Category: wireless charging

The Wireless Charging of Moving Electric Vehicles Just Overcame A Major Hurdle

Electric Cars

If electric cars could recharge while driving down a highway, it would virtually eliminate concerns about their range and lower their cost, perhaps making electricity the standard fuel for vehicles.

Now Stanford University scientists have overcome a major hurdle to such a future by wirelessly transmitting electricity to a nearby moving object. Their results are published in the June 15 edition of Nature.

Professor Shanhui Fan (left) and graduate student Sid Assawaworrarit have developed a device that can wirelessly charge a moving object at close range. The technology could be used to charge electric cars on the highway, or medical implants and cellphones as you walk nearby. (Image Credit: Mark Shwartz/Stanford University)

“In addition to advancing the wireless charging of vehicles and personal devices like cellphones, our new technology may untether robotics in manufacturing, which also are on the move,” said Shanhui Fan, a professor of electrical engineering and senior author of the study. “We still need to significantly increase the amount of electricity being transferred to charge electric cars, but we may not need to push the distance too much more.”

The group built on existing technology developed in 2007 at MIT for transmitting electricity wirelessly over a distance of a few feet to a stationary object. In the new work, the team transmitted electricity wirelessly to a moving LED lightbulb. That demonstration only involved a 1-milliwatt charge, whereas electric cars often require tens of kilowatts to operate. The team is now working on greatly increasing the amount of electricity that can be transferred, and tweaking the system to extend the transfer distance and improve efficiency.

Driving Range

Wireless charging would address a major drawback of plug-in electric cars —  their limited driving range. Tesla Motors expects its upcoming Model 3 to go more than 200 miles on a single charge, and the Chevy Bolt, which is already on the market, has an advertised range of 238 miles. But electric vehicle batteries generally take several hours to fully recharge. A charge-as-you-drive system would overcome these limitations.

tesla model 3 electric vehicles
The Tesla Model 3.

“In theory, one could drive for an unlimited amount of time without having to stop to recharge,” Fan explained. “The hope is that you’ll be able to charge your electric car while you’re driving down the highway. A coil in the bottom of the vehicle could receive electricity from a series of coils connected to an electric current embedded in the road.”

Some transportation experts envision an automated highway system, where driverless electric vehicles are wirelessly charged by solar power or other renewable energy sources. The goal would be to reduce accidents and dramatically improve the flow of traffic while lowering greenhouse gas emissions.

Wireless technology could also assist GPS navigation of driverless cars. GPS is accurate up to about 35 feet. For safety, autonomous cars need to be in the center of the lane where the transmitter coils would be embedded, providing very precise positioning for GPS satellites.

Magnetic Resonance

Mid-range wireless power transfer, as developed at Stanford and other research universities, is based on coupling. Just as major power plants generate alternating currents by rotating coils of wire between magnets, electricity moving through wires creates an oscillating magnetic field. This field also causes electrons in a nearby coil of wires to oscillate, thereby transferring power wirelessly. The transfer efficiency is further enhanced if both coils are tuned to the same magnetic resonance frequency and are positioned at the correct angle.

However, the continuous flow of electricity can only be maintained if some aspects of the circuits, such as the frequency, are manually tuned as the object moves. So, either the energy transmitting coil and receiver coil must remain nearly stationary, or the device must be tuned automatically and continuously — a significantly complex process.

To address the challenge, the Stanford team eliminated the radio-frequency source in the transmitter and replaced it with a commercially available voltage amplifier and feedback resistor. This system automatically figures out the right frequency for different distances without the need for human interference.

“Adding the amplifier allows power to be very efficiently transferred across most of the three-foot range and despite the changing orientation of the receiving coil,” said graduate student Sid Assawaworrarit, the study’s lead author. “This eliminates the need for automatic and continuous tuning of any aspect of the circuits.”

Assawaworrarit tested the approach by placing an LED bulb on the receiving coil. In a conventional setup without active tuning, LED brightness would diminish with distance. In the new setup, the brightness remained constant as the receiver moved away from the source by a distance of about three feet. Fan’s team recently filed a patent application for the latest advance.

The group used an off-the-shelf, general-purpose amplifier with a relatively low efficiency of about 10 percent. They say custom-made amplifiers can improve that efficiency to more than 90 percent.

“We can rethink how to deliver electricity not only to our cars, but to smaller devices on or in our bodies,” Fan said. “For anything that could benefit from dynamic, wireless charging, this is potentially very important.”

This article was provided by Stanford University. Materials may have been edited for clarity and brevity. 

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A Quantum Principle Could Change Wireless Charging Technology Forever

A Better Range

While wireless charging is an improvement over a mess of entangled wires, the technology does not solve the issue of mobility — your phone still needs to remain in one place to charge. This could change with the development of a new type of charging.

Things to Come: A Timeline of Future Technology [INFOGRAPHIC]
Click to View Full Infographic

Current wireless charging devices operate using an electromagnetic field. For the power transfer between the charger and the device to remain optimal, the distance between the two must remain fixed. However, a team out of Stanford has created a charger that can transfer power to moving devices up to a meter away. Their research has been published in Nature.

