Dr. John Boys, Emeritus Distinguished Professor and Dr. Grant Covic
Cutting the Chord: How & Why Wireless Charging is the Future
By Grant Covic
Grant Covic, Distinguished Lecturer, IEEE Transportation Electrification Community on the why and how inductive -- i.e. wireless -- EV charging is the future.
By 2025, more than 37 million electric vehicles (EVs) will be on the road worldwide, Navigant Research predicts. That’s also the time frame when technological and industry trends will reach the point that EVs become cost competitive against conventional vehicles, even without subsidies.
Extending the range of EVs is critical for growing their addressable market beyond a niche. After all, most consumers and fleet owners don’t want to constantly worry about running out of power. For them, the easiest way to avoid that drawback is to stick with conventional vehicles.
Advances in battery technology obviously will help minimize that concern and the sales barrier it creates. Less obvious is work on another aspect that’s equally important for making EVs mainstream: wireless charging. Instead of plugging in their vehicles, drivers would simply park as usual over a coil placed on the ground or buried in it.
Does Anyone Really Need It?
Wireless charging isn’t a solution in search of a problem. Just the opposite: Cutting the cord eliminates multiple problems, starting with the obvious one of forgetting to plug in.
For example, it’s easy for parents juggling groceries and a toddler to forget to plug in when they arrive at home—an oversight they don’t realize until it’s time to leave for day care and work. For fleet owners, the forgetfulness problem scales up, such as lost productivity when employees wind up stranded on the side of the road. And for consumers and fleet owners alike, wireless also eliminates the expensive problem of connectors damaged by debris and weather infiltration, and the need to plug in outside in all weather conditions.
Here’s another example: Suppose you pull into your garage and think, “I’m going back out in a half hour, so no point in bothering to plug in because that won’t give me much of a charge.” But then there’s a change of plans, and you wind up spending the evening at home. The next morning, your battery is as low as it was when you got home, and you’re kicking yourself for not just plugging in. Wireless charging eliminates that problem and the reasons for it.
Other benefits are less obvious. Making charging easily available and simple to use (without having to do anything other than park normally) means that people will take advantage of it more often. Without this many consumers will rely on plugging in at home. In developed countries, electric utilities look at consumption history to assume that each household will use a certain amount of power—about 2 kW, on average—and they build their infrastructure accordingly.
Now fast forward to, say, 2025, when EVs are more common. Suddenly there are many households with one or two EVs consuming 10 kW or more at night. To accommodate that demand, utilities would have to upgrade their neighborhood transformers and other infrastructure—something that takes a lot of money and lead time to implement.
Wireless charging can significantly reduce those upgrades by spreading demand over a larger amount of geography and time. Today, vehicles are charged at home or, in the case of fleets, at the owner’s place of business. Tomorrow, they’ll be charged in a variety of additional places, including at work, at the store, on the street and in places of interest (such as at the beach and parks which are often weekend locations which if some distance away raises natural concerns over the range of the EV). The provision of Wireless Electric Vehicle Charging (WEVC) points at these locations which are as easy to use as parking your car, may increase employee/customer loyalty, attract new customers, and encourage wider adoption of wirelessly charged vehicles in larger population centers, thus reducing air pollution. Ideally, vehicles can be charged whenever and wherever they are parked.
No Need to Wait
Many, if not all, of the automotive manufacturers have spent the past several years working with their suppliers evaluating, developing and refining wireless charging technologies. These WEVC systems have been successfully integrated and tested on a number of different vehicle platforms: Renault Fluence; Nissan Leaf; BMWi3; BMWi8 and Honda Accord.
Moreover, the technology has been used and tested in the harsh environment of motorsports over the past 3 years. Qualcomm Technologies, Inc. was an official technology and founding partner of FIA Formula E Championship and integrated 7.4 kW charging systems into the official FIA Formula E safety cars. Enabling these key support vehicles to be charged wirelessly ensured they remain fully charged at all time, ready to be rapidly deployed in case of an emergency.
The number of development contracts and requests for quotation from automotive manufacturers is on the increase and it is expected that production orders will be placed soon and we will start to see WEVC systems on production vehicles in the next 2-3 years.
Today’s wireless charging technologies have efficiencies north of 90 percent, which is just a percent or two less than plug-in systems. The magnetics of the wireless transformer are essentially split (the primary on the ground and the secondary on the vehicle), and power is coupled using fields that are shaped to exist in the gap. The power-transfer efficiency is further improved by turning on only when a vehicle is present and needing power.
