Wireless Charging Technology for Electric Vehicles

-By Yedhu Mohan

Necessity calls for action and the words come exactly true for electric vehicles, the latest product of technological evolution. The tremendous pace of this evolution process portrays our prolonged desire for a sustainable future.

The global drive to counter climate challenges has opened a new horizon for electric vehicles (EVs). Zero-emission and low cost of ownership have made it a perfect choice for many. The EV industry also has a bright future, considering the feats of several manufacturers like Tesla. The features of Electric Vehicles are further enhanced with the evolution of wireless charging technology which refills the battery even when the vehicle is in motion.

Though this is the case, several challenges cripple the EV market. Range anxiety has been one of the severe challenges faced by electric vehicles since their inception. The running cost per mile is only one-sixth compared to gasoline engines. But the range is less than half compared to conventional Internal combustion engine vehicles.

The EV industry employs several techniques to reduce the range anxiety of drivers. Some measures are given below.

Plug-in charging

More than 90% of EVs available in the market use this technology. The exhausted battery is refilled from the grid using plug chargers.

One disadvantage is that the owner needs to carry the charging plug wherever he travels!

Battery Swapping

Though this is not a promising solution, many have experimented with battery swapping. The exhausted battery is exchanged with a refilled battery at designated centers. This poses several challenges as the quality of the swapping battery may be compromised at times.

Hybrid Vehicles

Hybrid vehicles use both gasoline as well as electric energy to generate power. It helps users to recharge their automotive through the conventional system using gasoline. Though this is not as sustainable as an EV, it has succeeded in disrupting the existing technology and to generate a push for electric vehicles.

Wireless Charging Technology

Though still at the nascent stage, the wireless charger expects to rule the automobile industry.

Here, electric energy is transferred from one system to other through magnetic field conducted by various methods like inductive and capacitive coils.




Basic diagram of Static wireless electric vehicle charging system Cr: Science direct

Wireless Charging Technology and the future of Electric Vehicles

Wireless charging is an efficient solution to many challenges of EVs. Smart charging is a necessity for developing autonomous vehicles. When EVs are charged at home, there is a severe strain on the grid, causing frequent power disruptions several times of the day.

There are several fore runners in the field of electric charging. Renault has partnered with Electricite de France to test wireless charging in the street of France.

 BMW 530E is now available with a charging pad that facilitates wireless charging. The company claims that the 9.5KWh battery can be charged within 3.5 hours by the wireless technique.

Qualcomm has been reaping results in the field of wireless charging. The wireless charging system they developed, Halo, is used to replenish Formula E electric series cars.

Wireless Charging techniques for Electric Vehicles.

The wireless chargers employ electromagnetic induction for energy transfer. The common types of wireless charging techniques are as follows;

  1. Capacitive Wireless Power transfer

It makes use of coupling capacitors instead of coils or magnets. The technology is not extensively used in Electric Vehicles but used to charge small portable devices.

Schematic diagram of Capacitive Wireless Power Transfer. Cr: Science direct
  • Inductive Power Transfer (IPT)

Inductive Power Technique is by far the most traditional means of charging electric vehicles. The technique employs inductive coils to transfer power. In 1996, General Motors charged their EV using Inductive power transfer.

Schematic Diagram of Traditional Inductive Power Transfer Cr: Science direct
  • Resonant Inductive Power Transfer

It is an advanced version of IPT. The system utilizes a series of compensational networks in series and parallels to reduce losses. This technology is more efficient than conventional IPT.

Schematic Diagram of Resonant Inductive Power Transfer Cr: Science direct

    Disadvantages of static wireless charging

  • Since the primary coil is placed in the ground, there should be dedicated infrastructure to facilitate wireless charging at home.
  • The primary and secondary coils are separated by the air gap. Therefore a considerable amount of energy is lost during transmission.
  • Wireless charging also raises safety concerns. Conducting coils causes a heating effect and the possibility of flux leakage is also around the corner.
  • The wireless chargers are very similar to plug-in chargers because the driver needs to park the vehicle at designated slots and the process is also time-consuming. The financial burden is comparatively high in the case of wireless charging since it requires dedicated infrastructure.

The future of Wireless Charging – Dynamic Wireless Charging

From charging-while-resting to charging-while-driving, this is what the EV market looks to achieve.

Recent studies reveal that we can reduce 20% of the battery if we use dynamic wireless charging technology.

Qualcomm in 2017 successfully demonstrated that charging while driving is not a myth. The test results were impressive. They charged a vehicle moving at 100 km/hr with 20KW.

A 100-meter test track was equipped well-connected power supply. The power is transferred through the air gap to two 10 KW vehicle pads placed inside the EV, which capture the AC voltage. A converter system present in the vehicle converts AC to DC, thereby facilitating the charging process.

A series of researches were conducted in this field. A lot of them have been worked upon to understand the feasibility and implementation of this technology.

The Dynamic Wireless Charging System can be employed at traffic signals or at places where EVs move at a slower pace. The coil which is connected to the grid is installed in the roads. The vehicle while moving collects the magnetic field through the coil, placed at the base of the chassis. This is followed by a rectification process wherein the high-frequency AC is converted to DC.

Several challenges need to be addressed before dynamic charging becomes a reality. The air gap between the road and the vehicle pad which contains coils is not the same for all vehicles. For bigger vehicles like trucks, it can be troublesome.

Another disadvantage is the heavy initial investment. This novel technology needs a rapid transformation of urban infrastructure.

But nothing is impossible for a technology-driven world like this. An autonomous vehicle with self-charging capabilities will be a reality soon. Wireless charging technology can promote a sustainable economy with more adherence to renewable energy resources. Let us hope for a greener economy with safer locomotives!

References

1. https://doi.org/10.1016/j.jestch.2018.06.015

2. https://www.qualcomm.com/news/onq/2017/05/18/wireless-dynamic-ev-charging-evolution-qualcomm-halo

3. https://www.powerelectronics.com/markets/automotive/article/21864097/wireless-charging-of-electric-vehicles

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