Convenient charging system
for electric cars
Concept development of a charging system for BEVs and PHEVs.

Master’s thesis in Master Programme Product Development

Alexander Berggren

Department of Product & Production Development
CHALMERS UNIVERSITY OF TECHNOLOGY
Gothenburg, Sweden 2016





Master’s thesis 2016

Convenient charging system for electric cars

Concept development of a charging system for BEVs and PHEVs.

Alexander Berggren

Department of Product & Production Development
Chalmers University of Technology

Gothenburg, Sweden 2016



Convenient charging system for electric cars
Concept development of a charging system for BEVs and PHEVs.
Alexander Berggren

© Alexander Berggren, 2016.

Supervisor: Johan Ekbäck, CEVT
johan.ekback@cevt.se, +46731-441700
Examiner: Andreas Dagman, Product & Production Development, Chalmers
andreas.dagman@chalmers.se, +4631-7721472

Master’s Thesis 2016
Department of Product & Production Development
Chalmers University of Technology
SE-412 96 Gothenburg
Telephone +46 31 772 1000

Cover: WPT - simple and clean

Typeset in LATEX
Gothenburg, Sweden 2016

iv



Convenient charging system for electric cars
Concept development of a charging system for BEVs and PHEVs.
ALEXANDER BERGGREN
Department of Product & Production Development
Chalmers University of Technology

Abstract
”We are the first generation to feel the effect of climate change and the last generation
who can do something about it.” - President Obama, 23rd of September 2014.
In order to tackle the problem of climate change we need to change the way we are
living and the technologies we are using. One area that needs to change is the car
usage and the technology it is based on. We need to change to non-fossil fuelled
car technologies. A suggested solution is the plug-in electric cars - such as Battery
electric vehicles and Plug-in hybrid electric vehicles.
The plug-in electric car is an Electric vehicle that offers many advantages compared
to traditional combustion cars. Nevertheless, when electric cars is offered at the
same buying price and almost half total cost of ownership, compared to traditional
combustion cars, the customers still hesitates. Despite the many advantages the
concern regarding insufficient driving range, in combination with the charging avail-
ability and charging time, scares the customers. As the driving range, charging
availability, and charging time of plug-in electric cars are highly dependent of the
charging system for it, an improved and more convenient focused charging system
could remove these concerns and obstacles for plug-in electric cars.
A convenient charging system for plug-in electric cars was found to require an En-
ergy storage system in order to being able to deliver sufficient charging power as well
as better utilise the electrical infrastructure. Furthermore, a convenient charging
system for plug-in electric cars have three different chargers - standard (wireless)
charger, availability charger, and fast charger. The different chargers targets dif-
ferent kinds of charging, and with the different power levels of <22kW, <3.6kW,
respective >90kW. Where the last (and highest) power level is only necessary for
Battery electric vehicles and could be excluded from Plug-in hybrid electric vehicles.
The standard charger have two different sub-systems, one home charger and one
destination charger - both (but in different ways) sharing the principle of botherless
bringing the charger to the car. Moreover, the whole charging system should easily
be controlled and monitored via a mobile app, and enable a transition towards
the close connected technology of autonomous drive and -vehicles. Furthermore,
together with which the Electric vehicle may become a major disruptive technology.

Keywords: Plug-in electric vehicle, Electric vehicle, Battery electric vehicle, Plug-in
hybrid electric vehicle, Wireless power transfer, Energy storage system, mobile app,
Autonomous drive, Disruptive technology.

v





Contents

List of Figures xi

List of Tables xiii

Glossary xv

Acronyms xvii

1 Introduction 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Problem Formulation & purpose . . . . . . . . . . . . . . . . . . . . . 1
1.3 Project deliveries & Research questions . . . . . . . . . . . . . . . . . 2
1.4 Delimitation’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.5 Report Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Theory 5
2.1 Product Development Methodology . . . . . . . . . . . . . . . . . . . 5

2.1.1 The planning phase . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2 The concept development phase . . . . . . . . . . . . . . . . . 6
2.1.3 System-Level Design . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.4 Detailed Design . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.5 Testing & Refinement . . . . . . . . . . . . . . . . . . . . . . 7
2.1.6 Production Ramp-Up . . . . . . . . . . . . . . . . . . . . . . . 7

2.2 Product Development Tools . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1 Gantt-chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.2 Precedence diagram . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.3 Brainstorming . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.4 Affinity Diagram . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.5 Morphological matrix . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.6 Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.7 Semi-structured interview . . . . . . . . . . . . . . . . . . . . 11

2.3 Convenience in products . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.4 Sustainable aspects of Electrical Vehicles . . . . . . . . . . . . . . . . 13
2.5 Wireless Power Transfer . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.5.1 Resonant Inductive Power Transfer . . . . . . . . . . . . . . . 14
2.5.2 Standard for wireless power transfer . . . . . . . . . . . . . . . 16
2.5.3 Shielding for electromagnetic inductive applications . . . . . . 17

vii



Contents

2.6 Wireless Power Transfer & Vehicle alignment . . . . . . . . . . . . . . 17
2.7 WPT & Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.8 Autonomous Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.9 Electric Power at Home . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.10 Swedish EV capability . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.11 China EV capability system . . . . . . . . . . . . . . . . . . . . . . . 23
2.12 Energy Storage System . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.12.1 Li-ion batteries . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.12.2 Flywheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.12.3 Flow batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.12.4 Superconducting Magnetic Energy Storage (SMES) . . . . . . 28
2.12.5 Compressed air energy storage (CAES) . . . . . . . . . . . . . 29

2.13 Reference EV-car specifications . . . . . . . . . . . . . . . . . . . . . 30
2.14 Traditional charging connectors . . . . . . . . . . . . . . . . . . . . . 30
2.15 EU regulations of drivers’ hours . . . . . . . . . . . . . . . . . . . . . 31

3 Method 33
3.1 Planning & Opportunities . . . . . . . . . . . . . . . . . . . . . . . . 33

3.1.1 Research market & technology . . . . . . . . . . . . . . . . . . 34
3.1.2 Technological trajectory & Opportunities . . . . . . . . . . . . 34
3.1.3 Initial plans & System boundary . . . . . . . . . . . . . . . . 34
3.1.4 Analyse findings & Define mission statement . . . . . . . . . . 34
3.1.5 Set final plans . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.2 Concept Development . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2.1 Market, stakeholders, & Competitive products . . . . . . . . . 35
3.2.2 Identify needs . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.2.3 Set target product criteria . . . . . . . . . . . . . . . . . . . . 36
3.2.4 Establish a initial system boundary . . . . . . . . . . . . . . . 36
3.2.5 Concept generation . . . . . . . . . . . . . . . . . . . . . . . . 36
3.2.6 Concept screening . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2.7 Concept scoring, -testing, & first concept selection . . . . . . . 37

3.2.7.1 Defining a developed system boundary . . . . . . . . 37
3.2.7.2 Morphological solutions . . . . . . . . . . . . . . . . 37
3.2.7.3 First concept-scoring matrix . . . . . . . . . . . . . . 37

3.2.8 Review of first concept selection . . . . . . . . . . . . . . . . . 38
3.3 System-Level Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.3.1 Final product specifications . . . . . . . . . . . . . . . . . . . 39
3.3.2 Product Architecture . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.3 Industrial Design . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.4 Prototype Development . . . . . . . . . . . . . . . . . . . . . 40

3.4 Detailed design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4 Results 43
4.1 Method & Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2 Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.2.1 WPT Technology research . . . . . . . . . . . . . . . . . . . . 44
4.2.2 Driver Behaviour & Convenience . . . . . . . . . . . . . . . . 44

viii



Contents

4.2.2.1 Convenience Strategy . . . . . . . . . . . . . . . . . 44
4.2.3 The SAE TIR J2954 standardization . . . . . . . . . . . . . . 45
4.2.4 Alignment & Positioning . . . . . . . . . . . . . . . . . . . . . 45
4.2.5 Autonomous Drive . . . . . . . . . . . . . . . . . . . . . . . . 46

4.2.5.1 Driving range & battery capacity . . . . . . . . . . . 46
4.2.6 Health & Safety . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.2.7 Power Availability & EV capability . . . . . . . . . . . . . . . 48

4.3 Project Mission Statement . . . . . . . . . . . . . . . . . . . . . . . . 49
4.4 Survey & interviews to needs & metrics . . . . . . . . . . . . . . . . . 51
4.5 Concept selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

4.5.1 Target product criteria . . . . . . . . . . . . . . . . . . . . . . 54
4.5.2 Initial system boundary . . . . . . . . . . . . . . . . . . . . . 54
4.5.3 First concept generation & Affinity Diagram . . . . . . . . . . 55
4.5.4 First selection matrix . . . . . . . . . . . . . . . . . . . . . . . 55
4.5.5 Developed System Boundary . . . . . . . . . . . . . . . . . . . 56
4.5.6 Morphological Selection Matrix . . . . . . . . . . . . . . . . . 57
4.5.7 First concept scoring matrix . . . . . . . . . . . . . . . . . . . 59
4.5.8 Initialisation of the industrial design . . . . . . . . . . . . . . 59
4.5.9 Concept review . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4.5.9.1 Reviewed and final scored concepts . . . . . . . . . . 61
4.5.10 Final system boundary . . . . . . . . . . . . . . . . . . . . . . 62

4.6 Final product specifications . . . . . . . . . . . . . . . . . . . . . . . 62
4.7 Product architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.8 Industrial Design & Prototype development . . . . . . . . . . . . . . 65
4.9 Final delivery & solution description . . . . . . . . . . . . . . . . . . 65

4.9.1 The availability charger solution . . . . . . . . . . . . . . . . . 65
4.9.2 The fast charger solution . . . . . . . . . . . . . . . . . . . . . 66
4.9.3 Standard charger solution . . . . . . . . . . . . . . . . . . . . 67

4.9.3.1 Private parking station solution . . . . . . . . . . . . 67
4.9.3.2 Parking hub station solution . . . . . . . . . . . . . . 68

4.10 Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.10.1 Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.10.2 Convenience . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

5 Discussion 73
5.1 Methodology & project work . . . . . . . . . . . . . . . . . . . . . . . 73
5.2 Convenience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.3 BEV versus PHEV . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.4 Capability for EVs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.5 Transition towards sustainability . . . . . . . . . . . . . . . . . . . . 76
5.6 The proposed concept solution . . . . . . . . . . . . . . . . . . . . . . 77

6 Conclusion 79

7 Future work 81

Bibliography 83

ix



Contents

A Appendix - Gantt of the overall Plan I

B Appendix - Survey III

C Appendix - Interview Questions XIII

D Appendix - Needs list XVII

E Appendix - Metrics / Target product criteria XXI

F Appendix - Initial sub-system concepts XXV

G Appendix - Concept selection matrices XXIX

H Appendix - Full-system concepts XXXIII

I Appendix - Findings from Oslo & Kraftforum XXXVII

J Appendix - Full-system concept scoring matrices XLIII

x



List of Figures

2.1 The six phases described in Ulrich, K. & Eppinger, S.’s (2012) [2]
Product development methodology (PDM). . . . . . . . . . . . . . . . 5

2.2 Concept Selection Process defined by Ulrich & Eppinger [2] . . . . . . 6
2.3 An example of a gantt-chart, where ’black’ represent done progress.

