Stirling machine as auxiliary power unit for range extender hybrid electric vehicles

Transcription

1 Stirling machine as auxiliary power unit for range extender hybrid electric vehicles Sylvie BEGOT, Steve DJETEL, François LANZETTA Femto st Wissam BOU NADER Groupe PSA

2 Context and short term solutions ICE efficiency 130g CO2/km 95g CO2/km 80g CO2/km -37,5% 59g CO2/km aerodynamic Energetic demands Thermal energetic needs CO2 emission fuel consumption Powertrain & EMS Problematic arises for post 2025 due to more stringent reglementation regarding CO2 emissions Auxiliaries consumption weight Rolling resistancce CAFE = Corporate Average Fuel Economy / ICE=Internal Combustion engine / EMS = Energy Management Strategy 2

3 Internal Combustion Engine (ICE) powertrains main problematics ICE Max efficiency Split cycle Gas-Turbine Combined cycle Stirling ICE multi-fuel compatibility! Confort thermal energetic needs Solid combution E-fuel Hydrogen Bio-fuel 3

4 On the other hand ongoing development of Battery Electric Vehicles (BEV) Tesla Renault Zoe Citroën C0 Benefit of Zero Vehicle Emission (Tank to wheel emissions!!!) 4

5 Electric Motor However, BEVs present many drawbacks Large battery capacities for long autonomy range: Additional weight Thermal confort such as heating is not free compared to thermal based powertrains CO2 emission (well to wheel analysis) depends on the electricity production Geopolitical problematic for European automotive manufacturers Cost for the customer >100kW.h (500km) ( 600kg) Driver performance request Vehicle Controller APU Controller SOC Battery DC AC Traction/brake recovery command Hydraulic brake command Brake Wheel BEV = Battery Electric Vehicle 5

6 Range Extender powertrain seems to be a comprimise Powertrain and energy cost ( ) (15.000km /year/10 years) Electric Generator Electric Motor Tax Other Energy Electrical Energy Engine / APU Battery E-motor Reductor >100kW.h (500km) ( 600kg) 10kW.h (50km) ( 150kg) Driver performance request Vehicle Controller APU Controller SOC Battery DC AC Traction/brake recovery command Hydraulic brake command ICE REX SHEV BEV ZEV mode compared to ICE Low emission compared to ICE Cost compared to BEV and FCV Vehicle weight compared to BEV Fun to drive (such as BEV) FCV Auxiliary Power Unit (APU) Energy Converter Different energy converters with different thermodynamic configurations can be envisaged Wheel Brake BEV = Battery Electric Vehicle, FCV = Fuel Cell Vehicle, REX = Range Extender Vehicle, SHEV = Series Hybrid Electric Vehicle, ZEV = Zero Emission Vehilce 6

7 State of the art Energy converters for automotive application Conventional Non Conventional ICE Gas Turbine Rankine Stirling TA PEM Fuel Cell Split Cycle CCGT ECGT Ericsson TEG SOFC Internal Combustion External Combustion Electro Chemical Mature technology for automotive applications Mature technology for nonautomotive applications Non-mature technology CCGT = Combined cycle Gas Turbine TA = Thermoacoustic TEG = Thermoelectric Generator ECGT=External Combustion Gas-Turbine PEM = Proton Exchange Membrane SOFC = Solid Oxide Fuel Cell 7

8 Early development of Stirling machine for automotive applications Ford Torino Chevrolet Celebrity Opel Kadet Automotive intrinstic benefits: Multi-fuel capability, good thermal efficiency, high torque at low speed, silent operation, low vibration. Many reasons hindered their deployments: Leakage, controllability, Investment costs, and particularly the simplicity and price of the ICE at that time 8

9 Today with CO2 and emissions topics, Stirling for automotive applications gain interest Development of Series Hybrid Electric Vehicles (SHEV) : o efficiently operation under all driving cycle o quasi-stable operating state: reduce control complexity External combustion machine - Emission reduction through: o Choice of fuel and continuous combustion Development of magnetic coupling systems: o Complete sealing to avoid working fluid leakages Material advancement to reach higher temperature and pressure: o Higher thermodynamic cycle efficiency and higher power density 9

