of the internal combustion engine (ICE). </li></ul><ul><li>If a production plug-in hybrid is built, it should be able to get about twice the fuel economy of a conventional hybrid. The extra weight of the batteries will be offset, somewhat, by the reduced weight of a smaller ICE. </li></ul><ul><li>Counting fuel and service, the total lifetime cost of ownership will be lower than a conventional gasoline-powered vehicle. </li></ul>Continued
THE FUTURE FOR ELECTRIC VEHICLES <ul><li>The future of electric vehicles depends on many factors: </li></ul>Continued <ul><li>The legislative and environmental incentives to overcome the cost and research efforts to bring a usable electric vehicle to the market. </li></ul><ul><li>The cost of alternative energy. If the cost of fossil fuels increases to the point that the average consumer cannot afford to drive a conventional vehicle, then electric vehicles (EVs) may be a saleable alternative. </li></ul><ul><li>Advancement in battery technology that would allow the use of lighter-weight and higher-energy batteries. </li></ul>
<ul><li>Cold-Weather Concerns Past models of electric vehicles such as the GM electric vehicle (EV1) were restricted to locations such as Arizona and southern California that had a warm climate, because cold weather is a major disadvantage to the use of electric vehicles for the following reasons: </li></ul>Continued <ul><li>Cold temperatures reduce battery efficiency. </li></ul><ul><li>Additional electrical power from the batteries is needed to heat the batteries themselves to be able to achieve reasonable performance. </li></ul><ul><li>Passenger compartment heating is a concern for an electric vehicle because it would require the use of resistance units or other technology that would reduce the range of the vehicle. </li></ul>
<ul><li>Hot-Weather Concerns Batteries do not function well at high temperatures; some type of battery cooling must be added to the vehicle to allow for maximum battery performance. This results in a reduction of vehicle range due to the use of battery power needed to keep the batteries working properly. Besides battery concerns, the batteries would also have to supply the power needed to keep the interior cool as well as all of the other accessories. These combined electrical loads represent a huge battery drain and reduce the range of the vehicle. </li></ul>Continued
<ul><li>Recharging Methods and Concerns How far an electric vehicle can travel on a full battery charge is called its range . The range of an electric vehicle depends on many factors, including: </li></ul>Continued <ul><li>Battery energy storage capacity </li></ul><ul><li>Vehicle weight </li></ul><ul><li>Outside temperature </li></ul><ul><li>Terrain (driving in hilly or mountainous areas requires more energy from the battery) </li></ul><ul><li>Use of air conditioning and other electrical devices </li></ul>If electric vehicles are going to become widely used, charging stations will have to be established to allow necessary recharging for trips to work and back home.
<ul><li>Because electric vehicles have a relatively short range, charging stations must be available in areas where these vehicles are driven. For example, when the state of California mandated the sale of zero-emission vehicles (ZEV), charging stations were set up in many areas, usually in parking lots of businesses and schools. </li></ul>Figure 66–28 A typical electric vehicle charging station on the campus of a college in Southern California. Continued The parking spaces near the charging stations were designated for electric vehicles only and could be used for free to recharge electric vehicles.
