HYBRID VEHICLES

HYBRID VEHICLES

Pierre Duysinx

LTAS Automotive Engineering University of Liège

Academic year 2010-2011

References

„ R. Bosch. « Automotive Handbook ». 5th edition. 2002. Society of Automotive Engineers (SAE)

„ G. Genta. « The Motor Vehicle Dynamics». Levrotto & Bella di Gualini. Torino 2000.

„ C.C. Chan. The State of the art of Electric and Hybrid Vehicles.

Proc. IEEE. vol 90 pp 24-275. 2002

„ C.C. Chan and K.T. Chau. Modern Vehicle Technology. Oxford Science Publications. 2001.

„ M. Ehsani, Y. Gao, S. Gay and A. Emadi. Modern Electric, Hybrid electric and, Fuel Cell Vehicles. Fundamentals, Theory and Design. CRC Press, 2005.

„ www.hybridcars.com

„ www.howstuffworks/hybrid-car.htm

Outline

„

Introduction

„

History of HEV

„

How to save fuel and reduce emissions?

„

Definitions

„ Hybrid vehicle & Hybrid electric vehicle

„ Categories: Series, parallel and complex hybrids, full et mild hybrids, charge depleting, charge sustaining, plug-in hybrids

„

Key components of hybrid vehicles

„

Other systems for fuel efficiency improvement

„

Case studies: Honda Insight and Toyota Prius

Introduction

History

History

„ 1839: Robert Anderson of Aberdeen, Scotland built the first electric vehicle

„ 1870 : Sir David Salomon developed a car with a light electric motor and very heavy storage batteries. Driving speed and range were poor.

„ 1890-1910: Period of significant improvements in battery

technology, specifically with development of the modern lead-acid battery by H. Tudorand nickel-iron battery by Edison and Junger.

„ 1897: Harford, Connecticut – the Pope Manufacturing Company builds about 500 electric cars in a two-year period.

History

„ 1900: The German Dr. Ferdinand Porsche, at age 23, built his first car, the Lohner Electric Chaise. It was the world's first front-wheel-drive.

In 1900 for Paris International exhibition, Ferdinand Porsche designed and built the Elektromobil Lohner-Porsche, a vehicle equipped with 4 motors inserted in the wheel hubsin order to save room.

Porsche's second car was a hybrid, using an internal combustion engine to spin a generator that provided power to electric motors located in the wheel hubs. On battery alone, the car could travel nearly 40 miles.

History

„ 1899: The Pope Manufacturing Company merged with two smaller electric car companies to form the Electric Vehicle Company, the first large-scale operation in the American automobile industry.

„ 1900: American car companies made 1,681 steam, 1,575 electric and 936 gasoline cars. In a poll conducted at the first National Automobile Show in New York City, patrons favored electric as their first choice, followed closely by steam.

This car, made in 1903 by the Krieger company, used a gasoline engine to supplement a battery pack

History

„ 1899: Henri Pieper, an engineer and car manufacturer from Liege introduces a 3-1/2 horsepower "voiturette" in which the small gasoline engine was mated to an electric motor under the seat.

„ When the car was "cruising," its electric motor was in effect a generator, recharging the batteries. But when the car was climbing a grade, the electric motor, mounted

coaxially with the gas engine, gave it a boost.

„ Pieper’s idea to use electric motor to assist the internal combustion engine allows the vehicle to reach a 25 mph velocity.

History

„ As soon as 1905-1906 Henri Pieper creates the petroleo electrical cars, combining a thermal engine with a electric motor. The hybrid vehicle was born

„ The Pieper patents were used by a Belgium firm, Auto-Mixte(in Nessonvaux, near Liege), to build commercial vehicles from 1906 to 1912.

Pieper hybrid truck for Antwerp firemen (1912)

History

„ 1904: Henry Ford overcame the challenges posed by gasoline-powered cars— noise, vibration, and odor — and began assembly- line production of low-priced, lightweight, gas- powered vehicles. Within a few years, the Electric Vehicle Company will be failed.

„ 1910: A car maker builds an hybrid truck that uses a 4 cylinder engine spinning a generator, which eliminates the need for a transmission and a battery pack. These trucks are sold up to 1918

„ 1913: With the advent of the self-starter (making it easy for all drivers to start gas engines), steamers and electrics were almost completely wiped out.

Ford T no 2 on display in Seattle

History

„ 1913. In this year, sales of electric cars dropped to 6,000 vehicles, while the Ford Model T sold 182,809 gasoline cars.

„ 1920-1965: Dormant period for mass-produced electric and hybrid cars. So-called alternative cars became the province of backyard tinkerers and small-time entrepreneurs.

„ 1966: U.S. Congress introduced first bills recommending use of electric vehicles as a means of reducing air pollution.

„ 1973: The Arab oil embargo brings increased gasoline prices and a new interest in electric and hybrid vehicles

This 1921 Owen Magnetic Model 60 Touring uses a gasoline engine to run a generator that supplies electric power to motors mounted in each of the rear wheels.

History

„ 1970-1980: “VW Taxi”produced by Volkswagen in Wolfsburg, West Germany. The Taxi, which used a parallel hybrid

configurationallowing flexible switching between the gasoline engine and electric motor, logged over 8,000 miles on the road, and was shown at auto shows throughout Europe and the United States.

