INSIGHTS
- Powermat uses inductive power which they claim will reach 90W on future products with a short range of 0.04m.
- WiTricity will release their wireless charging technology for vehicles in 2018, this can be installed in the pavement and will be compatible with a wide range of cars.
- Companies using wireless charging technologies include; Powermat, Bosch, Murata, WiTricity, Integrated Device Technology, and Airfuel Alliance.
OVERVIEW
Wireless charging technology has existed for more than 100 years, but has seen increasing relevance in recent years with use across a wide range of devices. There are a number of vendors developing this technology. Due to the cutting edge nature of this technology, this report will look at technologies that are available to the public and those that are currently in development. Powermat is a lead in commercial inductive charging, while Bosch is currently working on new technology detailed below. Capacitive charging has some major uses by Murata in their AIR VOLTAGE technology that is used by Apple. While examples of other vendors are unavailable, a paper from Berkeley provides additional examples of the technology. Resonant charging is being developed by WiTricity who will launch their resonance charger for electric cars in 2018. Integrated Device Technology and Airfuel Alliance are other organizations that are working towards creating a global network of resonance chargers integrated into all sorts of objects and locations.
INDUCTIVE CHARGING
Inductive charging works by the ‘transfer of energy between a transmitter unit and a receiver unit’, both of which have an induction coil. The receiver unit is placed close to the transmitter and converts the electromagnetic field into power. The two units communicate with each other to regulate the power levels for a successful charge.
A leading vendor of the inductive charging technology is Powermat. In 2006, they were founded in Israel and were the first company to offer wireless technologies to international consumers.
They claim their SmartInductive Technology has increased the technology of magnetic induction while still maintaining compatibility with existing wireless charging technologies. They claim these developments are due to their "unique coil structure" and "advanced signal processing", which allows for a power density of up to 40W. Powermat claims this will increase to 90W on future designs. This technique has a short range through surfaces up to 0.04m, or 40mm thick. Powermat state their power efficiency ranges from 65%-90%. Their increased capabilities using this technique of inductive charging enables the powering of larger devices such as laptops, as well as smaller personal devices like headsets. They support a wide range of devices including Qi, Samsung Fast Charge, Apple 7.5W and AirFuel-Inductive (PMA) devices.
Another company that uses inductive charging cgommercially is Bosch, founded in Stuttgart in 1886 and now has regional offices globally. They have used this technology in electric toothbrush chargers. Bosch recently published a press release on their development of a charging system which can also "feed energy back into the grid". This will enable e-vehicles to be used as a mobile source of renewable energy. This work is being done with Fraunhofer Society and GreenIng GmbH & Co. KG primarily, and it will allow vehicles to be charged inductively while parked at charging stations. They are also working to use the inductive capabilities to create an "intelligent infrastructure" which will allow for use of renewable energies. The idea has been developed from electric car batteries, which use bidirectional charging. This technology allows the battery to feed energy back into the grid allowing for weather changes and the different levels of renewable energy that may be available at a given time.
CAPACITIVE CHARGING
The capacitive coupling method sends electrical power through the use of "electrostatic induction". The system is composed of a transmission side and a receiving side. The transmission side has a transmission module and a transmission electrode while the receiver has a reception module and a reception electrode. Electric power is converted to AC on the transmission side and is sent to the receiving side via electrodes through a capacitor. The device for charge contains the reception module and is placed on the charging stand which contains the transmission module.
Murata was founded in Japan in 1944 and today has grown to be a global company. They developed the charging technology for the iPad2 accessory in 2011. They are currently working on integrating this technology in various equipment such as smart phones, music devices, digital cameras, tables, small PCs, toys, lighting, and other household devices. Their technology is already used in a wide range of applications such as cars, energy management systems, and healthcare devices. This vendor has technology capable of transmitting 10W of energy. Again, they have a short range and will charge when the device is placed onto the charging stand.
Murata collaborated with Hitachi Maxell to produce the AIR VOLTAGE technology for the iPad2 wireless recharger technology. This was the first product using this capacitive coupling method. The previous release, "AIR VOLTAGE for iPhone4" is claimed by Murata to have created the lucrative wireless recharger market in Japan. The AIR VOLTAGE product for iPad2 received the "Nikkei Sangyo Shimbun Award".
While capacitive charging is expected to bring significant changes to the market, other examples of businesses or vendors offering this technology are not available currently. For further reference there is a paper from the University of California at Berkeley containing various examples of capacitive power transfers.
RESONANT CHARGING
Resonant charging occurs when the frequencies of a source and a receiver are the same. Resonance charging is understood as the "frequency at which energy can most efficiently be added to an oscillating system". A simple example of resonance is when a singer smashes a wine glass by singing a note. Here, the wine glass is the oscillating system. When the singer produces a note that matches the resonant frequency of the glass, the glass is able to take in this energy and starts to vibrate. This is what causes the glass to shatter.
WiTricity, founded in 2007, Massachusetts at MIT, claim their technology can provide solutions for "all sizes and power requirements".
Currently, the technology has been demonstrated by lighting a 60-watt bulb from a power source positioned at a distance of over 2 metres. The technology is exclusively patented to MIT intellectual property. WiTricity claims it will allow for the development of markedly new devices for consumers as well as commercial and industrial needs. Their stated aim is to create the technology to enable manufacturers to create truly "wireless" products.
Their wireless charging technology for electric vehicles and hybrid electric vehicles will be on the market in 2018. They state it can power 11kW "and beyond", with a 90-93% efficiency and "X-Y-Z parking freedom". The US Department of Energy states this is the "most efficient and most inter operable system available". However, there are no other sources available online to verify this claim. The distance range is larger than the previous 2 examples, it allows for charging pads to be installed in the ground while charging a range of vehicles from low sports cars, to high ground SUV's.
Another company that is working with resonance charging is Integrated Device Technology. The company is a member of the Airfuel Alliance, the not-for-profit organization committed to creating a "global wireless charging ecosystem" using Airfuel technology. These charging solutions can be embedded in almost any surface, including; "retail environments, airports, automobiles, home, and office furniture." Although these companies and organizations claim the technology functions, the worldwide integration that these companies envision has yet to be seen.
CONCLUSION
In conclusion, this report defines how inductive, capacitive, and resonance charging work. It provides examples of vendors of each method; Powermat, Braun, Murata, WiTricity, Integrated Device Technology, and Airfuel Alliance respectively. It also provides a number of qualities each vendor and method offered. For Powermat and Murata it states the claims of their successful technologies. For Braun, WiTricity, Integrated Device Technology, and Airfuel Alliance the report details claims the vendor have made for the technology they are developing.