NF: In the ideal vision of wireless devices, products like cell phones would not even need a cord to charge their batteries. Now, that dream may be becoming a reality, thanks to work from the Wireless Power Consortium (WPC) on its Qi (pronounced "chee") standard. Can you tell us about that standard?
MT: The Qi standard is a so-called "interface specification." That means that Qi specifies the minimum number of rules necessary to make sure that power transmitters and power receivers match each other efficiently. An interface specification, like Qi, gives design freedom for product developers to optimize products for their own applications.
NF: Please describe briefly exactly how this technology works.
MT: Qi uses a technique called magnetic induction that you may remember from your high-school physics classes. It uses a coil in the transmitter to create an alternating magnetic field that generates power in a coil in the receiver. This is the same technology that has been used for about 100 years in power transformers.
NF: How does a device become Qi-enabled? Is this an aftermarket add-on or is Qi-compliant circuitry included and licensed as part of the initial design? Are some device manufacturers building in Qi wireless-charging capability?
MT: Integrating the coil into the receiver of a device is the most efficient solution. But it is also possible to add the Qi receiver to an existing product as an accessory. You can add Qi to an iPhone, for example, by means of a sleeve. In Japan, Qi is already being integrated into phones. It is also possible to buy battery packs with integrated Qi receivers in Japan.
NF: What technical challenges were overcome in the creation of this standard?
MT: The main challenge was to maximize the design freedom for product developers. It is rather basic to transfer power with magnetic induction when you design the transmitter and receiver together as a single product. The Qi specification, however, makes it possible to develop transmitters that are guaranteed to work with a large variety of mobile phones, batteries, cameras, etc.
NF: As of the end of 2011, Qi is available in the form of charging stations at more than 120 popular venues throughout Japan. Has there been any feedback? How popular are the charging stations?
MT: User feedback has been positive. Once they use the charging stations, consumers start to realize the convenience and flexibility that a universal charging standard affordsand that drained batteries can be a thing of the past. The Qi-capable phones are selling very well.
NF: What were the biggest roadblocks that the WPC has faced in terms of getting this technology into the world?
MT: We have not seen significant roadblocks. Our membership continues to grow at a rapid pace. That means more designs and Qi-enabled devices will eventually hit the marketplace. In fact, the adoption of Qi is going quite fast compared with other consumer-electronics standards.
NF: What is next for Japan? Do you expect NTT Docomo to roll out more charging stations? Will other carriers get involved in supporting the Qi standard as well?
MT: NTT-Docomo will gradually roll out Qi so that it's integrated in all of their newly released phones. Other Japanese carriers are following.
NF: What is your prediction for the rest of the world?
MT: Europe, China, and the US will follow Japan's lead in 2012.
NF: Please describe the future of wireless charging as you see itsay, in the next five to ten years.
MT: We'll see broad adoption of Qi power receivers in all battery-powered products. Wireless charging will become embedded in cars, furniture, chairs, and kitchen tabletops. It also will be available in public infrastructure, such as hotels and coffee shops. By that time, people will stop worrying about charging their phones because they will get an additional charge wherever they go. We're also exploring a medium power standard so that you can wirelessly charge products like home appliances, laptops, PCs, etc. that require up to 120 W.
NF: Have you received any feedback from the designers and manufacturers of rechargeable battery cells on how they can work with the WPC on advancing their chemistries?
MT: That is an interesting question. Battery chemistry and wireless power have been developed independently until now. There may be synergies.