48v 10kwh energy storage solar system.Brief analysis of dynamic charging technology of electric vehicles

Charging is like a bug for electric vehicles. It would be great if one day, electric vehicles could get rid of the shackles of charging piles and no longer have to look for charging piles everywhere. Charging is more convenient than refueling. After seeing this, everyone should understand the topic to be discussed today.

Charging is like a bug for electric cars. It would be great if one day, electric cars get rid of the shackles of charging piles and don't have to look for charging piles everywhere. Charging is more convenient than refueling.


Seeing this, everyone should understand the topic to be discussed today, wireless charging. But unlike wireless charging in a parking space, what we are going to discuss today is charging technology while driving. Of course, it also has a very academic name, called Dynamic Electric Vehicle Charging (DEVC) technology.


Imagine that electric cars don’t need to be charged deliberately and can be charged while driving on the road every day, which brings many benefits. First of all, the load on the battery can be reduced, because the car can be charged anytime and anywhere, so large-capacity batteries are no longer necessary, and the load of the vehicle is also reduced.


Secondly, there is no need to wait for charging. At present, charging of electric vehicles is not as convenient as refueling of gasoline vehicles, but wireless charging can charge while driving, reducing time and cost. Finally, the cruising range issue is solved. The cruising range of electric vehicles is wirelessly extended, and the problem of range anxiety no longer exists.
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Sounds farfetched? In fact, theoretically speaking, it is not difficult to implement. Let's first understand its principle.


1. What is wireless charging?


Let’s start with wireless charging. We understand that wireless charging relies on current and magnetic field. Electricity and magnetism, a pair of love-hate CPs, often do things together.


In 1819, Danish scientist Oersted observed that if a current flows through a wire, a magnetic field will develop around it. Later, it was discovered that if the wires were formed into a ring or even a coil, the magnetic field generated would be stronger and more concentrated. This is called the current magnetic effect.


In 1831, Faraday discovered that if a magnet or other magnetic field source is brought close to a coil with no current, an induced current will occur in the coil. This is called electromagnetic induction.
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So how do we put electricity and magnetism to use and stably output current to us?


We need two coils. If one coil is energized, then there will be a magnetic field around the coil; then we move the other coil close to it, and then there will be current in this coil. When the current is directed into the battery, wireless charging can be completed.


Applied to the automotive field, this is electromagnetic induction wireless charging.


We apply alternating current to the coil on the ground. As the magnitude and direction of the current change, the strength and direction of the magnetic field around the coil also continue to change, forming an interactive magnetic field. At this time, the coil of the vehicle chassis is in a constantly changing magnetic field, and an interactive current will be generated inside the coil, which will be rectified through a series of circuits to charge the battery.


2. Wireless charging forced out of obsessive-compulsive disorder


Electromagnetic induction wireless charging is a technology that major automobile companies prefer to adopt in the early stages of research on wireless charging.


Car companies such as Mercedes-Benz, Audi, and Volvo have all developed a number of electromagnetic induction wireless charging models.


There will be something that looks like a mat in the parking space. In fact, it is a primary coil used to generate a magnetic field. Vehicle chassis that can be used for wireless charging will also have a coil, which we call a secondary coil, to generate electrical current.


However, electromagnetic induction wireless charging has a big drawback, and that is distance. In order for this technology to generate electric current, the two coils must be exactly opposite to each other. Once deviation occurs, the electric current will not be generated.


Therefore, such technology often needs to be paired with precise automatic parking technology to allow the vehicle to park just above the wireless charging pad.


Sounds like a lot of trouble? This is to let everyone practice the rhythm of Virgo's obsessive-compulsive disorder enhancement.


Therefore, scientists are studying another wireless charging technology, which is magnetic field resonance wireless charging. We understand that when two objects vibrate at the same frequency, or resonate at a specific frequency, they can exchange energy with each other.


Magnetic field resonance means that the primary coil generates a magnetic field that vibrates at a fixed frequency, that is, a resonant magnetic field, and then the vibration frequency of the secondary coil's magnetic field is the same, creating resonance, and ultimately achieving energy transfer.


In 2007, a research team at MIT successfully lit a 60W light bulb 2m away through an electromagnetic resonator.


In the automotive field, Toyota conducted experiments in 2012, adding a secondary coil that can vibrate at a certain frequency on a plug-in hybrid Prius. There is a resonant magnetic field on the parking space. When they all vibrate at the same frequency, the secondary coil can convert the current of the resonant magnetic field.


The output power of this wireless power supply system is 2kW. The frequency band used is 85kHz, which is internationally recognized, and the power transmission efficiency is about 80%.


In this verification test, the distance between the ground's resonant magnetic field and the secondary coil at the bottom of the vehicle was about 15cm. The maximum allowable range of horizontal misalignment is the width of a tire (about 20cm).


Qualcomm has also launched a wireless charging system called Halo, but it also stayed at static wireless charging.


The magnetic resonance effect is used to realize energy transmission between the ground charging pad and the electric vehicle charging plate. The power of this charging system can reach 20kW, and the battery pack of the Tesla MODEL SP85 with 85kWh takes about 5 hours.


3. Let electric cars move


If a charging pad or a resonant magnetic field is placed on the road, the vehicle can be charged while running, and no longer need charging piles.


In May this year, Qualcomm used a Renault all-electric Kangoo van to complete dynamic wireless charging road detection in Paris.


Two electric vehicles drove on this 100m-long road at different speeds and completed charging at the same time. During the detection, the speed of the Kango detection vehicle reached 100km/h, and the maximum charging power could reach 20kW.


This 100m-long road detection constructed by Qualcomm contains 4 energy supply units, each unit is responsible for the power supply of 25m of road. At the same time, each 25m long energy section has 14 sub-modules, including coils and energy conversion circuits.


As for the cost issue, a study by Renault, EDF and Northern France Highways Company pointed out that the cost of building dynamic charging roads is 4 million euros/km (dual lane), which can be said to be quite expensive.


It seems that such expensive roads can only be popularized on bus routes 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 City in the south. The electric buses running on it use magnetic field resonance to achieve wireless charging.


After talking about foreign countries, our country’s research on wireless dynamic charging is not lagging behind. One of the more well-known companies is ZTE, which has already launched wireless charging demonstration lines in Chongqing, Hubei and other places.


Wireless dynamic charging is still in a state of research and is still a long way from being widely popularized. Just thinking about it, there are a lot of issues that have not been resolved, such as whether the compatibility of vehicles is consistent, whether the road is open or closed, and whether the current on the road can carry multiple vehicles for charging? There is also road monitoring and maintenance. These are all obstacles to wireless dynamic charging, but technology is always developing. I believe in the power of technology, charging problems will always be solved. Charging an electric car while driving is definitely not a pipe dream.


Editor's comment: With the current technology, if you want to charge electric vehicles while driving, you need to modify the roads. Many people think that the cost is too expensive and the gain outweighs the loss. However, any advanced technology develops along with controversy. Let scientists be more creative. Maybe one day charging will be as convenient and fast as WIFI.