- Aug 24, 2022 3:25 pm GMT
This item is part of the Electrification of Transportation - August 2022 SPECIAL ISSUE, click here for more
There are many myths surrounding wireless charging for electric vehicles (EVs) – is it real, is it efficient, and does it work? The answer to all three is an unequivocal, “YES!”
Let’s look at some of the myths around wireless charging for EVs and its impact on utilities and the electric grid. And then the realities.
Myth: “It’s not real yet.”
As evidenced by what’s happening in Korea and China, this is clearly not the case. In addition to car manufacturers, fleets around the world are also charging wirelessly. It’s not just an experiment, it’s here. And there are compelling use cases for both personal and commercial application. Check out this Tesla, which charges wirelessly.
Myth: “It would take too long to charge.”
Nope. The wireless charging standard built on WiTricity’s patented solution charges just as quickly as a Level 2 plug-in charger. And since you don’t worry about remembering to plug it in – you simply park and go – it adds peace of mind as well.
Myth: “Plug-in charging is 100% efficient, and wireless, well…”
First, it’s important to understand that plug-in charging is not 100% efficient. Energy loss, primarily in the form of heat, occurs every step of the way from grid to battery. What’s more, regardless of the brand, a plug-in EV charger is made of many components, any one of which may be more or less efficient than similar components in another charger. So, the “efficiency” of the transfer of energy from the grid all the way to battery encompasses a range; a typical Level 2 home charger operates in the range of about 83-94% efficiency grid-to-battery depending on which one you buy.
In the plug-in AC EV charging scenario, much of the heavy lifting is done on the vehicle through the On-Board Charger (OBC) that includes the Rectifier PFC, Inverter, Transformer, and Rectifier – all of which are needed to make the grid power into power that the EV battery can consume. (The unit hanging on the wall is relatively uncomplicated as this video very well explains.)
But with wireless charging, the vehicle doesn’t need an On-Board Charger (OBC), so this helps to reduce the charging complexity on the vehicle. Some of those same switch-mode power operations happen in the wall box as opposed to in the vehicle:
Side Note: Mind the Gap
People ask why doesn’t the “gap” between the ground pad and the vehicle create loss? It seems counterintuitive that space wouldn’t introduce inefficiency. The ground pad and vehicle pad convert the alternating current into the magnetic field that transfers power over the air gap. And, because we use magnetic resonance with specially designed low-loss resonators to transfer power, the loss is very small. In fact, the air gap between the ground and vehicle serves the same safety function as the isolation that occurs for plug-in charging through the isolation transformer (in the OBC between the grid connection and the vehicle). With the highly resonant design of the wireless charger, it’s nearly as efficient as the isolation transformer used for plug-in charging. Wireless charging operates within a narrow band of efficiency (88-93%) that is equivalent to Level 2 plug-in charging, plus you get the added efficiency of not having to spend time plugging and unplugging the vehicle.
In addition, every time you park and charge wirelessly, you’re more likely to be operating in the 20-80% state of charge (SOC) range that the battery likes – and is the most efficient. With plug-in charging, it’s less likely that the 20-80% SOC range will be maintained since drivers tend to forget to plug-in, or don’t bother when they know they have enough battery left for their next journey. In fact, many people plug in once a week, drive all week, and then plug in on the weekend. Not only is this less efficient but it’s harder on the battery. If you’d like a deeper technical dive into magnetic resonance, check out our whitepaper here.
Myth: “It would take too much trouble to get the alignment just right.”
Wireless charging for EVs isn’t like the inductive charging you might use for your toothbrush or phone, where the coils must align perfectly to get a charge. The standard based on WiTricity’s design uses magnetic resonance, which is pretty forgiving. So you just drive up, park, and walk away.
Myth: “Is plugging in really that much of a hassle?”
It’s human nature to find easier, simpler solutions to things that may seem at the time to be “good enough.” (Indoor plumbing anyone?) So a simpler solution with no moving parts means a safer, more reliable charge: no dealing with an armful of squirming toddler while trying to wrangle the cord, nothing to fumble with in inclement weather, nothing to break or get stolen. In commercial applications, those charging cords just get bigger, more unwieldy, and more expensive, where they become tripping hazards to boot.
Myth: “V2G through wireless charging isn’t real.”
WiTricity and Honda demonstrated Wireless charging and V2G in 2017 – and it’s on our product roadmap today.
Myth: “Wireless charging is not as helpful as plug-in charging for utilities looking to assist with EV transformation.”
With Vehicle-to-Grid (V2G) technology enabled, electric vehicles can actually help stabilize the grid by addressing the imbalance between periods of peak demand and peak supply – enabling two-way power flow between the grid and the batteries in an electrified vehicle. For V2G to be dependable, however, the vehicles need to be connected to the charger. Just as wireless charging will simplify connection of vehicles to the grid for charging purposes, it also simplifies connection to the grid for V2G purposes – nobody has to remember to plug in.
Utilities are working with local governments and fleets to build out the infrastructure to support the electrification of fleets. Now is the time to start future-proofing those investments by anticipating the arrival of wireless charging and the many advantages it brings in safety, reliability, resilience and convenience. Want to learn more? Sign up for the WiTricity newsletter.
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