Electric Vehicle - City car

In WP4 (Electric Vehicle - City Car), 3 deliverables were completed in the OPTIMORE project:

D4.1 - Production intent component
D4.2 - Industrialized operating system (OS) software package
D4.3 - Cost reduction potentials

The targets for the city electric vehicle demonstrator can be concluded to optimising the system layout and the whole system bases on the detailed development, further more we improved the hardware and industrialised the software and reduced the costs.

The system layout of the city car was optimized based on real world conditions and the experience of the previous project FUEREX regarding drivability, fuel consumption, emissions, cost and NVH: 

  • By associated REX operating strategy, driven by State of Charge requirements
  • Thermal management under real-world conditions for the optional use of electric energy and/or waste heat generated in the RE unit
  • Comfort demand combined with the technical thermal management of the power train and the impact on efficiency, durability and emission

The system optimization was performed under two main aspects, the legal NEDC test cycle and representative load profiles for EVs. The operating point of the range extender has a high influence on NVH behavior in the vehicle especially under low speed conditions at city driving. This aspect was optimized once again with the final performance of the range extender in the vehicle. Based on these criteria the durability aspects are of minor priority at real live conditions. 

The hardware and SW were further developed by

  • Eliminating of expensive (prototype) materials and processes
  • Improved aftertreatment functionalities
  • Evaluation of different design solutions to improve packaging and NVH,
  • Developing next level of power electronics regarding automotive requirements, volume and weight reduction

The SW industrialization was concentrated on functional safety, comfort features and integration into operating software which finally represents a solid base for further specific applications:

  • Development and testing of fail-safe procedures for the charging process
  • Integration of optional communication to the charging infrastructure 
  • Safe start procedure for control units and proper initialization sequences
  • Integration of air conditioning and heating strategies
  • Optimized creeping mode for low speeds in city operation
  • Redundant control algorithms on vehicle and engine control unit for error detection and recognition of shutdown or limp home conditions
  • Variable recuperation modes on driver demand
  • Development of range extender multi-point operation for flexible adaptation
  • Implementation of emission relevant functions like charcoal-canister purge

The development was based on the Control Units and the E-Vehicle architecture shown in the figure below: EV Architecture and HV-Safety of the Range Extender City Car


The cost reduction of the Range Extender under reliability aspects addressed:

  • Evaluation of well-known volume production materials and technologies for the use in the rotary engine production.
  • Beside cost reduction on component level, various sub-systems were simplified or combined to reduce complexity and weight.
  • The cooling/heating system of the ICE, aftertreatment system, E-motor and battery regarding hardware, operating and control strategies were optimized.

The production cost assessment was performed for the range extender unit incl. exhaust system as shown in the figure below for two different production scenarios:

  • Scenario 1: Volume: 20.000 units/year, OEM production, brownfield approach
  • Scenario 2: Volume: 100.000 units/year, Tier 1 Supplier for different OEM’s, brownfield approach


Rotary Engine Range Extender Unit incl. Exhaust System


The final results of the rotary range extender are shown in Table 1. Compared to the project targets the NVH behavior, the weight, and space targets were fulfilled, while the cost targets can be kept at a production volume higher than 100.000 units per year. The specific fuel consumption is app. 5 % higher than the target value, the emission level at NEDC is at 65% of EU6 (target was 50 %). The reasons for that are the HC emissions.


Final results Rotary Range Extender


The final integration of the Wankel Range Extender into the city car is shown in the figure below. The targets, excellent driveability, excellent NHV behaviour and no constraints of the passenger compartment and car boot were achieved.



Vehicle integration of the Range Extender System


The vehicle concept provides an electric range for average daily need of approx. 50km with a high voltage battery of 12 kWh. The battery management is designed for an energy and power reserve required for full dynamic vehicle performance. The vehicle is equipped with an electric motor of 75kW & 240Nm peak torque, the energy consumption will be 16kWh/100km, and the fuel tank size is dimensioned for 250km total range. The fuel consumption of 1.8l/100km is measured under real driving conditions at daily use in a timeframe of March 2014 to October 2014.

Important for the electric driving range are the load profile, heating in wintertime and air conditioning in summer time. In the figure below it shows this for the city car based on measurements and accompanying calculations. The lower the average speed the more negative impact of heating and air conditioning appears. Whereas the electric operating range is decreasing by 40 % in the NEDC cycle due to air conditioning, in the New York City Cycle the electric operating range is shrinking by app. 60 %. 

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 314252

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