„ 1975: AM General, a division of American Motors, began delivery of 352 electric vans to the U.S. Postal Service for testing.

„ 1975: Government program to advance electric and hybrid technologyis implemented by the U.S. Energy Research and Development Administration.

History

„ 1976: U.S. Congress enacted Public Law 94-413, the Electric and Hybrid Vehicle Research, Development, and Demonstration Act of 1976. Among the law’s objectives were to work with industry to improve batteries, motors, controllers, and other hybrid-electric components.

„ 1976: General Electricwas chosen to construct a parallel-hybrid sedan, and Toyota built its first hybrid— a small sports car with a gas-turbine generator supplying current to an electric motor.

„ 1977-1979: General Motors spent over $20 million in electric car development and research, reporting that electric vehicles could be in production by the mid-1980s.

History

„ 1982: «All about Electric & Hybrid Cars» by Robert J. Taister.

The author emphasizes the battery problemwhich should be circumvented by using a generator onboard and charge the batteries while driving downhill for instance.

„ 1991: United States Advanced Battery Consortium(USABC) launches a program to make a “super” batteryin hopes of getting electric cars on the road as soon as possible. The USABC invests over $90 million in the nickel hydride battery which can

“accept three times as many charge cycles as lead-acid” and also works well in the cold weather.

„ 1992: Toyota Motor Companyreleases a document that outlines goals to develop and market vehicles with the lowest emissions possible. It is called the “Earth Charter.”

History

„ 1997: The Toyota Priuswas introduced to the Japanese market, two years before its original launch date, and prior to the Kyoto global warming conference held in December. First-year sales were nearly 18,000.

„ 1997-1999: A small selection of all- electric cars from the big automakers— including Honda’s EV Plus, GM’s EV1 and S-10 electric pickup, a Ford Ranger pickup, and Toyota’s RAV4 EV — were introduced in California. Despite the enthusiasm of early adopters, the electrics failed to reach beyond a few hundred drivers for each model. Within a few years, the all-electric programs were dropped.

Toyota Prius I

History

„ 1999: Hondareleased the two-door Insight, the first hybrid car to hit the mass market in the United States. The Insight won numerous awards and received EPA mileage ratings of 61 mpg city and 70 mpg highway.

„ 2000: Toyota released the Toyota Prius I, the first hybrid four-door sedan available in the United States

„ 2002: Honda introduced the Honda Civic Hybrid, its second commercially available hybrid gasoline-electric car.

The appearance and drivability of the Civic Hybrid was (and still is) identical to the conventional Civic

Honda Insight

Honda Civic IMA

History

„ 2004: The Toyota Prius IIwon 2004 Car of the Year Awards from Motor Trend Magazine and the North American Auto Show. Toyota was surprised by the demand and pumped up its production from 36,000 to 47,000 for the U.S.

market. Interested buyers waited up to six months to purchase the 2004 Prius.

Toyota Motor Sales U.S.A. President Jim Press called it "the hottest car we've ever had."

„ 2005: Fordreleased the Escape Hybrid, the first American hybrid and the first SUV hybrid. Toyota also released several models equipped with hybrid propulsion system LexusRX400h, Lexus GS300h etc.

„ 2007: Toyota sold one million of Prius II around the world

Toyota Prius II

Ford Escape

History

„

2010: Sales and market forecast

Reducing fuel consumption and

emissions

Development principles of new clean propulsion systems

source: www.nrel.org Stop engine when idle

Improve engine efficiency: downsizing, internal friction, new converters

Energy recovery while braking

Reduction of mass, S Cx, And tire rolling resistance Fuels with

less carbon

Reducing CO ₂ emissions

„

To reduce the emissions, several approaches

„ Substituting petrol fuels by fuels with low carbon emissions (per energy release) or fuels with a life cycle giving rise to low emissions (biofuels)

„ Improve the fuel efficiency of the converter (the most direct action)

„ Reduce the mass, which often antagonistic with the demand for greater safety, comfort, etc.

„ Internal friction and losses reduction: downsizing strategy=

keep same performance with a lower cylinder displacement

„ Reduction of aerodynamic drag

„ Improve drivetrain efficiency

Reduce CO ₂ emissions

Selection of fuels

„ Lower heat value of fuels

Substituting fuels by cleaner ones

„

Substitution fuels

„ Compressed Natural Gas (CNG)

„ Liquefied Petroleum Gas (LPG)

„ Alcohols (ethanol, methanol)

„ Bio diesel (DME, etc.)

„ Hydrogen, Ammoniac

„

Increasing market parts of substitution fuels

„ 2020 target : 20% of the market

„ Bio fuels: 6% in 2010

Highly variable operating conditions

„

Major difficulty of propulsion systems: the highly variable operating conditions (torque, regime)

„ Objective: sizing to average power consumption!

„ Approach: store the energy Öhybrid vehicle

Source G. Coquery, INRETS

Improve powertrain efficiency

„ Use energy storage to level energy flow

„ Recover braking energy

„ Smooth out the peak powers

„ Reduce the size of the prime mover as close as possible to the average power

„ Improve the energy efficiency of the engine

„ Reduce the engine size while preserving the torque

„ Reduction the internal engine frictions

„ Place the operating points of the engines in its most favourable regimes

-150 -100 -50 0 50 100 150

0 200 400 600 800 1000

Temps [s]

Puissance Machine électrique [kW]

Definitions

Definitions

„

Definition of hybrid vehicle: vehicle equipped with a propulsion system that combines two or several energy sources, storages and converters.

