20 kW Wireless Charging At 90% Efficiency Becomes Reality


SAE J2954 Wireless Charging - Timing Plan

SAE J2954 Wireless Charging – Timing Plan

Today’s residential wireless chargers are low current units, typically no higher than 7.7 kW, but that will change in the future as researchers at the Department of Energy’s Oak Ridge National Laboratory have already mastered a high-power system.

Today's Low Charge Rate Wireless Charger

Today’s Lower Charge Rate Wireless Charger for the Tesla Model S via Plugless Power

Per the ORNL press release:

“ORNL also received a special recognition award from R&D Magazine for the Wireless Power Transfer Based Electric and Plug-In Vehicle Charging System, submitted by Toyota Motor Engineering & Manufacturing North America and co-developed by a team of ORNL researchers with support from Cisco Systems and the International Transportation Innovation Center.”

“The team developed the world’s first 20-kilowatt wireless charging system for passenger cars and achieved 90 percent efficiency at three times the rate of the plug-in systems commonly used for electric vehicles today.”

This, of course, is a breakthrough for wireless charging. The press release states:

“Providing the same speed with the convenience of wireless charging could increase consumer acceptance of electric vehicles and is considered a key enabler for hands-free, autonomous vehicles. Higher power levels are also essential for powering larger vehicles such as trucks and buses.”

“The high-power wireless charging system relies on a unique architecture that includes an ORNL-built inverter, isolation transformer, vehicle-side electronics and coupling technologies.”

The wireless charging concept is a sound one, and now that power is way up and the efficiency is acceptable, we think this charging method will become increasingly prevalent in the very near future.

Categories: Charging


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56 Comments on "20 kW Wireless Charging At 90% Efficiency Becomes Reality"

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Shut up and take my money!
As the apple crowd says 😉

Roughly 10% is likely turned into waste heat. What is the duty cycle rated at? How hot does this get?

Given that a small ceramic space heater is about 1200 watts, 10% of 20 kW is a substantial amount of waste heat. How much is generated in the vehicle itself?

If they losses disappear as heat at the car, 2000 W is no big deal. But radios are sensitive down to few picowatts (trillonth of a watt, or -90 dBm). That means 2 kW (63 dBm) in air would have to be attenuated by 150 dB (factor of over million trillion) to be under noise floor of cell phones.

It’ll probably be out of band signal, but 150 dB is HUGE. I’d be curious how radios are affected by this charger.

Doubtful there will be any effect on gsm or umts, maybe ham radio, but as long as there is shielding on the vehicle, this effect should be negligible.
I wonder if the excess heat could be captured through a heat sync and used to precondition the cabin in colder months.

I’m thinking the opposite where the interference could cause GSM, etc. to drop out or become unintelligible while wireless charging. It would serve to raise the noise floor, and if Qualcomm is playing CDMA game, they’d modulate for better peak to average ratio. Obviously, it depends on how much margin you have at the location you’re trying to use the phone, but additional noise source is going to affect phones.

Ham will be affected, but they are much narrower band in Morse code. Wider band applications will be affected, but either way, home-brew guys could put in more effective filtering or move to different band.

A heat pipe might be a better idea

You know, as others have noted, 90% efficiency isn’t that bad… unless you’re talking about charging a car, in which case 10% of a LOT of energy = quite a bit. You fully charge a 60kWh EV, that’s frickin’ 6kWh lost to waste heat. That’s enough to run a normal house for a day.

10% for an average driver would be about 200 kWh per year.

For me that is about $10-20 a year and about 1,5% of my total electricity used.

Not a big deal…

Regular car chargers aren’t even that much more efficient. If this 90% efficiency includes the actual charging process, not only power transmission, the losses over level 1 are neglegable and even level 2 charging isn’t that much more efficient.

The currently best level 2 chargers are at 94%.

Thank you for that reality check!

Yeah, I think on average EV charging is at best about 91-92% efficient, and that may dip to 85% efficient as the car approaches maximum charge.

Waste heat won’t be a problem for slow charging. It might well be a problem if it’s used for fast or (future) superfast charging.

I think that conductive charging will have its place at the very cheap public and the very fast public charging.

350kW won’t be possible with inductive charging, not only because of the magnetic fields you are using, but also because of the gigantic internal charger you would have to build into the car.

And building a 50kW CCS, or even Level 2, station into a parking lot is still a lot more practical than digging it up and putting a coil in there.