The system uses a quantum mechanical principle called parity-time symmetry. Essentially, this means their charger can automatically adjust its power flow depending on the situation. The researchers demonstrated their device using an LED bulb. When the bulb moved further away, the distance was mitigated by the charger. This allowed the bulb to retain its brightness despite the motion.

Power Everywhere

Though this study only demonstrates the technology at a minor level, if scalable, it could essentially enable us to charge devices at the optimum rate despite a varying distance. This has exciting applications in a number of fields beyond just allowing you to comfortably use your phone while charging it.

Theoretically, it could revolutionize our ability to wirelessly charge electric vehicles as charging devices could be built into roads to charge the EVs as they drive past. The study also cites the potential to charge medical implants more efficiently. These devices are all implanted at slightly different depths, which can make charging them using existing technology complicated. This new technology would give patients the ability to move around while charging, as well.

While the team’s technology is still in its nascent stages and has only charged a single moving LED so far, the concept has the potential to radically change how we power our lives in the future. Now, it’s just a matter of scaling it up.

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Stanford Scientists Are Making Wireless Electricity Transmission a Reality

Charge As You Drive

Nikola Tesla envisioned supplying power to the world without the need for a tangle of wires strung everywhere. The closest he ever came to realizing wireless transmission was the Tesla coil, which he created in 1891. However, his dreams were much bigger, encompassing a global wireless power grid that any home, business, or vehicle could tap into at will.

Now, researchers at Stanford University think they may have gotten the wireless charging technology right, as they’ve been able to transmit electricity wirelessly to a moving object nearby. If their technology is scalable, they may have discovered a way to allow electric cars to recharge as they’re in motion, eliminating issues of charging station availability and EV battery range. If that final hurdle is truly overcome, electricity could easily become the standard vehicle fuel worldwide.

Senior study author and professor of electrical engineering Shanhui Fan said in an interview for Stanford News, “We still need to significantly increase the amount of electricity being transferred to charge electric cars, but we may not need to push the distance too much more.”

Image Credit: Sid Assawaworrarit/Stanford University
Image Credit: Sid Assawaworrarit/Stanford University

As the team described in their recently published Nature study, the transmission achieved was much smaller than would be needed to power vehicles. However, they did reach a kind of mid-range wireless power transfer based on magnetic resonance coupling. Electricity coursing through wires creates an oscillating magnetic field, and it’s this field that causes a nearby coil’s electrons to oscillate. This in turn transmits power wirelessly. However, it’s a complex process and is only efficient when the oscillating coils are tuned with respect to the moving object.

Until now, this has been one of the primary problems for wireless energy transmission, because there hasn’t been a way to get the coils to automatically tune to moving objects. The researchers solved this problem by using a feedback resistor and voltage amplifier system to detect where it should be tuned to without help from humans.

Tesla’s Wireless Future Arrives

This research is part of an overall push toward safer, clean energy highways with more manageable traffic that will eventually support self-driving cars.

“In theory, one could drive for an unlimited amount of time without having to stop to recharge,” Fan explained in the interview. “The hope is that you’ll be able to charge your electric car while you’re driving down the highway. A coil in the bottom of the vehicle could receive electricity from a series of coils connected to an electric current embedded in the road.”

The Technologies That Power Self-Driving Cars [INFOGRAPHIC]
Click to View Full Infographic

With coils embedded in the roads, we could eventually enjoy a totally automated highway system. Self-driving electric vesicles could be wirelessly charged en route, and GPS and other navigation systems would also be powered wirelessly. How different is this outcome compared to Tesla’s vision of the global power grid?

His “World Wireless System” would have dotted the globe with wireless towers that transmitted power — along with data — to each other, and individual users could tap into the network with antennae. Although his plan never got past the first tower, which was demolished exactly 100 years ago, his vision of the future was really very accurate. Now that the Stanford team has this piece in place, hopefully we’ll see the rest of it happening soon.

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Now You Can Use Light to Wirelessly Charge Your Devices

Going Wireless

It’s fair to say that wireless charging has yet to catch up with the advances we’ve made in mobile technology. But Israeli start-up, Wi-Charge, believes they can do something about it — using infrared technology.

Generally, wireless tech can be classified as near field and far field. Today, we see near field technology in close-range wireless charging options. Far field technology also exists, but are all in the very early stages of development. And while they offer more distance and more power, they’re still largely limited. Wi-Charge aims to change that.

Wi-Charge’s approach uses a transmitter mounted on the ceiling that  converts energy into infrared light. The light then gets beamed across an open area where a device receives the light and converts it into energy. The result is a wireless, dockless charging solution that can power devices with the same ease with which people connect to Wi-Fi — but without a password.

The Future of Wireless Charging

Wi-Charge’s technology can also deliver a wide range of wattage — from a few milliwatts capable of powering small sensors, to hundreds of watts, which can be used in industrial or even military applications. In contrast, Yank Tech’s The MotherBox is promising to provide wireless charging for Android and iOS devices at a rate of two to 10 watts, depending on the distance. The added power of Wi-Charge’s infrared system allows its applications to broaden beyond making sure everyone’s smartphones don’t die in the middle of a Netflix show.

