Combined Hybrid Talks

8/12/2019 Combined Hybrid Talks

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MAE 442 Automotive Engineering:

Hybrids

Ewan Pritchard, PE

October 5th, 2009


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Hybrid Definition

A hybrid is a combination of two things

In this case we mean a vehicle powered by two different

power plants> Electric motor

> Internal combustion engine


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Is a Hybrid Vehicle a New Idea?

Hybrids existed in the late 1800s

> Cars could be fuelled by either electric or ethanol

> No regenerative energy

> The invention of the IGBT

between 1960 and 1990

made way for the modern

hybrid electric


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The Modern Hybrid

Does not idle when stopped

Uses a battery pack to store energy

Uses an electric motor to accelerate

Recharges batteries when braking or coasting Allows for a smaller gasoline engine

Increased fuel economy, lower emissions, and lower enginewear


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Why Hybrid: Fuel Economy

As fuel prices riseso does the drive to improve fueleconomy

Reduced Dependence on Foreign Fuel

Fossil fuels are not sustainableit took millions of years tomake them, and about 300 years to consume them.


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Why Hybrid: Emissions

Environmental issues

>NOxnitrogen oxides Works with sunlight to form ozone (lung damage)

Forms nitric acid in the air (acid rain) Enters the upper atmosphere and causes a

greenhouse effect. (Global warming & climate change)>

CO2carbon dioxide Enters the upper atmosphere and causes a

greenhouse effect. (Global warming & climate change)


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Why Hybrid: Emissions

Environmental issues

> Particulate Matter

PM1010 microns in size, particulates enter the upperrespiratory system and cause congestion, smaller

particles cause lung damage.

PM2.52.5 microns in size, passes through the alveoli

in the lungs and enters the bloodstream to cause

pulmonary distress


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Why Hybrid: PerformanceA tale of two drivelines both 102 kW (137 HP)

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

100

200

300

400

500

600

Speed (rpm)

Torque(Nm)

Fuel Converter Operation

1991 Dodge Caravan 3.0L (102kW) SI Engine - transient data

0.10.14

0.1

0.18

0.1

0.20.2

0.22

0.22

0.240.26

0.28

0.28

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

100

200

300

400

500

600

Speed (rpm)

MotorTorque(Nm)

Motor/Inverter Eff iciency and Continuous Torque Capability -

Unique Mobility 100kW (peak) PM motor/inverter

0.82

0.84

0.86

0.880.9

0.92

0.94


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Conventional versus Hybrid Design

Conventional Design Characteristics:

> Total Power (Top Speed)

> mile time

> 0-60

Modern Design Characteristics:

>

Pep (acceleration at particular speeds)> Fuel economy on a specific drive cycle

> Ability to meet trace

> Minimized emissions on that cycle


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Drive Cycle

Hybrids and Plug-In hybrids add new dimensions to a

historically single dimension problem


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Where the Power Goes


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A Hybrid Electric System Can Help Minimize

These Losses

Engine losses

Standby/idle losses

Driveline losses

Braking losses

Electric accessories


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Engine Losses and Idling

~80% of Total Losses An engine will typically run at manydifferent efficienciesThis engine could run at 44% efficient

It will likely average at about 18%

By eliminating idling and low torque, the

average could be easily running over 30%


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Driveline Losses

~5.6% of Total LossesHybrid drivelines can be applied inseveral ways, one possibility (series

hybrid) can eliminate the driveline

completely, eliminating this loss

All Electric

Conventional


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Driveline Losses

~5.6% of Total LossesIn a series driveline, only anelectric motor is connected to the

drive wheels

In a parallel system, both the

gasoline and the electric motor are

connected to the drive wheels

Parallel

Series


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Braking Losses and Inertia

~5.8% of Total Losses A hybrid vehicle can significantly reducebraking losses by recapturing the energyelectrically in a generator

This also significantly reduces brake wear

The vehicle is also slowed while traveling

down hills by regeneration


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Auxiliary and Accessory Loads

~2.2% of Total Losses

Includes fans, pumps, compressors and alternator

When these are belt driven, they are subject to the current engine speed, which canrange from 800 RPM up to 6000 RPM

At varying speeds these accessories are typically VERY inefficient

Each of these is moving towards electrically driven components due to the inherentlyhigher efficiency of electric motors


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Hybrid and Electric Vehicle Components

All hybrid and electric vehicles have 4 basic components.