<ul><li>Charging Methods When the state of California set up electric vehicle charging stations, both a conductive- and inductive-type charger was made available at each station. Conductive Charging Uses an plug that makes physical contact with terminals in the vehicle. The charger can be powered by 110-V AC, or most commonly 220-V AC. This type of charger connection is used on some Ford and Honda electric vehicles. Inductive Charging Achieved by inserting a paddlelike probe into a charging receptacle (opening) in the vehicle. The charger is powered by 220-volt AC and does not make physical contact with the vehicle. See Figure 66–29 and 66-30. </li></ul>Continued
Figure 66–29 A conductive-type charging connector. This type of battery charging connector is sometimes called a AVCON connector, named for the manufacturer. Figure 66–30 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. Continued
<ul><li>An inductive charger paddle contains a coil of wire and the AC current from the charger flows through the winding, which creates a moving magnetic field around the paddle. Inside the charging receptacle of the vehicle is another coil of wire. The alternating magnetic field induces an AC voltage in the coil winding. The electronics in the vehicle then changes the induced AC current into DC current to charge the batteries. Inductive-type chargers are used with the General Motors EV-1, as well as Nissan and Toyota electric vehicles. </li></ul>Continued
<ul><li>NEDRA is the National Electric Drag Racing Association that holds drag races for electric-powered vehicles throughout the United States. The association does the following: </li></ul>What is NEDRA? <ul><li>Coordinates a standard rule set for electric vehicle drag racing, to balance the needs and interests of all those involved in the sport. </li></ul><ul><li>Sanctions electric vehicle drag racing events, to: </li></ul><ul><li>Promotes electric vehicle drag racing to: </li></ul><ul><li>Make the events as safe as possible. </li></ul><ul><li>Record and maintain official records. </li></ul><ul><li>Maintain consistency on a national scale. </li></ul><ul><li>Coordinate and schedule electric vehicle drag racing events. </li></ul><ul><li>Educate the public and increase people’s awareness of electric vehicles while eliminating any misconceptions. </li></ul><ul><li>Encourage participation in electric vehicle drag racing. </li></ul><ul><li>Have fun in a safe and silent drag racing environment. </li></ul>
Figure 66–3 (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. Visit the National Electric Drag Racing Association on the Internet at www.nedra.com
WIND POWER <ul><li>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 CO 2 emissions. Often, windmills are supplemental power in the evenings when it is most needed, and allowed to stop rotating in daylight hours when the power is not needed. Windmills are usually grouped to form wind farms , where the product is electrical energy. Energy from wind farms can be used to charge plug-in hybrid vehicles, as well as for domestic lighting and power needs. See Figures 66–32 and 66–33. </li></ul>Continued
Figure 66–32 Wind power capacity by area. (Courtesy of U.S. Department of Energy) Continued
Figure 66–33 A typical wind generator that is used to generate electricity. Continued
HYDROELECTRIC POWER <ul><li>Hydroelectric power is limited to locations where there are dammed rivers and hydroelectric plants. however, electricity can and is transmitted long distances—so electricity generated at the Hoover Dam can be used in California and other remote locations. Electrical power from hydroelectric sources can be used to charge plug-in hybrid electric vehicles, thereby reducing emissions that would normally be created by burning coal or natural gas to create electricity. Hydro electric plants are limited as to the amount of power they can produce, and constructing new plants is extremely expensive. See Figure 66–34. </li></ul>Continued
Figure 66–34 The Hoover Dam in Nevada/Arizona is used to create electricity for use in the southwest United States.
SUMMARY <ul><li>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. </li></ul><ul><li>A fuel cell produces electricity and releases heat and water as the only by-products. </li></ul><ul><li>The major disadvantages of fuel cells include: </li></ul>Continued <ul><li>High cost </li></ul><ul><li>Lack of hydrogen refueling stations </li></ul><ul><li>Short range </li></ul><ul><li>Freezing-temperature starting problems </li></ul>
SUMMARY <ul><li>Types of fuel cells include PEM (the most commonly used), PAFC, MCFC, and SOFC. </li></ul><ul><li>Ultracapacitors are an alternative to batteries for the storage of electrical energy. </li></ul><ul><li>A gasoline-powered engine can be more efficient if it uses a homogeneous charge compression ignition (HCCI) combustion process. </li></ul>Continued ( cont. )
SUMMARY <ul><li>Plug-in hybrid electric vehicles could expand the range of hybrid vehicles by operating on battery power alone. </li></ul><ul><li>Wind power and hydroelectric power are being used to recharge plug-in hybrids and provide electrical power for all uses, without harmful emissions. </li></ul>( cont. )