2012 IEEE Vehicle Power and Propulsion Conference Session GC5 – Energy and Power Management for xEVs Study on Power and Energy Demand for Sizing the Energy Storage Systems for Electrified Local Public Transport Buses Philipp Sinhuber 1,3, Werner Rohlfs 1,3, Dirk Uwe Sauer 1,2,3 1 Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA), RWTH Aachen University, Germany 2 Institute for Power Generation and Storage Systems (PGS), E.ON ERC, RWTH Aachen University, Germany 3 Jülich Aachen Research Alliance, JARA-Energy, Germany

■Recently in German media: Battery buses with astonishingly low energy consumption figures: □< 1 kWh/km □> 250 km driving range Motivation Philipp Sinhuber10/10/20122 Sources: Entire day without charging - most important for battery size, weight and costs:  Energy consumption

Other concepts Philipp Sinhuber Source: Source: PVI Source: Conductix-Wampfler Battery exchange Drive Charging station Battery Fast charge 10/10/ Charging during the day - most important for battery size, weight and costs:  Energy consumption

■How much energy does a battery bus consume? ■Size of the battery? 1.Extract characteristics of 5 representative bus lines from internet mapping services □Track (distance), Elevation 2.Use vehicle model to simulate relative energy consumption in kWh/km □driving resistances, model of regenerative braking 3.Apply consumption figures to 100 German bus lines along 2 scenarios: □Charging over night □Fast charge at both terminal stops 4.Evaluation of required battery size Approach of the study Philipp Sinhuber10/10/20124

■18.5 m bus, 21 tons (empty) ■240 kW traction machine ■150 kW fuel cell system ■Supercaps and NiMH battery ■Partners: □Operator: Regionalverkehr Köln (RVK) □Manufacturer: APTS (Netherlands) □Suppliers: Vossloh-Kiepe, Hoppecke □Academic partners: Cologne University of Applied Sciences – IA, RWTH Aachen University - ISEA ■The project is supported by: Verification data from project “H 2 -Bus-NRW“ Philipp Sinhuber10/10/20125 Source: APTS

■Simulation model and extraction of route characteristics ■Verification of modeling approach ■Results and discussion of battery size Outline Philipp Sinhuber10/10/20126

■Simulation model and extraction of route characteristics ■Verification of modeling approach ■Results and discussion of battery size Outline Philipp Sinhuber10/10/20127

Simulation model Philipp Sinhuber10/10/2012 Vehicle model Driving resistances Regen. braking El. machine & inverter Route characteristics P mech P el Driver v ref T ref Battery and battery converter 8

Simulation model Philipp Sinhuber10/10/2012 Vehicle model Driving resistances Regen. braking El. machine & inverter Route characteristics P mech P el Driver v ref T ref Battery and battery converter Reads in actual speed and route characteristics: GPS and elevation data (from internet mapping services) Speed limit Position of bus stops Returns: Reference speed (speed limit, v ref ) Slope Actual position on bus route 9

Simulation model Philipp Sinhuber10/10/2012 Vehicle model Driving resistances Regen. braking El. machine & inverter Route characteristics Driver Battery and battery converter Decides between acceleration and braking Tries to reach speed limit (v ref ) Reduces speed in turns / bends Stops vehicle at bus stops Returns reference torque (T ref ) P mech P el v ref T ref 10

Simulation model Philipp Sinhuber10/10/2012 Vehicle model Driving resistances Regen. braking El. machine & inverter Route characteristics Driver Battery and battery converter Driving resistances follow well-known equations: Less important at typical bus speed Mass is most important for energy consumption P mech P el v ref T ref 11

Simulation model Philipp Sinhuber10/10/2012 Vehicle model Driving resistances Regen. braking El. machine & inverter Route characteristics Driver Battery and battery converter Modelled as efficiency factors only, in total: 80%…90% P mech P el v ref T ref 12

Simulation model Philipp Sinhuber10/10/2012 Vehicle model Driving resistances Regen. braking El. machine & inverter Route characteristics Driver Battery and battery converter Required traction power: P el P mech P el v ref T ref 13

Simulation model Philipp Sinhuber10/10/2012 Vehicle model Driving resistances Regen. braking El. machine & inverter Route characteristics P mech P el Driver v ref T ref Battery and battery converter 14

Bus line – route characteristics Philipp Sinhuber10/10/2012 Source: Google maps ■Waypoint title  manual entry of: □Speed limit □Bus stops □…□… ■Tracks □GPS data □Clipping to course of street ■Extraction to gpx via kml file format 15

Bus line – route characteristics Philipp Sinhuber10/10/2012 Source: Google maps ■Example here: bus line no. 13, city of Aachen, Germany □Bus stop “Eurogress“ □Speed limit set to 50 km/h ■In addition: “GPSvizualizer“ provides elevation data from □NASAs Shuttle Radar Topography Mission (SRTM) □National Elevation Dataset (NED) of the U.S. Geological Survey 16