The wireless architecture is naturally isolated so there’s no risk of shock, and in operation fields are shaped and controlled, to both maximize power transfer efficiency and to minimize fields outside the vehicle footprint to remove potential interference or exposure to humans. Additional safety is incorporated in the ground pad using ancillary systems for foreign object detection (FOD) and living object protection (LOP). Should either FOD or LOP safety system be triggered, power transfer will be suspended. The driver will be notified via a phone or email alert, and charging will restart once the metallic or living object has been removed or moves on.
Multi-vendor interoperability is another desirable goal. Interoperability is the ability of any vehicle to charge on any ground pad irrespective of their design, manufacturer or vehicle to which they are fitted. Wireless charging won’t be attractive to vehicle owners if they have to wonder whether their destination has a compatible system. The good news is that the automotive industry is working towards standardization of WEVC. Over the past couple of years, automakers and others have been working to iron out these differences. They have a vested interest in interoperability because it eliminates the expense of developing country- or region-specific wireless charging solutions.
“SAE TIR J2954 Wireless Power Transfer for Light-Duty Plug-In/ Electric Vehicles and Alignment Methodology,” was published in May 2016. Although still work-in-progress, when complete this standard will define criteria for safety and electromagnetic limits, testing, and efficiency and interoperability targets.
“This first in a series of documents will enable consumers to simply park their vehicles into spaces equipped with TIR J2954 equipment and walk away without doing anything to charge their PH/EV,” says Jesse Schneider, chair of SAE International’s Wireless Power Transfer committee. “The frequency band, safety, interoperability, EMC/ EMF limits as well as coil definitions from SAE TIR J2954 enable any compatible vehicle to charge wirelessly from its WPT home charger, work, or a shopping mall WPT charger, etc. with the same charging ability. All of this makes it possible to seamlessly transfer power over an air gap with high efficiencies.”
The Fleet Factor
By late 2018 or early 2019, expect to see WEVC emerge as an option: initially on luxury vehicles, as is the case with just about every new technology, and then steadily downmarket. Some fleet owners could be early adopters even though they don’t buy premium vehicles.
For example, taxi companies were among the first and biggest buyers of hybrids. The aforementioned scenario of municipal-owned wireless charging stations on streets is an ideal fit for taxis. One reason is because taxi companies could buy EVs without worrying that those vehicles wouldn’t be able to return to their facility often enough to stay charged. Another reason, particularly in hot climates, is that EV taxis could use public wireless charging to keep their air conditioning going while waiting for customers.
Fleet adoption creates a snowball effect: The more taxis, rental cars and other fleet vehicles that have it, the greater the volume of wireless charging equipment and infrastructure. Those volumes drive down the cost, enabling it to be added to an even wider range of vehicles, including entry-level models, and used in a wider range of markets, such as developing countries.
Indeed, wireless charging could be a particularly good fit for countries with limited and/or low-capacity electrical infrastructure by helping customers to be easily connected to the grid more often and thereby helping to spread the charging demand over a wider time frame and geography. For example, solar and wind could power wireless charging stations because vehicles would use them only for short periods to top up rather than for hours or overnight. That’s one more reason why wireless charging is a matter of when rather than if or where.
Dynamic electric vehicle charging (charging on the move), is a potential future application of this technology. This could be applicable in slow moving traffic, for instance at taxi ranks and also at higher speeds, such as lanes on a highway. As an example, Qualcomm recently showcased such a demonstration that can provide 20 kW to a vehicle for charging while it is travelling at speeds up to and in excess of 100 km/h. The technology is an obvious fit with autonomous vehicles.
About the Author
Grant Covic is a distinguished lecturer for the IEEE Transportation Electrification Community and a Senior Member of IEEE. As a professor in the Department of Electrical and Computer Engineering at The University of Auckland (UoA), Grant’s research and consulting interests are focused on industrial solutions using inductive (contact-less) power transfer (IPT). Over the past 15 years he has published more than 100 international refereed papers in this field, worked with over 40 postgraduates and filed over 40 patents, all of which are licensed to various global companies in specialized application fields. Grant is a Fellow of both the Institution of Professional Engineers New Zealand, and the Royal Society of New Zealand. Presently he heads inductive power research at the UoA and co-leads the interoperability sub-team within the SAE J2954 wireless charging standard for EVs.
Originally published: 29 Jun 2017
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