Oak Ridge National Laboratory Demonstrates 20kW Inductive, Dynamic Charging System for Electric Cars With 90 Percent Efficiency

There’s a long-running joke among certain groups of hardware engineers, early adopters and geeks which suggests that adding wireless to something — be it wifi, bluetooth or 4g connectivity makes it immediately superior to a product without it. And it’s with good reason too: in the past two decades, we’ve seen a gradual change in consumer technology as more and more gadgets ditch physical wired connections in favor for wireless alternatives. Depending on the gadget you buy, it’s even possible to buy a device that uses wireless inductive charging to transfer power into your device’s battery without the need to physically plug a cable in.

Automakers have been working on inductive charging for some time.

Automakers have been working on inductive charging for some time.

While offering inductive charging in the gadget world is rapidly becoming a must-have feature for the latest and greatest, the latest generation of electric cars — which many view as being the ultimate electric gadget — have, for the most part, stuck to physical conductive charging systems. Although previous generations of electric cars like the much-missed GM EV1 and first-generation Toyota RAV4 EV used inductive charging to wirelessly transfer power from an external charging station into their battery packs, they required the user to physically plug-in a special short-distance inductive charging paddle into a slot on the front of the car to initiate charging. Despite being technically wireless in their operation (at the time the system was marketed as being far safer than an electromechanical conductive charging system due to there being no exposed wires or contacts) they were still essentially tethered by a cable, meaning the act of ‘plugging in’ was the same as it is for most of today’s electric cars.

In the past decade however, we’ve seen some major improvements in wireless inductive charging technology. Made possible by the latest materials, construction techniques and more advanced electronics, electric car wireless charging systems can now transfer power safely over far larger distances with far less power loss than their predecessors. Now, such systems — which we’re about to test on our 2013 Nissan LEAF staff car — are still being treated as aftermarket addons, custom build-to-order additions or features that will be added to next-generation versions of already popular electric cars.

Oak Ridge National Laboratory says it has a system capable of transferring 20 kW of power.

Oak Ridge National Laboratory says it has a system capable of transferring 20 kW of power.

Despite the progress made thus far however, most wireless inductive charging systems on the market today offer power transfer rates of between 3 kilowatts and 7 kilowatts (with more powerful ones being developed by most inductive charging specialists behind the scenes). While the advent of autonomous vehicle technology means that lower-powered inductive charging is starting to make sense in some use cases, wireless inductive charging hasn’t been able to match the high-power transfer rates offered by DC quick charge technology like the CHAdeMO and CCS quick charge standards or indeed Tesla’s proprietary Supercharger protocol.

Now however, a team of researchers at Oak Ridge National Laboratory have demonstrated a 20 kilowatt inductive charging system that is not only capable of transferring power from charging station to car with more than 90 percent efficiency but can also operate dynamically, meaning it can transfer power to a moving electric vehicle via a series of inductive charging plates embedded in the ground.

Taken independently, none of these three features are new. In the past few years, we’ve seen high-power inductive charging systems trialed by several charging specialists and several automakers. Similarly, we’ve seen demonstrations of dynamic wireless inductive charging systems in which power has been transferred at reasonably high power rates from a series of stationary plates to a moving vehicle.

What makes ORNL’s system special however is that it manages all of these.

The system has taken less than three years to design and build.

The system has taken less than three years to design and build.

Funded by money from the Energy Efficiency and Renewable Energy’s Vehicle Technology Office as part of a broad portfolio of different projects as part of the U.S. Department of Energy’s EV Everywhere Grand Challenge, ORNL’s current system took less that three years to develop and has been fitted to a 2012 Toyota RAV4 EV. The system itself, which consists of an ORNL-built power inverter, isolation transformer, vehicle-side electronics and coupling system, operates in conjunction with an additional 10 kilowatt-hour lithium-ion battery pack fitted to the RAV4 EV.

The system, which you can see above, isn’t exactly elegant at this stage — but with all research projects of this nature functionality comes before cosmetics. Once further testing has been completed, the technology could then be repackaged for commercial use, although it’s not clear at the current time if that is what will happen in this case.

Looking forward, the team says it hopes to soon build a prototype 50 kilowatt system capable of transferring the same kind of energy through inductive charging as a typical CHAdeMO DC quick charging station. Given the large amount of power being transferred, ORNL’s research team have developed special shielding and focusing technology to ensure the high-frequency magnetic fields generated by the inductive charging system are safely contained by the system and don’t cause harm to humans, animals or the vehicle’s other systems.

Given that most electric cars on the road today consume between 10 and 20 kilowatts during normal, everyday driving, only using more power during heavy acceleration or while climbing steep hills, the 20 kilowatt barrier is a major milestone for wireless inductive charging. That’s because a system capable of reliably transferring 20 kilowatts to a moving electric car could operate as a zero-emission range-extender on freeways. Transferring 50 kilowatts in a similar way would not only make it possible for an electric car to use inductive power transfer to move itself along but also replenish its battery pack without needing to have 30-minute recharging stops every hour or two.

For now, this technology is very much in the laboratory — but in the not-too distant future it may be cheaper in some situations to use inductive charging to supplement an electric car’s range rather than fit it with a massive and heavy battery pack.


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  • William

    Wait, that picture — “Toyota EV”? What is that car?

  • Jeff Songster

    Gotta love the rates and the mobility while charging… How much per mile would this cost to add to existing roads… and I wonder whether one would need autopilot features to keep car centered over it for maximum transfer.

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