Hence ’white’ to the left of ’current date’ means tasks fallen behind. . 8
2.4 An example of an precedence diagram. . . . . . . . . . . . . . . . . . 8
2.5 Illustration of brainstorming. . . . . . . . . . . . . . . . . . . . . . . . 9
2.6 The creation of an affinity diagram. . . . . . . . . . . . . . . . . . . . 9
2.7 An example of a typical morphological matrix with three ’total solu-

tions’ - red, green, respective blue. . . . . . . . . . . . . . . . . . . . . 10
2.8 Convenience continuum for the ’pizza’ product category. . . . . . . . 12
2.9 Illustration of the axis system for the measured values of ’displacement’. 17
2.10 Field limits recommendations from IEEE for controlled environments. 20
2.11 Field limits recommendations from IEEE for uncontrolled environments. 20
2.12 Field limit recommendations by ICNIRP. . . . . . . . . . . . . . . . . 21
2.13 China electricity production distribution. . . . . . . . . . . . . . . . . 24
2.14 Elecric power consumption for a residence for a) three workdays, and

b) a weekend (two days). . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.15 Comparison diagram of discharge duration versus rated power for

some energy storage technologies [25]. . . . . . . . . . . . . . . . . . . 27

3.1 Precedence diagram of Phase 0 - Planning . . . . . . . . . . . . . . . 34
3.2 Precedence diagram of Phase 1 - Concept Development . . . . . . . . 35
3.3 Picture of a page in the project book. . . . . . . . . . . . . . . . . . . 36
3.4 Precedence diagram of Phase 2 - System-Level Design . . . . . . . . . 39
3.5 Precedence diagram of Phase 3 - Detailed Design . . . . . . . . . . . 41

4.1 Illustration of how the process was described with a list and prece-
dence diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.2 Illustration of the initial system boundary with components and in-
teractions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

4.3 Illustration of the three selection matrices. . . . . . . . . . . . . . . . 55
4.4 Illustration of the developed system boundary with components and

interactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.5 The setup of sub-concepts in the morphological matrix. . . . . . . . . 57
4.6 The developed ’last iterated’ full-system concept. . . . . . . . . . . . 59
4.7 The "Home" part of the first concept selection. . . . . . . . . . . . . . 60

xi



List of Figures

4.8 The "Destination" part of the first concept selection. . . . . . . . . . . 60
4.9 The ’reviewed’ full-system concept. . . . . . . . . . . . . . . . . . . . 61
4.10 Illustration of the final system boundary with components and inter-

actions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.11 The initial cluster design of the product architecture. . . . . . . . . . 64
4.12 Final product architecture. ’Green’ represents ’Availability charger’,

’Blue’ represents ’Fast charger’, ’Grey’ represents ’Standard Charger’,
and ’Orange’ represents the ’Control & Management system’ of the
architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

4.13 The private parking station. . . . . . . . . . . . . . . . . . . . . . . . 67
4.14 Concept of the motorised linear slides for the charging pad, inside the

’case’. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.15 A removable lid to the internal compartment of the private parking

station. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.16 The inside of the private parking station, without any components or

supporting structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.17 The chargerbot module. . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.18 The relation between chargerbot modules and the private parking

station module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
4.19 The complete/assembled chargerbot (consisting of the chargerbot mod-

ules and the private parking station module). . . . . . . . . . . . . . 69

H.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXIII
H.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXIII
H.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXIII
H.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXIV
H.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXIV
H.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXIV
H.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXIV
H.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXV
H.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXXV

xii



List of Tables

2.1 The five dimension of convenience. . . . . . . . . . . . . . . . . . . . 12
2.2 Comparison over suitable wireless charger technologies for charging

electric vehicles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3 Mean displacement and distance in the x (lateral) and y (longitudinal)

axis, and distance from the centre of the vehicle to the centre of the
bay. ’Distance’ is the absolute value of the displacement. . . . . . . . 18

2.4 Mean displacement and distance in the (lateral) and y (longitudinal)
axis, and distance from the centre of the vehicle to the centre of the
charging pad. ’Distance’ is the absolute value of the displacement. . . 18

2.5 Recommended SAR levels. . . . . . . . . . . . . . . . . . . . . . . . . 19
2.6 Recommendation table for main fuse selection made by Vattenfall

(Vattenfall, 2013). The fourth column is a calculation of; Maximum
Power Output all hours á year (set to be 8766 hours). The fifth
column is the Vattenfall AB’s yearly price for respectively main fuse
size [20]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.7 Specifications on reference models of BEV respectively PHEV. . . . . 30

4.1 Project mission statement table. . . . . . . . . . . . . . . . . . . . . . 49
4.2 Some of the needs identified through survey & interviews. . . . . . . . 52
4.3 Some of the metrics created from the identified needs in table D.1. . . 53

A.1 Gantt-chart of the overall project plan . . . . . . . . . . . . . . . . . II

D.1 The needs identified through survey & interviews. . . . . . . . . . . . XVII

E.1 The metrics created from the identified needs in table D.1. . . . . . . XXI

G.1 First full-system concept selection matrix of "Charger". . . . . . . . . XXX
G.2 First full-system concept selection matrix of "Alignment". . . . . . . . XXXI
G.3 First full-system concept selection matrix of "Other". . . . . . . . . . XXXII

J.1 The matrix for the first iteration of the full-system concept scoring. . XLIV
J.2 The final first full-system concept scoring matrix, where the last it-

erated concept is labeled X1 and the reviewed concept X2. . . . . . . XLV

xiii



List of Tables

xiv



Glossary

cannibalisation Short for market cannibalisation, and meaning when a product or
service takes market shares on the behalf of another product or service.. xiii,
75, 76

disruptive technology A new technology that disrupt an other technology, and
have an cannibalisation effect on the older technology’s market.. v, xiii, 44, 76

electro-stimulating effect The human body uses electrical signals for its nervous
system. Exposure to electromagnetic fields can lead to un-natural stimulation
in the nervous system.. xiii, 18

SAR SAR is a acronym for ’specific absorbation rate’, and is a measurement of
power absorbed by a mass of tissue [W/kg]. It is commonly used in the
context of electromagnetic fields, but may also be used for sound waves.. xiii,
19

summon Search tool of Chalmers Library. Searches within Chalmers Library’s own
database as well as other databases.. xiii, 34

waste time A term used for describing time when a user does nothing and perceives
it as a waste of time.. xiii, 47, 71

well to wheels A way of comparing how efficient different energy sources for driv-
ing a car is, from its energy source to the movement of the car. EVs. xiii,
13

xv



Glossary

xvi



Acronyms

AD Autonomous drive. v, xiii, 21, 22, 46, 70, 71, 75, 76, 77, 79, 81
AV Autonomous vehicle. xiii, 21, 22, 70, 80

BEV Battery electric vehicle. v, xiii, 12, 35, 46, 47, 49, 63, 66, 70, 71, 73, 75, 79,
81

CAES Compressed air energy storage. xiii, 26, 29, 59
CEVT China-Euro Vehicle Technology. xiii, 1, 2, 49, I

EMI Electromagnetic interference. xiii, 14
ES Energy storage. v, xiii, 26, 28, 29, 59, 68, 69, 75, 76, 78, 81
ESS Energy storage system. v, xiii, 26, 59, 71, 76, 77, 79
EV Electric vehicle. v, xiii, xv, 1, 2, 13, 21, 23, 24, 26, 30, 38, 44, 46, 48, 49, 58,

63, 65, 66, 67, 69, 70, 71, 73, 76, 77, 79, 81

OLPT On-line inductive power transfer. xiii, 16

PDM Product development methodology. xi, xiii, 5, 7, 33
PEV Plug-in electric vehicle. v, xiii
PHEV Plug-in hybrid electric vehicle. v, xiii, 1, 2, 12, 35, 38, 47, 49, 67, 70, 73,

75, 79, 81

RIPT Resonant inductive power transfer. xiii, 14, 16, 44, 57

SMES Superconductive magnetic energy storage. xiii, 26, 28, 29, 59

WPT Wireless power transfer. iv, v, xiii, 2, 14, 16, 17, 43, 44, 45, 47, 48, 49, 57,
58, 62, 67, 70, 77, 79, 80, 81

xvii



Acronyms

xviii



1
Introduction

Following social, technological and environmental trends electric vehicle technologies
have evolved in a rapid pace, and has increasingly acquired larger market shares in
the passenger vehicle market.
The electric vehicle technologies are still in a relative early technological stage,
and solutions as well as standardisations has yet to be defined. One important
technological aspect of electric vehicles is the charging of their batteries.
The master’s thesis ’Convenient charging system for electric cars’ is a new prod-
uct development project for the concept development of a future charging system
solution.
This first chapter will present the background, problem formulation & purpose,
project deliveries & research questions, delimitation’s, and this report’s structure.

1.1 Background
The master’s thesis project ’Convenient charging system for electric cars’ was pro-
vided by CEVT (China-Euro Vehicle Technology).
CEVT was founded 2013 as an subsidiary of Zhejiang Geely Holding Group, and is
an engineering and development centre addressing the needs of the two passenger
car organisations, Volvo Cars and Geely Automobile. CEVT’s development work
involves the aspects of the cars architecture, -power train & drive line components,
-upper body structure, and -exterior design.[1]

1.2 Problem Formulation & purpose

CEVT has got the order to (among many things) develop a system for the future
charging of an electric passenger car platform.
In the development of the new car platform, one important problem that has been
identified is to develop a solution for how wireless charging of Plug-in hybrid electric
vehicles (PHEVs) and Electric vehicles (EVs) could be made user-friendly, safe,
effective and convenient.
The charging of EVs is one of the most distinguished differences compared to fuel
based vehicles. A difference that often may be seen as a disadvantage compared to
fuel based cars, for instance due to charging time and driving range. It is therefor
important to find a solution that makes customers and users perceive the whole
electric car as a better and more desirable product than fuel based cars.

1



1. Introduction

The benefits of a easy-usable, wireless charging system for electric cars, have already
been identified by CEVT as a future requirement. Hence, this project is to focus on
a system solution that includes wireless charging technology.
Furthermore, another important aspect of a future charging system is its conve-
nience.
Furthermore, the purpose of this project can be summarised into two major aspects:

• Investigate how to create a convenient charging system that creates trust and
additional values for the electric car.