„

Possible energy sources:

„ Chemical energy: fuel converted into thermal and then mechanical energy in thermal engines for instance

„ Electrical energy: batteries, electric machines (motor / generator)

„ Kinetic energy: fly wheels

„ Elastic energy: under strain energy, compressed fluids, hydraulic or pneumatic systems)

„ Nuclear

„ Thermal: latent heat of melted salts

Definitions

„

Remarks:

„ Definition is extremely flexible

„ The concept is quite old in transportation systems

„ A moped (motor bike equipped with pedals) is a hybrid vehicle inasmuch it can use engine and muscular propulsion

„ Most of diesel locos are based on a diesel engine powering a generator and electric motors but they have no electric energy storage

„ Bus and trolley bus equipped with a small diesel engine

„ Large mine vehicle are using hydrostatic (hydraulic) transmission and propulsion system

„ Submarines are mostly diesel electric or nuclear electric hybrid propulsion systems

Definitions

„ For road vehicle :

„ The prime mover (principal energy source)is generally the internal combustion engine (piston engine but sometimes gas turbine)

„ The auxiliary energy source (secondary source)is:

„ Electric (the most often)

„ Hydraulic

„ Pneumatic

„ Kinetic

„ In the future, the prime mover could also be a fuel cell

Definitions

„ Hybrid electric vehicle: a vehicle in which the propulsion energy is available from two or more kinds or types of energy stores, sources and converters, and at least one of them can deliver electrical energy (Chan, 2002)

There are many kinds of HEV: petrol/diesel/CNG/H2 ICE &

battery, fuel cell & battery, battery & supercaps/flywheels…

„ Hybrid hydraulic vehicle: same as HEV but in this case one of the energy sources, storage and converters are hydraulic systems

Definitions

„ One calls a «full hybrid» vehicle, the hybrid vehicle that can be moved at least at low speed without using their thermal engine or chemical energy converter. Another definition is that both energy sources can be used alone to move the car for a significant distance.

„ On the contrary the «mild hybrid» vehicles or part hybrid vehicles always need the prime mover to propel the car. The auxiliary power source is unable to move the car alone or only during very short times and only for prime mover assist.

Definitions

„ In the mild hybrid, one can further distinguish the different categories as micro hybrids, stop&start...

„ The stop&starthybrid aims at allowing to stop engine when idling and at restarting the engine very rapidly on demand.

„ Integrated Starter Alternator with Damping(ISAD) are micro hybrids that allow the electric motors to help move the vehicle in addition to providing stop/start capability.

„ The hybrid with Integrated Motor Assist(IMA) system is similar to the ISAD but it has a larger electric motor and more electrical storage to move the vehicle. This means that the power of electric motor is larger and sufficiently high to move effectively the vehicle.

Definitions

„ The Stop & Startsystem is based on the principle of a starter alternator combined with a robotized gear box.

„ When used this system is

characterized by stopping the engine when stopped at traffic jams for instance. The engine is restarted without extra fuel consumption and emissions when brake is released

„ The Stop & Start system reduces fuel consumption and CO₂emissions by about 10 %,mainly in urban driving situations without penalty on performances for intercity driving

Citroën C3 stop&start

Definitions

„ One also distinguish series hybridand parallel hybrid.

„ In a parallel hybrid, both types of motorization are connected to the wheels and can propel the car independently or in

combination.

Typically the fuel tank supply the ICE while the batteries are the energy source for the electric motor.

„ In a series hybrid, the prime mover and its energy source are used to spin a generator that supplies electrical energy to either the batteries or directly the electric motor that is the only one to be geared with the wheels.

Definitions

Series Hybrid Parallel hybrid

Definitions

Parallel Hybrid E

B

P M

G

T

F Series Hybrid

F

E

B P M

T

Complex Hybrid Series-Parallel Hybrid

B: Battery

E: Internal Combustion Engine F: Fuel Tank

G: Generator M: Electric Motor P: Power Converter T: Transmission to wheels

F

M/G

M M

T

E

T P

P P

B

B G

E

F Electric link

Hydraulic link Mechanical link

Definitions

„ In addition, with the increasing design complexity, on can distinguish new lay-out of hybrid traction (Chan, 2002)

„ The series-parallel configuration: both energy sources can propel the vehicle. Nonetheless the system is designed to allow recovering series architecture by inserting a generator between the ICE engine and the batteries.

„ The complex hybrid configurationextends also the couplings between the two kinds of propulsion chains. The more complex lay-out allows using the electric machine to receive from (generator mode) or to deliver (starter mode) energy to ICE engine.

Definitions

„ The engineer can decide whether the batteries can be charged from the electric network or only from the prime mover (thermal engine) via the generator. This gives rise to a new distinction among hybrid vehicles.

„ The «charge sustaining» hybrids are such that batteries can be charged only from the prime mover work and energy recovery from braking.

„ The «charge depleting» hybrids are equipped with large batteries which have to be charged from the network for normal operation, because prime mover is generally too small to be able to sustain the charge level during mission.

