Eco-driving strategies in battery electric vehicle use – what do drivers get to know over time?

Eco-driving strategies in battery electric vehicle use – what do drivers get to know over time?

Isabel Neumann, Thomas Franke, Franziska Bühler, Peter Cocron, and Josef F.Krems06.06.2014

Isabel NeumannEuropean conference on Human Centred Design for

Intelligent Transport Systems

EV user research at TU Chemnitz

EV research topics dealing with…

… low noise emission… regenerative braking function… acceptance of EVs … charging concepts (W2V)… multimodal electric mobility… adaptive drive train systems for EVs… user battery interaction… safety… user experience of limited range… eco-driving

2


Intelligent Transport Systems3

What is eco-driving?

- Sivak & Schoettle (2012):

“eco-driving includes those strategic decisions (e.g., vehicle selection and maintenance), tactical decisions (e.g., route selection), and operational decisions (e.g., driver behavior) that improve vehicle fuel economy” (p.96)

- more narrow sense:

All strategies a dirver could apply to reduce energy consumption while driving and when planning a trip

Source: usgreenchamber.com

Source: driverimprovement.co.nz



…and why is eco-driving different in BEV use?

4

(gentle) Handling of the battery

Limited range

Regenerative braking system (active energy retrieval)

Long charging durations;

Limited charging opportunities

Electric drive

Concept of electricity,consumption in kWh



Previous resarch & research objectives

- Eco-driving with conventional vehicles has been studied in depth (e.g., Wahlberg, 2007)

- Besides some research on predominantly technical issues and small samples, not much is known about eco-driving when driving a BEV (e.g., Bingham, Walsh & Carroll, 2011)

Current research objectives:(1) Which strategies do drivers know to drive energy efficiently with

BEVs before and after 3 months of experiencing a BEV under daily driving conditions?

(2) Do these strategies differ from strategies known with a conventional car?

(3) Is there a need for additional information regarding energy consumption and retrieval in the BEV?



Method: MINI E international field trial

6

- MINI E Berlin as lead-study for large-scale international field trial

USA450 vehicles on the east

and west coast (CA, NY, NJ)

Germany65 vehicles in

Berlin und Munich

Great Britain40 vehicles



Method: MINI E field trial

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Second period of 6 months with 40 users in private setting:

Screening- Online- N =728

(applicants)- Screening via

selection criteria- N = 40 users

1st Travel diary- 1 week, all trips

Before receiving the car (3h)

- Questionnaire (129 Items)- Face-to-face interview- Trip decision game- Conjoint anyalysis- Interview after first test drive

with EV

After 3 months (2h)- Questionnaire (306

Items)- Face-to-face interview- Trip decision game- Conjoint analysis

2nd Travel diary- 1 week, all trips

3rd Travel diary- 1 week, all trips

1st Charging diary- 1 week

2nd Charging diary- 1 week

Returning the car (2h)- Questionnaire (355

Items)- Face-to-face interview- Trip decision game- Conjoint analysis

May/June2010

February/April 2010

. August 2010

2 test drives with EV



Sample

N = 40; 35 men, 5 women

Age: about 50 years (SD = 10.19)

Previous experience with electric drive: - 60% no previous experience at

all- 40 % previous experience with

HEV or BEV (short test drive)

Annual milage: 80% between 10.000 to 30.000 km/year

< 5.000 5.000 - 1.0000

10.000 - 15.000

15.000 - 20.000

20.000 - 30.000

30.000 - 40.000

40.000 - 50.000

0

5

10

15

20

25

30

35

Annual milage (km/year)

Prop

ortio

n (%

)



Test vehicle

MINI E battery electric vehicle

- Range: about 170 km under normal driving conditions

- Regenerative braking implemented at the gas pedal

- Displays: SOC, remaining range, instantanous & average consumption



Results: Eco-driving strategies for convenztional vehicles

N = 40

Avoid braking/let the car roll

Drive evenly (speed & acceleration)

Optimal tires/tire pressure

Minimize load

Avoid idling

Avoid high speeds

Avoid auxiliary functions (e.g., AC)

Anticipatory driving style

Accelerate moderately

Use highest gear possible

0 10 20 30 40 50 60 70 80 90 100Proportion of drivers reporting the strategy (%)

Interview (T0): ‘Which strategies do you know to drive energy efficiently with your conventional car?’



Results: Eco-driving strategies for BEVs vs. conventional vehicles


Chooseenergy efficient route

Minimize load

Let the car roll (sailing)

Instantaneous power meter


Avoid high speeds


Use regenerative braking /avoid braking



0 10 20 30 40 50 60 70 80 90 100

ICE

after short test drive

after 3 months EV usage

Proportion of drivers reporting the strategy (%)N = 40

Sum of reported strategies:MdnT0 = 3MdnT1 = 4*MdnICE= 4*

**** **

Interviews (T0 & T1): ‘Which strategies do you know to drive energy efficiently with the BEV?’



Results: user requirements regarding additional enery consumption feedback

1

2

3

4

5

6

Additional information / assistance

Ass

essm

ent;

95%

CI

T1: ‘I would like to have some additional information regarding the energy consumption displayed in the BEV.’

1

2

3

4

5

6

Agr

eem

ent;

95%

CI

T1: ‘Please rate the benefit of the following possible additional systems.’



Conclusions Knowldege- Users report significantly more eco-driving strategies after 3 months of BEV driving than after a short test drive

- Users report different strategies for conventional vehicles and BEVs

- The most often mentioned eco-driving strategies with BEVs are:- Moderate acceleration*- Avoidance of auxiliary features*- Usage of regenerative braking

*also found to be influencing factors in driving tests (Bingham et al., 2011)- Users seem to learn which factors influence the energy consumption of a

BEV by experience

Requirements regarding additional feedback- Users express need for additional information & regard the given systems as helpful (might be more relevant for other user groups)



Thanks a lot for your attention! Contact: [email protected]

This study was funded by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety.

Source: Modiapple.com





Wissen: Eco-Driving Strategien mit dem EV

N = 40

**


Energy efficient route to destination

Minimize load

Let the car roll (sailing)

Instantaneous power meter


Avoid high speeds


Use regenerative braking /avoid braking



0 10 20 30 40 50 60 70 80 90 100

after short test driveafter 3 months EV usage

Proportion of drivers reporting the strategy (%)

Interviews (T0 & T1): Welche Strategien kennen Sie, um energieeffizient mit dem MINI E zu fahren?

Summe berichteter Strategien:MdnT0 = 3MdnT1 = 4

Z = -2.252; p = .024; r = -.25



Methode: Testfahrt nach 3 Monaten EV Erfahrung

- 2 Fahrten im Stadtverkehr; ca. 4 km Länge

- 2 Fahrten mit 2 Instruktionen:(1) Normaler Fahrstil

(Kalibrierungsfahrt)(2) Eco-driving

- Datenlogger (BMW): Geschwindigkeit (SD, Mean), Beschleunigung (SD, Mean), Motorleistung (inkl. Rekuperation), Rekuperationsleistung, Strecke, Zeit, Außen- & Batterietemperatur…

- Protokoll zur Testfahrt, Fragebogen & Interview



MINI E Berlin – powered by Vattenfall

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24.09.2009Isabel Neumann

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Eco-driving strategies in battery electric vehicle use – what do drivers get to know over time?