But for private users inductive charging will be a very practical solution, especially if you have a fully autonomous car.

Actually, the average American home uses ~29.6kWh/day. So 6kWh would power a home for < 5 hours. It's still a lot of energy, but not nearly what you claim.

Also, most people won't be fully charging a 60kWh battery every day. I drive ~20 miles every day. Assuming 4miles/kWh, that's 5kWh. 10% loss would be .5kWh. Still not nothing, but only a small fraction of my daily energy usage.

Finally, consider that electric cars are already 3x as energy efficient as gas cars, and if the convenience or cool factor of wireless charging gets people to move to electric cars, then it's a huge net energy reduction.

Another Euro point of view

When on a sailing yacht, a typical mistake many yachties have done is to leave port with the electric cable still connected to shore power. This often causes damages. Did this yet occur to some EV owners here ? (leaving their garages with their cars still charging/connected).
I am often very absent minded so it would inevitably happen to me one day, for people like wireless charging would be good.

Totally impossible.
The J1772 protocol and inboard safety won’t engage motion if you’re connected.
I know, I forgot a couple of time, nothing move.

Another Euro point of view

Thanks for info (makes me feel stupid, of course such security had to be built in, silly of me to think it wasn’t).

This has and does happen with conversions which are often not even close to being as well engineered as a factory made vehicle.

The resulting damage can be expensive. I have witnessed motor controller power transistors pop like popcorn when switched on at a high charging voltage. Of course, being a conversion, the controller was being run at close to it’s voltage limit in the first place.

Although all new EVs include this start-blocking it is not a stupid question. ICEs normally does not have this feature, resulting in lots of ICE cars driving away from the gas statiion with the fuel dispenser still Attached to the car, resulitng in severe and costly damage to the fuel pump (you can find pictures on the net with cars driving around in traffic with the fuel hose still Attached).

Another costly problem with ICE cars is that people fill gasoline into diesel vehicles and opposite. Especially common in areas where diesel cars are common. Starting a diesel car with gasoline typically gives you a usd 6k repair.

Most hoses these days decouple from the pump, due to people doing that. I did it once, stopped, got out, plugged the decoupled hose back in and drove away.

There has been a case reported here, where somebody left it in the charge port and the car started rolling of a sloped driveway.
Things like that, are not preventable at the moment, but would be technically feasible with an electric motor in short.

Not 100% true – if you park on a hill, and the EV starts rolling, then it will damage the connected cable and EV/EVSE.

This wil offer a big boost to luxury auto makers who are preparing to offer 300+ mile EVs.

The car can dock itself, charge and notify the owner when it’s done.

Submitted by Toyota. That’s new!

Yeah, Toyota. I guess that they are not that late to the EV Party. But, definatly not fashionably late!

If you are harnessing the solar on you roof, and your powerwall, a little waste (10% of car charging) is acceptable especially with teenagers in the house. This keeps your Tesla at topped up “always”. Good for the whole family!

Good to see an increase in the power available from wireless charging. But that’s rather a far cry from the 120+ kW available from some Tesla Superchargers, let alone the 500-1000 kW we’re going to need for future superfast charging.

I don’t think we should ignore what Kdawg says about leakage from wireless charging. Overheating can be dealt with. I’m not sure that RF (Radio Frequency) interference can, so easily. If every superfast wireless charging station has to be surrounded by a Faraday cage, that’s probably going to make it impractically expensive.

It may be that we’ll have to settle for a direct connection for superfast charging, even after wireless becomes the standard for slow charging. 500 kW charging has already been proven possible with Proterra EV bus chargers, but an automated high current setup like that won’t be cheap, either.

It is still possible to do the same as Proterra under the vehicle instead of above it. High power conductive without intervention.

I keep on saying two mini pantographs coming from under a Tesla towards electronically secured ground contacts on a small bump on the ground would be great for that, but somehow, I never see any prototype or announcement in that direction.

If no one is doing it, it sure is a great idea!

For me, 8KW is fine at home for everyday driving. ~25 miles of range per hour. Midnight to 6am gets 150 miles of range. If I needed more, I could start at 8 pm. and get 80 KWh or 6pm and get 96 KWh.

20 KW at home would take care of those who have to drive 300 miles a day every day. Can’t be a whole lot of people I hope.

Well, if can do more it can sure do less.

