MODULE-I Electric and Hybrid Vehicle technology: Introduction, LEV, TLEV, ULV & ZEV, Basic components of Electric vehicles, Batteries suitable for electric vehicles, motor and controllers, constructional features, Basic factors to be considered for converting automobiles to electric vehicle, electric hybrid vehicle, types - series and parallel hybrid, layouts, comparison, Power systems and control systems, Different modes of operation for best usage. Regenerative braking, Recent Trends in Automotive Power Plants: Stratified charged / lean burn engines – Hydrogen Engines- Electric propulsion with cables – Magnetic track vehicles. MODULE 11 Fuel Cells and Alternative energy systems: Introduction to fuel cells, Operational fuel cell voltages, Proton Exchange membrane fuel cells, Alkaline Electrolyte fuel cells, Medium and high temperature fuel cells, fuel and fuel chose, fuel processing, fuel cell stacks, Delivering fuel cell power, Integrated Air supply and humidification concepts for fuel cell systems, A comparison of High pressure and low pressure operation PEM Fuel cell systems, Fuel cell Auxiliary systems, Modern Developments in Automobiles: Air compression systems, Air powered vehicles, Vehicle Automated Tracks: Preparation and maintenance of proper road network-National highway network with automated roads and vehicles-Satellite control of vehicle operation for safe and fast travel. Module III Modem electronic and micro control systems in automobiles: Electronically controlled concealed headlight systems, LED and Audible warning systems Electro chromic mirrors, automatic review mirrors, OBD II, Day time running lamps (DRL), Head up display, Travel information systems, On board navigation system, Electronic climate control, Electronic cruise control, Antilock braking system, Electronically controlled sunroof, Anti-theft systems, Automatic door locks (ADL), engine management system, Electronic transmission control, chassis control system, Integrated system Vehicle Operation and Control: Computer Control for pollution and noise control and for fuel economy-Transducers and operation of the vehicle like optimum speed and direction.

1. PREFACE
Modern Automotive Technology is an important paper for B TECH
Mechanical stream -Automobile Engineering 7th
semester. This book is prepared
in accordance with Kerala University Syllabus which can be useful for the
preparation of exam. The subject is presented in simple language for easy
understanding. Students are advised to refer prescribed text books to know the
subject deeply. This book has been prepared within a short period. Suggestion
from students for making the book more useful will be received with pleasure
Prepared by
Vivek V Kamal
Vishnu B C
Hari Krishnan
1

2. MODULE-I
Electric and Hybrid Vehicle technology: Introduction, LEV, TLEV, ULV & ZEV, Basic components
of Electric vehicles, Batteries suitable for electric vehicles, motor and controllers,
constructional features, Basic factors to be considered for converting automobiles to electric
vehicle, electric hybrid vehicle, types - series and parallel hybrid, layouts, comparison, Power
systems and control systems, Different modes of operation for best usage. Regenerative
braking, Recent Trends in Automotive Power Plants: Stratified charged / lean burn engines –
Hydrogen Engines- Electric propulsion with cables – Magnetic track vehicles.
MODULE -II
Fuel Cells and Alternative energy systems: Introduction to fuel cells, Operational fuel cell
voltages, Proton Exchange membrane fuel cells, Alkaline Electrolyte fuel cells, Medium and
high temperature fuel cells, fuel and fuel chose, fuel processing, fuel cell stacks, Delivering
fuel cell power, Integrated Air supply and humidification concepts for fuel cell systems, A
comparison of High pressure and low pressure operation PEM Fuel cell systems, Fuel cell
Auxiliary systems, Modern Developments in Automobiles: Air compression systems, Air
powered vehicles, Vehicle Automated Tracks: Preparation and maintenance of proper road
network-National highway network with automated roads and vehicles-Satellite control of
vehicle operation for safe and fast travel.
Module III
Modem electronic and micro control systems in automobiles: Electronically controlled
concealed headlight systems, LED and Audible warning systems Electro chromic mirrors,
automatic review mirrors, OBD II, Day time running lamps (DRL), Head up display, Travel
information systems, On board navigation system, Electronic climate control, Electronic cruise
control, Antilock braking system, Electronically controlled sunroof, Anti-theft systems,
Automatic door locks (ADL), engine management system, Electronic transmission control,
chassis control system, Integrated system, Vehicle Operation and Control: Computer Control
for pollution and noise control and for fuel economy-Transducers and operation of the vehicle
like optimum speed and direction.
2

3. ELECTRIC AND HYBRID VEHICLE TECHNOLOGY
Most of the cars you see today are powered by IC engines, which use Fossil fuels to power up.
As we all know, Fossil fuels are the apt example for Non-Renewable source of energy, thus a time with
no fuel for our Vehicles is not too far. Also IC Engine powered Vehicles contribute a great amount of
Pollutants to our environment. Due to these main problems, we Automobile Engineers need to think
of new ways of powering our Wheels and the best answer to this puzzle is Electric and Hybrid
Vehicles.
As the name suggests, Electric vehicles are powered by Electricity and uses Electric Motors for Traction
purposes. Electricity may be stored on rechargeable batteries or on any other energy storage devices
in case of electric cars, and electric power may be collected from Generator Plants through overhead
lines as in the case of other form of EV (Electric Vehicle) like electric trains.
HYBRID Vehicles uses more than one Power Source to power our wheel. For example an ELECTRIC
HYBRID, like Toyota Prius uses an Electric motor as well as an IC Engine as power plants.
ZEV Concepts
An agency named CARB (California Air Resource Board) brings in some Measures to minimize
air pollution, and an interesting idea was to encourage the development and use of Zero Emission
Vehicles (ZEVs). The ZEV program was thus born and evolved since its birth in 1990s. The partial or low
emission categories of vehicles created as a part of ZEV program are listed below.
TLEV (Transitional Low Emission Vehicles):- Introduction of TLEV categories was introduced in the
year 1994 and the primary aim was to reduce emissions. Some of the vehicles manufactured in 1990s
were capable of meeting the TLEV standards without much Engineering modifications, if they were
operated ith Clea Fuels. TLEV sta dard as phased out the ear 2004.
LEV (Low Emission Vehicles):- They are Categories of vehicles with cleaner emissions than TLEVs and
all light vehicles sold on and after the year 2004 in California were required to full fill LEV standards.
The development of LEVs is a result of advancement in engineering and technology, like the
introduction of techniques like Preheating of catalytic converters, Variable Valve Timing, Lean Burn
Engines etc.
ULEV (Ultra Low emission Vehicles):- They are 50% more cleaner than average new vehicle sold in the
year 2003. Hybrid vehicles can fulfill ULEV standards like Honda Jazz Hybrid. They can be defined as
the cars which produce 75g or less CO2 per kilometer from the tail pipe.
ZEV (Zero Emission Vehicles):- They are 98% cleaner than Average new vehicle manufactured in the
year 2003. They have almost zero tail pipe emission of any Pollutants. Electric and Hydrogen fuel
vehicles are the best examples of ZEVs. Currently only few cars meet the ZEV regulations like Electric-
Tesla Roadster, Fuel cell car like Mercedes-Benz F-Cell, etc.
ELECTRIC VEHICLES
An Electric Vehicle (EV), also referred to as an electric drive vehicle, is a vehicle which uses one
or more electric motors for propulsion. Depending on the type of vehicle, motion may be provided by
3

4. wheels or propellers driven by rotary motor. All-electric vehicles (EVs) run on electricity only. They are
propelled by one or more electric motors powered by rechargeable battery packs. EVs have several
advantages over vehicles with internal combustion engines (ICEs):
 Energy efficient. Electric vehicles convert about 59%–62% of the electrical energy from the
grid to power at the wheels—conventional gasoline vehicles only convert about 17%–21% of
the energy stored in gasoline to power at the wheels.*
 Environmentally friendly. EVs emit no tailpipe pollutants, although the power plant producing
the electricity may emit them. Electricity from nuclear-, hydro-, solar-, or wind-powered plants
causes no air pollutants.
 Performance benefits. Electric motors provide quiet, smooth operation and stronger
acceleration and require less maintenance than ICEs.
 Reduce energy dependence. Electricity is a domestic energy source.
EVs do, however, face significant battery-related challenges:
 Driving range. Most EVs can only go about 100–200 miles before recharging, gasoline vehicles
can go over 300 miles before refueling.
 Recharge time. Fully recharging the battery pack can take 4 to 8 hours. Even a "quick charge"
to 80% capacity can take 30 min.
 Battery cost: The large battery packs are expensive and may need to be replaced one or more
times.
 Bulk & weight: Battery packs are heavy and take up considerable vehicle space.
However, researchers are working on improved battery technologies to increase driving range and
decrease recharging time, weight, and cost. These factors will ultimately determine the future of EVs.
ELECTRIC VEHICLE COMPONENTS
1. Motor
2. Controller
3. Charger
4. Dc/Dc Converter
5. Battery Management System
6. Instrumentation
7. Contactor(s)
8. Safety Equipment
4

5. Motors
Electric motors are the main source of power, for an Electric vehicle, which convert Electrical Energy
into Mechanical Energy. There are mainly 2 types of Electric Motors used in EVs; DC Motors and AC
Motors. The main components of DC motors are;
1. A set of field coils around the perimeter of the motor that creates magnetic force which provides
torque.
2. A Rotor or Armature mounted on the bearing.
3. A commutating device, which reverses the magnetic field and makes armature turn.
AC Motors are similar to DC otors ut the do t eed a Co utati g de i es, si e there is a
continuous current reversal. Both AC and DC Motors have their own advantages and disadvantages so
they are not superior to one another
Electric Motor Comparison
AC Motor
1) Fail-safe design, Low initial torque, higher at speed
2) Requires complicated electronics package
• AC speed control (similar to industrial)
• Inverter (convert DC to AC)
• High voltage (240-350 V)
• Bearings is the only mechanical maintenance item
DC series wound
1) Motors are available and inexpensive
2) 100% torque at 0 RPM
3) Controllers are very cheap compared to AC
4) No inverter stage required
5) Lower voltage system (72-156 VDC)
6) Bearings and brushes are potential maintenance items.
A: shunt B: series C: compound f = field coil
AC Motors DC Motors
Single-Speed Transmission Multi-Speed Transmission
For HP Po er, Light eight. For HP Po er, ore hea
Less expensive More expensive
95% efficiency at full load 95%-85% efficiency at full load.
Controllers are expensive Simple Controllers
Motor/Controllers/Inverters more expensive Motors/Controllers less expensive
5

