Electrical power from the road

09/11/2009 // Vision: non-contact power supply for electric cars

Berlin. The future of the automobile is electric; of that, there can be little doubt. However, the biggest challenge facing electric cars is their limited range, currently at most 150 to 200 kilometres – this despite the most modern lithium-ion battery technology. The engineering firm IAV (Ingenieurgesellschaft Auto und Verkehr) is pursuing a very promising approach to make the energy supply of future electric cars simpler, more reliable, and more comfortable, while achieving a significant increase in range. “The battery will be recharged while driving or parked, without the use of a cable,” explains Wilfried Nietschke, head of IAV’s Technology Monitoring business division. Inductive loops buried in the roadway generate a magnetic field to contactlessly supply the cars with energy; cables and connectors are not required. Lengthy charging periods or laborious battery exchanges are also eliminated.

Video: Electrical power from the road

Nietschke is confident that this innovative technology will be developed to production-ready status in the next few years. “In model tests, our new system is already functioning perfectly,” says the electrical engineer, and as proof offers a 1/28 scale model of the system. Construction of a demonstration section of “charging road,” and a full-scale test track, are in the planning stages in the German state of Lower Saxony.

For its futuristic project, IAV takes advantage of the Maxwell electromagnetic laws. Electric current flowing through a conductor generates a magnetic field. In the case of an alternating current this induces a voltage in a second conductor, even though the two conductors are not in contact with one another. This magnetic field is forced by materials with high iron content. Using precisely controlled frequencies of the applied alternating current, high-efficiency energy transmission from the sending to the receiving electrical circuits is ensured.

Topping up batteries while driving or parked

In practice, roadways of the future would be fitted with buried electrical conductors, which generate a magnetic field. The floorpan of the electric car would be fitted with their counterpart, a non-contacting inductive pickup. Current can be induced while the vehicle is underway, or “stockpiled” (until the battery is fully charged) while parked. Wilfried Nietschke graphically describes the concept: “In this way, the road itself becomes a range extender.” Even today, in automobile production plants and in large warehouse facilities, robotic floor conveyor vehicles are supplied with power and automatically steered using this method. Also, a major research topic at present is development of inductive power supply for computers or household electrical appliances, to eliminate the annoying tangle of power cables from mains outlets.

Wilfried Nietschke is convinced; “The long-familiar principle of electromagnetic induction offers numerous advantages over all previously discussed alternatives.” Induction is insensitive to weather conditions, and is free of mechanical wear. The vehicle’s inductive pickup is not visible externally, so automobile designers would continue to enjoy the styling freedom to which they are accustomed.

Even remote control would be possible

The primary conductor in the roadway could also carry a control signal, allowing remote control of the vehicle on virtual "rails.” The principle is familiar from model slot car tracks, for example the “Scalextric Digital” or “Carrera Digital” systems. This concept can also function contactlessly, without a slot in the roadway.

Inductive transmission losses are relatively low, at about ten percent, and are very sensitive to the distance between roadway and vehicle floorpan. The optimum distance could be automatically controlled by means of an active suspension and opto-electronic measurement techniques.

In production applications, a control system would in any case be needed so that the charging process would only be activated when sensors detect with absolute certainty that there is indeed an electric car over the inductive field. This applies equally to parking as well as driving. In the case of driving, the high efficiency of the system means that only limited sections of roadway need be fitted with induction loops. Exact identification of a specific vehicle (for example, by means of an RFID – a radio frequency identification chip) is also imperative for proper cost accounting. IAV is also working on this aspect of the system.

Optimising electric motors for automotive applications

IAV is not only conducting research on power supply topics, but is also intensively involved with improving automotive electric motors. Electrical machines for use in light rail applications (streetcar, tram) or electrical appliances are proven and well developed, but could and should undergo extensive optimisation for use in the automobile. Development targets include reduced motor weight and installation volume, increased power output while maintaining or even reducing energy demand, reduced power losses within transmissions or driveshafts in the drivetrain (for example, through the use of wheel hub motors), and more cost-effective manufacturing.

About IAV

Employing over 3,000 staff across the globe, IAV is one of the leading providers of engineering services to the automotive industry. The company has been developing innovative concepts and technologies for future vehicle generations for more than 25 years. Our core competencies include production-ready solutions in all aspects of powertrain, electronics and vehicle development. Our worldwide clients include all major automobile manufacturers and component suppliers. Along with development centres in Berlin, Gifhorn and Chemnitz, IAV has facilities in Europe, Asia, North and South America.