The same system can be used in your garage at 1 KW and a low 110 V if it can handle 1000 KW and 1600 V. It can also do 120 KW at 400 V. That’s what‘s great about it, it can do it all in one system. Low power, supercharging or megacharging.

Priusmaniac said:

“I keep on saying two mini pantographs coming from under a Tesla towards electronically secured ground contacts on a small bump on the ground would be great for that, but somehow, I never see any prototype or announcement in that direction.”

And I keep pointing out that if you put the contacts underneath the vehicle and/or bury them in the pavement, then there will be no way to keep dirt, dust, mud etc. from the road from getting into the contacts, even if they have covers. When you open the cover, in comes the dirt, dust, and mud.

Why do you think Proterra put the charger plug on top of the bus, instead of underneath? It certainly is more expensive to put it on the roof! But putting it underneath simply isn’t practical.

Isn’t there loss on a typical EVSE as well? What does Tesla Hpwc run at? 95%?

IIRC plug less and other current tech uses DC.
I haven’t seen the details on this one. But generally efficiencies quoted related to wireless charging are just the efficiency of the wireless transfer itself.

So an AC/DC conversion at (for example) 95% would be happening before this.

I.e. wired efficiency is 95% AC/DC times ~100% wire efficiency or 95% overall
Vs wireless is 95% AC/DC times 90% wireless efficiency, or 86% overall.

It depends of a couple things.
First, it depend how you count it.
Loss is everywhere, in your breaker panel, in the wiring from it to the EVSE, the quality of the contact in your EVSE that switch power to the inboard charger, the type of coil of that contactor (usually not locking type) the quality of the control circuit inside the EVSE and the quality of the contact of the J1772 gun and of the car receptacle.
More or less than 3% is typical.
Consider that many of those losses are also present with induction charging adding to the inevitable loss of the frequency generator and converter.
I think 10% loss is excessive with anything electric, because most appliances that get energy star rating favor the highest efficiency in comparable device
Plugging in is the best, no question.

EVSE’s are all over 99% efficiency since they are just a fancy light switch (on or off, not even a dimmer).

Overall EV charging efficiency is generally quoted at between 85-92% efficient. That includes all losses, not just the EVSE. It includes AC/DC conversion, wiring resistance, and the fact that the battery cells themselves have sufficient resistance to cause about 2% efficiency loss while charging.

And the frequently cited 91-92% charging efficiency is probably optimistic. That’s probably only the maximum efficiency when the battery is mostly drained, with efficiency dropping as the battery approaches full charge. At least, that’s my understanding; I’m not an electrical engineer.

So what is 2kW loss gonna do to my cat?

Jk, I don’t have a cat but it makes you wonder.

The 2kW are not out in the air. The 2kW probably warm the charging plate on the downside of the car a bit and the plate on the ground gets warm.

So your cat is free to lay down on this floor heating or not. Might depend on the season of the year.

I’m not conversant with how safe or unsafe this particular model is, but if the unit only needs 22+ kw to get 20 kw into the car – that is definitely pretty good.

The question is, how much will it cost, and which manufacturers will support it?

We could use the product in my area, although the utility wouldn’t like any concentration of them in any one place, since unlike commercial customers, residential customers don’t pay for any ‘difficult loads’.

Eric Loveday, please link to the source for this story (insert the link in above). All I can find is this ORNL press release from last March. https://www.ornl.gov/news/ornl-surges-forward-20-kilowatt-wireless-charging-vehicles

Chris, the source is ORNL directly. It is there press release

Can you link to that ORNAL press release please? All I’ve found is something from March, so I’m wondering what is new here. Or did they email it out, and it’s not on their website yet?

I did see an ORNL presentation on wireless charging at an EV conference a few days ago, and there were some interesting details. I want to see if the press release touches on those.


It is rather lengthy…specific to wireless is bottom ~7 paragraphs

There you go. Thanks! So, I’ll point everyone to the March PR I linked to above for more on this.

The presentation I saw last week talked about this, but also talked about wireless charging on the move, i.e. embedded in the road. The study clearly demonstrated, to me, that such mobile wireless charging is absolutely ludicrous and not remotely achievable, although the ORNL presenter did not say that directly. He just provided the results of the study and left it for the audience to draw their own conclusion. Which I’m afraid many may have not. Frankly, this silly idea needs to be put to bed, and we should stop fantasizing about it.

Stationary wireless charging, though? I’m all for it. Shut up and take my money!