10 Electric Generator Electric Motor APU ON/OFF Energetic needs Power (W) Velocity (km/h) Target of this work WLTC cycle Time (s) Driver performance request Vehicle Controller SOC APU Controller Battery Traction/brake recovery command Hydraulic brake command AC Auxiliaries Cabine heating AC DC DC AC Stirling machine Brake Vehicle Criteria: fuel consumption Requirements: Acceleration, Max speed, gradability Constraints: Weight, Size, Frontal surface Auxiliary Power Unit (APU) Cogeneration machine for automotive applications Wheel 10

11 P 3 Stirling cycle - Theory P 3 T T H 3 4 V Q R Q H Q R 2 Q L 4 1 V Q R 2 T L 1 S Robert Stirling (1816) Stirling engines External heat supply Closed cycle Regenerative engine Hot air engine Ideal Stirling Cycle 2 isothermal transformations Expansion 3-4 Compression isochoric transfromations Heating 2-3 Cooling

12 Configuration Mechanical configuration : Beta One cylinder with 2 pistons Work piston : compression and expansion Displacer piston : no work done, moves the gas from the expansion space to the compression space Proto Femto 300 W Beta Cycle moteur Cycle frigorifique

13 Designed prototype characteristics Engine characteristics Beta type Working gas Pressure Power Generator Power piston diameter Compression swept volume Hot temperature Cold temperature Single cylinder Nitrogen 60 x 10 5 Pa 12 kw 3 phase 10-1 m 4.5 x 10-4 m K 337 K Efficiency (target) 39 % Frequency 35 Hz PV Diagram from isothermal analysis (Schmidt)

14 Designed prototype characteristics First tests : engine is driven by an electric drive asynchronous engine Inverter Reduced pressure 15 bar instead of 60 bar Reversed cycle : heat pump or refrigerating cycle 1: hot exchanger, 2: cold exchanger, 3: gas burner, 4: torquemeter, 5: electrical engine, 6: power electronics converter.

15 Results: pressure, torque, rotational speed for a few cycles

16 Results: as a refrigerating machine -30 C dans le volume de détente

17 Vehicle model including an APU with ICE or Stirling engine Vehicle specifications Vehicle mass (+ driver) 1210 kg Wheel friction coefficient Air density kg/m 3 Wheel radius m Auxiliaries consumption 750 W Battery max. power 78 kw Battery capacity [5, 10, 20] kwh Battery mass [188, 259, 356] kg Battery state of charge [0.4, 0.6, 0.8, 1] Stirling system 12 kw Stirling efficiency 39 % ICE power 97 kw ICE max. efficiency 36 % Vehicle specifications Generator max. power 12 kw Generator max. efficiency 95 % Motor max. power 80 kw Motor max. efficiency 93 % Transmission ratio 5.4 Transmission efficiency 97 % Fuel heating value 42.5 MJ/kg

18 Model results Energy converters operation for both Stirling and ICE on plug-in SHEVs powertrains three repeated WLTP 10kWh battery capacity Stirling engine operates at a lower power and more continuously than ICE

19 Model results Battery and fuel energy trade-off for the plug-in configuration on one to five-repeated WLTP, under the three investigated battery capacities. Powertrain efficiency of the plug-in configuration, on one to five-repeated WLTP, under the three investigated battery capacities.a Fuel consumption results between Stirling-system and ICE of the plug-in on one to five-repeated WLTP, under the three investigated battery capacities.

20 Conclusion Alternative automobile powertrains are needed Series Hybrid Vehicles including a Stirling engine as APU is a good candidate Powertrain efficiencies and fuel consumption present good performances when compared to a conventional ICE APU A 10 kw Stirling engine prototype has been developed and is currently under tests