2 years ago

MDA Technologies 4/2014

MDA Technologies 4/2014

An intelligent electric

An intelligent electric taxi for tropical megacities Stefanie Reiffert, Ulrich Huber Particularly in Africa and Asia, the search for work is bringing more and more people to urban centers. The infrastructure of such cities needs to be adapted to the growing number of inhabitants. Author: Stefanie Reiffert, Technische Universität München, Media Relations, Munich, Germany Ulrich Huber, Project Manager, Sensor-Technik Wiedemann GmbH, Kaufbeuren, Germany Car exhaust fumes on the overcrowded streets are major contributors to the high level of air pollution in these large cities, while noise pollution places an enormous burden on people. For these reasons, there is a great need for efficient and clean transportation systems. Vehicles that are powered by an electric motor could be the solution to many of the problems caused by the transport infrastructure in megacities. These vehicles have no emissions and their motors are extremely quiet. Researchers from the Singapore-based TUM CREATE have developed an electric taxi that has been specially tailored to the 28 MDA Technologies 4/2014

Measurement and Control 01 Battery Management System including main switch and power measurement 02 The battery has a capacity of 50 kilowatt-hours, of which 35 kilowatt-hours are needed for the quick recharge requirements of tropical megacities. TUM CREATE is a joint research program of the Technische Universität München (TUM), Germany, and the Nanyang Technological University (NTU), and receives strong support from the National Research Foundation in Singapore. It is part of the “Campus for Research Excellence And Technological Enterprise” (CREATE) Program. The EVA project of TUM CREATE was launched in late 2011 with the aim of developing an electric taxi, specifically for use in Singapore. After two years, the team was able to present the prototype at the 43 rd Tokyo Motor Show in 2013. Taxis as role model Singapore, a city-state in South- East Asia, is home to approximately 5.3 million people and has a total land area of 712.4 square kilometers. One’s own car is associated with high costs in Singapore. For this reason, most people use the city’s sophisticated public transportation network to get from one place to another. Any gaps in the system are filled by the approximately 27,700 taxis in the city, which generally only make short trips. Although taxis make up less than three percent of Singapore’s vehicles, they account for 15 % of all trips taken in the city. Many taxis operate 24 hours a day, traveling an average of 520 kilometers during this period of time. Until now, the state of the art was such that electrically powered vehicles were only partially suitable for use as a taxi. Their reach was very limited, and battery charging could take up to eight hours. For taxi companies, whose vehicles sometimes operate continuously around the clock, such a vehicle would simply not be an option. Battery management system for safety The researchers developed a quick-charge system for EVA. The battery has a capacity of 50 kilowatt-hours, of which 35 kilowatthours are needed for the quick recharge. The battery is designed to be charged to 70 % in 15 minutes, which means enough energy to travel a distance of at least 200 kilometers. A voltage of up to 450 volts and a current of up to 360 amperes are applied during the charging process, which generates heat in the battery. To prevent this from affecting the service life of the lithium-polymer battery, the researchers developed a cooling system that comprises three different components. An active water cooling system and a climate compressor keep the temperature in the 216 pouch bag cells low. Furthermore, the cells are coated with a phase change material that behaves much like wax: if the temperature rises, the material becomes liquid and absorbs the excess energy. For safety reasons a battery management system (BMS) from the company Sensor- Technik Wiedemann (Germany) is installed. The BMS constantly measures the voltage and temperature of the lithiumpolymer cells and additionally monitors battery current and the insulation resistance. The BMS uses the measured data to calculate precisely the battery’s current charge level and power abilities. An electric motor drives the front wheels of EVA. The TUM CREATE team limited the power of the motor to 60 kilowatts so that it would be in line with the requirements of urban traffic. The speed limit in Singapore is 90 kilometers per hour. Energy-efficient It goes without saying that a taxi without air-conditioning would not be conceivable in Singapore. However, to save energy, researchers have developed a zone-based air-conditioning system for EVA. Each seat in the vehicle has its own zone in which the cooling can be regulated. As yet, EVA is still only a prototype. TUM CREATE is looking for partners from the automotive industry to be able to implement this project. About Company name: STW Technic LP Headquarters: Kaufbeuren GERMANY Employees: approx. 400 Established: 1985 Products: controllers, I/O modules, sensors, measurement technology, hybrid technology, teleservices MDA Technologies 4/2014 29


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