• Find out how wireless charging technology could increase the convenience of
charging.

1.3 Project deliveries & Research questions
The deliveries of this project are technical specifications-, and CAD-models of the
final suggested concept solution.
In order to successfully design a (wireless and convenient) charging system for a fu-
ture car platform for EVs and PHEVs, some research questions need to be answered:

• What components are needed in a charging system (with wireless charging
functionality) for cars?

• What current suitable technical solutions are there for cord- and wireless charg-
ing of electric cars. What benefits respectively drawbacks do they possess?

• How should a charging system (with wireless functionality) for electric cars be
designed in order to be convenient and meet the needs of a future car platform
developed by CEVT?

• How could a future charging system for charging electric cars address the needs
and demands in the aspects of:
– Human safety?
– Ease of use?
– Technical performance?
– Low environmental impact?
– Manufacturability?
– Different usage environments?
– Product lifetime?

1.4 Delimitation’s
The project will be executed from the beginning of February to the mid of June 2016,
and will use both Chalmers’ and CEVT’s facilities and resources. Furthermore,
specific delimitation’s are:

• The project will not cover calculations of the fields (physics), that derives from
the usage of Wireless power transfer (WPT).

• No working physical prototype will be produced.
• The detail level of the CAD will be such as that the product, and its func-

tionality may be fully understood and possible to assess. However, further
development will be needed in order to produce a functional physical product.

2



1. Introduction

• The definition of the product architecture will only include what is necessary
for the charging system to function, not the entire car or -society.

• The environmental assessments will only be analysed with a subjective ap-
proach, mostly based on general environmental facts and theory.

• The legal and economical aspects will only be considered and not assessed in
this project.

1.5 Report Structure
The structure of this report is as follows:

• Introduction
• Theory
• Method chapters
• Result chapters
• Discussion
• Conclusion
• Future work
• References
• Appendices

The introduction chapter explains why there is a need of the project, and what the
project will look like - what background, purpose, aim and delimitation’s it has.
The theory chapter contains areas of specific knowledge and data necessary for the
projects outcome.
In the method chapters the activities, process and tools used will be described.
What is produced, through the methods described in the method chapters, will be
described in the result chapters.
A Discussions chapter will then elaborate upon the results, after which an conclusion
chapter will conclude what the project has delivered.
Finally, possible future research and -work will be suggested in a future work chap-
ter.

3



1. Introduction

4



2
Theory

This chapter aims to describe relevant theory for the project and its content. The
theory for the project includes relevant scientific methodology description as well as
important methods and tools used in the project. The theory of the content regards
the theory needed to understand the problem and enables the creation of a final
project delivery.

2.1 Product Development Methodology
There are different Product development methodology (PDM), for instance methods
described by Paul & Beitz, Ullman, Roozenburg & Eekels, and Ulrich & Eppinger.
In the book ’Product Design and Development’ Ulrich, K. & Eppinger, S. (2012) [2]
describes their methodology.
In this PDM Ulrich & Eppinger have divided the development process into six
chronological phases. The phases are numbered from 0-5. The use of a ’0’-phase is
due to that this phase should be performed before a product development project is
initiated, in difference from the other phases which should all be part of a complete
product development project.

Figure 2.1: The six phases described in Ulrich, K. & Eppinger, S.’s (2012)
[2] Product development methodology (PDM).

2.1.1 The planning phase
Ulrich & Eppinger [2] states that; in order to start with the actual product devel-
opment process, the project needs to be approved. The approval may be gained

5



2. Theory

through the process of phase 0 - planning.
In the planning of the project it is important to have an overall plan as well as
more detailed plans. A tool for an overall plan is the gantt-chart (see chapter 2.2.1),
and a tool for detailed plans is precedence diagrams (see chapter 2.2.2) with related
description.
Furthermore, Ulrich & Eppinger states that the outcome of the planning phase
is the mission statement, which specifies the target market, business goals, key
assumptions, and constraints of the product.

2.1.2 The concept development phase

According to Ulrich & Eppinger [2], the first actual phase in product development
is the concept development phase. This phase will start the development process
according to the plan and opportunities identified in the planning phase.
In the concept development phase; stakeholder needs, competitive products, and
feasible product concepts are identified. Furthermore, industrial design is started,
along with development of concepts and building of prototypes. The concepts and
prototypes are then assessed regarding production feasibility, estimated manufac-
turing costs, and legally feasibility.
One major part of the concept development phase is the concept selection process.
The process described by Ulrich & Eppinger [2] (see figure 2.2), is an iterative process
were product specifications are defined in order to generate-, screen-, analyze-, and
test concepts.
The outcome of the concept development phase will be a first concept selection of
one, or possible a few, concepts for further development.

Figure 2.2: Concept Selection Process defined by Ulrich & Ep-
pinger [2]

6



2. Theory

2.1.3 System-Level Design
During the system-level design phase, the product architecture is developed along
with the industrial design, design for environment, design for manufacturing, robust
design, and prototype development. Moreover, legal- and economic aspects should
also be considered in this phase.
The purpose of this phase is to adapt and develop concepts into suiting the identified
and defined system, for which the product is intended for.

2.1.4 Detailed Design
The detailed design phase, is initialised by the final concept selection. In this phase
the detail level of the final concept selection is increased, and specifications as well
as drawings of components are to be created and compiled.
The outcome of the detailed design phase is the final prototype delivery.

2.1.5 Testing & Refinement
As its name suggest, this phase is about perform tests on prototypes. The testing
aims to reveal if further refinement of the prototype could and should be performed.
Furthermore, this phase includes the creation of ’promotion and launch materials’.

2.1.6 Production Ramp-Up
The last phase in Ulrich and Epping’s described PDM is the production ramp-
up phase. This phase aims to start a small scaled production and evaluate the
production method and get feedback on the final product from key customers.
The last and important part of this phase and the PDM is for the general manage-
ment to conduct post-project review.

2.2 Product Development Tools
Cambridge dictionary explains the word ’tool’ as something that helps you to do
a particular activity. Hence, in order to perform the activities for a methodology,
tools are needed. The major tools used in this product development project are:
gantt-chart, precedence diagram, brainstorming, affinity diagram, selection matrix,
morphological matrix, concept-scoring matrix, survey, and semi-structured interview.

2.2.1 Gantt-chart
Ulrich and Eppinger [2] argue that gantt-chart is the traditional tool used to show
the timing of tasks in a project. The tasks are ordered vertically in the diagram.
Moreover, each task is represented by a horizontal bar, thus showing the beginning,
duration, and end of a task, along an horizontal timeline. To visually show the
progress and whether a task is behind or ahead of schedule, a vertical ’current

7



2. Theory

date’-line could be used along with gradually color-filling the bars. An example of
a gantt-chart may be seen in figure 2.3.
However, Ulrich and Eppinger states that the dependency between the tasks are not
explicit displayed in a gantt-chart. The dependency for tasks describes if the relation
between tasks are parallel, sequential or iteratively coupled. The dependencies are
important to know in order to understand what must be accomplished before a tasks
may start or end.

Figure 2.3: An example of a gantt-chart, where ’black’ represent
done progress. Hence ’white’ to the left of ’current date’ means
tasks fallen behind.

2.2.2 Precedence diagram
According to Kezsbom, D.S. and Edward, K.A. (2001) [3] the precedence diagram-
ming method is well suited and could be used for describing dependency between
tasks.
The activities are made into a network, in which the activities are arranged se-
quentially with consideration to their respectively relations as well as the project
objectives. The precedence diagram could in excess of showing the relation between
activities also contain a proposed activity duration for each activity. In figure 2.4 a
example of a precedence diagram is shown. Each activity is represented as a rectan-
gle, with a letter for which task it is and a number of the proposed activity duration
(time unit).

Figure 2.4: An example of an precedence diagram.

8



2. Theory

2.2.3 Brainstorming

Figure 2.5: Illustration of brain-
storming.

According to Wallace, S. (2015) [4] brainstorm-
ing is a method for idea generation through a cre-
ative process. Brainstorming is often performed
by a group of people, but can also be performed
individually.
A brainstorming should be performed on a board
(or similar visual space) and ideas are writ-
ten down on notes that can be attached to the
board. The brainstorming starts with a chose
of topic, for which ideas then are generated and
presented. Responses to an idea are immediately written down and added to the
board uncritically and without editing (to not disturb the creative process). In order
to identify what ideas are useful, all ideas are after each brainstorming session (or
iteration) considered and discussed more freely. It is important to use the bene-
fit and ideas of all participants. The brainstorming can be iteratively repeated to
develop ideas further.

2.2.4 Affinity Diagram
Westcotte Russel, T. (2014) [5] explains that an affinity diagram is used to organise
items of a large group into smaller chunks, in order to make it more manageable.
Affinity diagrams are often used in order to organise the ideas from a brainstorming.
The creation of categories (chunks) of an affinity diagram can either be created before
or after the items to be chunked are known. An item may also belong to more than
one chunk.
Moreover, Westcotte Russel, T. claims that another benefit with affinity diagrams,
is that it creates discussion between individuals and the final diagram will be a
collective mental model of what have been analysed.
The affinity diagram process may continue until the performers reckon it to be done.
A typical affinity diagram process is illustrated in figure 2.6.

Figure 2.6: The creation of an affinity diagram.

9



2. Theory

2.2.5 Morphological matrix
According to Eversheim, W. (2009) [6] a morphological matrix is used for develop
new ideas in the form of solution concepts, product concepts, and structuring ideas.
A morphological matrix is applicable both individually and as a team.
First, in creating a morphological matrix, all functions of a product (system) are
listed. Then solutions are developed for each respectively function. For a two-
dimensional matrix, the functions are typically listed vertically on separate rows,
with all the respectively solutions to the right, one per column. By choosing among
these partial solutions of the different functions, a new total solution can be created.
This new total solution will have all of the functionality of all the combined functions
that were listed.
Moreover, Eversheim states that the major benefit with a morphological matrix is its
good capability in developing solutions for complex problems and -product systems.
However, the weakness with a morphological matrix is the huge number of different
potential total solutions (number of combinations), which leads to difficulties in
decision making of what combinations to create from the matrix. More so, the
method does not have any real support for the decisions made in it, and not all
combinations are feasible.

Figure 2.7: An example of a typical morphological matrix with three ’total solu-
tions’ - red, green, respective blue.