6. Controller
A motor controller is a device or group of devices that serves to govern in some predetermined
manner the performance of an electric motor.
A motor controller might include a manual or automatic means for
 Starting and stopping the motor
 Selecting forward or reverse rotation
 Selecting and regulating the speed,
 Regulating or limiting the torque
 Protecting against overloads and faults
Battery management system
There are three main objectives common to all Battery Management Systems
• Protect the cells or the battery from damage
• Prolong the life of the battery
• Maintain the battery in a state in which it can fulfil the functional requirements of the
application for which it was specified.
Most electric vehicles use lithium ion batteries. Lithium ion batteries have higher energy density,
longer life span and higher power density than most other practical batteries. Complicating factors
include safety, durability, thermal breakdown and cost. Li-ion batteries should be used within safe
temperature and voltage ranges in order to operate safely and efficiently. Increasing the battery's
lifespan decreases effective costs. One technique is to operate a subset of the battery cells at a time
and switching these subsets.
Dc /Dc convertor
An electric car still uses a 12 volt system to power all of the original 12 volt accessories: Lights, horn,
etc. This may also power some control circuits for the electric drive system. However, unlike a gas car,
there is no alternator to keep this battery charged. One option in the early days of EVs was to use a
deep cycle 12 volt battery, as heavy duty as possible, and recharge it when you charge the main
battery pack. This is not adequate if any amount of night driving is intended
The solution is a DC/DC convertor. This taps the full battery pack voltage and cuts it
down to a regulated output, similar to that from an alternator. By tapping the full pack, there is no
uneven discharge. Amperage required is so low that there is little effect on range. Isolation of the high
and low voltage systems is maintained inside the DC/DC converter. This also eliminates the need for a
separate 12 volt charging circuit for an auxiliary battery.
6

7. Contactor
A contactor is basically an electronically controlled switch, designed to carry a large amount of power.
They consist of a coil (electromagnet) which is energised from a low voltage (typically 12V for EV use).
When energised, the coil pulls contacts close allowing current to flow through the device.
In EVs, they are used to isolate the battery pack when the key is turned off - the equivalent of ignition
in an ICE vehicle. For typical EVs, contactors rated to around 200 amps continuous are recommended.
Contactors up to 600 amps continuous are available for high-performance EV applications.
Pot box
Petrol vehicles use a cable between the accelerator pedal and the engine's throttle. In EVs, the
throttle end is replaced with a connection to a pot box, which is basically an electronic throttle
connected to your motor speed controller. Most pot boxes are simply an industrial variable resistor
(5Kohm is the standard) in a robust packaging. Some newer motor speed controllers are using digital
pot boxes with optical encoders, which tend to be more reliable
7

8. Instrumentation
The main two gauges you will need to add for an EV are a voltmeter to monitor your battery pack
voltage, and an ammeter which measures either the current coming out of the battery pack or the
current flowing through the motor.
Instead of a fuel gauge, some EVs also have a "state of charge" meter. These usually include some
clever electronics to calculate the amount of power which has come out of the battery, and from this
work out how much of your battery capacity you have left. Some will even act like a trip computer,
telling you how much range you have remaining. Vehicles with a good battery management system
may also have a display showing the voltage levels of all batteries in the pack. This is a great way to
monitor the health of individual cells, and to make sure none get over-discharged
Electric Cars (working)
When the pedal is pushed;
1) The controller gathers energy from the battery
2) Controller delivers the appropriate amount of electrical energy to the motor
3) Electric energy transforms to mechanical energy
4) Wheels turn, vehicle moves
8

9. Basic factors to be considered for converting Automobiles to Electric Vehicle
 Almost any vehicle can be converted to electric. Many people prefer to pick a vehicle that is light
and aerodynamic in order to maximize distance traveled per battery charge. There must also be
adequate room and load capacity for batteries.
 The following components should be selected. The battery pack, which provides a source of
electrical power. The most commonly available and affordable batteries are lead-acid flooded
type. Next are the AGM (Absorption Glass Mat) sealed maintenance free batteries, a little more
powerful and expensive. Then there are the more exotic batteries like Ni-MH and Li-ion; more
difficult to find but light and longer lasting, maintenance free, and much more expensive. The new
lithium batteries are showing some promise for EVs in the near future.
 The charger which restores energy to the batteries (which may be mounted within the vehicle or
at a special charging station at some fixed location)
 The power controller, which regulates the flow of energy between the battery and the electric
motor(s), controlled by an electronic throttle.
 One or more electric motors and their mechanical attachment to the driveline
 Power conductors connecting the battery, controller, and motor(s)
 Accessory equipment to power auxiliary equipment such as power brakes and heating system
 Control circuitry and equipment to allow control and interlocking of the various components
 Instrumentation specific to the operation and maintenance of the conversion
HYBRID ELECTRIC VEHICLE
A hybrid electric vehicle (HEV) is a type of electric vehicle that combines a
conventional internal combustion engine (ICE) propulsion system with an electric propulsion system
(hybrid vehicle drive train). The presence of the electric power train is intended to achieve either
better fuel economy than a conventional vehicle or better performance. There are a variety of HEV
types, and the degree to which they function as EVs varies as well. The most common form of HEV is
the hybrid electric car, although hybrid electric trucks (pickups and tractors) and buses also exist.
Modern HEVs make use of efficiency-improving technologies such as regenerative brakes, which
converts the vehicle's kinetic energy into electric energy to charge the battery, rather than wasting it
as heat energy as conventional brakes do. Some varieties of HEVs use their internal combustion
engine to generate electricity by spinning an electrical generator (this combination is known as
a motor–generator), to either recharge their batteries or to directly power the electric drive motors.
Many HEVs reduce idle emissions by shutting down the ICE at idle and restarting it when needed; this
is known as a start-stop system. A hybrid-electric produces less emissions from its ICE than a
comparably sized gasoline car, since an HEV's gasoline engine is usually smaller than a comparably
sized pure gasoline-burning vehicle (natural gas and propane fuels produce lower emissions) and if not
used to directly drive the car, can be geared to run at maximum efficiency, further improving fuel
economy
Classification
1. Types by drive train structure
1.1. Series hybrid
9

10. In a series hybrid system, the combustion engine drives an electric generator (usually a three-
phase alternator plus rectifier) instead of directly driving the wheels. The electric motor is the only
means of providing power to the wheels. The generator both charges a battery and powers an electric
motor that moves the vehicle. When large amount of power is required, the motor draws electricity
from both the batteries and the generator.
Series hybrid configurations already exist a long time: diesel-electric locomotives, hydraulic earth
moving machines, diesel-electric power groups, loaders.
Structure of a series hybrid electric vehicle
10

11. Series hybrids can be assisted by ultra caps (or a flywheel: KERS=Kinetic Energy Recuperation
System), which can improve the efficiency by minimizing the losses in the battery. They deliver peak
energy during acceleration and take regenerative energy during braking. Therefore, the ultra caps are
kept charged at low speed and almost empty at top speed. Deep cycling of the battery is reduced; the
stress factor of the battery is lowered.
A complex transmission between motor and wheel is not needed, as electric motors are efficient over
a wide speed range. If the motors are attached to the vehicle body, flexible couplings are required.
Some vehicle designs have separate electric motors for each wheel. Motor integration into the wheels
has the disadvantage that the unsprung mass increases, decreasing ride performance. Advantages of
individual wheel motors include simplified traction control (no conventional mechanical transmission
elements such as gearbox, transmission shafts, and differential), all wheel drive, and allowing lower
floors, which is useful for buses. Some 8x8 all-wheel drive military vehicles use individual wheel
motors.
A fuel cell hybrid electric always has a series configuration: the engine-generator combination is
replaced by a fuel cell.
Structures of a fuel cell hybrid electric vehicle
Weaknesses of series hybrid vehicles:
The ICE(Internal Combustion Engine), the generator and the electric motor are dimensioned
to handle the full power of the vehicle. Therefore, the total weight, cost and size of the power train
can be excessive.
The power from the combustion engine has to run through both the generator and electric motor.
During long-distance highway driving, the total efficiency is inferior to a conventional transmission,
due to the several energy conversions.
Advantages of series hybrid vehicles:
 There is no mechanical link between the combustion engine and the wheels. The engine-
generator group can be located everywhere.
 There are no conventional mechanical transmission elements (gearbox, transmission shafts).
Separate electric wheel motors can be implemented easily.
 The combustion engine can operate in a narrow rpm range (its most efficient range), even as
the car changes speed.
 Series hybrids are relatively the most efficient during stop-and-go city driving.
Example of SHEV: Renault Kangoo.
11

12. 1.2. Parallel hybrid
Parallel hybrid systems have both an internal combustion engine (ICE) and an electric motor in
parallel connected to a mechanical transmission.
Structure of a parallel hybrid electric vehicle
Most designs combine a large electrical generator and a motor into one unit, often located
between the combustion engine and the transmission, replacing both the conventional starter motor
and the alternator (see figures above). The battery can be recharged during regenerative breaking,
and during cruising (when the ICE power is higher than the required power for propulsion). As there is
12

13. a fixed mechanical link between the wheels and the motor (no clutch), the battery cannot be charged
he the ar is t o i g.
When the vehicle is using electrical traction power only, or during brake while regenerating
energy, the ICE is not running (it is disconnected by a clutch) or is not powered (it rotates in an idling
manner).
Operation modes:
The parallel configuration supports diverse operating modes
Some typical modes for a parallel hybrid configuration
PE = Power electronics
TX = Transmission
(a) Electric power only: Up to speeds of usually 40 km/h, the electric motor works with only the
energy of the batteries, which are not recharged by the ICE. This is the usual way of operating around
the city, as well as in reverse gear, since during reverse gear the speed is limited.
(b) ICE power only: At speeds superior to 40 km/h, only the heat engine operates. This is the normal
operating way at the road.
OR
(b) ICE + electric power: if more energy is needed (during acceleration or at high speed), the electric
motor starts working in parallel to the heat engine, achieving greater power
(c) ICE + battery charging: if less power is required, excess of energy is used to charge the batteries.
Operating the engine at higher torque than necessary, it runs at a higher efficiency.
(d) Regenerative breaking: While braking or decelerating, the electric motor takes profit of the kinetic
energy of the he moving vehicle to act as a generator.
13

