Evaluation of Electric Buses

Transcription

1 Evaluation of Electric Buses Antti Lajunen, Aalto University ECV national seminar on Tuesday

2 Contents Aalto research in ECV-eBus Research challenges Alternatives for electric powertrains Energy consumption Cost effectiveness Ongoing research Electric bus route simulation CO 2 emissions

3 Aalto research in ECV-eBus Modeling and simulation Dimensioning powertrain components Evaluating performance and energy consumption Thermal management of powertrain components Comparison of powertrain technologies Different electric powertrain configurations Different powertrain technologies Diesel, CNG, Parallel and series hybrid, Fuel cell hybrid, Electric Energy consumption and cost effectiveness

4 Research challenges Minimizing energy consumption Energy efficient powertrain and auxiliary devices Thermal management of components and interior space Modeling, simulation and prototype testing Costs effective operation Battery capacity vs. charging method and power capacity Operation and fleet management Electric bus route simulation

5 Alternatives for electric powertrains (1/2) A) Battery and a single traction motor B) Battery, a single traction motor and a multi-gear transmission C) Battery and two traction motors with a single-gear transmission D) Battery, ultracapacitors and a single traction motor Difference (%) Energy consumption comparison L3 Braunschweig New York Bus Orange County B1 B2 C1 C2 D1 1) Permanent magnet motor, 2) Induction motor Lajunen, A., Powertrain Design Alternatives for Electric City Bus, IEEE Vehicle Power and Propulsion Conference (VPPC'12), Seoul, Korea, 212.

6 Alternatives for electric powertrains (2/2) A BATT AUX FD A) Single traction motor and a final drive B) Single traction motor, two-speed gearbox and a final drive C) Two separate traction motors with reduction gears B BATT GB FD D) Two separate in-wheel traction motors on rear wheels AUX E) Four separate in-wheel traction motors Energy consumption difference (%) BR MAN NYC C D BATT AUX BATT AUX RG RG -8 B C D E Lajunen, A., Comparison of Different Powertrain Configurations for Electric City Bus, IEEE Vehicle Power and Propulsion Conference (VPPC'14), Coimbra, Portugal, 214. E BATT AUX

7 Distribution of energy losses Diesel bus Energy consumption: 37 kwh (3.64 kwh/km) Electric bus Energy consumption: 1.5 kwh (1.2 kwh/km) Engine Acessories Transmission Tyres Brake Aero 9 Wh/km (3%) 37 Wh/km (1%) 35 Wh/km (1%) 13 Wh/km (3%) 27 Wh/km (26%) 2 Wh/km (2%) 9 Wh/km (9%) 2 Wh/km (2%) Battery Acessories Transmission Tyres Brake Aero 48 Wh/km (13%) 35 Wh/km (35%) 222 Wh/km (61%) 27 Wh/km (26%) Espoo 11 cycle, bus total weight = 1425 kg, moderate auxiliary power consumption

8 Energy consumption comparison Decrease (%) Energy (kwh/km) Energy cons. variation Average consumption CONV PAR_1 PAR_2 SER_1 SER_2 EV -18 % Energy cons. average decrease -29 % -34 % -64 % -79 % CONV PAR_1 PAR_2 SER_1 SER_2 EV Energy consumption variation due to different driving cycles Comparison of six different powertrain technologies: CONV = Diesel PAR_1 = Parallel Hybrid (Ucap) PAR_2 = Parallel Hybrid (Batt) SER_1 = Series Hybrid SER_2 = Series Hybrid (Plug-In) EV = Battery Electric Energy consumption decrease on average Lajunen, A., Energy Consumption and Cost-benefit Analysis of Hybrid and Electric City Buses, Journal of Transportation Research, Part C, vol. 38, pp. 1 15, Jan. 214.