2.2.6 Survey
A survey represents the quantitative data collection, which Edward F. McQuarrie
(2016) [7] suggest should imply responses counted in the hundreds. A quantitative
research aims to acquire data in the form of precise numbers (numerically, frequen-
cies and magnitudes), while qualitative research aims to collect data in form of
human being functions - where not only ’what’ is expressed is important but also
’how’ it is expressed.
Edward F. McQuarrie claims that one of the first steps in designing a survey should
be to define to whom the survey should target - the population. The survey should
then through its questions and structure aim to divide the population into differen-
tiated sub-populations, in order to later being able to draw conclusion on the data
between different sub-populations.
Sub-populations could for instance be based on demographics or owners of a specific
device.

10



2. Theory

Moreover, it is explained that a survey should be much more detailed than for
instance interviews. Compared to interviews, the survey should not explore or dis-
cover - it should describe exactly and pin down precisely. Therefore, the questions
are the same for all respondents and do essentially only allow responses according
to predefined answers.

2.2.7 Semi-structured interview
In ’The Market Research Toolbox’ by Edward F. McQuarrie (2016) [7], interview
is defined to be a qualitative data collection tool. The interview should be design
around three elements:

• Selecting the questions to be asked.
• Arranging the questions into an effective sequence.
• Deciding what if any supplements should be added.

When creating and selecting questions to be asked, considerations should be done
regarding if a question should be ’close-ended’ or ’open-ended’. Close-ended ques-
tions typically only allows predefined answers such as ’yes’ or ’no’, and multiple
choices. In contrast to the close-ended question, the open-ended question leaves the
formulation of the answer to the respondent.
In order to construct good interview questions the close-ended questions should
be minimised (but not eliminate) and open-ended questions should be emphasised.
That is, the interview time should mainly be allocated to, and lead by, the open-
ended question, in order to trigger discussion. But the use of close-ended questions
are a good support in the interview, to ’close’ an extended discussion triggered by
an open question.
The value of the interview lies not only in the spoken answers, but rather what the
interviewer takes away from the dialogues.
McQuarrie also suggests that the interview and its structure should only be partly
prepared in advance, in order to leave room for spontaneity and flexibility. The
combination of prepared structured unprepared structure will give the best answers
if the fluency and variation (exploring and confirmation) is good.

2.3 Convenience in products
Product development should according to Ulrich & Eppinger [2] be based on sat-
isfying needs. The Cambridge Dictionaries Online defines the word ’convenient’ in
two ways:

1. Suitable for your purposes and needs and causing the least difficulty.
2. Near or easy to get to or use.

The definitions in Cambridge Dictionaries Online describes different dimensions,
that can be related to what Ulrich & Eppinger describes as important in the iden-
tification process of finding- and satisfying user needs.
In an old article by Brown L.G (1989) [8] the meaning of convenience in the consumer
product market is described. Brown suggests that the demand for convenience will

11



2. Theory

grow rapidly as a result of households increased amount of work and income. "With
more money and less time, these consumers seek time-saving goods and services."
Furthermore Brown suggests that convenience is a multidimensional construct with
five dimensions, described in table 2.1.

Table 2.1: The five dimension of convenience.

1. Time Dimension Products may be provided at a time that is most
convenient for the customer.

2. Place Dimension Products may be provided in a place that is more
convenient for the customer.

3. Acquisition
Dimension

Firms may make it easier for the customer, finan-
cially and otherwise, to purchase their products.

4. Use Dimension Products may be made more convenient for the
customer to use.

5. Execution
Dimension

Having someone else provide the product for the
consumer.

Brown states that the five different dimension of convenience can both be used
differently (from single time to continuously), and be combined in order to compete,
on the market, in adding to a users’ comfort.

Figure 2.8: Convenience con-
tinuum for the ’pizza’ product
category.

Furthermore, Brown describes that the execution
of the convenience dimensions results in an "con-
venience continuum". He uses the example in the
product category of pizza, see figure 2.8. The place
in the continuum should be an active chose by the
company, as it may change the cost as well as the
product’s competitiveness. Finally, Brown con-
cludes that "The continuum makes it necessary to
consider both the nature of the product at differ-
ent points as well as the distribution of customers."
Moreover, convenience have been understood by
the company as vital in the development of a fu-
ture charging system for BEVs and PHEVs - hence
the project title Convenient charging system.

12



2. Theory

2.4 Sustainable aspects of Electrical Vehicles
For a society Heinicke, M. & Wagenhaus, G. (2015) [9] claims that mobility is nec-
essary in order to facilitate valuable forms of communication and exchange physical
goods.
With the increasingly demand of non-fossil based and more sustainable vehicles (es-
pecially in urban environments) the EVs becomes more attractive, due to not having
any direct CO2 emissions. Furthermore, Yong, J.Y. et al. (2015) [10] describes how
the severe climate change and the green house gas emissions have reached a dan-
gerous level, with effects as global warming and extensive melting of icebergs. The
implementation of EVs could lead to an reduction of green house gas emissions.
However, Yong, J.Y. et al. also states that if EVs are charged via a power grid
with polluting fuels generation, such as coal-fired, it can cause EVs to have a higher
’well to wheels’ emissions than traditional combustion cars. Thought, with the in-
creasingly electricity generation from renewable energy sources, the wells-to-wheels
emissions for EVs will be reduced and below traditional combustion vehicles’ emis-
sions. Which also is the current situation for many European countries.
A benefit mentioned by Heinicke, M. & Wagenhaus, G. is that EVs have a significant
lower direct cost of operation, compared to traditional combustion vehicles. This
is due to that the technology enables a higher efficiency (less fuel/electricity), and
more so as electricity is relatively cheap.
Another benefit with EVs is that they could increase the energy security, due to
enable more and a greater variance in energy sources. Hence supporting the today’s
increasing number of renewable energy sources and production.
A hidden benefit of EVs is described in an article by Li, C. et al. (2015) [11]. It
is described how big cities have problems with ’urban heat island effect’, which is
when the city becomes warmer than rural areas. This is claimed to be a major
problem in big cities as Beijing, China. Increasing temperature in warm cities like
Beijing, leads to higher usage of air conditioning, which also have a high negative
environmental impact. Compared to conventional vehicles, EVs emits 80.2% less
heat during operation. If conventional vehicles had been replaced by EVs in Beijing,
during the summer of 2012, the city temperature could have been decreased with 0.94
°C. Due to decreased air-condition energy consumption, this lowering in temperature
could have saved 14.4 million kWh and thus reduced the CO2 emissions by 10,686
tonnes, per day.

2.5 Wireless Power Transfer
One suggested (by the company) sort of technology in a convenient charging system
for cars could be wireless power transfer.
There are different kinds of technologies that allows for wireless power transfer. In
the article by Musavi, F., & Eberle, W. (2014) [12] they compared different wireless
charging technologies that they thought to be interesting in electric vehicle charging
applications. The technologies they investigated were:

• Inductive power Transfer (IPT)

13



2. Theory

• Capacitive power Transfer (CPT)
• Permanent magnet coupling power transfer (PMPT)
• Resonant inductive power transfer (RIPT)
• On-line inductive power transfer (OLPT)
• Resonant antennae power transfer (RAPT)

In the article, Musavi, F., & Eberle, W. describes the different technologies, and
what benefits respectively drawbacks each technology possesses. They evaluated
the different technologies feasibility regarding existing limitations in power electron-
ics technology, cost, consumer acceptance, health hazards and limits for human
exposure to radio frequency radiation. The comparison between their studied tech-
nologies is presented in table 2.2.
Furthermore, Musavi, F., & Eberle, W. suggests RIPT and OLPT to be most
promising among the compared wireless charging technologies. RIPT and OLPT
are similar technologies, but with different applications. RIPT typically only allows
stationary charging of vehicles (vehicle is standing still), while OLEV allows vehi-
cles to charge on the road while moving. In the article the authors claims RIPT to
currently be the most popular technology for WPT.

2.5.1 Resonant Inductive Power Transfer
The currently most popular WPT technology is, according to Musavi & Eberle,
the RIPT technology, which was initially pioneered by Nikola Tesla (1856-1943).
With the use of modern electronic components the technology have recently become
popular again.
The essential difference between IPT and RIPT is the method of creating resonance,
with the use of resonant circuits. In short, this is created by tuning two or more
resonant tanks with resonant capacitors in order to make the circuits resonate at
the same frequency. This resonant circuit technique have the primary functions of:

• Maximise the power transfer.
• Optimising efficiency of transmission.
• Frequency variation control for the transmitted power.
• Variation compensation of the magnetic coupling.
• Compensate for magnetising currents (reduces losses).
• Matching coil impedance’s.
• Suppress higher harmonics from the generator.

Furthermore, Musavi & Eberle claims that the advantages acquired with the use
RIPT (compared to a non resonant inductive power transfer) are for instance:

• Increased transfer range.
• Reduced EMI.
• Higher frequency operation (in kHz range).
• Higher efficiency.

The increased transfer range and higher efficiency allows less constrained applica-
tions usages of the technology. However, the frequency operation range is suggested
to be the technology’s main advantages, as is supported by current state of the art

14



2. Theory

T
ab

le
2.
2:

C
om

pa
ris

on
ov
er

su
ita

bl
e
w
ire

le
ss

ch
ar
ge
r
te
ch
no

lo
gi
es

fo
r
ch
ar
gi
ng

el
ec
tr
ic

ve
hi
cl
es
.

T
ec
hn

ol
og
y

P
er
fo
rm

an
ce

C
os
t

Si
ze
/

V
ol
um

e
C
om

pl
ex
it
y

of
sy
st
em

Su
gg
es
te
d

po
w
er

le
ve
l

E
ffi
ci
en

cy
E
M
I

Fr
eq
ue

nc
y

In
du

ct
iv
e
po

we
r
tr
an

sfe
r
(I
PT

)
m
ed
iu
m

m
ed
iu
m

10
-5
0
kH

z
m
ed
iu
m

m
ed
iu
m

m
ed
iu
m

m
ed
iu
m
/h

ig
h

C
ap

ac
iti
ve

po
we

r
tr
an

sfe
r
(C

PT
)

lo
w

m
ed
iu
m

10
0-
50
0
kH

z
lo
w

lo
w

m
ed
iu
m

lo
w

Pe
rm

an
en
t
m
ag
ne
t
co
up

lin
g

po
we

r
tr
an

sfe
r
(P

M
PT

)
lo
w

hi
gh

10
0-
50
0
H
z

hi
gh

hi
gh

hi
gh

lo
w
/m

ed
iu
m

R
es
on

an
t
in
du

ct
iv
e
po

we
r

tr
an

sfe
r
(R

IP
T
)

m
ed
iu
m

lo
w

10
0-
50
0
kH

z
m
ed
iu
m

m
ed
iu
m

m
ed
iu
m

lo
w
/m

ed
iu
m

O
n-
lin

e
in
du

ct
iv
e
po

we
r

tr
an

sfe
r
(O

LP
T
)

m
ed
iu
m

m
ed
iu
m

10
-5
0
kH

z
hi
gh

hi
gh

m
ed
iu
m

hi
gh

R
es
on

an
t
an

te
nn

ae
po

we
r

tr
an

sfe
r
(R

A
PT

)
m
ed
iu
m

m
ed
iu
m

1-
20

M
H
z

m
ed
iu
m

m
ed
iu
m

m
ed
iu
m

lo
w
/m

ed
iu
m

15



2. Theory

power electronic technologies, thus enabling good efficiency at relative high power
levels.