14. Weaknesses of parallel hybrid vehicles:
Rather complicated system.
The ICE does t operate i a narrow or constant RPM range, thus efficiency drops at low
rotation speed.
As the ICE is not decoupled from the wheels, the battery cannot be charged at standstill.
Advantages of parallel hybrid vehicles:
Total efficiency is higher during cruising and long-distance highway driving.
Large flexibility to switch between electric and ICE power
Compared to series hybrids, the electromotor can be designed less powerful than the ICE, as it
is assisting traction. Only one electrical motor/generator is required
COMBINED HYBRID
Combined hybrid systems have features of both series and parallel hybrids. There is a double
connection between the engine and the drive axle: mechanical and electrical. This split power path
allows interconnecting mechanical and electrical power, at some cost in complexity.
Power-split devices are incorporated in the power train. The power to the wheels can be either
mechanical or electrical or both. This is also the case in parallel hybrids. But the main principle behind
the combined system is the decoupling of the power supplied by the engine from the power
demanded by the driver.
Simplified structure of a combined hybrid electric vehicle
In a conventional vehicle, a larger engine is used to provide acceleration from standstill than one
needed for steady speed cruising. This is because a combustion engine's torque is minimal at lower
RPMs, as the engine is its own air pump. On the other hand, an electric motor exhibits maximum
torque at stall and is well suited to complement the engine's torque deficiency at low RPMs. In a
14

15. combined hybrid, a smaller, less flexible, and highly efficient engine can be used. It is often a variation
of the conventional Otto cycle, such as the Miller or Atkinson cycle. This contributes significantly to
the higher overall efficiency of the vehicle, with regenerative braking playing a much smaller role.
At lower speeds, this system operates as a series HEV, while at high speeds, where the series power
train is less efficient, the engine takes over. This system is more expensive than a pure parallel system
as it needs an extra generator, a mechanical split power system and more computing power to control
the dual system.
Control System in HEVs and EVs
The major functions of the control system are:
i. to maximize the fuel efficiency
ii. to minimize the exhaust emissions.
The fuel efficiency and emissions are mutually conflicting and some of the reasons why this happens
are:
i. when more energy is extracted by the ICE (thereby increasing the ICE efficiency) the exhaust
temperature goes down. At lower temperatures, the chemical reactions associated with the
combustion of unburned hydrocarbons may not occur.
ii. Increase in compression ratio, which enhances fuel economy, also raises temperature in ICE.
Increased temperature increases both CO and oxides of nitrogen represented by NOx. The minor
functions of the control system are component monitoring and protection such as:
i. battery state of charge (SOC) monitoring
ii. Battery temperature monitoring
iii. EM overheating
iv. ICE overheating
The battery merits special attention to avoid failure and to assure long life. The control system
generally provides a fail safe mode in the event of failures. One of the functions of control systems,
which is minor in cost but valuable in practice, is onboard diagnostics (OBD).The switching from one
ode to a other ust e as s ooth. As the HEV s operatio ode ha ges, se eral para eters of the
ICE that have to be controlled are:
i. Ignition timing
ii. Tuned intake manifold
iii. Camshaft angle for exhaust valves
iv. Camshaft angle for intake valves
v. Fuel injector settings which includes
a. Timing of injection
b. Fuel flow rate
15

16. Elements of Control Theory
The basis for control is the feedback loop shown in Figure 2a. The input is the desired behavior of the
system and it is compared with the actual behavior to determine the error signal. The error signal is
fed i to o e or ore o trol ele e ts that o e a tuators at the pla t. The ord pla t is the a e
for the object being controlled. The actual value of the controlled variable from the plant is
transmitted via the feedback loop to the summation loop.
In Figure 2b a simple example of ICE control is shown with its control element and plant. The
control element is a general term and identifies the elements that receives the error signal and change
the pla t s behavior. In Figure 2b the fuel injector is the control element and the ICE is the plant. To
understand the working of the control system, shown in Figure 2b, let us assume that the desired
speed of ICE is 2000 rpm and the actual speed is 2200 rpm. An error signal of -200 rpm is generated
and this negative error signal is fed to the fuel injector. The fuel injector responds to the negative
error by decreasing the flow of fuel to the ICE. With less fuel, the speed of ICE drops
A modern control system for HEV may use only a few feedback control loop similar to the one
shown in Figure 2c. The control architecture shown in Figure 2c uses a single feedback loop and has
desired velocity as the variable being controlled. The driver is one of the control elements and acts on
the error. If the HEV is moving too slowly, the driver steps on the accelerator pedal and it the vehicle is
too fast, the driver steps on the brake pedal. The hybrid ECU is the master controller and it controls
the other subcomponents of the vehicle such as ICE, EM, power electronics, etc.
16

17. Overview of Control System: The Electronic Control Unit (ECU)
Typical control architecture of HEV is shown in Figure 3. In Figure 3 it can be seen that there are
multiple ECUs such as:
i. Hybrid ECU
ii. ICE ECU
iii. EM ECU
iv. Transmission ECU
v. Power Electronics ECU
vi. Battery ECU or Battery Management System
A brief description of each of the ECUs is given below.
Hybrid ECU: The Hybrid ECU is in command of all other ECUs and selects the operational mode based
on the dri er s i put. The h rid ECU is respo si le for s ste ide e erg a age e t. T pi all the
goal of control is to minimize the fuel consumption. For each litre of petrol, the hybrid ECU tries to
provide maximum mileage. To do this, the hybrid ECU allows or prohibits ICE shutoff. The hybrid ECU
commands
1. the amount of torque and power from the motor and ICE
2.the amount and timing of power generation to charge battery.
ICE EMU: This controls the various ICE parameters discussed in previous section
EM ECU: The EM ECU is responsible for switching of the EM from motoring mode to the generator
mode and also controls the motor to deliver the torque demanded by the hybrid ECU. The EM ECU
consists of various control strategies such as Constant Torque Control, Field Weakening Control, etc.
Transmission ECU: The transmission ECU provides the correct gear ratio to control the torques and
angular speeds of the EM and the ICE.
17

18. Power Electronics ECU: Having power from a battery is only the first step. The power must be
delivered to the EM, in the motoring mode, at the voltage and current needed. For regenerative
braking, the power must be accepted from the EM. The function of the power electronic ECU is to
receive commands from hybrid ECU, to control inverter energy flow both ways, that is, charge and
discharge, to control switching of EM between motor and generator modes and to control switching
of EM between motor and generator modes.
Battery ECU or Battery Management System: The battery ECU or the battery management system
(BMS) monitors and measures temperature and assures cooling is adequate. The BMS avoids the
stress of heat and over-temperature and the effects of excessive charging or discharging are
eliminated or lessened. The BMS is essentially for long battery life and optimum fuel efficiency
18

19. Control Area Network (CAN)
A typical CAN network in an HEV is shown in Figure 4. The CAN is a fast, high rate network which
enables communication between ECUs. In CAN most data can be updated every 10ms and the data is
checked to assure data reliability.
Regenerative braking
As i toda s orld, here there are e erg rises a d the resour es are depleti g at a higher
rate, there is a need of specific technology that recovers the energy, which gets usually wasted. So, in
case of automobiles one of these useful technologies is the regenerative braking system. Generally in
automobiles whenever the brakes are applied the vehicle comes to a halt and the kinetic energy gets
wasted due to friction in the form of kinetic energy. Using regenerative braking system in automobiles
enables us to recover the kinetic energy of the vehicle to some extent that is lost during the braking
process. In these two methods of utilizing the kinetic energy, that is usually wasted by converting it
into either electrical energy or into mechanical energy. Regenerative braking system can convert the
kinetic energy into electrical energy with help of electric motor. And it can also convert the kinetic
energy into mechanical energy, which is supplied to the vehicle whenever it is needed, with the help
of a flywheel.
Conventional Braking System
Braking in a moving vehicle means the application of the brakes to slow or stop its movement,
usually by depressing a pedal. The braking distance is the distance between the time the brakes are
applied and the time the vehicle comes to a complete stop. When brakes are applied to a vehicle using
conventional braking system, kinetic energy is converted into heat due to the friction between the
wheels and brake pads. This heat is carried away in the airstream and the energy is wasted. The total
amount of energy lost in this process depends on how often, how hard and for how long the brakes
are applied.
19

20. Regenerative Braking System
Regenerative braking is one of the emerging technologies which can prove very beneficent.
The use of regenerative braking in a vehicle not only results in the recovery of the energy but it also
increases the efficiency of vehicle(in case of hybrid vehicles) and saves energy, which is stored in the
auxiliary battery.
Block Diagram of Regenerative Braking System
In cities, driving involves many braking events resulting in much higher energy losses with greater
potential savings. With buses, taxis, delivery vans and so on there is even more potential for economy.
Since regenerative braking results in an increase in energy output for a given energy input to
a vehicle, the efficiency is improved. The amount of work done by the engine of the vehicle is reduced,
in turn reducing the amount of energy required to drive the vehicle. This technology of regenerative
raki g o trols the speed of the ehi le o erti g a portio of the ehi le s ki eti e erg i to
another useful form of energy. The energy so produced could then be stored as electrical energy in
the automobile battery, or as mechanical energy in flywheels, which can be used again by the vehicle.
20

21. Regenerative braking refers to a process in which a portion of the kinetic energy of the vehicle
is stored by a short term storage system. Energy normally dissipated in the brakes is directed by a
power transmission system to the auxiliary battery during deceleration. The energy that is stored by
the vehicle is converted back into kinetic energy and used whenever the vehicle is to be accelerated.
The magnitude of the portion available for energy storage varies according to the type of storage,
drive train efficiency, drive cycle and inertia weight. The effect of regenerative brakes is less at lower
speeds as compared to that at higher speeds of vehicle. So the friction brakes are needed in a
situation of regenerative brake failure, to stop the vehicle completely
Working of Regenerative Braking using Electric Motor
The working of the regenerative braking system depends upon the working principle of an
electric motor, which is the important component of the system. Generally the electric motor, is
actuated when electric current is passed through it. But, when some external force is used to actuate
the motor (that is during the braking process) then it behaves as a generator and generates electricity.
That is, whenever a motor is run in one direction the electric energy gets converted into mechanical
energy, which is used to accelerate the vehicle and whenever the motor is run in opposite direction it
functions as a generator, which converts mechanical energy into electrical
energy. This makes it possible to employ the rotational force of the driving axle to turn the electric
motors, thus regenerating electric energy for storage in the battery and simultaneously slowing the
car with the regenerative resistance of the electric motors [2]. This electricity is then used for
recharging the battery
Advantages
 Better fuel economy.
 Reduced CO2 emissions.
 Approximately 30% saving in fuel consumption.
 The lower operating and environment cost of the vehicle with regenerative braking system.
 Increase of overall energy efficiency of a vehicle
 Increases vehicle range
 Cuts down on pollution related to electricity generation
 Increases the lifespan of friction braking systems
 Less use of traditional mechanical brakes leads to less wear over time
Disadvantages
 Added complexity of brake control system
 Only works for wheels connected to motors
 Most vehicle operation is done in 2WD
 Friction brakes are still necessary
 Safety
 Motor braking power decreases as the kinetic energy of the vehicle decreases
21