This kind of charging capacity and capability could lend itself to our efforts to further the adoption of electric vehicles, as it would enable electric cars to support long-range driving.

Wi-Charge’s novel approach does have some disadvantages, though. Because it uses light from lasers to deliver energy, you won’t be able to charge devices if they’re inside a purse or your pocket. But considering typical smartphone habits, where we usually have our phones in our hands or on a table, Wi-Charge technology will likely be able to beam energy into our devices. Many of Wi-Charge’s products are still in Beta testing, so it may be a while before they can brighten our lives.

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A Company Has Finally Said They Will Bring “Real” Wireless Charging

Tech start-up Yank Tech, named after its founder Josh Yank, wants to deliver “the first wireless charger that can REALLY wirelessly charge your device.” The company set up an Indiegogo campaign to fund their endeavor, and has already far exceeded their $25,000 goal.

The MotherBox promises to provide wireless charging of your Android or iOS devices at a rate of two to ten watts, depending on the device’s distance from the MotherBox. The device itself looks like a mini soccer ball, and does need to remain plugged in. The company is also offering a smaller battery-operated version that does not need constant power. Also, your device must be fitted with a receiver via its USB charging port.

While the product does have its limitations, this could be the first step in widespread wireless charging for devices. As more devices are joining the Internet of Things, and connecting us in unprecedented ways, traditional wires and plugs are not going to be enough to power the sheer number of devices.

You can reserve your MotherBox via the Indiegogo campaign today, taking advantage of an extended early bird special for $79. The first shipments are scheduled to begin in September of this year.

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Charging Your Devices Could Soon Be as Simple as Connecting to WiFi


It seems like almost everything has gone wireless. Yet somehow, when it comes to charging electronic devices, we still have to deal with cords. Sure wireless charging exists, but only for small devices like your smartphone. And even then, it’s not convenient as you might hope. To actually power a device, a phone must maintain contact with a charging pad, which means it can’t be used while charging. This seems to be even a bigger hassle than dealing with cords and cables.

That’s not to say, however, that advances aren’t being made in this field. For instance, researchers from Disney Research just demonstrated a new method of charging called quasistatic cavity resonance (QSCR) that allows power to be wirelessly transmitted throughout a room, which means you can easily go about using your devices while you charge your battery.


QSCR works similar to how WiFi hotspots provide internet connectivity wirelessly. To demonstrate, the team built a 16×16-foot room with aluminum walls, ceiling, and a floor with a bolted aluminum frame. The interior was then filled with near-field standing magnetic waves. The result was a room that was able to power cell phones, fans, and lights simultaneously without the use of cords, cables, or awkward charging pads.

By inducing electrical currents in the metalized interior, they were able to generate uniformed magnetic fields that then transmitted to receiving coils which follow the same resonant frequency. Devices that operate in the same megahertz frequency could receive power at any point in the room, while magnetic waves that don’t have the same frequency are unaffected.

Research simulations show that this method can effectively transmit 1.9 kilowatts of power, which could fully charge 320 smartphones.

Real Wireless Charging

Scientists have been working for years to create stable and reliable wireless power transmission. But, the closest we have come to achieving it today, prior to this breakthrough, was through using charging pads and cradles, which don’t offer much distance. This new development is the first step towards truly wireless charging tech.

To make this technology commercially available, there won’t be a need to construct entirely new, metal rooms. The researchers believe that as they refine the technology, it will be possible reduce the required metal for interiors. They also think that people will be able to simply add modular panels, use conductive paint, or install copper poles in existing structures to get the same results.

This innovative method could be a technological game changer because it essentially makes electrical power as accessible as WiFi, lending itself to new applications—from portable electronics to robotics.

“In this work, we’ve demonstrated room-scale wireless power, but there’s no reason we couldn’t scale this down to the size of a toy chest or up to the size of a warehouse,” said researcher Alanson P. Sample.

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New Partnership is Bringing Wireless Charging to Electric Vehicles

General Motors and WiTricity have begun working together to make wireless charging of electric vehicles not only more efficient but also more accessible. The collaboration involves testing WiTricity’s prototype Drive 11 park-and-charge system, which could work with vehicles that have 7.7 kilowatt or 11 kilowatt systems. Electric vehicles could just park over a designated area, and the batteries would start filling up.

Juli Clover
Juli Clover

This hopes to address the unexpected hassles that came with owning EVs, particularly that of recharging. Although owners of EVs have foregone countless tedious trips to gasoline stations to pump fuel, they have had to deal with the new troubles of cables and adapters. Imagine coming home and forgetting to plug in your electric car, then waking up to find that it has no juice left to run.

Other partnerships have had a head start on the wireless EV charging game, but GM and WiTricity hope to take it one step further, like installing “charging pads” in public spaces and parking lots. Further, the technology is being developed so that it could be compatible with all EV models. International standards, however, are yet to be finalized. According to SAE International, the authority in wireless charging, commercialization isn’t likely until 2020.

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