Holistic Method of Thermal Management Development Illustrated by the Example of the Traction Battery for an Electric Vehicle

Transcription

1 20 th Aachen Colloquium Automobile and Engine Technology 10 th 12 th October 2011 Holistic Method of Thermal Management Development Illustrated by the Example of the Traction Battery for an Electric Vehicle Aachen, 12. October 2011 Dipl.-Ing. Peter Jeck Institut für Kraftfahrzeuge RWTH Aachen University Slide Nr. 1

2 Agenda Motivation Holistic Method (modelling principle) Exemplary applications Thermal behaviour of different battery design approaches Control strategies for battery preheating Summary Slide Nr. 2

3 Motivation Shuichi Nishimura, Nissan Motor Company Current chaos of technologies has to be well managed 20 th Aachen Colloquium Automobile and Engine Technology Slide Nr. 3

4 Introduction Motivation Higher number of new components Substitution of the combustion engine Challenge between climatisation and range Different operating temperatures (heat recovery) 20 C 120 C Decentralised package Anode Increasing efficiency by electrification the power train Higher overall system complexity Alternative climatisation strategies (heat pump) Alternative technologies Holistic development / simulation tool is necessary Slide Nr. 4

5 Agenda Motivation Holistic Method (modelling principle) Exemplary applications Thermal behaviour of different battery design approaches Control strategies for battery preheating Summary Slide Nr. 5

6 Modelling principle 1. vehicle level 1. vehicle level AC / heat pump Power supply Passenger cabin Power train (including longitudinal dynamics) Cooling circles Combines all vehicle submodels Definition of global boundary conditions driving cycle route profile ambient conditions, initial conditions Slide Nr. 6

7 Modelling principle 2. energy flow level 2. energy flow level HV battery tunnel HV battery rear control unit e -pump Combines all component models Definition of circuit respectively control loops mechanics (power train, lungitudinal dynamics) thermal (AC, heat pump, cooling circuits) electrics (high voltage and low voltage power supply) Slide Nr. 7

8 Modelling principle 2. energy flow level simulation example 2. energy flow level Slide Nr. 8

9 Modelling principle 3. component level 3. component level Combines all component sub-models mechanics (e.g. power loss calculation) thermal (heat flows via a 3D-disceret volume model) electrics (e.g. cell characteristics) signals (component internal control units) Slide Nr. 9

10 Modelling principle 4. physical base level 4. physical base level cell volume element Describes all physical laws differential energy and mass balance differential linear force and torque balance material properties Slide Nr. 10

11 Agenda Motivation Holistic Method (modelling principle) Exemplary applications Thermal behaviour of different battery design approaches Control strategies for battery preheating Summary Slide Nr. 11

12 Exemplary applications Vehicle information 1. Thermal behavior of different battery design approaches. 2. Control strategies for battery preheating. vehicle information: vehicle class vehicle mass two seated sports car 1400 kg electric machine 1 x ASM: 45 kw, 172 Nm (peak performance) 2 x PMSM: 45 kw, 150 Nm (peak performance) battery system type of cells number of cells performance energy content mass Li-Ion-Cell 2080 cells (tunnel battery) / 3120 cells (rear battery) appr. 220 kw appr. 42 kwh appr. 310 kg Slide Nr. 12

13 Exemplary applications Requirements and limits requirements deformable and energy absorbing battery system low overall system weight low installation space thermal requirements / limits maximum operating temperatures < 40 C maximum axial cell temperature gradient maximum temperature difference between two cells < 4 K < 4 K minimum cell temperature for charging 5 C Slide Nr. 13

14 Exemplary application I Influences of different design approaches energy flow level component level base level heat exchanger chiller heater cell t wall tube Variations: material of the cell reinforcement to improve battery crash safety (foam, aluminum, copper) thickness of the reinforcement (0,5 mm up to 2,5 mm) Assumptions: thermal equilibrium at the beginning starting temperature is 25 C adiabatic battery system behavior thermal contact of the cells only via the cooling plate Slide Nr. 14 cooling plate cell distance