22. MAGNETIC TRACK VEHICLES
Maglev (derived from magnetic levitation) is a transport method that uses magnetic
levitation to move vehicles without touching the ground. With maglev, a vehicle travels along a
guideway using magnets to create both lift and propulsion, thereby reducing friction by a great extent
and allowing very high speeds.
The Shanghai Maglev Train, also known as the Transrapid, is the fastest commercial train
currently in operation and has a top speed of 430 km/h (270 mph).
Maglev trains move more smoothly and more quietly than wheeled mass transit systems.
They are relatively unaffected by weather. The power needed for levitation is typically not a large
percentage of its overall energy consumption; most goes to overcome drag, as with other high-speed
transport. Maglev trains hold the speed record for rail transport. Vacuum tube train systems might
allow maglev trains to attain still higher speeds, though no such vacuum tubes have been built
commercially yet.
Compared to conventional (normal) trains, differences in construction affect the economics of
maglev trains, making them much more efficient. For high-speed trains with wheels, wear and tear
from friction along with the "hammer effect" from wheels on rails accelerates equipment wear and
prevents high speeds. Conversely, maglev systems have been much more expensive to construct,
offsetting lower maintenance costs.
1) Electromagnetic suspension
In electromagnetic suspension (EMS) systems, the train levitates above a steel rail while
electromagnets, attached to the train, are oriented toward the rail from below. The system is typically
arranged on a series of C-shaped arms, with the upper portion of the arm attached to the vehicle, and
the lower inside edge containing the magnets. The rail is situated inside the C, between the upper and
lower edges.
Magnetic attraction varies inversely with the cube of distance, so minor changes in distance
between the magnets and the rail produce greatly varying forces. These changes in force are
dynamically unstable – a slight divergence from the optimum position tends to grow, requiring
sophisticated feedback systems to maintain a constant distance from the track, (approximately 15
millimeters (0.59 in))
The major advantage to suspended maglev systems is that they work at all speeds, unlike
electrodynamics systems, which only work at a minimum speed of about 30 km/h (19 mph). This
eliminates the need for a separate low-speed suspension system, and can simplify track layout
Track Train magnets
22

23. 1) Electrodynamic suspension (EDS)
In electro dynamic suspension (EDS), both the guide way and the train exert a magnetic field,
and the train is levitated by the repulsive and attractive force between these magnetic fields. In some
configurations, the train can be levitated only by repulsive force. In the early stages of maglev
development at the Miyazaki test track, a purely repulsive system was used instead of the later
repulsive and attractive EDS system. The magnetic field is produced either by superconducting
magnets (as in JR–Maglev) or by an array of permanent magnets. The repulsive and attractive force in
the track is created by an induced magnetic field in wires or other conducting strips in the track. A
major advantage of EDS maglev systems is that they are dynamically stable – changes in distance
between the track and the magnets creates strong forces to return the system to its original position.
In addition, the attractive force varies in the opposite manner, providing the same adjustment effects.
No active feedback control is needed.
However, at slow speeds, the current induced in these coils and the resultant magnetic flux is
not large enough to levitate the train. For this reason, the train must have wheels or some other form
of landing gear to support the train until it reaches take-off speed. Since a train may stop at any
location, due to equipment problems for instance, the entire track must be able to support both low-
and high-speed operation.
Another downside is that the EDS system naturally creates a field in the track in front and to
the rear of the lift magnets, which acts against the magnets and creates magnetic drag. This is
generally only a concern at low speeds (This is one of the reasons why JR abandoned a purely
repulsive system and adopted the sidewall levitation system). At higher speeds other modes of drag
dominate.
The drag force can be used to the electrodynamic system's advantage, however, as it creates a
varying force in the rails that can be used as a reactionary system to drive the train, without the need
for a separate reaction plate, as in most linear motor systems. Laithwaite led development of such
"traverse-flux" systems at his Imperial College laboratory. Alternatively, propulsion coils on the
guideway are used to exert a force on the magnets in the train and make the train move forward. The
propulsion coils that exert a force on the train are effectively a linear motor: an alternating current
through the coils generates a continuously varying magnetic field that moves forward along the track.
The frequency of the alternating current is synchronized to match the speed of the train. The offset
between the field exerted by magnets on the train and the applied field creates a force moving the
train forward.
23

24. STRATIFIED CHARGE ENGINE
Introduction
Of many types of internal combustion engines, two types namely petrol and diesel engines are
well established. However, each one of them has certain limitations. Petrol engine has very good full
load power characteristics. Example, high degree of air utilization, high speed and flexibility but has
rather poor part load efficiency, where as the diesel engine has good part load characteristics but has
poor air utilization, low smoke-limited power and higher weight-to-power ratio. The use of higher
compression ratio for better starting and good combustion over a wide range of engine operations are
other requirements which cause additional problems of maintenance and high losses in diesel
operation. For an automotive engine both part load efficiency and full load power are very important
because, for about 90 per cent of their total operating life, the engines work under part load
conditions and in maximum power output controls the speed, acceleration and other characteristics of
the vehicle.
Therefore, there is a need to develop an engine which combines the advantages of both petrol
and diesel engines and at the same time avoids as far as possible their disadvantages. Stratified charge
engine is an attempt in this direction. It is an engine which is mid-way between the homogeneous
charge spark-ignition engine and the heterogeneous charge compression-ignition engine.Charge
stratification means providing different fuel-air mixture strengths at various places in the combustion
chamber- relatively rich mixture at and in the vicinity of the spark plug and a leaner mixture in the rest
of the combustion chamber. That is, the whole fuel-air mixture is distributed in layers or stratas of
different mixture strengths across the combustion chamber while the overall mixture is rather lean.
Thus the stratified charge engine is usually defined as a spark ignition internal combustion
engine in which the mixture in the soul of the spark plug is very much richer than that in the rest of
the combustion chamber, i.e., one which burns leaner overall fuel-air mixtures.
Methods of Charge Stratification
The stratified charge engines can be classified into two main types., according to the method
of formation of the heterogeneous mixture in the combustion chamber.
1) Those use fuel injection and positive ignition
2) Those using carburetion alone
Stratification by fuel injection and positive ignition
The first approach-The first attempt to obtain charge stratification was made by Ricardo around 1922.
A relatively rich mixture was formed at the spark plug by an auxiliary spray while another spray
injecting fuel along the major axis of the combustion chamber formed a leaner mixture.
This arrangement could give combustion over a relatively wide range of overall mixture
strengths and allowed very lean engine operation giving efficiency as high as 36 per cent. However,
the range was limited at higher speeds and loads higher than about 50 per cent of the full load the
engine did not work properly presumably due to too rich a mixture near the spark plug.
24

25. Pre-chamber Stratified charge engine
This approach also involves many problems of engine operation. The first problem is that of
getting good performance over the full load range. At part loads the lean mixtures are effectively
burnt but at a full-load due to improper fuel distribution and incomplete scavenging of the pre
chamber the rich mixture is not properly burnt. The use of pre chamber means loss of thermal
efficiency due to throttling and rather costly fuel injection equipment. The fuel injection equipment
has to be highly sophisticated in order to provide regular injection at low fuel deliveries, good
distribution in pre chamber and avoiding an over-rich mixture at high loads.
Broderson method of Stratification
The Broderson method of charges stratification is shown in the figure. It consists of an engine
with a divided combustion chamber. The small or pre-chamber contains the injector, the intake valve,
and the spark plug. Whole of the fuel is injected into the pre-chamber. The direction of air flow in the
combustion chamber changes as the piston passes bdc position. It is this fact which forms the basis of
charge stratification in this method. Due to suction effect, the fuel injector before bdc is carried into
the main chamber by the air where it is mixed with all the air in the chamber. Fuel injected after bdc
remains in the pre-chamber because of the reversal of the air flow direction, and thus forms a
25

26. combustible mixture near the spark plug. It is apparent that by varying the time of beginning of
injection and the duration of injection any desired mixture ratio in each chamber can be obtained.
At high loads the fuel may be injected after bdc, i.e., after the start of compression
stroke. This is a situation in which the air is moving from main chamber to pre-chamber and almost all
of the fuel injected into the pre-chamber will remain there and will form an ignitable mixture near the
spark plug while the main chamber will contain air only or very lean mixture. Due to the blast of flame
from the pre-chamber, sometimes referred a torch effect, burning of this lean charge the main
chamber must be designed to ensure proper turbulence and mixing of the hot burning mixture coming
out of the pre-chamber with the mixture in the main chamber. At full load the fuel is injected before
bdc, i.e., during the suction stroke and is intimately mixed with whole of the air resulting in a mixture
of uniform strength throughout the combustion space. The flame produced by the spark plug will
spread throughout both the chambers just like in normal spark ignition operation.
Stratification by Carburetion alone
Russian stratified charge concept: - The figure sho s the Nilo jet ig itio
engine developed by Russians. This is a divided chamber design using carburetion to supply both the
pre-chamber and the main chamber. A special carburettor and an inlet valve supply relatively rich
mixture to the pre-chamber while another carburettor supplies a lean mixture to the main chamber.
Ignition is initiated by a spark plug situated in the pre-chamber. The flame front advances from the
pre-chamber and burns the lean mixture in the main chamber.
26

27. This system gave an economy of about 10 per cent over the conventional carburetted
engines. The high loss due to pre-chamber result in reduced maximum engine output and full
potential obtainable from the use of lean overall mixtures cannot be realized.
Institute Francias Du Petrols (IFP) Process:-
The figure shows the arrangement of the IFP process for charge stratification. In this process the
mixture is fed into two separate streams of different mixture strengths. A small diameter pipe is
placed in the intake port such that it supplies through an auxiliary carburettor, a rich mixture near the
intake valve. Pure air or very lean mixture is inducted by the main carburettor during the suction
stroke. Therefore, a heterogeneity or stratification is obtained which persists during the compression
stroke and a rich mixture near the spark plug is obtained by proper orientation of the rich mixture
tube.
General characteristics of Stratified Charge Engines
The following are some general characteristics of the stratified charge engines:
1) All types of stratified charge engines have good part load efficiency while the full load
performance is either equivalent to the petrol engine or slightly inferior.
2) Almost all stratification processes have inherent in them some degree of knock resistance,
smooth combustion and multi-fuel capability. Depending upon the particular design, it can
operate on low-octane gasoline or a range of quality down to diesel fuel and kerosene.
3) The volumetric efficiency of the unthrottled engines is higher than that of the carbureted
engines.
4) The exhaust emission characteristics of most of the stratification schemes are good.
Applications
All these characteristics promise for the stratified charge engine a bright future because of its
compact, lightweight design, good fuel economy, speed, range, antiknock resistance, multi-fuel
capability, and smooth and quiet engine operation over the entire speed and load range. A number of
companies are actively working on this engine for automotive applications.
27

