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New Era of Wireless Power Technology

“Wires suck,” says WiTricity’s CEO Eric Giler. Whether knotted up behind our desks or entertainment centers, or interfering with our view of the landscape, these entangled messes have placated our insatiable demand for electricity for over a hundred years.

Since 2007 however, WiTricity has been working towards a cure for our attachment disorder. Based upon the highly resonant wireless electric power transfer technology spearheaded by the company’s founder, Professor Marin Soljačić of MIT, WiTricity has been developing technologies that deliver safe and efficient wireless electric power ranging from milliwats to kilowatts and over distances spanning a few centimeters to several meters.

Taming the Electron

Delivering electric power from one point to another without wires is not a new idea. Nikola Tesla worked on wireless power transfer using electromagnetic induction in the 1890s. Discovered by Michael Faraday in 1831, electromagnetic induction is the process of inducing current in a wire via current flowing through another wire nearby. According to Kaynam Hedayat, Director of Product Management at WiTricity, most people use this type of wireless power on a daily basis. “Perfect examples of induction are today’s rechargeable electric toothbrushes, which get charged by resting in their charging bases. This type of magnetic induction is a type of wireless power transfer since the toothbrush itself is not plugged directly into the wall.” Other familiar applications of electromagnetic induction include recharging mats for small electronic devices.

R3 Deployment Kit

R3 Deployment Kit

Electromagnetic induction has certainly opened up the market for many different wireless charging applications, but as Hedayat explained, this technology has major limitations. “With this type of magnetic induction, the products that can be developed must work in very close proximity to the charging unit, with very limited positional freedom. This means that products have to be designed so they are positioned precisely on the charging units. For example, with induction charging mats for mobile phones, you have to ‘play’ with the phone until it couples with the mat correctly. It’s not very user friendly.”

Going the Distance

In 2007, Soljačić and colleagues at MIT published a paper for a solution to the distance problem and reported an experimental demonstration of their technique in 2007. Using a concept called highly resonant wireless power transfer, Soljačić’s team lit up a 60-watt incandescent light bulb using power transferred between two coils separated by a little more than two meters.

How did they do it? In a recent TED talk, WiTricity CEO Eric Giler explained, “Imagine a coil. For those of you that are engineers, there’s a capacitor attached to it too. And if you can cause the coil to resonate, what will happen is it will pulse at alternating current frequency – at a fairly high frequency by the way. And if you can bring another device close enough to the source, that will only work at exactly that frequency, you can actually get them to do what’s called strongly couple, and transfer magnetic energy between them. And then what you do is, you start out with electricity, turn it into magnetic field, take that magnetic field, turn it back into electricity, and then you can use it.”

Unlike traditional magnetic induction technology that loses efficiency as the distance between the device and power source increases, WiTricity’s magnetic resonance technology has been shown to stretch the distance over which energy can travel significantly. “For automotive applications, we have achieved distances of up to 15 centimeters that provide over 90% of efficiency for 3.3 kilowatts of power transfer,” indicated Hedayat.

But, the distance between the power source and the device is far from the ultimate limit. Properly applied, magnetic resonance technology can be used to power an entire room or even a house. As Dr. Katie Hall, WiTricity’s Chief Technology Officer told EEWeb last April, “Another interesting thing about the technology is that the resonators don’t just have to be in sources that supply power and devices that capture it; you can have what are called repeaters – resonators that aren’t attached to anything at all but can be used to extend the transmission distance. Some people think of it as if the power or energy is hopping from one resonator to another. Imagine you want to get from one side of a stream to the other side without getting wet, but it’s too far to make it in one jump. You could hop from rock-to-rock to get to the other side without falling in.”

Utilizing WiTricity Technology

WiTricity’s technology is designed to be directly embedded in the products and systems of OEMs and the company provides all the necessary tools, services, and training to streamline the process. Last month, WiTricity unveiled WiCAD, a subscription based software product that helps developers quickly model, design, and fine-tune their wireless products.

WiCAD Interface

WiCAD Interface

“WiCAD provides simulation and modeling for wireless power transfer systems ranging from milliwatts to kilowatts. At a high level, our goal is to help customers reduce their time-to-market by leveraging our years of experience in electromagnetic simulation, modeling, and electronics for resonant wireless power systems. We focus on helping our customers accelerate the integration of resonant wireless power so they can focus on the value proposition of their products,” Hedayat told us.

For companies that do not have the necessary in-house expertise or experience to create their own designs, WiTricity provides consulting services that typically involve simulation and modeling, followed by a product design and prototype they provide the customer. At the end of the engagement, WiTricity provides a technology transfer to their customers.

Applications

WiTricity resonant wireless power technology has applications in a number of markets, but as Hedayat explained, “The automotive industry has been one of the first markets that has shown strong interest in our technology, primarily because induction simply does not work in EV charging applications. Currently, there is no viable solution that brings the coils close enough for inductive charging in vehicles. With the ability to transfer power over a distance, resonant wireless power is the first technology that the automotive industry is embracing.”

Beyond that, the medical field is another interesting market where induction has a lot of challenges—the challenges are primarily around the proximity of coils. When you develop a device you can’t have a transmitter touching the receiver. In the industrial and military, there are a lot of applications where wireless power for charging over distances is a must requirement.

With highly resonant wireless power transfer technology, WiTricity has ushered in a new era that will fundamentally change the way we use electricity. The applications and implications of resonant wireless power are far reaching, but moreover, they promise to cure our attachment disorder for good.

Tags: witricity, wireless power transfer, wicad, electron, wireless power,

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