„ The «plug-in» hybrids are able to sustain the charge level with the prime movers, but batteries is advantageously charged from the network for best environmental and fuel consumption performances

Definitions

„ The « charge sustaining » hybrids

„ They are characterized by their tail pipe emissions and the engine fuel consumption.

„ They do not require any modifications of user behaviour to plan battery charging, and skip this long operation.

„ The solution does not depend on particular infrastructure except existing ones, especially for battery charging.

„ The batteries can be kept rather small, which reduces the extra cost of hybrid system.

„ The fuel and emission savings from hybrid systems are often milder because of the necessity to charge the batteries from ICE engine and energy recovery.

Definitions

„ The « charge depleting » vehicles:

„ They are characterized by the fuel consumption + the electricity consumption (in kWh/100km). The later are related to the (average) emissions of production of kWh on the network.

„ The sizing of the batteries requires to have usually heavy batteries, which is a penalty for the weight of the car and for the cost the vehicle.

„ Charging the batteries on the networks takes some time and requires a certain discipline from the user.

„ The major advantage is the reduction of the CO₂emissions and the pollutants, because of the lower environmental impact of electricity in large power plants, green electricity (renewable energy sources, nuclear plants).

Key components of hybrid electric vehicles

Key components of hybrid vehicles

„

The components of hybrid vehicles are the following:

„ A prime mover, generally a internal combustion engine

„ An auxiliary power source: electric machines (generator / motor) or hydraulic motor/pump…

„ An storage system for the auxiliary energy : a battery pack, a fly wheel, or hydraulic accumulator…

„ Electronic Control Unit for power modulation of power source and converters: modulation of speed, torque, power…

„ Mechanical transmission and transfer box: mechanical system to connect the different motors to the wheels

„ Energy management unit (power electronic): optimization of energy flow…

Prime mover

„ The prime mover is the main energy source of the vehicle.

„ Most of the time the prime mover is an internal combustion engine, and often a piston engine.

„ Gasoline, diesel, CNG, H₂piston engine

„ High energy density of liquid fuel

„ High autonomy of ICE

„ Reliable technology, taking benefit of a century of continuous developments

„ Established infrastructure

„ Modern developments to improve ICE performances and reduce the consumption and the emissions: catalytic converters, variable injection, direct injection, PM filters, etc.)

Prime mover

„ Other combustion engines:

„ Possibility to operate the engine at given fixed load and constant rotation speed

„ New focus on gas turbinesand steam engines

Prime mover

„ In mid or long term, fuel cellscould be the prime mover:

„ Fast growing technology

„ Hydrogen or methanol fuel cell

„ Major issues: storage or on-board production of the fuel

„ Reforming process

„ Storage under high pressure, under liquefied, adsorption, etc.

„ Retail and distribution network to be established

„ Problems still to be addressed : reliability, life time…

Electric machines

„ For hybrid electric vehicles, the secondary / auxiliary energy source is electricity.

„ The electric converters are reversible machines, working as motor or generators.

„ The electric machines used for HEV are very similar to those used in pure electric vehicles.

„ Remind that most popular electric traction machines are the following:

„ DC seriesmotors or separately excited DC machines

„ AC induction machines

„ AC synchronous machines

„ Motor with electronically commanded commutation: Permanent Magnet (PM) electric machines, Switched Reluctance(SR) machine…

Electric machines for HEV

23 23

25 26

22 Total

3 4

3 5

4 Cost

3 4

4 5

5 Maturity

4 3

4 4

5 Reliability

4 3

4 4

5 Controllability

5 3,5

5 3,5

2,5 Efficiency

4 3,5

5 3,5

2,5 Specific power

Hybrid PM motor SR motor

Brushless motor Induction

machine DC motor

Evaluation of electric motor for HEV by Chan (2002)

Electric machines

„ The study conducted by Chan (2002) shows that induction machines and brushless motorsseems to be the most interesting technologies for hybrid electric vehicles.

„ The smaller cost of induction machinesmake them the most suited choice for starter alternatorused in integrated motor assist systems but also in Start & Stop systems.

„ The focus on hybrid vehicles rise a growing interest to electric machines and to an important research effort:

„ Ultra thin motors: e.g. electric IMA for Honda Insight

„ Permanent Magnet AC motors as in the new THSII of the Prius

Electric machines

DC brushless motor of the Honda IMA

The electric machine must be short and develop a large torque so the thin multi pole configuration

The motor is mounted directly on fly wheel at the end of the crankshaft

Electric machines

DC brushless motor

of the Honda IMA The motor is

mounted directly on fly wheel at the end of the crankshaft

The electric machine must be short and develop a large torque so the thin multi pole

Electric machines

Electric machines

Motor / generator AC synchronous Permanent Magnet of the Prius II

Electric machines

MG1: ~12-15 kW, MG2: 50 kW 1st-gen slightly less

295 ft-lb @ 0-1200 RPM

~ 150 lbf tangential per pole at air gap -- times eight!

and that's *before* final reduction Three-phase permanent-magnet synchronous AC

Eight poles, four electrical revs per rev

1st-gen motors are parallel- wound

2nd-gen motors are series-wound Higher voltage, but less current

Electric machines

Electric machines

Transmissions

„ For series hybrid vehicles, the wheels are only connected to the electric machine so that generally as in pure electric vehicle, there isno need for a gear box and a clutch.

