Siemens and BMW announced Tuesday at Hannover Messe 2011 that they will be testing a prototype in May that will use inductive energy charging to charge electric vehicles. EV’s would be able to roll over charging stations and not need to plug in a cord, which would be ideal for service cars like taxi cabs because it works even during a short stop.
From the Siemens press release:
“The charging station is connected to the public grid by a primary coil that is completely underground. A secondary coil is attached to the car, and the distance between the two coils is typically between eight and 15 centimeters. When the driver starts the charging process, an electric current begins to flow through the primary coil.
The resulting magnetic field induces an electric current in the secondary coil, which recharges the battery. Electricity is transmitted from the grid through all of the components to the battery at an efficiency of more than 90 percent. The magnetic field is generated only in an exactly predetermined area between the two coils.
The system therefore generates a magnetic field whose strength in and around the vehicle is far below the internationally recommended limit of 6.25 microteslas.”
Delphi Wireless Charging Systems
The technology seems to be like a system from Delphi,in conjunction with a company called WiTricity Corp, who holds two patents on wireless charging. I thought someone else would have held a patent for wireless charging, and I was right.
From the Delphi product site:
“Delphi is developing Wireless Charging Products that will automatically transfer power to a vehicle providing a convenient, wireless energy transfer system. The system was developed in cooperation with WiTricity Corp., a wireless energy transfer technology provider. It will enable an electric vehicle’s battery to be recharged without the hassle of cords or connections.
This hands-free charging technology is based on highly resonant magnetic coupling which transfers electric power over short distances without physical contact, allowing for safer and more convenient charging options for consumer and commercial electric vehicles.
Delphi has rights under a patented MIT-developed wireless energy transfer technology based on the following principle: Two properly designed devices with closely matched resonant frequencies can strongly couple into a single continuous magnetic field.
The wireless charging system is comprised of the following:
- Vehicle mounted capture resonator and interface electronics — fitted to the bottom of the vehicle
- Vehicle power and signal distribution systems
- Stationary source resonator pad — mounted on the ground
- Stationary charging controller
Compared to inductive systems, this highly resonant magnetic coupling technology will efficiently transfer power over significantly larger distances and will allow more parking-related vehicle misalignment. The system can fully charge an electric vehicle at a rate comparable to most residential plug-in chargers, which can be as fast as four hours.”
From a recent Delphi press release:
“A wireless charging system eliminates the need for a charging cord. Drivers can simply park their electric vehicle over a wireless energy source situated on the garage floor or embedded in a paved parking spot.
Other wireless charging systems under development make use of traditional inductive charging, the same technology used in electric toothbrushes, which is based on principles first proposed in the mid-nineteenth century.
These systems only work over a limited distance range, require precise accurate parking alignment and can be very large and heavy, making them impractical for widespread use on electric vehicles.
“The Delphi Wireless Charging System offers more practical and flexible installation than traditional inductive systems because it uses highly resonant magnetic coupling, a modern technology that safely and efficiently transfers power over significantly larger distances and can adapt to natural misalignment often associated with vehicle positioning during parking,” said Randy Sumner, director, global hybrid vehicle development, Delphi Packard Electrical/Electronic Architecture.
This means that Delphi charging sources can be buried in pavement, are unaffected by environmental factors such as snow, ice or rain, can accommodate a wide range of vehicle shapes and sizes and their differing ground clearances. The Delphi system is also more forgiving to vehicle parking positions on top of the charger without requiring any moving parts to accommodate. The system transfers energy using an oscillating magnetic field, which is intrinsically safe for humans and animals. ”
WiTricity power sources
From the WiTricity site: “WiTricity power sources and capture devices are specially designed magnetic resonators that efficiently transfer power over large distances via the magnetic near-field. These proprietary source and device designs and the electronic systems that control them support efficient energy transfer over distances that are many times the size of the sources/devices themselves.”
The WiTricity power source, left, is connected to AC power. The blue lines represent the magnetic near field induced by the power source. The yellow lines represent the flow of energy from the source to the WiTicity capture coil, which is shown powering a light bulb. Note that this diagram also shows how the magnetic field (blue lines) can wrap around a conductive obstacle between the power source and the capture device.”