2.5.2 Standard for wireless power transfer
The global standard association SAE International [13] claims to be a knowledge
source for the engineering profession over a broad spectrum of industries, by uniting
over 128,000 engineers and technical experts.
SAE have defined two areas of priority:

• Encouraging a lifetime of learning for mobility engineering professionals.
• Setting the standards for industry engineering.

With emerging technologies and trends regarding wireless charging, SAE Interna-
tional have identified that there is a need to establish a standard for wireless charging
of electric cars. Therefore, SAE International have now approved upon May 31st
publish SAE TIR J2954 Wireless Power Transfer for Light-Duty Plug-In/Electric
Vehicles and Alignment Methodology.
For the development of TIR J2954 important criteria that are addressed regards
safety and electromagnetic limits, efficiency and interoperability targets, as well as
acceptance of WPT.

Jesse Schneider (Chair of SAE International’s WPT committee and Fuel Cell, Elec-
tric Vehicle & Standards Development Manager at BMW North America) said May
17, 2016 at Warrendale, Pa.:

Wireless power transfer, using SAE TIR J2954 is a game changer for PH/EVs. This
first in a series of documents will enable consumers to simply park their vehicles into
spaces equipped with TIR J2954 equipment and walk away without doing anything
to charge their PH/EV,” and “Standardization of both the vehicle and ground in-
frastructure WPT has started with SAE TIR J2954. The frequency band, safety,
interoperability, EMC/ EMF limits as well as coil definitions from SAE TIR J2954
enable any compatible vehicle to charge wirelessly from its WPT home charger, work,
or a shopping mall WPT charger, etc. with the same charging ability. All of this
makes it possible to seamlessly transfer power over an air gap with high efficiencies.
SAE TIR J2954 WPT automates the process for charging and extends the range for
the vehicle customer only by parking in the right spot."

SAE TIR J2954 defines the frequency band for all light duty vehicle systems for
WPT to be 85 kHz (81.39 - 90 kHz). Furthermore, four classes of WPT with
different power levels are to be specified in SAE TIR J2954:

• WPT1 - 3.7 kW (specified in TIR J2954).
• WPT2 - 7.7 kW (specified in TIR J2954).
• WPT1 - 11 kW (to be specified in future revision of TIR J2954).
• WPT1 - 22 kW (to be specified in future revision of TIR J2954).

Moreover, even higher power levels may be included in future revisions of TIR J2954.

16



2. Theory

2.5.3 Shielding for electromagnetic inductive applications
In their article about Coil design and shielding for OLPT, Kim, J. et al. (2013) [14]
describes how the coils could need shielding in order to meet the levels described in
guidelines for electric and magnetic field exposure (see chapter 2.7). As described
in chapter 2.5, OLPT and RIPT are based on the same technology, suggesting that
this aspect of shielding should also be important for RIPT. Furthermore, Kim, J.
et al. describes how the shielding of coils could improve the WPT efficiency, which
in other case could decrease due to unwanted magnetic field leakage around the
magnetic field source. The magnetic field leakage is due to induced currents in the
surrounding conductive materials, like for instance typical materials of a car chassis.
Furthermore, metallic shielding is described as popular, useful and effective for
shielding in radio-frequency applications. However, by suppressing a WPT sys-
tems possible leakage of magnetic field, considerations should be made regarding
the effects on the WPT’s electrical performance.

2.6 Wireless Power Transfer & Vehicle alignment
In their article Birell et al. (2015) [15] describes how wireless charging technologies
as inductive charging demands some degree of alignment in order to have a high
efficiency or even function at all. With the conclusion that current inductive charging
system have a typical tolerance of approximately ±10cm between transmitting and
receiving coils. They have however found that in both of their two different studies,
regarding parking alignment, that only 5% of the vehicles in their studies would
have efficient charging, due to insufficient parking alignment.

Figure 2.9: Illustration of the
axis system for the measured val-
ues of ’displacement’.

Furthermore, it is stated in the article that the
loss of efficiency in inductive charging also may
endanger human safety. A good alignment be-
tween the two coils may enable wireless power
transfer efficiency over 95%. To increase the
tolerances of the inductive technology, a reso-
nant circuit may be used. However, even with
the use of resonant circuits the efficiency will
drop rapidly at an approximately misalignment
of 15cm in either air gap-, lateral-, or longitudi-
nal distance. They also states that the angular
misalignment have a major effect on the wire-
less transfer efficiency. It is described how they
made two different tests for the displacement in
parking lots. The displacements were plotted in
a diagram such as is illustrated by figure 2.9.
One test, the retrospective analysis, was per-
formed without the drivers of the cars knowing
that their parking performance, of parking in a
bay, was to be measured. In the other test, the dynamic parking study, the drivers
were instructed to park a Nissan Leaf EV over an charging pad on an relatively

17



2. Theory

open parking lot. Furthermore, the dynamic parking study was performed with the
two scenarios of a charging receiver placed in the front, respective centre of the cars.
The result from the retrospective analysis and dynamic parking study as presented
by Birell et al. [15] can be seen in table 2.3 respective table 2.4.

Table 2.3: Mean displacement and distance in the x (lateral) and y (lon-
gitudinal) axis, and distance from the centre of the vehicle to the centre of
the bay. ’Distance’ is the absolute value of the displacement.

Mean Standard
Deviation

X-displacement (cm) -3.21 14.64
Y-displacement (cm) 15.59 25.02
Distance from centre (cm) 29.30 15.13
X-distance (cm) 12.12 8.74
Y-distance (cm) 23.73 29.12
Parking angle (°) 0.018 2.27
Absolute angle (°) 0.027 0.029

Table 2.4: Mean displacement and distance in the (lateral) and y (longi-
tudinal) axis, and distance from the centre of the vehicle to the centre of
the charging pad. ’Distance’ is the absolute value of the displacement.

Front Centre

Mean Standard
Deviation Mean Standard

Deviation
X-displacement (cm) 0.54 7.21 7.33 15.07
Y-displacement (cm) -66.86 60.81 -34.05 92.09
Distance from centre (cm) 75.39 49.01 75.93 60.41
X-distance (cm) 5.95 3.61 13.20 9.64
Y-distance (cm) 74.65 49.71 72.31 62.92
Parking angle (°) 2.00 2.14 0.18 5.64
Absolute angle (°) 2.14 2.00 3.35 4.40

2.7 WPT & Health
According to Das Barman et al. (2015) [16] one major concern for wireless power
transfer technology is the question about safety of the human body. The risk for
the human body, in wireless power transfer, to be exposed to electric, magnetic,
and EM fields is increased with higher power levels and transmission distances. The
frequency in WPT-systems are an important factor, as it is necessary for magnetic
and electromagnetic fields. Das barman et al. claims that there is a general crossover
frequency at 100 kHz. Over 100 kHz the field has a dominating heating effect, while
under 100 kHz the field has a dominating electro-stimulating effect.

18



2. Theory

Dar Barman et al. implies that the the magnetic and electromagnetic fields effects
on the human body should be further researched, as there are still some uncer-
tainties. Nevertheless, regarding human exposure guidelines WHO (World Health
Organization) generally recommends two - IEEE’s and ICNIRP’s. The purpose of
their respectively guidelines are:

• The purpose of IEEE standard is to provide exposure limits to protect against
adverse health effects to human induced by exposure to RF electric, magnetic,
and EM fields over the frequency range of 3 KHz–300 GHz.

• The main objective of ICNIRP standard is to set up guidelines for limiting the
EM field exposure to protect against harmful health effects. An adverse health
effect causes a detectable impairment of the health of the exposed individual or
of his or her offspring; a biological effect on the other hand, may or may not
result in an adverse health effect.

Moreover, there are some differences in their recommended values. A comparison
of their recommended values regarding SAR and induced electric field levels are
presented in table 2.5.

Table 2.5: Recommended SAR levels.

Regulation SAR (W/Kg) Induced electric field
(V/m), (f in Hz)

Whole body
average

Head
trunk Limbs All tissue

ICNIRP 2010 0.08 2 (10 g) 4 (10 g) 1.35 × 104 f
IEEE 2006 0.4 2 (10 g) 4 (10 g) 2.1 × 104 - 6.3 × 104 f

19



2. Theory

Furthermore, in figure 2.10 and 2.11 the recommended limits stated by IEEE for
controlled respectively uncontrolled environments are presented. ICNIRP’s corre-
sponding recommendations are presented in figure 2.12.

Figure 2.10: Field limits recommendations from IEEE for controlled en-
vironments.

Figure 2.11: Field limits recommendations from IEEE for uncontrolled
environments.

20



2. Theory

Figure 2.12: Field limit recommendations by ICNIRP.

2.8 Autonomous Drive

Suggestions of what positive aspects Autonomous drives (ADs), (in a vehicle also
referred to as Autonomous vehicles (AVs)), could bring to the future United Kingdom
is presented in the publication ’Making better places - Autonomous vehicles and
future opportunities’ by R. Skinner and N. Bidwell (2016) [17].
According to R.Skinner and N.Bidwell the introduction of driver-less and AVs are
on its way, and the technology will bring transformation in the aspects of quality of
life, economic growth, health, and social connections.
Moreover, they describe AVs by using the definition of the UK Department for
Transport - A fully autonomous vehicle is capable of completing journeys safely and
efficiently, without a driver, in all normally encountered traffic, road and weather
conditions.
Furthermore, it is suggested that EVs not only need to be able to drive themselves,
but that they also should use the possibility to communicate with other vehicles.
There are different levels of AD, which makes differences regarding if, and to what
degree, a qualified person needs to sit behind the wheels and be ready to (if required)
take over the control of the vehicle.
Concerning COMFORT the suggested benefits with AVs are:

• Amore smooth travel, due to better driving with less risk for shockwave breaks.
• Instead of driving, other tasks may be performed.
• No need to search for and drive to parking places.

Regarding the aspects of PARKING, they suggests and claims:

• Between 30-45% of city centre traffic is due to drivers searching for parking
spaces.

• AD could eliminate the need of parking space at destination.