28. Advantages and Disadvantages
Advantages
 It can tolerate a wide quality of fuels.
 It has low exhaust emission levels.
 It can be manufactured by existing technology.
Disadvantages
 Charge stratification results in reduced power for a given engine size.
 Its manufacture is more complex and hence, its manufacturing cost is higher.
 It has higher weight than that of a conventional engine.
 Its reliability is yet to be well established.
Hydrogen internal combustion engine (HICEV)
Hydrogen internal combustion engine vehicle (HICEV) is a type of hydrogen vehicle using
an internal combustion engine. Hydrogen internal combustion engine vehicles are different from
hydrogen fuel cell vehicles (which use electrochemical conversion of hydrogen rather than
combustion); the hydrogen internal combustion engine is simply a modified version of the traditional
gasoline-powered internal combustion engine.
The combustion of hydrogen with oxygen produces water as its only product:
2H2 + O2 → 2H2O
Of high temperature combustion fuels, such as kerosene, gasoline, or natural gas, with air can
produce oxides of nitrogen, known as NOx emissions. Although these are only produced in small
quantities, research has shown that the oxides of nitrogen are about 310 times more harmful as a
greenhouse gas than carbon dioxide
Combustive Properties of Hydrogen
The properties that contribute to its use as a combustible fuel are its:
 Wide range of flammability
 Low ignition energy
 Small quenching distance
 High auto-ignition temperature
 High flame speed at stoichiometric ratios
 High diffusivity
 Very low density
28

29. Wide Range of Flammability
Hydrogen has a wide flammability range in comparison with all other fuels. As a result,
hydrogen can be combusted in an internal combustion engine over a wide range of fuel-air mixtures. A
significant advantage of this is that hydrogen can run on a lean mixture. A lean mixture is one in which
the amount of fuel is less than the theoretical, stoichiometric or chemically ideal amount needed for
combustion with a given amount of air. This is why it is fairly easy to get an engine to start on
hydrogen. Generally, fuel economy is greater and the combustion reaction is more complete when a
vehicle is run on a lean mixture. Additionally, the final combustion temperature is generally lower,
reducing the amount of pollutants, such as nitrogen oxides, emitted in the exhaust. There is a limit to
how lean the engine can be run, as lean operation can significantly reduce the power output due to a
reduction in the volumetric heating value of the air/fuel mixture.
Low Ignition Energy Hydrogen
has very low ignition energy. The amount of energy needed to ignite hydrogen is about one order of
magnitude less than that required for gasoline. This enables hydrogen engines to ignite lean mixtures
and ensures prompt ignition. Unfortunately, the low ignition energy means that hot gases and hot
spots on the cylinder can serve as sources of ignition, creating problems of premature ignition and
flashback. Preventing this is one of the challenges associated with running an engine on hydrogen.
High Auto ignition Temperature
Hydrogen has a relatively high autoignition temperature. This has important implications
when a hydrogen-air mixture is compressed. In fact, the autoignition temperature is an important
factor in determining what compression ratio an engine can use, since the temperature rise during
compression is related to the compression ratio
High Flame Speed
Hydrogen has high flame speed at stoichiometric ratios. Under these conditions, the hydrogen flame
speed is nearly an order of magnitude higher (faster) than that of gasoline. This means that hydrogen
engines can more closely approach the thermodynamically ideal engine cycle. At leaner mixtures,
however, the flame velocity decreases significantly
High Diffusivity
Hydrogen has very high diffusivity. This ability to disperse in air is considerably greater than gasoline
and is advantageous for two main reasons. Firstly, it facilitates the formation of a uniform mixture of
fuel and air. Secondly, if a hydrogen leak develops, the hydrogen disperses rapidly. Thus, unsafe
conditions can either be avoided or minimized.
Low Density
Hydrogen has very low density. This results in two problems when used in an internal combustion
engine. Firstly, a very large volume is necessary to store enough hydrogen to give a vehicle an
adequate driving range. Secondly, the energy density of a hydrogen-air mixture, and hence the power
output, is reduced.
29

30. Working of Hydrogen Engine
Engine Design
The most effective means of controlling pre-ignition and knock is to re-design the engine for hydrogen
use, specifically the combustion chamber and the cooling system. A disk-shaped combust ion chamber
(with a flat piston and chamber ceiling) can be used to reduce turbulence within the chamber. The
disk shape helps produce low radial and tangential velocity components and does not amplify inlet
swirl during compression. Since unburned hydrocarbons are not a concern in hydrogen engines, a
large bore-to-stroke ratio can be used with this engine. To accommodate the wider range of flame
speeds that occur over a greater range of equivalence ratios, two spark plugs are needed. The cooling
system must be designed to provide uniform flow to all locations that need cooling. Additional
measures to decrease the probability of pre-ignition are the use of two small exhaust valves as
opposed to a single large one, and the development of an effective scavenging system, that is, a
means of displacing exhaust gas from the combustion chamber with fresh air
Fuel Delivery Systems
Adapting or re-designing the fuel delivery system can be effective in reducing or eliminating pre-
ignition. Hydrogen fuel delivery system can be broken down into three main types: central injection
or ar ureted , port i je tio a d dire t i je tio . Ce tral a d port fuel deli er s ste s i je tio
form the fuel-air mixture during the intake stroke. In the case of central injection or a carburetor, the
injection is at the inlet of the air intake manifold. In the case of port injection, it is injected at the inlet
port. Direct cylinder injection is more technologically sophisticated and involves forming the fuel-air
mixture inside the combustion cylinder after the air intake valve has closed
1) Central Injection or Carbureted Systems
The simplest method of delivering fuel to a hydrogen engine is by way of a carburetor or central
injection system. This system has advantages for a hydrogen engine. Firstly, central injection does not
require the hydrogen supply pressure to be as high as for other methods. Secondly, central injection
or carburetors are used on gasoline engines, making it easy to convert a standard gasoline engine to a
hydrogen or a gasoline/hydrogen engine. The disadvantage of central injection is that it is more
susceptible to irregular combustion due to pre-ignition and backfire. The greater amount of
hydrogen/air mixture within the intake manifold compounds the effects of pre-ignition
2) Port Injection Systems
The port injection fuel delivery system injects fuel directly into the intake manifold at each intake port,
rather than drawing fuel in at a central point. Typically, the hydrogen is injected into the manifold
after the beginning of the intake stroke. At this point conditions are much less severe and the
probability for premature ignition is reduced. In port injection, the air is injected separately at the
beginning of the intake stroke to dilute the hot residual gases and cool any hot spots. Since less gas
(hydrogen or air) is in the manifold at any one time, any pre-ignition is less severe. The inlet supply
pressure for port injection tends to be higher than for carbureted or central injection systems, but less
than for direct injection systems. The constant volume injection (CVI) system uses a mechanical cam-
operated device to time the injection of the hydrogen to each cylinder.
30

31. The electronic fuel injection (EFI) system meters the hydrogen to each cylinder. This system uses
individual electronic fuel injectors (solenoid valves) for each cylinder and is plumbed to a common fuel
rail located down the center of the intake manifold. Whereas the CVI system uses constant injection
timing and variable fuel rail pressure, the EFI system uses variable injection timing and constant fuel
rail pressure.
3) Direct Injection Systems
More sophisticated hydrogen engines use direct injection into the combustion cylinder during the
compression stroke. In direct injection, the intake valve is closed when the fuel is injected, completely
avoiding premature ignition during the intake stroke. Consequently the engine cannot backfire into
the intake manifold. The power output of a direct injected hydrogen engine is 20% more than for a
gasoline engine and 42% more than a hydrogen engine using a carburetor. While direct injection
solves the problem of pre-ignition in the intake manifold, it does not necessarily prevent preignition
within the combustion chamber. In addition, due to the reduced mixing time of the air and fuel in a
direct injection engine, the air/fuel mixture can be non-homogenous. Studies have suggested this can
lead to higher NOx emissions than the non-direct injection systems. Direct injection systems require a
higher fuel rail pressure than the other method
Ignition Systems
Due to h droge s lo ig itio e erg li it, ig iti g h droge is eas a d gasoli e ig itio
systems can be used. At very lean air/fuel ratios (130:1 to 180:1) the flame velocity is reduced
considerably and the use of a dual spark plug system is preferred. Ignition systems that use a waste
spark system should not be used for hydrogen engines. These systems energize the spark each time
the piston is at top dead center whether or not the piston is on the compression stroke or on its
exhaust stroke. For gasoline engines, waste spark systems work well and are less expensive than other
systems. For hydrogen engines, the waste sparks are a source of pre-ignition. Spark plugs for a
hydrogen engine should have a cold rating and have non-platinum tips. A cold-rated plug is one that
transfers heat from the plug tip to the cylinder head quicker than a hot-rated spark plug. This means
the chances of the spark plug tip igniting the air/fuel charge is reduced. Hot rated spark plugs are
designed to maintain a certain amount of heat so that carbon deposits do not accumulate. Since
hydrogen does not contain carbon, hot-rated spark plugs do not serve a useful function. Platinum-tip
spark plugs should also be avoided since platinum is a catalyst, causing hydrogen to oxidize with air
Crankcase Ventilation
Crankcase ventilation is even more important for hydrogen engines than for gasoline engines.
As with gasoline engines, unburnt fuel can seep by the piston rings and enter the crankcase. Since
hydrogen has a lower energy ignition limit than gasoline, any unburnt hydrogen entering the
crankcase has a greater chance of igniting. Hydrogen should be prevented from accumulating through
ventilation. Ignition within the crankcase can be just a startling noise or result in engine fire. When
hydrogen ignites within the crankcase, a sudden pressure rise occurs. To relieve this pressure, a
pressure relief valve must be installed on the valve cover
31

32. The working of hydrogen engine is similar to that of a two stroke engine. Ports are used as
shown in figure. A metering device meters the amount of hydrogen that is to be supplied to the
engine and gives it to the injector at high pressure.
COMPARISION FOR NORMAL ENGINE AND HYDROGEN ENGINE EFFICIENCY
NORMAL ENGINE
Engine efficiency refers to an engine's ability to transform the available energy from its fuel
into useful work power. The modern gasoline combustion engine operates at an average of roughly 20
to 30 percent engine efficiency. The remaining 70 to 80 percent of the gasoline's heat energy is
expelled from the engine as exhaust heat, mechanical sound energy or friction loss. At idle, the engine
efficiency is zero since the engine is not moving the vehicle and is only operating accessories, such as
the water pump and generator.
HYDROGEN ENGINE
Hydrogen engine provides a high torque density, high power density, efficient engines. Hydrogen is
used because it burns 7 to 9 times faster than high carbon fuels. Due to the relative instantaneity of
the explosive event during ignition, there is less of the wasted translational energy that is found in
traditional internal combustion engines. The combustion chamber is effectively cooled by massive
amounts of air prior to hydrogen ignition. Hydrogen engine efficiency will be approximately 65%.
32

