However, technology is constantly evolving, and with the power of technology, the charging problem will eventually be solved. The idea of charging electric vehicles while driving is definitely not a pipe dream.
Charging is like a bug for electric vehicles. How wonderful it would be if one day electric vehicles could be freed from the constraints of charging stations, and there was no need to search for charging stations everywhere, and charging would be more convenient than refueling.
By now, you should all understand the topic we're discussing today: wireless charging. However, unlike wireless charging in a parking space, today we're talking about technology that allows you to charge your car while driving. It also has a more academic name: Dynamic Charging for Electric Vehicles (DEVC) technology.
Imagine an electric car that doesn't need to be deliberately charged; it can be charged while driving every day, bringing numerous benefits. First, it would "lighten the load" on the battery. Since the car can be charged anytime, anywhere, a large-capacity battery would be less necessary, and the vehicle's load would decrease accordingly.
Secondly, charging will no longer require waiting. Currently, charging electric vehicles is still not as convenient as refueling a gasoline car, but wireless charging allows you to charge while driving, reducing time costs. Finally, it solves the range anxiety problem. The driving range of electric vehicles is wirelessly extended, eliminating range anxiety.
Sounds like a fantasy? Actually, theoretically it's not difficult to implement. Let's first understand its principle.
I. What is wireless charging?
Let's start with wireless charging. We know that wireless charging relies on electric current and magnetic fields. Electricity and magnetism, this love-hate pair, often get into trouble together.
In 1819, Danish scientist Ørsted observed that a magnetic field would appear around a conductor when an electric current was flowing through it. Later, it was discovered that when the conductor was coiled into a loop or even a coil, the magnetic field would be stronger and more concentrated; this is known as the current magnetic effect.
In 1831, Faraday discovered that if a magnet or other source of magnetic field is brought near a coil without current, an induced current will appear in the coil; this is called electromagnetic induction.
So how can we make electricity and magnetism work together to stably output current to us?
We need two coils. When we energize one coil, a magnetic field is created around it. Then we bring the other coil closer, and a current flows through it. This current is then guided into the battery, completing the wireless charging process.
When applied to the automotive industry, this is known as electromagnetic induction wireless charging.
We apply alternating current to a coil located on the ground. As the magnitude and direction of the current change, the strength and direction of the magnetic field around the coil also change, forming an interactive magnetic field. At this time, the coil in the vehicle chassis is in a constantly changing magnetic field, and an interactive current will appear inside the coil. After being rectified by a series of circuits, it charges the battery.
II. Wireless charging that triggered my obsessive-compulsive disorder
Electromagnetic induction wireless charging is a technology that major car companies preferred to use in the early stages of their research on wireless charging.
In parking spaces, there's a mat-like object that's actually a primary coil used to generate a magnetic field. Vehicles that can be wirelessly charged also have a coil in their chassis, called a secondary coil, used to generate current.
However, electromagnetic induction wireless charging has a major drawback: distance. For this technology to generate current, the two coils must be perfectly aligned; if there is any deviation, no current will be generated.
Therefore, such technology often needs to be paired with precise automatic parking technology to ensure that the vehicle is parked exactly on top of the wireless charging pad.
Doesn't that sound complicated? It's like it's trying to turn everyone into a Virgo with OCD.
Therefore, scientists researched another wireless charging technology: magnetic resonance wireless charging. We understand that when two objects resonate at the same frequency, or in other words, at a specific frequency, they can exchange energy with each other.
Magnetic resonance occurs when a primary coil generates a magnetic field that oscillates at a fixed frequency, known as a resonant magnetic field. When the secondary coil's magnetic field oscillates at the same frequency, resonance occurs, ultimately resulting in energy transfer.
In 2007, a research team at MIT successfully lit a 60W light bulb 2 meters away using an electromagnetic resonator.
In the automotive field, Toyota conducted an experiment in 2012, adding a secondary coil that could vibrate at a certain frequency to a plug-in hybrid Prius. There is a resonant magnetic field in the parking space, and when they all vibrate at the same frequency, the secondary coil can convert the current of the resonant magnetic field.
This wireless power supply system has an output power of 2kW. It uses the internationally agreed-upon 85kHz frequency band, with a power transmission efficiency of approximately 80%.
In this verification experiment, the distance between the resonant magnetic field on the ground and the secondary coil at the bottom of the vehicle was approximately 15cm. The maximum permissible range for horizontal misalignment was the width of one tire (approximately 20cm).
Qualcomm also launched a wireless charging system called Halo, but it only supported static wireless charging.
The system utilizes the magnetic resonance effect to achieve energy transfer between the ground charging pad and the electric vehicle charging plate. This charging system has a power of up to 20kW and takes about 5 hours to fully charge an 85kWh TSL AMODEL SP85 battery pack.
III. Getting Electric Vehicles Moving
If a charging pad or resonant magnetic field were placed on the road, vehicles could charge while driving, eliminating the need for charging stations.
In May of this year, Qualcomm completed a dynamic wireless charging road test in Paris using a Renault all-electric Kangoo van.
Two electric vehicles traveled at different speeds along this 100m-long road and completed charging simultaneously. During the test, the Kango test vehicle reached a speed of 100km/h and a maximum charging power of 20kW.
The 100m-long road test built by Qualcomm includes four power supply units, each responsible for powering 25m of the road. Each 25m section also contains 14 sub-modules, including coils and energy conversion circuits.
Regarding the cost, a study by Renault, EDF, and MESSENGERS (Mercedes-Benz-France Highways) indicates that the cost of building a dynamically charging road is €4 million per km (two lanes), which is quite expensive.
Such "precious" roads can only be popularized on bus lanes first. In South Korea, the Korea Advanced Institute of Science and Technology (KAIST) has built a 12km-long dynamic charging road at the train station in Gumi, a city in the south. The electric buses running on it use magnetic resonance to achieve wireless charging.
Having discussed international examples, our country is also keeping pace in its research on wireless dynamic charging. ZTE Corporation is a notable example, and it has already begun testing wireless charging demonstration lines in Chongqing, Hubei, and other locations.
Wireless dynamic charging is currently still in the research stage and is far from widespread adoption. A multitude of problems remain unsolved, such as whether vehicle compatibility will be consistent, whether roads are open or closed, and whether the highway's current capacity can handle multiple vehicles charging simultaneously. There are also road monitoring and maintenance challenges. These are all obstacles to wireless dynamic charging. However, technology is constantly evolving, and with the power of technology, the charging difficulties will eventually be resolved. Electric vehicles charging while driving is definitely not a pipe dream.