„ When internal combustion engine is connected to the wheels as in parallel hybrid, then a clutch and a gear box are needed:

„ To allow the vehicle to start from rest

„ To allow the vehicle to stop without blocking the engine

„ To allow gear ratio change if a manual gear box is used

„ To adapt the rotation speed and the torque to the driving conditions to take benefit of the full power

„ The different types of transmission systems can be applied to hybrid vehicles

Transmissions

„ The transmissions with manual gear boxhave the best mechanical efficiency but they require some expertise of the user to reduce the fuel consumption.

„ The transmissions with automatic gear boxare providing the best driving comfort, gear changes without power interruption to the wheels, they remain more complex and more expensive.

Their mechanical efficiency is generally lower than manual gear box because of the hydraulic torque converter.

„ The continuous variable transmissions(CVT) are promising.

They allow the engine working in rotation speed and torque conditions that are (nearly) independent of the speed and torque of the wheels. They are more expensive and heavier.

They also lead to unusual working conditions for the driver.

Toyota Prius transmission

Transmission of Toyota Prius II

Toyota Prius transmission

Transmission of Toyota Prius II

Planetary gear

„

The planetary gear is the key component of the automatic transmission and torque coupler

Sun = planétaire Planet = satellite Annulus = Couronne

Planetary gear

„ Torque coupling: torque split

„ Kinematic relation between the sun, the planet carrier and the annulus (Willy formula)

„ With the gear ratio

ω

ω

ω

ω

ω

( )

PS C P

M = − M + M

(1 )

P

i

i

ω = + ω − ω

C P

i Z

= Z

Toyota Prius transmission

Honda IMA transmission

CVT de la Honda Civic

Van Doorme system

Honda IMA transmission

Energy storage and peak power source

„ The requirements on batteries and energy storage devices depend on the hybrid vehicle configuration.

„ For full hybrid, the energy storage capacity must be sufficiently large to level the energy demand and supply for the energy necessary to drive a given distance in pure electric mode (zero emission mode)

„ For mild hybrids, the energy storage can have a smaller capacity and sufficient to assist the prime mover when

accelerating or recovering braking energy. However because of frequent fluctuation, the batteries plays more as peak power sourceand specific power has a greater influence

„ For both lay-out, the braking energy is a major factor of batteries sizing.

Energy storage and peak power source

„

As for electric vehicle, the following parameters have to be considered for battery selection:

„ Specific energy [Wh/kg]

„ Volumetric energy [Wh/m³]

„ Specific power [W/kg]

„ Energy efficiency: the ratio between output energy over input energy [%]

„ Self discharge rate: the time necessary to loose 20% of the state-of-charge

„ The life time in number of charge – discharge cycles

Energy storage and peak power source

150 400-600 200-300

60-90 30-45

VRLA

<100 1000

400 300

200 USABC

>200 800-1200

250-450 140-200

90-130 Li-ions

230-350 1000

150 149

86 Na-NiCl₂

250-450 800

200 150

100 Na–S

NA NA

7-16 190-200

190-250 Al–Air

90-120 NA

105 269

230 Zn–Air

200-350 600-1200

150-300 130-170

60-70 Ni-MH

100-300 300

150-300 120-130

60-65 Ni-Zn

300 600-1200 150-350

80-110 40-60

Ni-Cd

Cost [$/kWh]

# Cycles [Cycles]

Spec. Pow.

[W /kg]

En. Dens.

[Wh / l]

Spec. En.

[Wh/kg]

Comparison of HEV batteries by Chan & Chau 2001

Energy storage and peak power source

Battery Pack of Toyota Prius II

Energy storage and peak power source

Battery Pack of Toyota Prius II

Control systems

„ Electronic control systems are of a primary importance in hybrid electric vehicles.

„ The hybrid management systemis in charge of the strategy to minimize fuel consumption and emissions while guaranteeing the best performances to the vehicle

„ One major issue is to maintain state-of-charge of the batteries and accumulators

„ Hybrid management system rules the energy flux between the different components and powertrains

Control systems

„ Besides the hybrid management system, one has the subordinated controllerthat control particular components

„ Electronic engine Control Unit (ECU)is in charge of engine management

„ Battery management Systemsupervises the battery operations controlling the state-of-charge, current density, the cell temperature, etc.

„ The Electric Motor control unitsare the chopper or the inverter that carries out electric machine behavior

Control systems

Hybrid management system (synergy drive) of Toyota Prius II

More about hybrids…

Hybrid powertrains

„ Hybrid electric vehicles combine two different kinds of energy storages: electricity and chemical

„ Allows to take benefit of electric cars advantages while keeping the advantages of internal combustion engines (range, easiness of refueling, etc.)

„ Architectures:

„ Two basic architectures: series or parallel

„ Complex architectures

„ Commercial success is beginning (e.g. Toyota Prius II, Honda Insight, etc.)