33. MODULE II
FUEL CELLS AND ALTERNATE ENERGY SYSTEM:
Introduction to fuel cells
A fuel cell is like a battery in that it generates electricity from an electrochemical reaction. Both batteries
and fuel cells convert chemical potential energy into electrical energy and also, as a by-product of this
process, into heat energy. However, a battery holds a closed store of energy within it and once this is
depleted the battery must be discarded, or recharged by using an external supply of electricity to drive the
electrochemical reaction in the reverse direction. A fuel cell, on the other hand, uses an external supply of
chemical energy and can run indefinitely, as long as it is supplied with a source of hydrogen and a source of
oxygen (usually air).
There are several different types of fuel cell but they are all based around a central design. A fuel cell unit
consists of a stack, which is composed of a number of individual cells. Each cell within the stack has two
electrodes, one positive and one negative, called the cathode and the anode. The reactions that produce
electricity take place at the electrodes. Every fuel cell also has either a solid or a liquid electrolyte, which
carries ions from one electrode to the other, and a catalyst, which accelerates the reactions at the
electrodes. The electrolyte plays a key role - it must permit only the appropriate ions to pass between the
electrodes. If free electrons or other substances travel through the electrolyte, they disrupt the chemical
reaction and lower the efficiency of the cell
In electrolysis of water the water is separated into hydrogen and oxygen by the passage of an
electric current. In a fuel cell the electrolysis is being reversed the hydrogen and oxygen are
recombining, and an electric current is being produced. Another way of looking at the fuel cell is to
sa that the h d oge fuel is ei g u t o o usted i the si ple ea tio
2H2 + O2 → 2H2O
At the anode of an acid electrolyte fuel cell, the hydrogen gas ionizes, releasing electrons and
creating H+ions
33

34. 2H2 → 4H+ + 4e−
This reaction releases energy. At the cathode, oxygen reacts with electrons taken from the electrode, and
H+ ions from the electrolyte, to form water
O2 + 4e− + 4H+ → 2H2O
Clearly, for both these reactions to proceed continuously, electrons produced at the anode must pass
through an electrical circuit to the cathode. Also, H+ ions must pass through the electrolyte. An acid is a
fluid with free H+ ions, and so serves this purpose very well. Certain polymers can also be made to contain
mobile H+ ions. These materials are called proton exchange membranes, as an H+ ion is also a proton.
Advantages and Applications
• Efficiency: Fuel cells are generally more efficient than combustion engines whether piston or turbine
based. A further feature of this is that small systems can be just as efficient as large ones. This is very
important in the case of the small local power generating systems needed for combined heat and power
systems.
• Simplicity: The essentials of a fuel cell are very simple, with few if any moving parts. This can lead to
highly reliable and long-lasting systems.
• Low emissions: The by-product of the main fuel cell reaction, when hydrogen is the fuel, is pure water,
hi h ea s a fuel ell a e esse tiall ze o e issio . This is thei ai ad a tage he used i
vehicles, as there is a requirement to reduce vehicle emissions, and even eliminate them within cities.
However, it should be noted that, at present, emissions of CO2 are nearly always involved in the production
of hydrogen that is needed as the fuel.
•Noise: Fuel cells are very quiet, even those with extensive extra fuel processing equipment. This is very
important in both portable power applications and for local power generation in combined heat and power
schemes.
The advantages of fuel cells impact particularly strongly on combined heat and power systems (for both
large- and small-scale applications), and on mobile power systems, especially for vehicles and electronic
equipment such as portable computers, mobile telephones, and military communications equipment.
These areas are the major fields in which fuel cells are being used.
Disadvantages
• High market entry cost, production cost.
• Unfamiliar technology to the power industry.
• Almost no infrastructure.
• Still at level of development.
Operational Fuel Cell Voltages
For the hydrogen fuel cell, two electrons pass round the external circuit for each water molecule produced
and each molecule of hydrogen used. So, for one mole of hydrogen used, 2N electrons pass round the
34

35. external circuit – where N is A ogad o s u e . If −e is the charge on one electron, then the charge that
flows is
−2 Ne = −2F coulombs
F being the Faraday constant or the charge on one mole of electrons. If E is the voltage of the fuel cell, then
the electrical work done moving this charge round the circuit is
Electrical work done = charge × voltage = −2FE joules
If the system is reversible (or has no losses), then this electrical work done will be equal to the Gibbs free
energy eleased ∆gf.
∆gf = −2F ・ E
Thus E =−∆gf / 2F
This fundamental equation gives the electromotive force (EMF) or reversible open circuit voltage of the
hydrogen fuel cell.
∆gf- Gibbs free energy released,
F- Faradays constant.
For example, a hydrogen fuel cell operating at 200◦C has ∆gf = −220 kJ, so
E = 220,000/ (2 × 96,485)
= 1.14V
This gives a value of about 1.2V for a cell operating below 100◦C. However, when a fuel cell is made and put
to use, it is found that the voltage is less than this, often considerably less.
The following observations are obtained while plotting cell voltage vs. current density
• Ope circuit voltage is less than the theoretical value.
• The e is a apid i itial fall i oltage.
• The oltage the falls less apidl , a d o e li ea l .
• The e is so eti es a highe u e t de sit at hi h the oltage falls apidl
35

36. The variation in theoretical value is due to the following losses
1. Activation losses
2. Fuel crossover and internal currents
3. Ohmic losses
4. Mass transport or concentration losses
1. Activation losses. These are caused by the slowness of the reactions taking place on the surface of the
electrodes. A proportion of the voltage generated is lost in driving the chemical reaction that transfers the
electrons to or from the electrode.
2. Fuel crossover and internal currents. This energy loss results from the waste of fuel passing through the
electrolyte, and, to a lesser extent, from electron conduction through the electrolyte. The electrolyte
should only transport ions through the cell, However, a certain amount of fuel diffusion and electron flow
will always be possible. Except in the case of direct methanol cells the fuel loss and current is small, and its
effect is usually not very important. However, it does have a marked effect on the OCV of low-temperature
cells,
3. Ohmic losses. This voltage drop is the straight forward resistance to the flow of electrons through the
material of the electrodes and the various interconnections, as well as the resistance to the flow of ions
through the electrolyte. This voltage drop is essentially proportional to current density, linear, and so is
called ohmic losses, or sometimes as resistive losses.
4. Mass transport or concentration losses. These result from the change in concentration of the reactants
at the surface of the electrodes as the fuel is used.Concentration affects voltage, and so this type of
irreversibility is sometimes called concentration loss. Because the reduction in concentration is the result of
a failure to transport sufficient reactant to the electrode surface, this type of loss is also often called mass
transport loss.
Proton Exchange Membrane Fuel Cell (PEMFC)
Proton exchange membrane fuel cells, also known as polymer electrolyte membrane (PEM)
fuel cells (PEMFC), are a type of fuel cell being developed for transport applications as well as for stationary
fuel cell applications and portable fuel cell applications. They have lower temperature/pressure ranges (50
36

37. to 100 °C) and a special polymer electrolyte membrane. The most commonly used membrane is
sulphonated fluoropolymers (Nafion) which relies on liquid water humidification of the membrane to
transport protons act as the solid electrolyte.
This implies that it is not feasible to use temperatures above 80 to 90 °C.PEMFCs are built out of
membrane electrode assemblies (MEA) which include the electrodes, electrolyte, catalyst, and gas diffusion
layers. An ink of catalyst, carbon, and electrode are sprayed or painted onto the solid electrolyte and
carbon paper is hot pressed on either side to protect the inside of the cell and also act as electrodes. The
pivotal part of the cell is the triple phase boundary (TPB) where the electrolyte, catalyst, and reactants mix
and thus where the cell reactions actually occur. The best catalyst for both the anode and the cathode is
platinum.
Reactions
A proton exchange membrane fuel cell transforms the chemical energy liberated during
the electrochemical reaction of hydrogen and oxygen into electrical energy, as opposed to the
direct combustion of hydrogen and oxygen gases to produce thermal energy. A stream of hydrogen is
delivered to the anode side of the membrane electrode assembly (MEA). At the anode side it
is catalytically split into protons and electrons. This oxidation half-cell reaction or hydrogen oxidation
reaction (HOR) is represented by:
At the anode:
H2→ H+
+2e-
The newly formed protons permeate through the polymer electrolyte membrane to the cathode
side. The electrons travel along an external load circuit to the cathode side of the MEA, thus creating
the current output of the fuel cell. Meanwhile, a stream of oxygen is delivered to the cathode side of the
MEA. At the cathode side oxygen molecules react with the protons permeating through the polymer
electrolyte membrane and the electrons arriving through the external circuit to form water molecules.
This reduction half-cell reaction or oxygen reduction reaction (ORR) is represented by:
37

38. At the cathode:
½ O2+2H+
+ 2e-
→ H2O
Overall reaction:
H2+ ½ O2→ H2O
PEMFC operate at a temperature of around 80°C. Each cell produces around 0.7 volts, about enough
power to run a light bulb. To generate high voltage, a number of individual cells are combined in series.
Advantages
 Operate at low temperatures which allow them to start up rapidly from cold.
 High power density which makes them really compact and lightweight.
 Compact construction
 Solid electrolyte
 Low working temperature
 Fast start-up
Disadvantages
• Needs pure hydrogen to operate as they are very susceptible to poisoning by carbon monoxide.
• Water management
• Noble metal catalyst
• CO sensitive (must be < 20 ppm)
• Cooling issues
38

39. Application
• Due to their light weight, PEMFCs are most suited for transportation applications.
• PEMFCs for busses, which use compressed hydrogen for fuel, can operate at up to 40% efficiency.
• Decentralized power generation for industrial and domestic applications
• Portable generation systems for domestic,industrial,military etc
ALKALINE ELECTROLYTE FUEL CELLS
Alkaline fuel cells (AFCs) normally use a mobilized or immobilized aqueous solution(30–45 wt %) of
potassium hydroxide (KOH) as an electrolyte. The electrolyte obviously needs to be an alkaline solution.
Sodium hydroxide and potassium hydroxide solution, being of lowest cost, highly soluble, and not
excessively corrosive, are the prime candidates. It turns out that potassium carbonate is much more soluble
than sodium carbonate, and this is an important advantage. Since the cost difference is small, potassium
hydroxide solution is always used as the electrolyte
H + OH− → H O + e− anode reaction
O + e− + H O→ OH− cathode reaction
H + O → H O overall reaction
Hydroxyl anions diffuse continuously from the cathode to the anode and water diffuses the opposite way.
Most of the reaction water leaves on the anode side, but a small amount of reaction water is removed via
the electrolyte loop, if a circulating system is considered.
The oxygen reduction in alkaline environments is more favorable than in acid environments, i.e., the
voltage drop is lower. It yields the highest voltage at comparable current densities, leading to a higher
efficiency of the system. Consequently, the use of smaller amounts of noble metal electro catalysts is more
favorable in an AFC than in any other system. AFCs also operate well at room temperature and have a good
cold start capability.
39