Chris C. said:

“…mobile wireless charging is absolutely ludicrous and not remotely achievable…

Indeed. It’s unfortunate that “green tech” advocates so often seem to let their wishful thinking so totally swamp (or should I say “trump”?) practical concerns. Equally ludicrous is the idea of the “solar roadway”, and the “hydrogen economy” is hardly any more practical, despite current efforts to actually make the latter a reality.

Dan Dan the driving man

maybe Musguri saker is right after all why don’t we go back to Battery tack Exchange Point systems?

Technically charging efficacy is about 80%.

Given wireless power delivery, (as quoted above), is 90%; we also need to consider conversion of the AC power to DC by the onboard charger (typically ~90%) to calculate overall charging effiency.

Combined the net charging efficacy would be ~80% (0.90 * 0.90).

Still a major advancement, particularly being able to deliver a 20 kW rate of power wirelessly!

I hope they mean 90% overall efficiency, thus including ACDC converter. But there are no details what so ever on how do they measure this. Untill then, don’t ever trust a chart if u did’t faked it yourself!

Common sense says that the 90% claim must only be for the wireless transfer of power. They can’t simply handwave away the other losses involved. There is a chain of transferring power from house wiring to battery cells, with a certain efficiency loss in every step in the chain. For example, you lose about 2% in the battery cells themselves, because charging them isn’t 100% efficient. There is also some loss in AC/DC conversion, which is unavoidable because wireless power transfer has to be AC, while batteries require DC power to charge.

I’m pretty sure that wireless charging promoters elide the other charging losses when promoting wireless charging. In reality, at it’s probably about 90% x 92% = 83% efficiency, and at that only under optimum conditions. Real world average efficiency will be less than 83% with wireless charging.

And if I’m wrong, then let’s see one or more citations of actual data from real-world, independent, qualified third-party testing.

ICE car manufacturers would kill to get a 10% improvement on fuel consumption. And some EV folks are wasting 10% just because they are too lazy to use a cable 🙂
Of course 10% would not be a large amount of money since the electricity is a lot cheaper than fossil fuels. But those 10% are also a increase in charging time, or 10% more electricity grid capacity (if you don’t want to lose them from your charging time…)

I am using European numbers for mixed driving for vW Golf as it comes in both BEV and diesel versions and are comparable.
e-Golf uses 1,27 kWh/10km
Golf diesel uses 0,49 L/10km or about 5kWh/km
Of course it is a lot better to reduce 10% from 5 kWh than from 1,27 kWh.

Don’t forget that the battery itself gets warmed up by the charging process, so that is also a heat loss. When releasing the charge, the battery warms up again, that is a heat loss. Then the charger warms up when charging. The controller heats up when driving. All those bits add up. Still, driving electric is much more energy efficient than a gas guzzler.

Yes, and also don’t forget that in colder climates that heatloss is not always wasted. A warmer battery gives better efficiency when driving. Driving longer trips in winter with a car like Leaf I notice that after a few fastcharges the battery gets “bigger” and also charges faster.

Nice, but not really something that’d make a difference for EV sales. Nice option for luxury car owners or for people who’re using a PEV* for business that involves lots of trips each day.

An important potential use of wireless charging that I can see is for buses and taxis that have regular locations where they stop, but not for long enough that it’s worth getting out and plugging in to a DCFC.

20kW would mean 1kWh for every 3 minutes stoppped. Or consider the benefit in cold weather, where an electric taxi or bus could use the power to keep the cabin heated, rather than running down the battery.

* If we’re talking wireless charging, should we stop calling them PEVs. :p

I wrongly thought during a long time that I needed >20KW charger at my home car park. But this is false. I need no more than 4KW at home, where I stay parked 8h per night and # all week-ends, as I consume less than 12KWH per work day for my local commutes, and in 8h I can recharge 24KWH each night, means charge every 2 x days even at that low speed. And in France 4KW is a lot cheaper subscriptions and much easier to mutualize at co-property / Building level too. Same for workplace carparks during working days. This said faster chargers xan still be very usefull outside the home and work places, for medium size inter-city trips for exemple. So that could be a very good solution for this. But not needed for my home nor my Work Place carparks.

It’s good enough, the bonus is going to be if they release this product it will incrementally be improved upon…The other aspect is the packaging…Whether residential or commercial, if you spend the money to install one, in a few years if a 40KW with 95% efficiency comes out, goal should be you can easily swap some hardware…