Hybrid powertrains

Clutch

Electric

Motor ^Batteries

Batteries

Electric Motor

Tank Tank

IC motor

Parallel Hybrid Vehicle

Series Hybrid Vehicle

IC motor Generator

Series Hybrid Electric Vehicle

„ Hybrid rate (%) : Τ_s= P_APU / P_e,with

„ P_APU : generator max power

„ P_e: electric motor max power

„ ZEV (km)possible over some range

„ Battery charging

„ Regenerative braking (motor Î generator)

„ Generator only : charge sustaining

„ Dual fuel with electric net : charge depleting / plug in hybrids

„ Can be extended tofuel cell as prime mover

Engine

Battery Generator

M/G

Wheels Node

Chemical

Electrical

Mechanical

Gruau MicroBus

Series Hybrid Electric Vehicle

„ The electric motor is the only one to be connected to the wheels. The ICE is used solely to spin a generator an supply electricity.

„ In urban situation, the batteries allows to drive in pure electric mode (zero emission)

„ On intercity driving, ICE is used intensively to provide the electrical energy to the batteries and the motor.

„ Efficiency is penalized by the product of all the components!

„ The hybridation rate of series : T_s= P_th/P_el

(generally in the range of 40 to 80%, so come to downsizing)

„ Possible extension to fuel cells as prime mover

Series Hybrid Electric Vehicle

„ Electric motor: Induction motor - max 48 kW

- 57 kg - liquid cooled

„ Batteries: Ni-Cd batteries - 200 V; 250 A

- 50 kW; 21.6 kW.h - liquid cooled; 422 kg

„ Alternator: Permanent magnets synchronous

- Max 26 kW

„ ICE: turboDiesel 900 cm³engine - direct injection

- catalysator - EGR

Series Hybrid Electric Vehicle

Performances:

„ 33%-cut in total CO2 emissions

„ Euro 3 emissions compliant

„ Over 25 km in electric mode

„ Unlimited range in hybrid mode

Fuel Cell Powered Cars

„ Special case of series hybrid architecture

„ Exhaust : H₂O Öfull ZEV

„ Silent operation

„ H₂or dual fuel (electricity/H₂)

„ H₂production, supply ?

„ H₂storage Öpoor range

Battery

M/G Fuel cells

Wheels Node

Tank

Chemical

Electrical

Mechanical

Toyota FCH4

Parallel Hybrid Electric Vehicle

„ Hybrid rate (%) : Τ_p= P_e/ (P_e+ P_t), with

„ P_t : engine max power

„ P_e: electric motor max power

„ Micro < mild < full

„ ZEV mode (km)is possible in urban areas

„ To deal with peak power demand, the simultaneous operation of both engines is possible (parallel mode)

„ Charge sustaining / depleting

Differential Tank

Engine

Wheels Chemical

Electrical

Mechanical

Gear change

M/G Battery

Node

VW Lupo hybrid Green Propulsion

Parallel Hybrid Electric Vehicle

„ The parallel hybrid vehicle is equipped with a double propulsion system thermal + electrical powertrain both connected to the wheels

„ The vehicle keeps its usual performances: autonomy, max & cruise speed…

„ The electric motors may have a sufficient power to propel the car alone in pure electric mode (full hybrid) or only in combination with the IC engine (motor assist)

„ For responding to peak power demand, both thermal and lectrical motors work together

„ There are various variants to the base configurations

„ Hybridizing rate of parallel hybrid: T_p= P_el/(P_el+ P_th)

Parallel Hybrid Electric Vehicle

„ Prototype of parallel hybrid vehicle built at ULg in 1999.

„ The front drivetrain is propelled by a DC motor of 20 kW and Ni-Cd batteries.

„ The rear drivetrain is driven by a small 1.4 3cylinder TDI from VW.

„ Coupling of electric and internal combustion

powertrain is realize through the road.

Parallel Hybrid Electric Vehicle

„ Na NiCl batteries - 278 V; 32 A.h - 16 kW; 108 kg - 300 °C

„ 14 kW induction motor

„ 3 operating modes : - Pure electric - Ideal hybrid - Diesel Charge

„ Grid-charging allowed Lupo hybrid: BTD malmedy, Green

Propulsion, Université de Liège

Parallel Hybrid Electric Vehicle

Lupo hybrid: BTD malmedy, Green Propulsion, Université de Liège

Parallel Hybrid Electric Vehicle

Performances:

„ Emissions record : 60 gr CO₂/km !

„ More than 40 km in electric mode

„ Unlimited range in hybrid mode

„ Improved performances

Complex Hybrid Electric Vehicle

„ Versus series hybrid

„ Smaller motor and generator

„ Higher transmission efficiency

„ Versus parallel hybrid

„ Controlled engine speed

„ Smooth transitions

„ Versus other combined

„ Planetary gear requested

„ No mechanical lock @ high load

Toyota Prius II

Complex Hybrid Electric Vehicle

Toyota Prius II

Combined Hybrid Electric Vehicle

„ Versus series hybrid

„ Smaller motor and generator

„ Higher transmission efficiency

„ Versus parallel hybrid

„ No gearbox requested

„ Smooth transitions

„ Versus other combined

„ Uncontrolled engine speed when clutch is closed

„ Mechanical lock at high load/speed

Tank

Wheels Engine

Chemical

Electrical

Mecanical Differential

Battery

Generator

M/G

Clutch

Combined Hybrid Electric Vehicle

The project:

„ City center parcel delivery

„ Transformation of a production vehicle

„ Ultra low CO₂emissions

„ The technology of tomorrow, available today

Combined Hybrid Electric Vehicle

Combined series/parallel hybrid

„ Li-ions batteries - 260 V; 200 A - 50 kW; 9,4 kW.h - liquid cooled; 100 kg

„ Induction motor 48 kW

„ Asynchronous generator 12 kW

Combined Hybrid Electric Vehicle

Performances:

„ 33%-cut in total CO2

emissions (vehicle from cradle to grave)

„ More than 40 km in electric mode

„ Unlimited range in hybrid mode

„ Improved performances

Parallel Mild Hybrid Electric Vehicle

„ Mild architecture

„ Small electric machines

„ Stop & start function

„ Small capacity regenerative braking

„ Additional power to prime mover

„ Replaces flywheel, starter and alternator

„ Static generator (ex. for domestic use)

„ NO pure electric mode

Transmission

Mechanical Node

Tank

Wheels

Engine Chemical

Electrical M/G

Battery

Mild Hybrid Electric Vehicle

„ Mild hybrids sound to be a promising way for many European Car Manufacturers

„ Generally the mild hybrid is built on a parallel configuration with a single shaft.

Batteries Machine Electrique Moteur

à C.I. Embrayage 2

Transmission Embray-

age 1

Mild Hybrid Electric Vehicle

„ In mild hybrid, a clutch (1) is inserted between the engine and the electric machine in order to disconnect the IC engine from the transmission line to use the car in pure electric mode (full hybrid mode) if it is possible

„ Several solutions to connect the electric machine to the engine shaft (crankshaft) :

„ Belt link

„ Direct meshing using a gear box

„ Mounting directly the electric machine onto the flywheel and the crankshaft

„ The later (direct mounting onto the flywheel) is often retained for mild hybrid

Mild Hybrid Electric Vehicle

„ Mild hybrid uses generally small electric machines with power range from 5 to 25 kW.

„ Main purpose of IMA: assisting the engine by providing an extra torque to the transmission when strong accelerations.

„ The motor assist reduces peak powerdemand to engine and then engine can downsized to provide a sufficient power for normal operating conditions

„ Integrating the electrical machine and the engine leads to compact solution.

„ The integrated motor assist also allows to use the usual gear box and clutch.

Mild Hybrid Electric Vehicle

„ By preserving usual transmission, mild hybrids can carry out high efficiency

„ They also achieve low production costs.

„ However they provide some of the advantages of full hybrids:

„ Regenerative braking(up to a certain limit because of small size of electric motor and limited capacity of batteries)

„ Stop and startsystem

„ Leveling peak powerby assisting the engine during acceleration, hill climbing, etc.

„ The major drawback of this solution is the fact that all components are connected to a single shaft and that electric machine and engine must always work at the same rotation speed, which reduces strongly the flexibility of the system

HEV strategies to save energy and emissions

HEV energy saving strategies

„ In order to reduce the fuel consumption and emissions, the hybrid electric vehicles use several mechanisms

„ Improve the engine performances

„ Reduce the losses

„ Optimize energy management

HEV energy saving strategies

„ Improving engine performances

„ Reducing the size of the Internal Combustion Engine (downsizing)

„ Operate the ICE in its most efficient working conditions

„ Stop the engine when idling

„ Substitute petrol by fuel with low CO2 emissions

„ Implement energy recovery during braking

„ Reduction of losses

„ Reduce the vehicle mass

„ Reduce the aerodynamic drag

„ Use low rolling resistance tires

„ Optimize the energy management

„ Automate some of driving decisions such as gear box management

Energy recovery during braking

„ Braking is one of the most importantenergy loss

„ The car kinetic energy is lost by heating the brakes

„ Use reversibility of electric/hydraulic machines and energy storage capabilitiesto recover at least part of this energy

„ Efficiency of energy recovery during braking depends on:

„ The more or less important capacity of the batteries, the efficiency of the converters

„ The topology of the energy recovery system: mostly dependent on the braking system

„ The number of driven wheels in the transmission: most of the time only one axle is driven which restricts braking for safety reasons

Energy recovery during braking

Principle of energy recovery during braking with an hydraulic system

Energy recovery during braking

„ Energy recovery capability depends on:

„ The size of the alternator/ generator of the electric machine (~10 kW)

„ The energy capacityof the battery, that is sensitive to charge current for instance

„ The max power of the battery(function of the maximum admissible current)

„ But also

„ Safety conditions for braking: stability of braking, 2 or 4 wheels braking?

„ Practically, energy braking is activated during downhill for mild slopes. The mechanical brakes is still used when deceleration is required.

Energy recovery during braking

To understand the braking problem, one investigates the following situation. Car (m=1200 kg ) braking from 60 km/h to 0 on a dry road (µ=0,8)

„ Kinematics

„ Dynamics

„ Stopping time

„ Dissipated energy:

g m F

ma = = η µ v = − a t + v

s a

v

t

=

/ = 2 , 12

² / 8 , 7 m s g

a = η µ =

kJ mv

mv

E

166 , 66

2 1 2

1

0

− =

=

∆

Energy recovery during braking

„ Dissipated power:

78, 480

average stop

P E kW

t

=∆ =

t kW P E

stop

960 , 2 156

max

∆ =

=

Lightweight structures

„ Using lightweight materials:

„ Aluminum

„ Magnesium alloys

„ Composite materials

„ New and innovative manufacturing and forming process

„ Tailored blanks

„ Hydro forming

„ Thixo forming…

„ Optimizing shapes, geometries, topologies and materials

Advanced aerodynamics

„ Reduction of drag forces has a great impact on fuel consumption on highway and peri urban driving

„ Depends on

„ Cx: drag coefficient (Cx usually around 0,30-0,35 for modern cars)

„ S: frontal surface

„ Cx depends on

„ The external shape: front design, rear design, floor

„ The wheels

„ The details

„ Internal aerodynamics

Drag source in road vehicles

„ 65% of the drag is coming from the body shape (front body, after body, underbody, skin friction)

„ Large field of improvement, especially for the after body in which most of the turbulence occurs, but restrictions due to aesthetic!