21



2. Theory

• Autonomous vehicle zones (only for AVs) could increase the developable area
between 15-20% compared to a typical central urban layout. As cars can travel
more efficiently and drive to designated parking hubs with possible charging
infrastructure.

• AD and the use of parking hubs could eliminate the need and benefits of
private parking lots at ’home’. Thus enable area for other things, such as more
green areas.

• AD and parking hubs could reduce the general parking areas. General parking
coverage for cities such as London, New York, Paris, Vienna, Boston, and Hong
Kong is between 15-30%.

Among the benefits mentioned, the ones that concerns SAFETY were for instance:
• AD have the possibly to reduce the number and severity of road accidents

substantially. Due to that upwards to 90% of all accidents are caused by
driver error. Less accidents saves costs for the city. With reduction in road-
related casualties of 50% and 90% there could be cost saves of £360 million
respectively £650 million per year.

• Today’s cars use 5% of a typical motorway lane at any given time, under
good conditions. Considering safe distances due to driver response time, a
fully driver-less motorway with communicating cars could allow as much as
3.7 times higher capacity, compared to today.

The UTILISATION of AVs is suggested to be:
• More fundamentally; AVs should enable higher utilisation rate of vehicles, as

they can move while empty.
• The traffic flow and journey time reliability should be improved.
• ADs could decrease the number of cars, as AVs could be used in greater pro-

portion of time. Research suggests that for UK a typical car is parked 96% of
the time (80% at home and 16% elsewhere).

• Two different market options have been identified for AVs; private ownership
and shared use (as in a service).

• Shared vehicles travelling 24,000 km per year may have cost savings up to
75%, compared with typical running costs of non shared vehicles.

2.9 Electric Power at Home
According to the Swedish company Vattenfall AB (2013) [18] an average Swedish
house (144m2) have the total electricity consumption of 26.200 kWh. Of this total
power consumption 57% is for heating, 19% is for heating water, and 24% is for
household electricity.
Vattenfall AB states on their website [19] that the total power consumption of a
house is dependent on the sort of central heating system of the house, for instance if
it uses district heating, heat pump, or electric heater. Furthermore, it is stated that
it is important to chose a main fuse which may deliver enough power for the house.
In recommendations [18], which is presented in table 2.6, they suggest what size of
the main fuse is suitable for different yearly power consumption spans, and what

22



2. Theory

respectively maximal power outtake they stand. The yearly power consumption
recommendations considers that the power usage varies over the day’s, and thus not
the the fully utilised yearly output (maximal total output for all hours á year).
Moreover, at Vattenfall AB change of the main fuse size may only be performed
once per a twelve months period.

Table 2.6: Recommendation table for main fuse selection made by Vattenfall (Vat-
tenfall, 2013). The fourth column is a calculation of; Maximum Power Output all
hours á year (set to be 8766 hours). The fifth column is the Vattenfall AB’s yearly
price for respectively main fuse size [20].

Main Fuse
Size

Yearly Power
Consumption

Maximum
Power
Output

Fully Utilized
Yearly Output

Yearly
Cost

16 A 0-20 000 kWh 11 kW 96 426 kWh 3 675 kr
20 A 20 000-25 000 kWh 14 kW 122 724 kWh 5 140 kr
25 A 25 000-30 000 kWh 17 kW 149 022 kWh 6 425 kr
35 A 30 000-40 000 kWh 24 kW 210 384 kWh 8 795 kr
50 A 40 000-55 000 kWh 35 kW 306 810 kWh 12 640 kr
63 A 55 000-70 000 kWh 44 kW 385 704 kWh 17 050 kr

2.10 Swedish EV capability

In the master’s thesis by Knutfelt, M. (2015) [21], it is investigated what charging
capability Sweden has for EVs. Knutfelt, M. describes available power produced
and the assumptions that EVs are charged during the night and using a dynamic
charging (for maximal utilisation). Dynamic charging is described as that all the
charges are connected and a charging plan is set up after all the charging stations
individually needs and demands. One conclusion in the thesis is that the Swedish
car fleet could at highest (for function all year around) consist of 30% electric cars,
that is about 1.4 million cars.

2.11 China EV capability system

In the book ’Electric power and energy in China’ the author Liu, Z. (2013) [22]
describes what the EV energy supply model looks like in China, and compares it to
the world.
Liu, Z. describes that there have been a rapid development of the EV-market in
the world. This has led to rapidly increasing infrastructural demands. To meet the
demands, the Chinese governmental company State Grid had at the end of 2011
built and put in operation 13,000 AC charging poles, and 243 standard charging
and battery swapping stations, resulting in that China become the largest charging
and battery swapping operator in the world.

23



2. Theory

According to Liu, Z. cities are the focus area for EV development. This could be
problematic for China, due to its differences to developed countries. Where devel-
oped countries have a norm of living in detached houses with dedicated parking
spaces and possibly garages, China have a situation with dense population, high-
rising apartment buildings, and with extreme shortage of parking spaces (even more
so in the future). The construction of infrastructure (such as charging stations,
transformers, lines, and meters) in public spaces and residential areas faces chal-
lenges in the aspect of cost and time. Considerations should also be taken regarding
the possibility of revamp and upgrade the charging infrastructure, which could be
difficulty and costly.
Furthermore, the fast charging mode still faces problems with its negative impact
on battery life, and further technological breakthroughs should be needed for it to
gain popularity.
Liu, Z. claims that China has a somewhat limited potential for improving its energy
supply. With aspects such as environmental capacity and the developing condi-
tions of the country (due to rapid economic & social growth), China faces immense
demands in guaranteeing future energy supply.
However, development of EVs is significantly optimising and restructuring the energy
consumption. Due to development of EVs the USA is estimating to annually save
15% of its oil consumption year 2030, but with only an corresponding increased
electricity demand of about 5-6% (compared to a scenario with no EVs).
As may be seen in figure 2.13, China’s electricity production is at largest based on
thermal power, which is mainly coal.

Figure 2.13: China electricity production distribution.

24



2. Theory

Furthermore, Liu, Z. claims that the long-term emphasis of power generation and
to little regarding power supply, has resulted in imbalance of power grid and power
source development. The network structure is irrational and have a weak cross-
regional backbone network, resulting in a weak capacity to possible accidents and
severe natural disasters. In combination to the rapidly increasing demands, com-
plexity of external environment, and a large number of new generating units, Liu,
Z. states that "there is a real risk of widespread blackouts across power grids".

2.12 Energy Storage System
In the research of by Oberhofer, A. (2012) [23] it is stated that the amount of
electricity demanded in an electric grid by consumers must always be met with the
same level of electricity fed into the grid. This is necessary for preventing blackouts
and damage to the grid. Furthermore, the demand and consumption of electricity
in a electrical grid varies over hour, day and year.
In an article written by Faria et al. (2014) [24] they have analysed the electricity
power consumption of a typical Portuguese residence, for three work days (figure
2.14, diagram ’a’) and a weekend (figure 2.14, diagram ’b’).

Figure 2.14: Elecric power consumption for a residence for a) three work-
days, and b) a weekend (two days).

25



2. Theory

Moreover, Faria et al. states that it is not only private residences that have a high
variance in electricity consumption, the whole electricity grid have a high variance
over hour, day, month and year (due to electricity consumption). It can therefore be
difficult and costly to always met the electricity consumptions with the same level
of electricity fed into the grid.

According to Yong, J.Y. et al. (2015), the system cost for the electric grid can be
reduced up to 60% in a future controlled EV charging. In a controlled EV charging
system the charger only charges when it needs and when it does not create or add to
peak consumptions in the grid. Hence, distributing potential peaks, such as the ones
at some occasions occurs in the diagrams of figure 2.14. With more (fluctuating)
renewable energy (especially wind energy) the cost reduction would be even better.

Moreover, Yong, J.Y. et al. also describes another study that have been performed,
regarding investigation of what impact EV charging will have on the Germany’s
grid-load profile, in year 2030. In the case of all conventional internal combustion
engine vehicles (claimed to be 42 million) were to be replaced by EVs that charged
uncontrolled, then the peak load would be increased by about two times.

Another aspect and finding Yong, J.Y. et al. describes is that by using EVs for grid
stabilising storage’s a reduction of 16% on the maximum peak lead may be achieved.

According to Oberhofer, A. (2012) [23] there will be a great need in the future to
distribute the demanded electric power. The increasing share of wind and solar
generation of electricity creates a more fluctuating power generation and with less
stability. In order to deliver sufficient energy and power at specific times (according
to demands), the energy needs to be stored. Energy storage systems (ESSs) is a
technical solution that can store (electric) energy, and when needed make it available
to the grid.

By storing the energy the electricity consumption is not directly dependent to the
current electricity availability in the grid, only to what is stored in ESSs. Hence,
power which is not available in the grid may be available from the ESSs.

There are different kinds of ES technologies described by Oberhofer. Each ES tech-
nology have it respective strength and weaknesses, which makes them suitable for
different applications and usages. Some described ES technologies are:

• Li-ion batteries.

• Flywheels.

• Flow batteries.

• Superconductive magnetic energy storage (SMES).

• Compressed air energy storage (CAES).

The different technologies can typically be differentiated by their differences regard-
ing discharge duration (energy loss), and for which level of electrical power demand
application they are suitable for. This relation is presented in figure 2.15.

26



2. Theory

Figure 2.15: Comparison diagram of discharge duration versus rated
power for some energy storage technologies [25].

2.12.1 Li-ion batteries
Oberhofer, A. (2012) [23] describes that a Li-ion (or lithium-ion) battery is like
all batteries a device that through a chemical reaction produces electrical energy.
The chemical for li-ion batteries is lithium ions (just as the name suggests) but the
chemical compound, in which the lithium is contained, may vary between different
sorts of Li-ion technologies. The battery is divided into two sides or chambers -
anode and cathode. The chambers are separated by a separator, where only the
lithium ions may pass. By using external electrical energy, the lithium ions is drawn
to the anode (through the separator). When the battery is used/discharged the
lithium ions is instead drawn to the cathode, as the electrons moves from the anode
to the cathode.
The advantages (’+’) and disadvantages (’-’) listed for Li-ion batteries are:

+ The commercial battery with highest energy density, and a future with huge
potential.

+ Higher cell voltages (3.7V compared to 2.0V for lead-acid batteries).
+ Low energy losses (about 5 percent per month).
+ Resources available in large amounts (lithium and graphite).
− Expensive.
− Cells are ruined if completely discharged.
− Typical 5 years life-cycle (deteriorates even if unused).
− In contact with atmospheric moisture, lithium is flammable.

2.12.2 Flywheels
The principle of a flywheel is described by Oberhofer, A. (2012) [23] to be a disc
(wheel) with a defined mass is mounted on an axis. The axis is connected to an
(combined) electric motor and generator. By using the electric motor to set the
disc into rotation, the disc acquires a kinetic energy. The kinetic energy can then,
when desired, be transformed into electricity through the use of the generator. The
kinetic energy is dependent on the mass of the disc and its rotation speed.

