High pollution levels in urban areas and rising fuel costs lead to a need for new drive concepts that provide an alternative to conventional internal combustion engines. Electric and hybrid electric vehicle drives offer the opportunity for emission-free local driving. At the same time, hybrid vehicles enable long range drives thanks to sufficient energy reserves on board the vehicle. Thus, they facilitate the economic implementation of individual mobility in urban and rural areas.

Previous hybrid concepts are based on parallel and serial topologies or mixed forms (power split hybrids). In all these propulsion concepts, the electrified components of the drive system are used primarily to change the operational boundary conditions of the internal combustion engine to an energetically more efficient level or to recover kinetic energy while driving. An adapted electrification of the passenger car powertrain makes it possible to convert a part of the internal combustion exhaust heat, with the aid of suitable converters (e.g. the Rankine system or turbogenerators), into electrical energy, to feed this energy into the electrical system, and thus to use it directly (traction assist) temporally decoupled from the supply of waste heat (storage in the traction battery).

Antriebsstrangkomponenten mit Messtechnik

Test bench inspection of powertrain components using accelerometers and strain gauges


Together with a virtually unlimited number of hybrid variants, the associated solution space for electrified drive solutions becomes larger and more complex. This raises the question of what a future-proof drive system actually looks like and which drive train topology has the greatest potential in terms of energy efficiency.

The aim of the Initialization Project V - Electric and Hybrid Electric Mobility is therefore the investigation of methods and procedures to identify energy efficient hybrid drive concepts for a defined requirement profile based on the concrete example of the region Karlsruhe. In particular, the possibilities of recuperating thermal energy components in partially electrified powertrains are to be verified in order to significantly improve energy efficiency as well as emission output. The functions and energy efficiency of the powertrain will be demonstrated using the networked XiL validation approach on test benches and in simulations of application-relevant operating scenarios.

Detailansicht Prüfstand
Detail view of a test device for electric motors

To achieve this goal, a suitable application profile for a hybrid vehicle in the Karlsruhe region will be identified in the first three work packages. The Institute for Energy Efficient Mobility (IEEM) of the Karlsruhe University of Applied Sciences works to identify a typical customer profile in the form of usual routes as well as their division into city, rural and motorway areas. Likewise, customer-specific vehicle and performance classes are used to determine the customer profile for the region. In addition to determining the customer profile, the Institute of Product Engineering (IPEK) at the Karlsruhe Institute of Technology (KIT) analyzes the current and future legal constraints on mobility in the Karlsruhe region. These include both national certification guidelines and emissions legislation as well as regional boundary conditions such as current and planned low-emission zones or charging infrastructures. Based on these results, a target vehicle will be identified together. The project group New Drive Systems (NAS) of the Fraunhofer ICT works to identify customer-relevant driving cycles on the basis of customer profiles and legal boundary conditions, which are systematically derived from a database with real driving data. The identified requirement profile then enables to derive and develop efficient hybrid drive system solutions. To do the large scope of solutions justice and to create a possibility for comparing different drive systems, two drives with different degrees of hybridization are developed. The primary power source of one of these drive systems is an internal combustion engine, and the primary power source of the second is an electric motor. The powertrain variants are developed by all partners collaboratively with the introduction of their individual competencies as well as preliminary work. The ETI – Institute of Electrical Engineering at the Karlsruhe Institute of Technology (KIT) defines the optimal characteristics of the respective e-machines. On the other hand, the NAS defines the characteristics of internal combustion engines and analyzes their potential through thermal recuperation. At IPEK, the required power converters are developed for the energy-efficient provision of the power requirement to the wheel. The operating strategy for the respective powertrains is coordinated under the leadership of the IEEM. Efficiency is analyzed and evaluated based on a common model of the overall system.