Chalmers University Demonstrates 500kW Wireless Charging Technology

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New wireless charging technology from Chalmers University can provide up to 500kW of power with less than 2% loss.
Researchers at Chalmers University in Sweden say they have developed a wireless charging technology that can charge batteries up to 500 kilowatts without connecting them to a charger with cables. They say the new charging equipment is complete and ready for series production. This technology will not necessarily be used to charge personal passenger vehicles, but it can be used in electric ferries, buses, or unmanned vehicles used in mining or agriculture to charge without using a robotic arm or connecting to a power source.
Yujing Liu, Professor of Electrical Engineering in the Department of Electrical Engineering at Chalmers University, focuses on renewable energy conversion and the electrification of transportation systems. “The marina could have a system built in to charge the ferry at certain stops when passengers get on and off the ship. Automatic and completely independent of weather and wind, the system can be charged 30 to 40 times a day. Electric trucks require high power charging. charging cables can become very thick and heavy and difficult to handle.”
Liu said that the rapid development of certain components and materials in recent years has opened the door to new charging possibilities. “The key factor is that we now have access to high-power silicon carbide semiconductors, the so-called SiC components. In terms of power electronics, they have only been on the market for a few years. They allow us to use more higher voltages, higher temperatures and higher switching frequencies,” he said. This is important because the frequency of the magnetic field limits the power that can be transferred between two coils of a given size.

“Previous wireless charging systems for vehicles used frequencies around 20kHz, just like conventional ovens. They became bulky and power transfer was inefficient. Now we are working at frequencies four times higher. Then induction suddenly became attractive,” explained Liu. He added that his research team maintains close ties with two of the world’s leading manufacturers of SiC modules, one in the US and one in Germany.
“With them, the rapid development of products will be directed towards higher currents, voltages and effects. Every two or three years, new versions will be introduced that are more tolerant. These types of components are important factors, there is a wide range of applications in electric vehicles, not just inductive charging.” “.
Another recent technological breakthrough involves copper wires in coils that respectively send and receive an oscillating magnetic field that forms a virtual bridge for the flow of energy across an air gap. The goal here is to use the highest possible frequency. “Then it doesn’t work with coils surrounded by regular copper wire. This causes very large losses at high frequencies,” Liu said.
Instead, the coils now consist of braided “copper ropes” made up of 10,000 copper fibers only 70 to 100 microns thick – about the size of a strand of human hair. Such so-called litz wire braids, suitable for high currents and high frequencies, have also appeared more recently. A third example of a new technology that enables powerful wireless charging is a new type of capacitor that increases the reactive power needed by the coil to create a strong enough magnetic field.
Liu stressed that charging electric vehicles requires multiple conversionsteps between DC and AC, as well as between different voltage levels. “So when we say we’ve achieved 98 percent efficiency from DC at the charging station to the battery, that number probably doesn’t matter much unless you’re clear about what you’re measuring. But you can say the same. , Regardless of whether you use Losses occur either with conventional conductive charging or with inductive charging. The efficiency we have now achieved means that the losses in inductive charging can be almost as low as in a conductive charging system. The difference is so small that in practice it is negligible, about one or two percent.”
CleanTechnica readers love specs, so here’s what we know from Electrive. Chalmers’ research team claims its wireless charging system is 98 percent efficient and capable of delivering up to 500kW of direct current per two square meters with a 15cm air gap between the ground and onboard pads. This corresponds to a loss of only 10 kW or 2% of the theoretical maximum charging power.
Liu is optimistic about this new wireless charging technology. For example, he doesn’t think it will replace the way we charge electric cars. “I drive an electric car myself, and I don’t think inductive charging will make any difference in the future. I drive home, plug it in… no problem.” on cables. “Perhaps it should not be argued that the technology itself is more sustainable. But it could make it easier to electrify large vehicles, which could speed up the phase-out of things like diesel-powered ferries,” he said.
Charging a car is very different from charging a ferry, plane, train, or oil rig. Most cars are parked 95% of the time. Most business equipment is in constant service and can’t wait to be recharged. Liu sees the benefits of new inductive charging technology for these commercial scenarios. No one really needs to charge a 500 kW electric car in the garage.
The focus of this study is not on wireless charging per se, but on how the technology continues to introduce new, cheaper, and more efficient ways of doing things that could accelerate the electric vehicle revolution. Think of it like the heyday of the PC, when the latest and greatest machine was obsolete before you even got home from Circuit City. (Remember them?) Today, electric vehicles are experiencing a similar burst of creativity. Such a beautiful thing!
Steve writes about the relationship between technology and sustainability from his home in Florida or anywhere the Force takes him. He prides himself on being “awake” and doesn’t care why the glass breaks. He believes what Socrates said 3,000 years ago: “The secret of change is to focus all your energy on creating the new, not fighting the old.”
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Post time: Mar-16-2023