27



2. Theory

The advantages (’+’) and disadvantages (’-’) listed for a flywheel are:

+ Long lifespan (up to 20 years) and low maintenance.
+ Almost no carbon emission.
+ Low response times.
+ Components and material are non-toxic.
− High cost for procurement.
− Relative low ES capacity.
− Self-discharges at a high rate (3-20 percent per hour).

2.12.3 Flow batteries
Oberhofer, A. (2012) [23] explains that there are different kinds of flow battery
technologies, two of them are redox-flow battery and sodium battery.
Redox-flow batteries are like conventional batteries (such as li-ion batteries), but
the electrolyte with the electrical charge may be replaced.
The advantages (’+’) and disadvantages (’-’) listed for Redox-Flow batteries are:

+ Possible to recharge by refuelling.
+ Long life span (about 40 years).
− Low energy density (35Wh/kg compared to<200Wh/kg for Li-ion).

The sodium, or the liquid sodium sulphur battery is still being developed. It has
relatively high energy density, long life span, high efficiency. Thou, it has some
disadvantages such as only operational at high temperatures, and liquid sodium
reacts easily with water in the atmosphere.
The advantages (’+’) and disadvantages (’-’) listed for Sodium batteries are:

+ High energy density (up to 240Wh/kg).
+ Long life span (10-15 years).
+ High efficiency (75-90 percent).
− High temperature needed to operate (around 350°C).
− Liquid sodium reacts in atmosphere.

2.12.4 Superconducting Magnetic Energy Storage (SMES)
In a SMES the energy is, according to Oberhofer, A. (2012) [23], stored as a elec-
tromagnetic field around a coil. In order to keep the field around the coil (without
great losses), the coil needs to be a superconductor. In theory the storage should
be loss-less (due to the superconductor phenomenon), but practically it is made at
an 90-95% efficiency.
The major problem and disadvantage of SMES is that current superconducting
materials are only superconductive below very low temperatures (less than -253°C).
However, superconductors functional at higher temperatures is being developed.

28



2. Theory

Nevertheless, the need to keep the superconducting material cold enough have a
high impact on the technology’s storage efficiency.
The advantages (’+’) and disadvantages (’-’) listed for SMES are:

+ Low respond times.
+ Able to discharge both partial and deeply.
+ No environmental threat.
− High self-discharge rate (about 12 percent per day).
− Very costly production and maintenance.
− Efficiency losses due to required cooling process.

2.12.5 Compressed air energy storage (CAES)

Oberhofer, A. (2012) [23] describes that the CAES technology stores energy by
compressing air into tanks or caves, and it is an CO2 neutral technology. Only two
CAES plants exists and are used in the world today. These plants were built for
25-30 years ago, indicating the long lifespan of the technology.
By using an electric compressor, air is compressed to about 60 bars and stored in
underground spaces (such as old salt caverns). The stored compressed air may then
be used to power turbines, which through generation produces electricity (when it
is demanded). However, the two major problems of CAES derives from compressing
and decompressing a gas (air). When the air is compressed heat is generated, which
if unused creates power loss. When the air is decompressed, it freezes material it
comes in contact with. Thus, the power turbines of a CAES needs to be heated
in order for not to freeze. The technology is still not mature, and a currently in
development plant in Germany tries to solve the great power losses (due to the two
mentioned major problems) by an "Advanced adiabatic"-CAES. Instead of letting the
heat generated from compressing air dissipate into the environment, heat exchangers
will transfer the heat to a thermal storage. This stored heat may then be used to
prevent the power turbines from freezing, when there is a demand of produce (return)
electricity again. With this advanced adiabatic technology, the CAES technology
may enable up to about 70% efficiency.
The advantages (’+’) and disadvantages (’-’) listed for CAES are:

+ Huge ES capacity.
+ Up to 70% efficiency (with heat exchanger for produced heat).
+ Low response time.
+ Very low cost for storing energy.
− Economical for storing energy up to one day.
− Requires sealed storage caverns.
− Competes against other needs of storage (natural gas, and hydrogen).
− The technology is not yet fully developed.

29



2. Theory

2.13 Reference EV-car specifications
As references for BEV and PHEV cars the Tesla Model S respectively VW Passat
GTE Plug-in Hybrid. Their specifications, as presented in table 2.7, where acquired
from the website ’laddaelbilen.se’ [26][27].

Table 2.7: Specifications on reference models of BEV respectively PHEV.

Reference models’ specifications
Car Tesla Model S

(BEV)
VW Passat GTE Plug-in
(PHEV)

Maximal Velocity 177-209 km/h 225 km/h,
130 km/h in E-Mode

Acceleration,
0-100 km/h 4.4 - 6.5s 7.6s

Battery type Lithium-ion Lithium-ion
Electric Engine <324 kW 85.5 kW
Combustion Engine 115.5 kW
Combined Engine
Power <324 kW 163 kW

Battery capacity 85 kWh 9.9 kWh
Battery Charging Mode 3 - 3.6 kW
Fast Charging Yes, 90 kW No
Electric Range 483km 50 km
Electricity
consumption ca 1.88 kWh per 10km 1.98 kWh per 10km

Fuel Consumption 2.0 l/100 km (NEDC)
Emissions, CO2 0 0 or 45 g/km
Length x Width x
Height 4970 x 1960 x 1430 [mm] 4767 x 1832 x 1477 [mm]

Weight (NB) 2180 kg 1665 kg
Battery Warrant 8 years 8 years/160 000 km

Price, basic/low
(in Sweden)

Ca 607 000 - 950 000 SEK
(+36 000 SEK in
"reservation fee"),
with subventions

Sedan from 409 900 SEK,
without subventions
Wagon from 419 900 SEK,
without subventions

2.14 Traditional charging connectors
Current charging for electric cars of today in Norway (a country with a large share
of EVs) is typically only based on wired solutions with different connectors and
respective charging power capability. The Norwegian electric car association [29]
and ’ladestasjoner.no’ [28] describes different charging connectors on their websites.
Two typical connectors are the Schuko and Type 2. These two connectors is used
as references for traditional charging connectors in this master thesis.

30



2. Theory

Schuko is the name of the standard connector for grounded home electronic devices
in countries such as Sweden and Norway. The Type 2 connector is made for charging
electric vehicles, and is common on charging poles of larger infrastructural charging
systems for electric cars, such as the one used in Norway.
Both connectors are for AC charging systems. While the Schuko typically allows
charging powers around 2.5kW (but a maximum of 3.6kW), the Type 2 connector
enables charging powers up to around 43kW.

2.15 EU regulations of drivers’ hours
From the ’European Union (EU) rules on drivers’ hours and working time - Simplified
guidance’ regarding the ’Regulation (EC)561/2006’ (2016) [30].
The guidlines are divided into the three aspects of Driving, Breaks, and Rest.
Driving

• 9 hour daily driving limit (can be increased to 10 hours twice a week).
• Maximum 56 hour weekly driving limit.
• Maximum 90 hour fortnightly driving limit.

Breaks
• 45 minutes break after 4.5 hours driving.
• A break can be split into two periods, the first being at least 15 minutes

and the second at least 30 minutes (which must be completed after 4.5 hours
driving).

Rest
• 11 hour daily rest; which can be reduced to 9 hours no more than three times

a week (or split into 3 hours + 9 hours as often as desired).
• 45 hours weekly rest, which can be reduced to 24 hours, provided at least

one full rest is taken in any fortnight. There should be no more than six
consecutive 24 hour periods between weekly rests.

31



2. Theory

32



3
Method

The method that this project was based on is the PDM described by Ulrich, K. &
Eppinger, S, (2012)[2]. Extensive work had to be performed in order to interpret
their methodology into a suitable process for this project.
This interpretation and process planning was created in the first phase - ’Planning
& Opportunities’ (corresponds to Ulrich & Eppingers described ’phase 0’). Further-
more, the other phases, which the process is divided into in the method used, is
’Concept development’, ’System-level design’, and ’Detailed design’, which corre-
sponds to Ulrich & Eppingers ’phase 1’, ’phase 2’, respective ’phase 3’.

3.1 Planning & Opportunities
The planning phase of the project started with an preliminary project scope, -
definition, and expected deliveries. The main methodology were decided to be a
product development methodology. Due to earlier experiences and practising the
methodology described in the book ’Product Design and Development’ by Ulrich,
K. & Eppinger, S. (2012) [2] were chosen for this project.
The methodology of Ulrich & Eppinger describes a general methodology for a com-
plete product development process in a company. Aspects of how an organisation
could set up a strategy, project teams, find opportunities, and prioritise project
is some of the aspects they include in the planning phase. As the project were
proposed by the company CEVT, assumptions were made that some of the initial
planning phase tasks had already been performed. Furthermore, this project is a
master thesis project performed by one student. Therefor, the planning phase of
this project have been narrowed down to consist of following tasks, where 7.1 & 7.2
are the deliveries (illustrated in figure 3.1):

1. Research market & technology.
2. Reflect upon possible technological developments.
3. Define possible opportunity.
4. Forming of initial plans.
5. Initial system boundary.
6. Analyse the findings.
7.1. Define a project mission statement.

• Product description.
• Benefit proposal.
• Key business goals.
• Primary market.

33



3. Method

• Secondary market.
• Assumptions & Constraints.
• Stakeholders.
• Technological trajectory.

7.2. Set final Gantt & Detail plans.

1. 2. 3 4. 5. 6

7.1.

7.2.

Figure 3.1: Precedence diagram of Phase 0 - Planning

3.1.1 Research market & technology
The initial scope of the project was ’wireless charging for electric cars’, and thus
’research market & technology’ was focused on exploring and gather information
regarding current market and technologies for that scope. Relevant technologies
and existing solutions were researched and documented to help further research.
In general the databases search tool of Summon and Xplore (IEEE) were used for
searching articles and data, while free searching and browsing of the Internet were
used for probing.
Further research were to be made during the whole project, if necessary, but the
important part taking place at this stage.

3.1.2 Technological trajectory & Opportunities
When sufficient data had been acquired, regarding market, and technological- &
technical solutions, a ’2. Reflection upon possible technological developments’ was
made in order to ’3. Define possible opportunity’. The opportunities gave an sug-
gestion of what the project should deliver in order for it to be successful.

3.1.3 Initial plans & System boundary
When the opportunities had been identified and an initial understanding of the
projects content and extent had been understood, it continued with the ’4. Forming
of initial plans’. A Gantt chart was created for the overall project plan along with
precedence diagrams for the different phases of the product development process.
An ’5. Initial system boundary’ for the system were then defined.

