TREND: Electromobility: Stay charged.

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The first smartphones that can be charged via wireless magnetic induction are now available. Electric cars are set to follow this development, which will also help stabilize the power grid.

Electric toothbrushes have been able to do it for some time and a few electric buses are also now able to charge their batteries without any cable clutter. Electric cars are next in line. Industry and science have been working on the issue for years.

For example, in 2009 inductive power transfer (IPT) technology was presented by the University of Auckland. With magnetic induction, batteries charge via charging plates on the bottom of the vehicle and an induction pad on the ground. Two years ago, HaloIPT, the spin-out acquired from the New Zealand university by Qualcomm, began a series of trials in London in which 30 electric taxis were able to recharge their batteries at the taxi stand. However, a full charge still requires several hours.

Power from the highway

In the future, long charging times could become a thing of the past if UK transport minister Andrew Jones has his way. This year, for an 18-month trial period electric cars will be able to recharge while driving on test areas in the UK. The coils for this will be buried beneath the highway. The technology used will be SMFIR (shaped magnetic field in resonance), a development by the Korea Advanced Institute of Science and Technology (KAIST). Two electric buses are already running on a 12-kilometer pilot route in South Korea.

If the test pGB Electric Lanehase is successful in the UK, the most frequently used roads will then be equipped with this technology. This approach would resolve almost all the problems that still prevent widespread use of electric cars: no charging infrastructure, long waiting times, batteries too large and too expensive, and the short distances that can be traveled between charges. The only question is, who will pay for the high infrastructure costs?

Wireless charging and discharging

The solution from Fraunhofer IWES is even further in the future. The idea is that with a wireless charging system electric vehicles will not only charge their batteries but also feed energy back into the power grid to stabilize the grid. The vehicle batteries could act as temporary storage units and take surplus “green” electricity from the grid and feed it back to the grid as required. The result: more renewable energy in the electricity mix.

Scientists plan to use standard components and the induction systems need fewer ferrite slabs. This makes the coils lighter and cheaper. Special power electronics and coils also guarantee an efficiency level of 93 to 95 percent, if the coil in the car is about 20 cm from the coil in the road. And this will be achieved over the entire power range from 400 W to 3.6 kW.

The approach from Fraunhofer IISB promises even more savings. Because of distances of up to 15 centimeters between the vehicle and the ground, underground charging systems require large coils. In addition, objects or animals can disrupt the power transfer. The new approach envisages a sort of mini wireless charging column that charges the electric vehicle from the front. Consequently, the vehicles can get closer to the induction source. This considerably reduces the diameter of the coils, which makes the system more efficient and less expensive.

The prototype currently transfers three kilowatts (KW) with an efficiency level of 95 percent. Current electric vehicles are fully charged overnight. In other words, this is a wireless charging option intended more for home use that would be purchased together with the electric vehicle.

Of course, car manufacturers are involved in the developments. There are several specific approaches to install wireless charging systems in the vehicles. However, there are no international standards for transfer between two coils. Among other things, they have to include limit values for the magnetic field. For example, to prevent electronic devices such as pacemakers being affected.

Wireless charging for electric cars is still a long way off. But it's getting a little bit closer every day. (Image: Fraunhofer IISB).

Wireless charging for electric cars is still a long way off. But it's getting a little bit closer every day. (Image: Fraunhofer IISB).