9 Lifecycle cost Cost ( /km) Capital cost factor ESS replacements Maintenance cost Energy cost Capital cost 55 CONV PAR_1 PAR_2 SER_1 SER_2 EV 4% 5% 5% 6% 1% Cost parameters Parameter Value Diesel city bus capital cost ( ) 225 Diesel fuel cost without VAT ( /l) Electricity cost without VAT ( /kwh).1 Maintenance cost for diesel bus ( /km).14 High power battery cost ( /kwh) 1 High energy battery cost ( /kwh) 75 Ultracapacitor system cost ( ) 15 Operation time in a year (h) 4 Service life in years 12 Discount rate (%) 7 Lajunen, A., Energy Consumption and Cost-benefit Analysis of Hybrid and Electric City Buses, Journal of Transportation Research, Part C, vol. 38, pp. 1 15, Jan. 214.

10 Cost effectiveness Capital and energy storage costs have the major impact on the cost effectiveness of hybrid and electric buses Reference 5% lower ESS cost 5% higher ESS life 25% higher fuel cost 25% lower capital costs (vs. reference) Total impact Difference (%) PAR_1 PAR_2 SER_1 SER_2 EV Lajunen, A., Energy Consumption and Cost-benefit Analysis of Hybrid and Electric City Buses, Journal of Transportation Research, Part C, vol. 38, pp. 1 15, Jan. 214.

11 Ongoing research Electric bus route simulations 1. What kind of electric buses should be selected for achieving energy and cost efficient operation in given operating conditions? 2. How to define requirements of the charging infrastructure for the operation of electric buses? Comparisons of city buses Energy consumption, costs and CO 2 emissions (with UC Berkeley) Including Natural Gas and Fuel Cell hybrid buses Finland and California as case studies for costs and CO 2 emissions Manuscript to be submitted in March 215

12 CO 2 emission results (case Finland) CO 2 (kg/km) Well-to-Tank Operation DI CNG PAR SER FCH EV1 EV2 Energy pathways for Finland Energy Model Diesel (Edwards et al., 213) Natural gas CNG imported by pipeline Hydrogen Reforming on-site from CNG Electricity Finnish electric grid mix Decrease (%) % -23 % -23 % -21 % -87 % -86 % CO 2 emission decrease DI CNG PAR SER FCH EV1 EV2 Electric buses have potential to decrease CO 2 emissions more than 85% in comparison to diesel buses Edwards, R., Larivé, J-F., Rickeard, D., Weindorf, W., 213. Well-to- Tank Report Version 4., JRC Technical Reports.

13 Summary Electric city buses have a significant potential to increase energy efficiency and decrease CO 2 emissions High purchase cost is the main barrier for the electric buses Thermal management is a challenge which needs dedicated research and advanced solutions Electric city buses can be more cost efficient than diesel buses already in the near future

14 Related publications Lajunen, A., Improving the Energy Efficiency and Operating Performance of Heavy Vehicles by Powertrain Electrification, Doctoral Dissertation, Aalto University, 214. Lajunen, A., Energy Consumption and Cost-benefit Analysis of Hybrid and Electric City Buses, Journal of Transportation Research, Part C, vol. 38, pp. 1 15, Jan Lajunen, A., Comparison of Different Powertrain Configurations for Electric City Bus, IEEE Vehicle Power and Propulsion Conference (VPPC'14), Coimbra, Portugal, 214. Lajunen, A., Energy-Optimal Velocity Profiles for Electric City Buses, IEEE International Conference on Automation Science and Engineering, Madison, WI, USA, 213. Lajunen, A., Powertrain Design Alternatives for Electric City Bus, IEEE Vehicle Power and Propulsion Conference (VPPC'1), Seoul, Korea, 212. Lajunen, A., Development of Energy Management Strategy for Plug-in Hybrid City Bus, IEEE Transportation Electrification Conference and Expo (ITEC 12), Dearborn, MI, USA, 212. Lajunen, A., Evaluation of battery requirements for hybrid and electric city buses, Electric Vehicle Symposium (EVS26), Los Angeles, CA, USA, 212.