15 Influence of different design approaches Maximum temperatures & temperature differences maximum average cell maximum average cell temperature [ C] temperature [ C] speed foam 2 mm aluminium 2 mm time [s] speed [km/h] speed [km/h] maximum temperature difference [K] 3 2,5 2 1,5 1 0, foam T axial foam T cell aluminium T axial aluminium T cell Slide Nr. 15 time [s]

16 Influence of different design approaches Multi-criteria analysis maximum average cell temperature [ C] 36,0 35,0 34,0 33,0 32,0 0,5 mm* 2,5 mm* 0,5 mm 0,5 mm 2,5 mm 2,5 mm tube mass [g] axial cell temperature difference [K] 3,00 2,50 2,00 1,50 1,00 0,50 0,00 0,5 mm* 2,5 mm* 0,5 mm 0,5 mm foam aluminium copper 2,5 mm foam aluminium copper Slide Nr. 16 2,5 mm tube mass [g]

17 Agenda Motivation Holistic Method (modelling principle) Exemplary applications Thermal behaviour of different battery design approaches Control strategies for battery preheating Summary Slide Nr. 17

18 Exemplary application II Battery preheating strategies / opposite effects 1. Could a realistic drive cycle be driven without preheating? 2. If not which preheat temperature should be chosen to get a good compromise between potential start time vehicle performance overall energy demand criteria low (preheat) high (preheat) temperature temperature battery / vehicle performance internal cell resistance / battery losses recuperation potential energy demand for heating period potential start time surplus power energy demand start time Slide Nr. 18

19 Exemplary application II Battery preheating strategies energy flow level component level 5 kw T min control unit HV battery tunnel HV battery rear base level e -pump Variations: switch off temperature of the coolant heater (from -15 C up to +25 C) Assumptions: strong winter scenario, starting temperature is -20 C thermal equilibrium at the beginning adiabatic battery system behavior (form is used for the reinforcement) Slide Nr. 19

20 Without battery preheating T start = -20 C temperature [ C] tunnel max tunnel min rear max rear min coolant at heater drive recuperation cycle aborted possible power [kw] speed power demand max discharge power time [s] speed [km/h] Slide Nr. 20

21 Battery preheating T heater,off = -5 C temperature [ C] tunnel max tunnel min rear max rear min coolant at heater highway recuperation drive cycle driving heater possible finished cycle disabled start power [kw] speed power demand max discharge power Slide Nr. 21 average surplus power time [s] speed [km/h]

22 Battery preheating T heater,off = 20 C temperature [ C] power [kw] tunnel max tunnel min rear max rear min coolant at heater highway driving cycles driving heater finished cycle disabled start speed power demand max discharge power time [s] Slide Nr. 22 average surplus power speed [km/h]

23 Battery preheating Multi-criteria analysis related average surplus power [kw] C 0 C 5 C 10 C 15 C 20 C 25 C related energy demand [kwh] 0,50 0,25 0,00-0,25-0,50-0,75-1,00 25 C -5 C 20 C 15 C 0 C 10 C 5 C related start time [min] Slide Nr. 23

24 Agenda Motivation Holistic Method (modelling principle) Exemplary applications Thermal behaviour of different battery design approaches Control strategies for battery preheating Summary Slide Nr. 24

25 Summary Increasing overall system complexity Holistic simulation tool is necessary Simulation of mechanical, electrical and thermal energy flows Support the design process (e.g. functional or structural development) Flexible holistic support tool is been developed at ika/fka Exemplary applications demonstrate the benefit of the holistic approach Slide Nr. 25

26 Thank you for your attention. Many thanks also to all team members of the project eperformance Slide Nr. 26

27 Contact Dipl.-Ing. Peter Jeck Institut für Kraftfahrzeuge RWTH Aachen University Steinbachstraße Aachen Germany Phone Fax Internet jeck@ika.rwth-aachen.de Slide Nr. 27