Verification of bus line model Philipp Sinhuber10/10/ Bus stop / traffic light / … (manual entry)

Verification of bus line model Philipp Sinhuber10/10/ Bus stop / traffic light / … (manual entry)

Verification of bus line model Philipp Sinhuber10/10/201219

Verification of bus line model Philipp Sinhuber10/10/ Energy consumption - here: difference < 5%

■Simulation model and extraction of route characteristics ■Verification of modeling approach ■Results and discussion of battery size Outline Philipp Sinhuber10/10/201221

Selected German bus lines Philipp Sinhuber10/10/201222

Results – energy consumption Philipp Sinhuber10/10/201223

■Traction energy from vehicle simulation □1.6 kWh/km ≤... ≤ 2.1 kWh/km □Most important: vehicle weight □Smaller vehicles (12 m bus)  scaling by kWh/km per ton □Meeting the claim: consumption of 1 kWh/km  approx tons (including passengers!)  not possible with a battery of 2 tons weight! ■In addition: auxiliary devices □AC / heating, steering assist, lights, compressors, cooling of components, … □Assumptions here:  Winter / summer: 21 kW (continous consumption) □  0.4 kWh/km ≤... ≤ 1.3 kWh/km (depending on travel speed and amb. temp.) Results – energy consumption – 18 m bus Philipp Sinhuber10/10/201224

Total energy consumption - scenarios Philipp Sinhuber10/10/2012 ■Scenario A – “charging at both terminal stops“ □Driving scenario:one direction of bus line □Vehicle mass:28 tons (maximum passenger load) □Auxiliries:21 kW continous consumption (winter or summer day) ■Scenario B – “charging over night“ □Driving scenario:eight hours operation day □Vehicle mass:25 tons (increased, but not maximum passenger load) □Auxiliries:21 kW continous consumption (winter or summer day) 25 City

Total energy consumption - scenarios Philipp Sinhuber10/10/2012 ■Scenario A – “charging at both terminal stops“ □Driving scenario:one direction of bus line □Vehicle mass:28 tons (maximum passenger load) □Auxiliries:21 kW (winter or summer day) 26 City

Total energy consumption - scenarios Philipp Sinhuber10/10/2012 ■Scenario B – “charging over night“ □Driving scenario:eight hours operation day □Vehicle mass:25 tons (increased, but not maximum passenger load) □Auxiliries:21 kW (winter or summer day) 27

Discussion of battery size – 18 m bus Philipp Sinhuber10/10/2012 ■Scenario A – “charging at both terminal stops“ □Assumption for battery system:  80 Wh/kg  700 $/kWh  Depth of cycling: 80 %  to cover 33 % of the bus lines: 50 kWh625 kg35,000 $  to cover 85 % of the bus lines: 87.5 kWh1.1 tons61,000 $ 28 (LiIon high power cell, active cooling necessary) City

Discussion of battery size – 18m bus Philipp Sinhuber10/10/2012 ■Scenario B – “charging over night“ □Assumption for battery system:  160 Wh/kg  350 $/kWh  Depth of cycling: 80 %  Minimum: 500 kWh3.1 tons175,000 $  to cover 85 % of the bus lines: 625 kWh3.9 tons219,000 $ (LiIon high energy cell, no active cooling necessary) 29

Conclusion Philipp Sinhuber10/10/2012 ■Energy consumption is most important for sizing the battery system ■Internet mapping data  extraction of route charactersitics ■Energy consumption ranges from 2.1 to 3.4 kWh/km (18 m bus) (factor 0.67 for 12m bus) ■Battery size – “charging over night“: □> 500 kWh,> 3.1 tons,> 175,000 $ □“Almost feasible“, battery mass and price are challenging ■Battery size – “fast charge at terminal stops“: □Cost and weight reduction by factor 4 □but additional infrastructural costs, less flexible ■Not considered here: battery aging could influence necessary battery size! 30

2012 IEEE Vehicle Power and Propulsion Conference Session GC5 – Energy and Power Management for xEVs Study on Power and Energy Demand for Sizing the Energy Storage Systems for Electrified Local Public Transport Buses Philipp Sinhuber 1 Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA), RWTH Aachen University, Germany 2 Institute for Power Generation and Storage Systems (PGS), E.ON ERC, RWTH Aachen University, Germany 3 Jülich Aachen Research Alliance, JARA-Energy, Germany Thank you very much for your attention!

Verification of vehicle model Philipp Sinhuber10/10/2012 ■Good results in general ■Deviation due to different positions of simulation and measurement Vehicle model Driving resistances Regen. braking 32

Selected German bus lines Philipp Sinhuber10/10/201233

Discussion of battery size Philipp Sinhuber10/10/2012 Values at “cell level“! 34