...The Visio.M has a driving range of around 160 kilometers and space for two people and luggage. With only 15 kilowatts of engine power, the car can achieve a top speed of 120 km/h (75 mph)...
The electric motor draws its energy form a 13.5 kWh lithium-ion battery comprising consumer cells and is mounted behind the seats. The battery weighs almost 85 kg and can be charged from a 230 V socket in only three to four hours. The total cost of ownership, including initial investment and operating costs, will be lower than that of a comparable combustion engine car.
Decisive for the great energy efficiency of the Visio.M is its light weight. The passenger compartment is made of carbon fiber reinforced plastic with aluminum in the front and rear sections, as well as the roof frame. All windows are made of polycarbonate. This material weighs only half as much as glass but, thanks to a special coating, is equally resistant to scratches and weathering. The researchers also saved weight in chassis, steering and transmission by using special light-weight constructions. Without the battery, the Visio.M weighs only 450 kilograms.
“Light weight is essential for an electric vehicle,” says Prof. Markus Lienkamp, Chair of the TUM Institute of Automotive Technology, “because more weight requires more battery performance for the same range and thus generates higher costs. More weight also means poorer driving dynamics at the same performance. But we want a car that is affordable and fun to drive.”...
Many aspects must be brought together before the vehicle can achieve a large driving range in spite of its relatively small battery. These include light weight, low aerodynamic drag, an efficient drive train, minimal rolling friction and energy-saving air conditioning.
The researchers have optimized these parameters in the context of the Visio.M project. Thus the 1.55 m wide and 1.31 m high two-seater now has excellent aerodynamics. In addition to low vehicle weight, the combination of low coefficient of drag of only 0.24, small frontal area of 1.69 square meters and tires optimized for low rolling resistance (115/70 R 16) further reduce the energy consumption.
The active “torque vectoring” differential also contributes to overall efficiency: A small electric machine in the gearbox that can be operated as an electric motor or as an electric generator distributes the force optimally between the two back wheels. Because of the improved stability while braking in curves, significantly more energy can be recovered than without torque vectoring. At the same time the car becomes much more agile and safe, because of the optimal distribution of drive ad braking forces...
Special attention was paid in the Visio.M to the design of the air-conditioning and heating systems. Wherever warmth is generated, it is recovered for heating the car when required. So-called Peltier elements are integrated into both the cooling aggregate and seats. These electrothermal converters can heat as well as cool. This allows environmentally friendly operation without the use of coolant fluids.
During very cold weather an ethanol-based heater can be switched on for driving range independent heating. The aggregate with a thermal performance of approx. 4.5 kW is especially useful for deicing the windscreen. An intelligent controller finds the optimal solution for energy efficient and comfortable operation of the air-conditioning system...