40. However, a major disadvantage is the CO2 sensitivity of the alkaline electrolytes as carbonates are formed.
In strong alkaline environments, the solubility of carbonates is rather poor. This leads to the formation of
carbonate crystals, capable of blocking electrolyte pathways and electrolyte pores.
CO + OH− −−−→ CO − + H O
As a consequence, the use of AFCs has been restricted to special applications, where no CO2 is present, for
example in space vehicles, where pure hydrogen and pure oxygen are used. The formation of carbonates is
one of the causes of the poor long-term stability of AFCs.
Types of Alkaline Electrolyte Fuel Cell
Mobile electrolyte
The basic structure of the mobile electrolyte fuel cell is shown below The KOH solution is pumped around
the fuel cell. Hydrogen is supplied to the anode but must be circulated, as it is at the anode where the
water is produced. The hydrogen will evaporate the water, which is then condensed out at the cooling unit
through which the hydrogen is circulated. The hydrogen comes from a compressed gas cylinder, and the
circulation is achieved using an ejector circulator, though this may be done by a pump in other systems.
The majority of alkaline fuel cells are of this type. The main advantage of having the mobile
electrolyte is that it permits the electrolyte to be removed and replaced from time to time. The carbon
dioxide in the air will react with the potassium hydroxide electrolyte
2KOH + CO2 → K2CO3 + H2O
The potassium hydroxide is thus gradually changed to potassium carbonate. The effect of this is that the
concentration of OH− ions reduces as they are replaced with carbonate CO3 2− ions, which greatly affects
the performance of the cell. but one way of at least reducing it is to remove the CO2 from the air as much
as possible of, and this is done using a CO2 scrubber in the cathode air supply system. However, it is
impossible to remove all the carbon dioxide, so the electrolyte will inevitably deteriorate and require
replacing at some point. This mobile system allows that to be done reasonably easily and of course
potassium hydroxide solution is of very low cost. The disadvantages of the mobile electrolyte centre
around the extra equipment needed. A pump is needed, and the fluid to be pumped is corrosive. The extra
pipe work means more possibilities for leaks, and the surface tension of KOH solution makes for a fluid that
is prone to find its way through the smallest of gaps. Also, it becomes harder to design a system that will
work in any orientation.
Static electrolyte alkaline fuel cells
A alte ati e to a f ee ele t ol te, hi h i ulates is that, fo ea h ell i the sta k to ha e its
own, separate electrolyte that is held in a matrix material between the electrodes. The KOH solution is held
in a matrix material, which is usually asbestos. This material has excellent porosity, strength, and corrosion
resistance. The system uses pure oxygen at the cathode, and this is almost obligatory for a matrix-held
electrolyte, as it is very hard to renew if it becomes carbonated .The hydrogen is circulated, as with the
previous system, in order to remove the product water. In the spacecraft systems, this product water is
used for drinking, cooking, and cabin humidification
40

41. MOBILE ELECTROLYTE TYPE
STATIC ELECTROLYTE ALKALINE FUEL CELL
41

42. Advantages
 Very high ionic conductivity compared to other fuel cells, achieved by using high hydroxide ion
concentrations.
 Relatively low-cost electrodes compared to the platinum electrodes required for reactions in acidic
media
Disadvantages
They need to be installed in a carbon dioxide free environment. This is to avoid poisoning of the electrolyte.
If carbon dioxide comes into contact with the alkaline environment, carbonates are formed. These
carbonates are insoluble salts that clog the porous electrodes and block the flow of hydrogen and oxygen,
resulting in power failure. To prevent such an event from occurring, the input gasses need to be purified
extremely well. Although the technology for purification is fully developed and available, the process adds
to the total cost of the fuel cell and makes it less practical.
Medium and high temperature fuel cells
There are three types of medium- and high-temperature fuel cells they are solid oxide fuel cell, The
phosphoric acid electrolyte fuel cell (PAFC), molten carbonate (electrolyte) fuel cell (MCFC).
1.Solid Oxide Fuel Cells.
Solid oxide fuel cells (SOFCs) use a solid material, most commonly a ceramic material called yttria-stabilized
zirconia (YSZ), as the electrolyte. Because SOFCs are made entirely of solid materials, they are not limited to
the flat plane configuration of other types of fuel cells and are often designed as rolled tubes. They require
high operating temperatures (800–1000 °C) and can be run on a variety of fuels including natural gas.
SOFCs are unique since in those, negatively charged oxygen ions travel from the cathode to
the anode instead of positively charged hydrogen ions travelling from the anode to the cathode, as is the
case in all other types of fuel cells. Oxygen gas is fed through the cathode, where it absorbs electrons to
create oxygen ions. The oxygen ions then travel through the electrolyte to react with hydrogen gas at the
anode. The reaction at the anode produces electricity and water as by-products. Carbon dioxide may also
be a by-product depending on the fuel, but the carbon emissions from an SOFC system are less than those
from fossil fuel combustion plant. The chemical reactions for the SOFC system can be expressed as follow
Anode Reaction: 2H2 + 2O −
→ H2O + 4e−
Cathode Reaction: O2 + 4e−
→ O −
Overall Cell Reaction: 2H2 + O2 → 2H2O
SOFC systems can run on fuels other than pure hydrogen gas. However, For the fuel cell to operate, the fuel
must be converted into pure hydrogen gas. SOFCs are capable of internally reforming light hydrocarbons
such as methane (natural gas), propane and butane These fuel cells are at an early stage of development
42

43. Challenges exist in SOFC systems due to their high operating temperatures. One such challenge is the
potential for carbon dust to build up on the anode, which slows down the internal reforming
process.Another disadvantage of SOFC systems is slow start-up time, making SOFCs less useful for mobile
applications. Despite these disadvantages, a high operating temperature provides an advantage by
removing the need for a precious metal catalyst like platinum, thereby reducing cost. Additionally, waste
heat from SOFC systems may be captured and reused, increasing the theoretical overall efficiency to as
high as 80%–85%.
Intended mainly for stationary applications with an output of 1 kW and larger. They work at very high
temperatures (some at 1000ºC). Due to the high operating temperature of SOFC's, they have no need for
expensive catalyst.
Applications
Suitable for decentralized electricity production
While the major application of SOFCs are seen in stationary plants, auxiliary power units in
• Transportation vehicles
• On-board power for aircraft
Drawbacks
• The high temperature limits applications of SOFC units and they tend to be rather large
• While solid electrolytes cannot leak, they can crack.
• Complex materials
• Assembling
• Maintenance
• Design Cost & choice of material
43

44. Molten Carbonate Fuel Cell
The molten carbonate fuel cell uses a molten carbonate salt as the electrolyte. It has the
potential to be fuelled with coal- derived fuel gases, methane or natural gas. These fuel cells can work at up
to 60% efficiency In molten carbonate fuel cells, negative ions travel through the electrolyte to the anode
where they combine with hydrogen to generate water and electrons. Molten carbonate fuel cells (MCFCs)
are currently being developed for natural gas and coal-based power plants for electrical utility, industrial,
and military applications.
MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten
carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminum oxide (LiAlO2)
matrix. Since they operate at extremely high temperatures of 650ºC and above, no precious metals need
not to be used as catalysts at the anode and cathode, reducing costs. Unlike alkaline, phosphoric acid, and
polymer electrolyte membrane fuel cells, MCFCs don't require an external reformer to convert more
energy-dense fuels to hydrogen. Due to the high temperatures at which they operate, these fuels are
converted to hydrogen within the fuel cell itself by a process called internal reforming, which also reduces
cost. Although they are more resistant to impurities than other fuel cell types, scientists are looking for
ways to make MCFCs resistant enough to impurities from coal, such as sulfur and particulates.
Anode Reaction: CO3 - + H → H O + CO + e-
Cathode Reaction: CO2 + ½O2 + 2e- → CO3 -2
O e all Cell ‘ea tio : H + ½O → H O
44

45. The primary disadvantage of current MCFC technology is durability. The high temperatures at which these
cells operate and the corrosive electrolyte used accelerate component breakdown and corrosion,
decreasing cell life. Scientists are currently exploring corrosion-resistant materials for components as well
as fuel cell designs that increase cell life without decreasing performance.
Phosphoric acid Fuel Cell(PAFC)
It s a Medium temperature fuel cell. A phosphoric acid fuel cell (PAFC) consists of an anode
and a cathode made of a finely dispersed platinum catalyst on carbon and a silicon carbide structure that
holds the phosphoric acid electrolyte. Phosphoric acid (H3PO4) is the only common inorganic acid that has
enough thermal stability, chemical, and electrochemical stability, and low enough volatility (above
about150◦C) to be considered as electrolyte for PAFC. Most importantly, phosphoric acid is tolerant to CO2
in the fuel and oxidant, unlike the alkaline fuel cell
In phosphoric acid fuel cells, protons move through the electrolyte to the cathode to combine with oxygen
and electrons, producing water and heat. This is the most commercially developed type of fuel cell and is
being used to power many commercial premises Phosphoric acid fuel cells use liquid phosphoric acid as an
electrolyte the acid is contained in a Teflon-bonded silicon carbide matrix and porous carbon electrodes
containing a platinum catalyst.
This type of fuel cell is typically used for stationary power generation, but some PAFCs have been used to
power large vehicles such as city buses PAFCs are more tolerant of impurities They are 85 percent efficient
when used for the co-generation of electricity and heat, but less efficient at generating electricity alone (37
to 42 percent). PAFCs are also less powerful than other fuel cells, given the same weight and volume. As a
45

46. result, these fuel cells are typically large and heavy. PAFCs are also expensive. Like PEM fuel cells, PAFCs
require an expensive platinum catalyst, which raises the cost of the fuel cell.
Fuel and fuel choice.
The fuel cell types that have been described in detail so far employ hydrogen as the preferred fuel, on
a ou t of its high ea ti it fo the ele t o he i al a ode ea tio it a t e sto ed. Vehi les e plo i g
proton exchange membrane (PEM) fuel cells running on hydrogen may therefore be termed zero-emission,
because the only emission from the vehicle is water. Unfortunately, hydrogen does not occur naturally as a
gaseous fuel, and so for practical fuel cell systems it usually has to be generated from whatever fuel source
is locally available. Methane, Ammonia, Methanol, Ethanol, and Gasoline are commonly used to produce
Hydrogen
The primary fuels that can be directly utilized within fuel cell stacks today are
hydrogen, carbon monoxide, methanol, and dilute light hydrocarbons like methane, depending upon the
fuel cell type.
46