1. Electric Motor

2. Controller/Inverter/Drive

3. Batteries

4. Logic

Improvements in high power electronics, materials and

computing capacity have led to significant changes in the

past 20 years.


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INDUCTIONMOTOR COMPONENTS

Rotating components

> [1] Shaft

> [2] Rotor

> [3] Rotor fins> [4] Fan

[1] [2] [3] [4]


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Housing components

> [5] End bells / bearing

housings

>

[6] Stator housing> [7] Cooling fins

> [8] Junction box

> [9] Fan shroud

[5] [6] [7] [8] [9]


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Fixed components

> [10] Seals

> [11] Stator windings

> [12] Core iron / laminationstack

> [13] Bearings

[10] [11] [12] [13]


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Components:Electric Motor - DC

Graphic courtesy of SMMA | www.smma.org


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Components:Electric Motor - AC



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Components:Electric Motor - Controlled



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Controller

Converts Battery DC to a chopped DC power

Can chop in amplitude (DC) or frequency (AC)

Power is based on low voltage input signal

> 4-20 mA or 0-5V

In other fields this is called a drive or inverter

> Variable Frequency (AC)

> Pulse Width Modulation (AC)

> Buck Conversion (Reduce - DC)

> Boost Conversion (Increase - DC)


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Batteries

Batteries rule the performance of the vehicle> They dictate how much power you get (kW)

> They dictate how much energy you get (kWh)

A single cell dictates the battery voltage each cell mates twodissimilar materials

> Lead Acid (2.1 V)

>

Nickel Cadmium (1.2 V)> Nickel-Metal Hydride (1.2 V)

> Lithium-Ion (3.7 V)

Anode (+) Cathode Electrolyte

Pb PbO2 KOH

NiOOH Ni H2SO4

NiOOH AB5 * KOH

LiC6 Li2FePO4F LiPF6

* AB5is a combination of (A) rare earth mixture and (B) Zirconium or Nickel


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Batteries: Packaging

Cylindrical

Prismatic

Button

Pouch

Source: www.batteryuniversity.com
http://www.batteryuniversity.com/http://www.batteryuniversity.com/


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Cylindrical

Prismatic

Button

Pouch



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Cylindrical

Prismatic

Button

Pouch



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Batteries:PackagingCylindrical

Prismatic

Button

Pouch



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Batteries (section 12.1.2)

State of Charge (SOC)

> Measured as a percentage of total

battery energy (0-100%)

>

Typically should not go below 20%

Depth of Discharge (DoD)

> Inverse of SOC

Power (kW)

Energy (kWh)

The 18650 cell is proving to be

common for hybrids. Similar to

a AA cell, the dimensions are

18mm in diameter and 650mm

in length.


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Batteries: Basic Characteristics

A-h> Typically used for power batteries

> Cells often described in mA-h

C Rate

> A normalized rate of power use to qualify testing

>100% discharge divided by the time in hours

> C2 means the discharge rate was 100% in hour

> C/2 means the rate was less aggressiveover 2 hours

Cycle Life

> Always measured based on DoD

>

Ex. 1000 cycles at 80% DoD Weight/Volume

> Measures in terms of

W/kg and W-h/kg

W/l and W-h/l


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Cycle Life

Source: Duvall, EPRI Study of cycle life versus depth of discharge


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Energy Densities



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Ragone Plot

Source: Lawrence Berkeley National Labs


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MAE 442 Automotive Engineering:

Hybrids II

Ewan Pritchard, PE

October 7th

, 2009


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Agenda

Batteries

Engine Coupling

Prius Transmission School Bus Program

FinishViewing ATEC Plug-In Prius Outside


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Battery Prices


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Lithium Ion

Battery PbA Ni-MH Li-Ion

Energy/weight (W-h/kg) 40 80 160

Energy/size (W-h/l) 75 300 270

Power/weight (W/kg) 180 1000 1800

C/D efficiency (%) 80% 66% 99.9%

Price ($/kW-h) 200 400 600

Self-discharge rate (%/month) 10% 30% 3%

Cycle durability (80% cycles) ~900 ~6,500 ~10,000

Nominal Cell Voltage (V) 2.0 1.2 3.6/ 3.7


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Engine Map: Efficiency


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Engine Map: Efficiency


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Engine Map: NOxEmissions


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Engine Map: PM


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Powertrain Integration

Series Hybrid

> Driveline (Volt)

> Hub motor (Volvo)

Parallel Hybrid

> Pre-transmission (Honda, Eaton)

> Post-transmission (Enova School Buses)

> Transmission Integrated (Ford, Toyota, GM, Allison)


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Electric (Easiest)


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Series


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Through The Road (Parallel)


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Parallel


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Transmission Integrated

Planetary Gearset (Prius, Ford, GM Two-Mode)

Sun MG1

Planet Carrier - Internal

Combustion Engine

Outer Ring MG2


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Transmission IntegratedImage from

http://privatenrg.com/#Nomograph
http://privatenrg.com/http://privatenrg.com/


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Planetary Gearset (Toyota, Ford, GM)

Flash animation from Eric Hart at:

http://eahart.com/flash/PSDAnim.swf

Sun:30 Teeth MG1PM AC Sync

6,500 RPM

18 kW. This has been increased

to 10,000 RPM

Planets:23 Teeth Combustion

engine+5000 RPM

57 kW

Outer Ring:78 Teeth

MG2 PM AC Sync.
http://eahart.com/flash/PSDAnim.swfhttp://eahart.com/flash/PSDAnim.swf


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Prius Transmission

Due to the gear ratios, we can say that:

> If Planet Carrier (ICE) is held:

MG1(sun)= -78/30*MG2 (Outer Race)= -2.6*MG2

> If Outer Race is held:

MG1= 3.6 * ICE

MG1 = 3.6 * ICE - 2.6 * MG2


53/75

Prius Transmission

Due to the gear ratios, we can say that:

> If Planet Carrier (ICE) is held:

MG1(sun)= -78/30*MG2 (Outer Race)= -2.6*MG2

> If Outer Race is held:

MG1= (1 + 2.6 )*ICE

MG1 = 3.6 * ICE - 2.6 * MG2

Excerpt from:

http://prius.ecrostech.com/original/Understanding/PowerSplitDevice.htm
http://prius.ecrostech.com/original/Understanding/PowerSplitDevice.htmhttp://prius.ecrostech.com/original/Understanding/PowerSplitDevice.htm


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Hybrid School Bus Project


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IC Corporation (International)selected based on specific criteria

Plug-in

PHEV-22.5kWh Li-Ion

$220k (or $139k premium)

First bus delivered March 2007

11 buses delivered to date

Early success for HD-PHEV


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PHEV components


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Estimated benefits

Plugging-in is optional

90-100% fuel economy improvement for first 45 miles,

40% increase for remainder

90% reduction in particulate matter

60% reduction in NOx

Increased engine, transmission and brake life Electricity cost of 60 / gallon equivalent

Option for renewable energy at $1 / gallon


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Nationwide plug-in deploymentDelivered

Arkansas (1)

California (1)

Florida (2)

North Carolina (2)

Pennsylvania (1)

South Carolina (2)

Texas (1)

Washington (1)

Funded / Ordered

Iowa (2)

New York (2)

Pending

Texas (1)

Virginia (1)

Washington (1)

Washington DC (1)


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Next steps

Four more buses have been ordered

Two year monitoring period to record performance

> Emission

> Fuel economy> Maintenance

> General operation

> Driving performance

How closely we monitor them is dependent upon funding

Facilitation of 300 bus purchase

> Anticipated $80,000 premium


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Preliminary monitoring results

