Motors and batteries

A complete transition to electric drives could potentially boost efficiency in the transport sector. A variety of electric motors can be used for this purpose. These electric motors are characterised by much higher efficiency than internal combustion engines. Electric motor efficiencies of over 90 percent and vehicle efficiencies of around 85 percent can thus be achieved. With regard to CO2 emissions, the increased use of electric vehicles offers a particular advantage when the electricity used is largely from renewable energies.

In the area of mobility, three-phase motors are commonly used. Due to their contactless power transmission and mechanically simple construction, wear on these motors is low and their efficiency constantly high. Energy recovery can also occur here thanks to the motor’s generator operation.

For efficient use of electric mobility, the first priority is reducing the weight and space requirements of the installed batteries. At the moment, however, batteries still have a low energy density compared to conventional fuels. This energy density is steadily growing as a result of technological developments, while the battery weight is being reduced.

In addition, vehicle weights are decreasing, thanks to greater use of lightweight construction. Composite materials such as carbon fibre composites are used in this construction. In addition to reducing the weight and the energy requirements of the vehicle, these composites also improve the vehicle dynamics.

An important question in the field of electromobility is: How is the necessary energy fed into the vehicle and which charging technology is used? At present, most charging systems are cable-based.

Depending on the capacity of the connected power source, charging capacities of 10 to 22 kW are currently achieved in Germany. Newer alternatives are also available besides this classic charging model. Inductive charging, in particular, which requires no cable connection, is becoming increasingly important. In this method, electricity is transferred between the battery and charging device wirelessly, by means of a magnetic field. This enhances user convenience and also solves the problem of compatibility with charging systems. Charging at up to 7.2 kW is already possible with this method.

Further developments in technology that allow charging facilities to be installed under roads also offer huge opportunities for increasing vehicle range. Successful implementation of electromobility will also require expansion of the charging infrastructure.

Charging infrastructures that provide access to a higher number of users can generate high demand. In this case, the use of a load management system for the charging point is advantageous. Such a system can alleviate the problem of peak charging loads and make the charging process more efficient.

In future, electromobility will also be integrated into the power grid infrastructure on the basis of smart grid concepts. With smart grid services, the vehicle batteries provide electronic storage capacity for excess electricity and, in the event of a supply shortage, return this electricity to the grid, a process also referred to as “vehicle to grid”. The charging stations required to feed the electricity back to the public grid are currently in development. The same applies to the power electronics required to coordinate the flow of electrical energy.