47. The table below presents various fuel cell types and the primary fuels that they are amenable to
using. Note that the presence of sulfur is not tolerated by fuel cells in general and that the SOFC is the
most inherently fuel flexible of the fuel cell types. MCFC units are also quite fuel flexible.
a. In reality CO reacts with H2O producing H2 and CO2 and CH4 with H2O reforms to H2 and CO faster
than reacting as a fuel at the electrode.
b. A fuel in the internal reforming MCFC and SOFC.
c. The fact that CO2 is a poison for the alkaline fuel cell more or less rules out its use with reformed fuels
H2 is preferable for a closed environment such as space vehicle application. There
are sources of H 2-rich gases, such as an off-gas at a chemical plant, that require only fuel cleaning. The fuel
choice for small, stationary power plants is pipeline gas (natural gas) due to its availability for multiple
commercial, light industrial and residential applications. Liquid fuels for light vehicles could be available like
gasoline or methanol (it may have an edge if it proves too difficult to process gasoline). The present
infrastructure fuel for heavy vehicles is high sulfur diesel (now ~500 ppm sulfur by weight) but this may
change to a nearly sulfur-free diesel as proposed by the EPA. On-board vehicle auxiliary power is increasing
dramatically to satisfy consumer convenience demands. Sulfur specification will remain high because the
military has to consider worldwide fuel sources. Methanol is the easiest of the potential liquid fuels to
convert to hydrogen for vehicle use. It generates CO and H 2 at 250 °C with catalyst (but methanol is from
natural gas requiring energy and is more toxic and dangerous than gasoline). Gasoline has many
advantages over methanol, but conversion to H 2 requires temperatures in excess of 650 °C with catalyst.
Processing Required for Fuels
Fuel processing may be defined as the conversion of the raw primary fuel, supplied to a fuel cell
system, into the fuel gas required by the stack. Each type of fuel cell stack has some particular fuel
requirements. Lower the operating temperature of the stack, the more stringent are the requirements, and
the greater the demand placed on fuel processing. For example, fuel fed to a PAFC needs to be hydrogen-
rich and contain less than about 0.5% carbon monoxide. The fuel fed to a PEM fuel cell needs to be
essentially carbon monoxide free, while both the MCFC and the SOFC are capable of utilizing carbon
monoxide through the water-gas shift reaction that occurs within the cell. Additionally, SOFCs and internal
reforming MCFCs can utilize methane within the fuel cell, whereas PAFCs and PEMs cannot. It is not widely
known that PEMFCs can utilize some hydrocarbons, such as propane, directly, although the performance is
poor
47

48. Fuel processing technology Fuel cell anode
Exhaust
Desulphuriser
Vapouriser
Water
Fuel air
The diagram shows the main process stages applied to fuel cell processing technology. The main
components of fuel processor are Reformer and a shift reactor.
Desulphurization: Natural gas and petroleum liquids contain organic Sulphar compounds that normally
have to be removed before any further fuel processing can be carried out. Even if Sulphar levels in fuels are
below 0.2 ppm, some deactivation of steam reforming catalysts can occur. Shift catalysts are even more
intolerant to sulphur and to ensure adequate lifetimes of fuel processors the desulphurization step is very
important Some of Fuel processing techniques which are used for the production of hydrogen is mentioned
below. They are
 Steam Reforming
 Partial oxidation
 Auto thermal reforming
 Plasma reforming
 Indirect internal reforming
 Direct internal reforming
Steam methane Reforming (SMR)
Sulphar
CH4
CO2
H2
High temp
shift
Low temp
shift
Reformer
Pre reformer
Heat reactionReformerDesulfurization
Shift
reactionPurification
48

49. Steam reforming is a method for producing hydrogen, carbon monoxide, or other useful products
from hydrocarbon fuels such as natural gas. This is achieved in a processing device called a reformer which
reacts steam at high temperature with the fossil fuel. The steam methane reformer is widely used in
industry to make hydrogen. Steam reforming includes catalytic reaction of hydro carbon fuel with steam in
o de to li e ate fuel ou d a d ate ou d h d oge
Pre-Treatment of the Feed
The hydrocarbon feedstock is desulphurised using e.g. activated carbon filters, pressurized
and, depending on the reformer design, either preheated and mixed with process steam or directly injected
with the water into the reformer.
Shift reaction
Methane and steam are converted within the compact reformer furnace at approx. 900 °C in the presence
of a nickel catalyst to a hydrogen rich reformate stream according to the following reactions
CH + H O→ CO + H
CO + H O → CO + H
The water gas shift reaction is an important industrial reaction; it is often used in steam reforming with
methyl or hydrocarbons which is important for producing high purity hydrogen.
Partial Oxidation
Fuel Sulphar
Air
N2
CO2
H2
CH4+O2→CO+ H2
A sub-stoichiometric amount of air or oxygen is used to partially combust the fuel.
Partial oxidation is highly exothermic, and raises the reactants to a high temperature. The resulting reaction
products, still in a reduced state, are then quenched through the introduction of superheated steam. The
addition of steam promotes the combined water-gas shift and steam reforming reactions In most cases the
overall reaction is exothermic and self-sustaining. Non catalytic processes for gasoline reforming require
temperatures in excess of 1,000 °C (special materials). The use of a catalyst can substantially reduce the
operating temperature (common materials and higher efficiency). Typical values range from as low as 870
DesulfurizationGasificationAir separation
Purification
Shift
reaction
49

50. °C for catalytic POX upwards to 1,400 °C for non-catalytic POX. Advantages of POX in comparison with SR:
POX does not need indirect heat transfer. POX is capable of higher efficiency than SR.
Auto thermal Reforming
Auto thermal reforming uses oxygen or steam in a reaction with methane to form hydrogen rich
gas. The reaction takes place in a single chamber where the methane is partially oxidized. The reaction is
exothermic due to oxidation when auto thermal reforming uses CO2 the H2-CO ratio is 2:5:1. Temperature
of gas is et ee 9 ˚C a d ˚C a d the outlet p essu e highest at a .
Reaction: CH4 + H2O→ CO + H2 or CH4 +O2→ CO2 + 2H2
Auto thermal reforming integrates partial oxidation & steam reforming process. It has low energy
requirement and gas velocity. Auto thermal reforming provides a fuel processor compromise that operates
at a lower O/C and lower temperature than the POX. It is smaller, quicker starting, and quicker responding
than the SR, and results in high H 2 concentration.
Plasma reforming of glycerol
The plasma configuration is used for producing H2 from glycerol.The anode is made of stainless steel tube
with a 1/16th
inch tube inside and 1/8th
inch tube outside. A hollow needle with an inner diameter of
0.26mm is put inside 1/8 inch tube close to the tip of tube electrode.
The feed is fed through the anode with a calibrated pump. The cathode is made of 3/8 inch
stainless steel tube with a filter cap over top. The porous structure of the filter cap distributes the plasma
on the cathode and allows the gases to pass through it. A catalyst may be put under the filter cap to
enhance a specified reaction. For example catalyst water shift reaction can be successfully tested in this
o figu atio . The tip of the a ode is the hottest poi t app o i atel 9 ˚C, follo ed plas a zo e
˚C a d the plate ele t ode. Ele t ode te pe atu e is ˚C to ˚C. gl e i a e di e tl
decomposed into H2 and CO. a small amount of water(steam) or oxygen (partial oxidation or auto thermal
50

51. reforming) is added in the process to inhibit carbon formation that essentially lead to deactivation of
catalyst.
Reaction: C3H8O3→ H2+3CO
Pure glycerol can be effectively converted into hydrogen and carbon monoxide. Using a non-
equilibrium plasma at low temperature and atmospheric pressure without external heating. In a non-
equilibrium plasma, high energy electrons are generated and activate the reactance initiating radical
reactions, while the work gas phase temperature remains low. The advantage of low temperature is quick
startup and free from the catalyst deactivation of these plasma leads to increasing attention for utilization
in fuel conservation.
Some miscellaneous methods of Hydrogen production
 Electrolysis
 Thermolysis
 Photo catalytic water splitting
 Sulphar-iodine cycle
 Biohydrogen routes
 Fermentative hydrogen production
Electrolysis:- Approximately 5.1% industrial hydrogen is produced by electrolysis. Two types of cells
which are popular- Solid oxide electrolysis cell and Alkaline electrolysis cell. These cells optimally
operate at high concentration electrolyte potassium carbonate and at high temperature. The catalyst
used is Zirconium together with Nickel.
Photo catalytic water splitting:- The conversion of solar energy to hydrogen by means of water
splitting process is one of the most interesting ways to achieve clean and renewable energy system. If
this process is assisted by photocatalyst suspended directly in water instead of using photo voltaic and
electrolytic system the reaction occurs in one step and it is more effective
Sulphar-iodine cycle:- The Sulphar-iodine cycle is a thermo chemical process which generate hydrogen
from water at a higher efficiency than water splitting. The Sulphar acid and iodine used in the process
and recovered and reused and it is not consumed by the process it is well suited production of
hydrogen at high temperature
Biohydrogen routes:- Biomass and biowaste can be converted into biohydrogen with biomass
gasification with steam reforming or biological conservation like biocatalysed electrolysis or
fermentative hydrogen production.
Fermentative hydrogen production:- Fermentative hydrogen production is fermentative conservation
of organic substrate to biohydrogen by biodiverse group of bacteria using multi enzyme system
involving 3 steps similar to anaerobic conversion
C6H10O5+7H2O→ H2+6CO2
51

52. Fuel Cell Stacks
A single fuel cell is only capable of producing about 1 volt, so typical fuel cell designs link together
many individual cells to form a "stack" to produce a more useful voltage. A fuel cell stack can be configured
with many groups of cells in series and parallel connections to further tailor the voltage, current, and
power. The number of individual cells contained within one stack is typically greater than 50 and varies
significantly with stack design.
The basic components of the fuel cell stack include the electrodes and electrolyte with additional
components required for electrical connections and/or insulation and the flow of fuel and oxidant. These
key components include current collectors and separator plates. The current collectors conduct electrons
from the anode to the separator plate. The separator plates provide the electrical series connections
between cells and physically separate the oxidant flow of one cell from the fuel flow of the adjacent cell.
The channels in the current collectors serve as the distribution pathways for the fuel and oxidant. Often,
the two current collectors and the separator plate are combined into a single unit called a "bipolar plate."
52