0

1

2

3

4

5

6

7

8

9

8/5/20

07

8/15/200

7

8/25

/200

7

9/4/20

07

9/14/200

7

9/24

/200

7

10/4/200

7

10/1

4/20

07

10/2

4/20

07

Date (DD/MM/YYYY)

604 Control

607 Hybrid

604 Control Average: 5.4 MPG

607 Plug-In Hybrid Average: 7.4 MPG

Plug-In Hybrid Benefit:

2 MPG increase

30% increase

* Control Route Shifted by 2 w eeks to align route and driver

FuelEconomy(MPG

)

Florida Buses (Track 1)


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0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

7/17/2007 7/27/2007 8/6/2007 8/16/2007 8/26/2007 9/5/2007 9/15/2007 9/25/2007 10/5/2007

Date

MPG

Not Plugged In

Plugged In

Plug-in benefitsWake County, N.C., Hybrid School Bus


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Enova data logging

-100

-80

-60

-40

-20

0

20

40

60

80

100

0 10 20 30 40 50 60

Speed (mph)

Power(kW) First Gear

Second Gear

Third Gear

Fourth Gear

Fifth Gear

Power versus Speed


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Incremental cost per unit

$0

$40,000

$80,000

$120,000

$160,000

$200,000

0 200 400 600 800 1000 1200 1400 1600 1800 2000

IncrementalCost($

)

Number of Units Sold

School districts

portion

In need of funding


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School Bus Modeling

The characteristics are used to virtually build a

bus in ADVISOR NRELsADvanced VehIcle

SimulatOR

ADVISOR uses Matlab and Simulink to model

a vehicle based on a specific route and vehicleinformation.

The results are Performance, Fuel Economy,

and Emissions.


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School Bus Modeling

By defining each component, any vehicle can

be adequately modeled.

There is a LOT to define and wide assumptions

can lead to a lot of error.

We ran many trials to understand thesensitivity of the variables


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School Bus Modeling

By defining each component, any vehicle can

be adequately modeled

There is a LOT to define and wide assumptions

can lead to a lot of error

We ran many trials to understand thesensitivity of the variables


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School Bus Modeling

Each model can be run through a predefined

route

We used the West Virginia Suburban Cycle six

times

The vehicle can also be run throughacceleration and grade trials.

Each model takes about 3 minutes to run.


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School Bus Modeling

The results show acceleration rates, fuel usage

and emissions

Many parameters can be analyzed such as

overall ratio

Additional information can be gathered aboutenergy use

This model appears to be off, we know the fuel

economy should average at about 8.2 miles per

gallon


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School Bus Modeling

The loss plot shows usages of each

component

From this loss plot we can imaging how

much energy could have been saved.


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School Bus Modeling

The Parallel Model

80 kW engine (~107 hp)

Lead Acid Batteries

100 kW Electric Motor


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School Bus Modeling

11.4 mpg

But.. It is depleting the battery pack

9.107 grams per mile NOx

Much Faster acceleration times, this

model is likely oversized


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School Bus Modeling

Series Model

112 kW engine (150 hp)

116 kW Electric Motor (155 hp)

131 kW generator (175 hp)

1 speed transmission


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School Bus Modeling

9 mpg

Still depleting the battery pack

1.583 grams per mile NOx

Slightly better acceleration

Engine is ALWAYS on.


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Where can you fit in?

Currently seeking graduate students to perform research

under ATEC

Join Eco-Car Challenge

Go work for a major auto manufacturer and join ATEC

Tell others about the work going on at NCSU


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Please Call with QuestionsEwan Pritchard, PE

Program ManagerAdvanced Transportation Energy Center (ATEC)

North Carolina State University

MRC - Suite 339Campus Box 7237

Raleigh, NC 27695-7237

919.515.2194 (office)

919.819.0098 (cell)[email protected]

www.atec.ncsu.edu

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