„ Sensitivity also

„ Wheels (21%)

„ Details (7%)

„ Internal drag (6%)

Gillespie Fig 4.11

Low rolling resistance tires

„ Usual tires are optimized for comfort, friction properties in various conditions and noise reduction.

„ New generation of tires are designed for reducing the rolling resistance (LRR low rolling resistance tires)

„ Inflation pressure is very important!

„ Rubber quality

„ Examples:

„ Michelin Energy

„ Bridgestone Potenza RE92

„ Continental Eco Tires

Some order of magnitudes…

Some order of magnitudes…

„

Series hybrid car (m=1373 kg)

„ P_IC= 41 kW

„ P_élec= 75 kW

„ V = 300 – 500 V

„

Parallel hybrid Vehicle (m=1330 kg)

„ P_IC= 50 - 60 kW

„ P_élec= 30 - 50 kW

„ V = 300 – 500 V

„

Parallel Hybrid bus (Bus : m=16 800 kg)

„ P_IC= 170 kW

„ P_élec= 190 kW

„ V = 600 V

Case study: Toyota Prius

TOYOTA PRIUS II

Toyota Prius II

Toyota Prius II

Toyota Prius II

Toyota Prius II

Toyota Prius II

Toyota Prius II

Case study: Honda Insight

Honda Insight

„ Mild hybrid architecture

„ Small electric machine (~10 kW)

„ Function « Stop & start»

„ Small capability of energy recovery during braking

„ Motor assist of main power source

„ Replace the flywheel by and integrated starter alternator

Honda Insight Transmission

Motor/Generator

Engine

Battery Inverter

Honda Insight

At the time of motor assist At the time of regeneration

Ultra- thin Brushless Motor (10kW)

Ultra- thin Brushless Motor (10kW)

New 1-liter

Lean-burn VTEC Engine

New 1-liter

Lean-burn VTEC Engine Nickel Metal Hydride (Ni-MH) Battery

Nickel Metal Hydride (Ni-MH) Battery

PCU

(Power Control Unit)

PCU

(Power Control Unit)

Honda Insight

„

Downsizing: motorization 1 L

„ Reduction of internal friction

„ Reduction of fuel consumption

„ Improving the exhaust gas treatment

CIVIC 1.5L

Friction reduction effect

- - 38 38 % %

15 20 25

Comparison of fuel efficiency Comparison of fuel efficiency

Conventional VTEC Lean-burn Engine Conventional

Engine

New VTEC Lean

New VTEC Lean--burn Engineburn Engine

Air/fuel ratio

Honda Insight

„

Downsizing: example of Honda Insight

„ Improving the exhaust gas treatment: new catalytic converter for NOx able to work in lean burn

3030%%

57 57

CO HC NOx

1998 EURO2 standards

Standards to be applied in EU 2000

Reduction rate of emissions

D4

D4 adaptation

47 47

50 50

Honda Insight

„ A brushless permanent magnet motor with a high efficiency and lightweight with a power of 10kW

„ Lightweight motor with a high torque

„ Large diameter, multipole

„ Ultra thin motor

„ Stator split with salient poles

„ Centralized distribution

Honda Insight

„ Ni-MH batteries

„ Battery pack of 144 V

„ 20 modules = 120 cellules

„ Characteristics are stable and high, and stable in time

State of battery charge

Full Empty

100

Ni-MH

Lithium ion Lead

0

Output ratio

Honda Insight

„ Motor assist for the Honda Insight

Engine speed [rpm] x 1000

Output [kW]

Torque [Nm]

60 80 100 120 140 160 180 200

1 2 3 4 5 6 7

0 20 40

56

50

91 113

Motor assistance Motor assistance

Honda Insight

Weight Weight

Conventional hybrid model

- - 57% 57%

100%

Engine

Generator Motor

Battery Inverter Inverter Transmission Motor/Generator

Engine

Battery Inverter

Conventional hybrid model Conventional hybrid model

Honda Insight

„ Lightweight vehicle

„ Using aluminum

„ New manufacturing technologies for production and recycling of aluminum

„ Extrusion, Thixo forming

„ High properties for crashworthiness and high stiffness

„ -47 % for mass saving

„ Vehicle aerodynamic

„ -30 % saving on S Cx ~ 5% on consumption

„ Low rolling resistance tires

„ -40% saving on rolling resistance ~ -6 % on fuel consumption

„ Selection of accessories with low energy consumption

„ Electric steering assistance…

Honda Insight

Door mirrors Front grill

Rear wheel skirt

Aerodynamics

Aerodynamics