3.1.4 Analyse findings & Define mission statement
By ’6. Analyse the findings’ of all previous steps enough data could be concluded
to ’7.1. Define a project mission statement’. The project mission statement was

34



3. Method

expressed to answer the areas defined in the list defined for step 7.1.

3.1.5 Set final plans
With the project mission statement set, adjustments were made in the plans to ’7.2.
Set final Gantt & Detail plans’.
Furthermore, the outcome of the planning phase was also a change in scope and aim
of the project, from ’wireless charging for electric vehicles’ to ’convenient charging
system for BEVs and PHEVs.

3.2 Concept Development

The concept development phase had the following process (may be seen in figure 3.2):

1.1. Define market & stakeholders.
1.2. Explore market & competitive products.
1.3. Identify needs.
2. Set target product criteria.
3. Establish a initial system boundary.
4. Concept generation.
5. Concept screening.
6. Concept scoring.
7. Concept testing/review.
8. First concept selection.
9. Analyse the concept(s) selected with respect to the identified system..

1.2.

1.1.

1.3.

2. 3. 4. 5. 6. 7. 8. 9.

Figure 3.2: Precedence diagram of Phase 1 - Concept Development

3.2.1 Market, stakeholders, & Competitive products
The project mission statement from the end of the planning phase was thoroughly
reviewed and the market, stakeholders and competitive products were initially un-
derstood and -defined before the needs in the market and for the stakeholders were
to be identified.

35



3. Method

3.2.2 Identify needs
The data collection method for identifying the needs were secondary research, one
survey, and three semi-structured interviews.
When the data of needs had been collected, it was reviewed and interesting find-
ings and answers was individually formulated in a list of ’customer statements’. A
’interpreted need’ was formulated for each respectively ’customer statement’. The
’interpreted needs’ list was reviewed and similar needs was combined, in order to
create the final ’customer needs list’.
In order to create a ’metrics list’, metrics were created for each respectively need. As
for the previous refinement of the needs list, the metric formulations were reviewed
and similar metrics were combined. Thus one metric could represent more than
one need. When each need had a respectively metric, the measurable unit for each
respectively metric was defined. These measurable units could be subjective, yes/no,
compared to listed data/values, or a physical unit. The metrics list was complete
when all metrics had measurable units.

3.2.3 Set target product criteria
Next step was the creation of a ’target product specifications list’. A target product
specifications list is created by setting initial target values for each respectively
metric (in its respective unit). However, due to time constraints, sufficient research
was concluded to not be possible. Instead, the metric list was decided to be sufficient
to use instead of the target product specification, but then referred to as ’target
product criteria’.

3.2.4 Establish a initial system boundary
With the acquired understanding of problem and target product criteria, next step
was to establish an ’initial system boundary’. The system boundary is a schematic
and drawing of the essential parts that the system solution has been identified to
have. The system boundary were to be reviewed and redefined at later stages in the
process. The importance of the initial system boundary was to support the concept
generation, concept screening, concept scoring, and concept testing.

3.2.5 Concept generation

Figure 3.3: Pic-
ture of a page in the
project book.

From the initial start of the project every idea that were had,
was instantly documented in a project book (see figure 3.3.
Therefor, some concepts did already exist before the planned
concept generation process were initiated. In order to gen-
erate more concepts, the already generated concepts were
categorised with an affinity diagram. The diagram’s cate-
gories were created with considerations to the current iden-
tified system boundary. One 20 minutes brainstorming for
each respectively category was performed to generate more
concepts.

36



3. Method

3.2.6 Concept screening
When concepts had been generated they were screened with ’selection matrices’.
The concepts had through the affinity diagram been divided into the three separate
screening categories
The selection criteria were defined through finding suitable areas and aspects for
satisfying all the identified needs in the needs list.
For each respective concept category the same full system reference was used.
The concepts were screened and ’graded’ as ’Develop’, ’Not Develop’, and ’Combine’.
A ’not develop’-graded concept could also be marked as interesting, if it had potential
to be interesting at later stages or for discussion.

3.2.7 Concept scoring, -testing, & first concept selection
The concepts that passed the concept screening were analysed, refined, and divided
into the functional groups (categories) Standard Charger, Robot Charger, Super-
charger, Emergency Charger, Alignment, and Energy Storage System.

3.2.7.1 Defining a developed system boundary

With these new functional groups along with the growing understanding of the
problem (partly due to continued secondary research), a new ’developed system
boundary’ was defined. This new system boundary was an important support to
further concept development processes.

3.2.7.2 Morphological solutions

In order to move from sub-system concepts to full system concepts a morphological
matrix with the six different functional groups was created. In total seven full system
concepts were morphologically created at this stage.

3.2.7.3 First concept-scoring matrix

In order to score these full system concepts a concept-scoring matrix was created.
The selection criteria of the matrix were created from the target product criteria.
In comparison to the selection matrix (during the concept screening) these selection
criteria were more detailed, larger in number, and also weighted.
The different weights were established by first give the same weight to all criteria.
Then subjective analysing of all collected and researched data in combination with
the identified system boundary, allowed for increase the weight for the more impor-
tant criteria, and thus have to decrease the weight from the least important criteria.
This ended when a the weighting were considered good.
All of the full-system concepts were compared and scored in relation to a reference
concept. The four concepts with highest total scores were then analysed.
To analyse the four full-system concepts, each specific criteria scores, for all concepts
together, were used for calculation of average and maximal score results. The criteria
scores’ results between the average score and halfway up to the highest score were
colour-graded in a white to green scale, where highest score were the most green

37



3. Method

colour. The score results higher than the colour range also had the most green colour.
This enabled to visually see the criteria that (with weight) made the different full-
system concept good.
The four full-system concepts were then one-by-one (and as a whole) compared
and analysed with the help of the colour grading. Each one of the four full-system
concept was graded according to ’Develop’, ’Combine’, ’Analyse’, and ’Not-Develop’.
The Develop, Combine, and Analyse concepts were used to, with iterations from
the morphological matrix, create one new single best full-system concept. This
new full-system concept had (after the allowed iterations) the highest scores in the
concept-scoring matrix, and when that happened also appointed as the (initial) first
concept selection, but to be reviewed.

3.2.8 Review of first concept selection
In order to test assumptions, ideas, and the first concept selection, a field-trip to
Oslo (Norway) was performed as well as participation in a seminar-day called ’Kraft-
forum’, Gothenburg.
Oslo is commonly known to have a relatively large proportion of BEV and support-
ing infrastructure. It was an two days field-trip, made by travelling in an PHEV
(VW Passat Plug-in, see reference cars chapter 2.13). In Oslo, visits and unstruc-
tured interviews were made with first the municipal (and person responsible for
the charging infrastructures), and then with an representative of ’The Norwegian
Electric Vehicle Association’.
The field-trip gave an increasingly understanding that both strengthened and dis-
mantled some of the thoughts and ideas.
At the seminar-day ’Kraftforum’, representatives from Swedish companies and uni-
versities, with interests of the future electricity grid and users of it (for instance
EV users), participated. The seminar-day was interesting and gave a further deeper
understanding, strengthening the ideas and findings from the field-trip.
The ideas and findings from the field-trip to Oslo and the participation at ’Kraft-
forum’ were concluded and documented into a brief report. This report in addition
to analysing the concepts previously marked as ’develop’, ’combine’ and ’analyse’,
led to the creation of a new full-system concept - the review concept. This new
full-system concept was compared to the (initial) first concept selection by inserting
it into the final concept-scoring matrix.
The best concept in this final concept-scoring matrix was chosen as the (final) first
concept selection. The system boundary was reviewed according to the (final) first
concept selection, which led to the creation/establishing of the ’final system bound-
ary’.

3.3 System-Level Design
When the concept development phase was concluded and both a first concept se-
lection as well as a final system boundary were set, the system-level design phase
began. The process of the system-level design phase were as follow:

38



3. Method

1. Set final product specifications.
2. Establish product architecture.

• Create a schematic of the product.
• Cluster the elements of the schematic.
• Create a rough geometric layout.
• Identify cluster interaction.
• Platform planning - differentiation & commonality.

3.1. Develop industrial design.
3.2. Design for environment.
4. Begin prototype development.

1. 2.

3.1.

3.2.

4.

Figure 3.4: Precedence diagram of Phase 2 - System-Level Design

3.3.1 Final product specifications
The system-level design phase started with setting the final product specifications.
This was performed by consider the first concept selection (outcome of the concept
development phase), final system boundary, user needs, target product criteria, as
well as researched constraints and feasibility’s.

3.3.2 Product Architecture
The process of creating a product architecture began with creating an initial schematic
of elements, of the system. The schematic was based on the identified system (final
system boundary) and first concept selection.
The elements of the schematic were then clustered and made into an initial cluster
design. The initial cluster design were reviewed and refined in a rough geometri-
cal layout. With a rough geometrical layout the respectively cluster’s interactions
could be better understood, identified and combined. However, it was decided to
be to time-consuming to create a full geometrical layout for the whole product ar-
chitecture. Therefore, only a rough geometrical layout, which was enough to show
the interface principles to the car, was created for the final product architecture.
In order to complete the establishing of a product architecture, a short descriptive
text were written about the platform and modularisation aspects of the product
architecture.

3.3.3 Industrial Design
After a product architecture had been established an industrial design were cre-
ated. While creating the industrial design considerations were also made regarding

39



3. Method

the aspects of environmental, manufacturability, and robust design. As defined in
the introduction the industrial design was not to be comprehensive, due to lim-
ited project resources. Thus, no cost figures were calculated and can be presented.
Decisions was based on subjective estimations with limited research data.

3.3.4 Prototype Development
In order to enriching and support the drawings of the industrial design, simple CAD
drawings of the ’standard charger’ and ’destination charger’ were created.

40



3. Method

3.4 Detailed design
The detailed design phase has the following process (may be seen in figure 3.5):

1. Final concept selection.
2. Complete industrial design.
4.1. Assess environmental impact.
4.2. Assess Convenience
5. Overall assessment.
6. (Eventually) Refinement.
7. Complete specification.
8. Finale delivery.

1. 2.

3.1.

3.2.

4. 5. 6. 7.

Figure 3.5: Precedence diagram of Phase 3 - Detailed Design

Due to time limitations and satisfaction with the development of the concept through-
out the industrial design and prototype development, the decision was made that the
current concept solution would be sufficient as a ’final concept selection’. Therefore,
the detailed design phase started with the industrial design and the final concept
selection consisted of the stages of industrial design and prototype development.
Furthermore, the part geometry were also to be based on the industrial design and
prototype development.
After a industrial design had been created, assessments were done in the areas
environmental impact and convenience.
The findings of the assessments resulted in minor redef