Michael Schier

Thermal properties of a special commuter vehicle concept

Thermal management is one of the main energy consumers of todays electric vehicles. To optimize its energy use it is necessary to develop more efficient or new thermal systems. Detailed measurements of HVAC (Heating, Ventilation and Air Conditioning) system parameters are mandatory for designing, creating and evaluating new vehicle energy concepts. In further studies a virtual car was simulated using the Alternative Vehicles Library [1] created by the Institute of vehicle Concepts of German Aerospace Center. The paper is devoted to the measurements on a commercially available electric vehicle to verify the simulation results as well as to assess the mentioned parameters.

Thermal management concepts for vehicles of next generation

The present paper is a review of the selected research activities at the German Aerospace Center on the field of terrestrial vehicles thermal management. The methods and some results of the passenger cabin measurements and human comfort studies are described. Several shortly depicted concepts for the cabin air-conditioning present the challenges of current and future research topics. Some examples of newly developed highly integrated components and the component tempering strategies for next generation vehicles are given.

Innovation examples for ecological vehicles based on aerospace research

In this paper innovative technologies from the aerospace research are presented, which are usable for a successful electric mobility of the future. They represent a selection of the German aerospace center research projects, where synergies between space and aviation applications as well as between rail and road traffic applications are used. The work relates to the fields of vehicle-energy concepts, alternative energy converters and lightweight design. Within the individual development projects hardware demonstrators were created and are shown here.

Increasing efficiency of ecological vehicles by integrating auxiliary units directly to the traction shaft

The climatisation requirements of Electric Vehicles (EVs) largely depend on its usage location. For example, EVs operated in European countries require heating during the winter season, while those operated in equatorial regions face cooling load throughout the year. To date, the low range for a given battery charge remains the single-most important factor hindering the widespread acceptance of EVs. The principal electrical loads of an EV comprises of the traction and air-conditioning (A/C) compressor motors. These high power loads expedites the battery drain, leading to poor cruise range. The paper proposes a novel design solution geared towards improving the overall operating efficiency of these motors by integrating them into a single housing. The integrated unit is expected to operate close to 100 % efficiency during recuperation mode. The unprecedented improvement in efficiency is achieved through direct mechanical coupling of the traction motor with the A/C compressor during breaking events. The mechanical configuration of the unit is such that the torque and speed characteristics of traction and compressor motors can be independently controlled during drive mode. In addition to improved efficiency, the integrated unit boosts numerous other advantages such as increased reliability, compact design and weight saving.

Design of a 2 in 1 motor to increase the efficiency of electric vehicles

The requirements for the climatisation of electric vehicles largely depend on the vehicles usage location. For example, electric vehicles operated in European countries require heating during the winter season, while those operated in equatorial regions face cooling load throughout the year. To date, the low range for a given battery charge remains the single-most important factor hindering the widespread acceptance of electric vehicles. The principal electrical load of an electric vehicle used in equatorial regions comprises of the traction motor and the air-conditioning compressor motor. These high power loads expedites the battery drain, leading to poor cruise range. The paper proposes a novel design solution geared towards improving the overall operating efficiency of these motors by integrating them into a single housing.

Direct Coil Cooling of a High Performance Switched Reluctance Machine (SRM) for EV/HEV Applications

This paper presents the development of a novel direct coil cooling approach which can enable high performance for electric traction motor, and in further significantly reduce motor losses. The proposed approach focuses on bypassing critical thermal resistances in motor by cooling coils directly in stator slots with oil flow. Firstly, the basic configuration and features are shown: sealed stator slots to air gap, pressure reservoirs on both side of the slots and slot channels for oil flow. The key to enhance thermal performance of the motor here is based on introducing fluid guiding structure in the slot channels. Next, heat transfer in the channel with guiding structure is investigated by CFD and compared with bare slot channel without guiding structure. For studying the effectiveness of proposed cooling concept, numerical analysis is conducted to compare it with HEV favored oil impingement cooling. Finally, thermal performance of the proposed cooling approach is verified and compared with water/glycol jacket cooling on a switched reluctance machine prototype for EV application inside a public funded project ODIN.

Highly integrated electric drives for automotive application

Aerospace development needs an optimum in weight and volume reduction. In addition there is a high research potential on vehicle energy concepts and alternative energy converters by using synergies from aerospace research [1]. The understanding of the system behavior leads to the development of several concepts of electric drives which combine more than one function in a single technical component. The paper describes three examples of highly integrated electric drive concepts which can be used in next generation cars. The concepts are partly based on international cooperation and also on individual investigation work.

Methodical approach for designing electric propulsion systems containing two motors

To reduce the environmental impact of the petroleum-based transport, new safe, cost and energy optimized electric vehicle propulsion concepts are mandatory. Besides the activities for improving the battery and power electronics technologies, highly integrated units and new functional component operation strategies are of special interest. In this paper, a methodical approach for deriving electric motor design values for electric propulsion systems, especially usable for urban vehicles, including two electric machines, is shown. Considering the overall results a new highly integrated electric drive containing two different sized electric motors, two clutches and a compressor in one single unit is used as an example. The design led to a variety of functional motor modes presented in the paper. On upscaled measurement results, the efficiency tables for 50 kW and 10 kW PSM- and ASM-motors are used for a combined working strategy. Using the 10 kW motor on low torque and speed requests the traction energy demand of a urban vehicle could be reduced in the range up to 5% on several drive cycles.

Innovative Two Wheeler Technologies for Future Mobility Concepts

With the requirements of European Commissions White Book that demand emission-free city logistics in major urban areas until 2050, cargo bicycles may play a significant role for last mile deliveries. They require less space than vans and can be parked on the sidewalk. These electrically assisted bicycles, tricycles or quadracycles do not emit any local emissions and are capable to transport 50-250 kg of cargo. But, in topologically moved areas the capacity of conventional battery concepts constrains the transport range: delivery tours by bike can have a daily mileage up to 50-80 km. In the urge of finding energy carriers with a higher energy density than lithium-ion batteries hydrogen comes into the focus for innovative and sustainable cargo bike propulsion systems. This paper outlines the DLR activities to develop a versatile hydrogen fuel cell and its thermal management which suits the transport needs of commercial last mile deliveries with cargo bikes. First studies show that cargo cycles have high potentials not only in postal services but also for the growing courier and parcel service. Active thermal management systems to increase the range and the hill climb capability, the life time and the operational capability like shortening the refilling time are introduced in this paper.

Influences of different heating strategies on the energy demand of an airfield luggage tug

In this paper an energetic cabin model in Dymola is created to compare different heating strategies of a luggage tug. The cabin model is validated using a mock up in the climate chamber of the Institute of Vehicle Concepts at the German Aerospace Center. A virtual 20 kW fuel cell luggage tug has been created using Alternative Vehicles Library in Dymola. Heating concepts based on fuel cell thermal waste heat and conventional PTC heating strategies and compared using the virtual luggage tug model. The combination of waste heat and electric heating strategy led to the integration of a 60 liter enthalpy storage in the primary fuel cell cooling system. As a result, electric energy usage for heating is reduced by 60% while cabin temperature could be increased at 5 K up to 20 °C at -10 °C environmental conditions.