Siemens and BMW believe in Wireless EV charging station

Electric cars (EV) now fall in short-term production plans of most of the car manufacturers. It is a news of these days, in fact, the market expected at the end of the year (at an estimated price of less than 7000 euros) of the Renault Twizy, a zero-emissions two-seater equipped with a 20 hp electric motor, battery life of around 100 km, and charging time of approximately 3 hours and a half. Just charging seems to be one of the troubles of these new-generation cars, ecological, yes, but forcing the user to adopt new habits with regard to refueling operations.

Some European countries (one of these is the Netherlands) have already endorsed projects to create ad hoc service stations specifically equipped to perform the rapid charging of the next coming electric cars. The evolution is however still at an early stage, so the only valid alternative, for now, is to have a garage or parking space with electrical outlet to be able to recharge batteries when the vehicle is not used and by using the appropriate electrical wiring (the equivalent of the "gun" in the traditional gas station). Actually, there is already today a technology that can fully address this problem, a technology that harnesses the wireless power transmission to charge the batteries without requiring ing any electrical connections.

The first practical applications of this technology have been achieved by HaloIPT, a company founded as a spin-out of Auckland University. HaloIPT was the first company in the world capable of marketable wireless charging systems for electric vehicles. These systems are based on the IPT (Inductive Power Transfer) technique, that exploits the physical mechanism of electromagnetic induction to transfer (or rather, to induce) a power supply at a short distance. At the recent Hannover Fair (now the largest industrial trade fair in the world), Siemens and BMW presented their own system for wireless recharging of electric vehicles, based on the same principle, namely electromagnetic induction.

If this technology will take hold, future electric cars will no longer need cumbersome and annoying cables for charging. Contactless technology also provides another significant advantage: the charging stations will be able to be installed almost anywhere (the housing is made under the soil), effectively making them almost invisible and protected from vandals and wear. The project was funded by the Ministry of the Environment of Germany, and a first test has been scheduled for next June 2011 in Berlin, with the use of different types of vehicles. The inductive charging system developed by Siemens allows charging even for short stops, making the charging process less costly in terms of duration. An example is provided by cabs, used to stand for long periods in the special lanes reserved for them: these stops could be used to carry out a battery recharging operation in a transparent way, working in "background".

The system consists of a primary coil placed completely below the ground, connecting the contactless charging station with the power supply (mains). The electric current through the coil creates nearby an electromagnetic field, which generates, by induction, a current in the secondary coil, placed at a distance of 8-15 cm from the primary coil and installed aboard the electric or hybrid car. The secondary coil, in turn, allows thus to recharge the battery. The theoretical efficiency of this system was estimated to be at least 90%, but we must wait until next May, when a 3.6-kW prototype will be thoroughly tested. The system is designed and installed so that the electromagnetic field generated interest only to a well determined area between the two coils. By law, it must meet international standards, which recommend an upper limit for the generated electromagnetic field equal to 6.25 microtesla. Siemens has ensured that the intensity of the electromagnetic field generated by their system meets this requirement, so there is no risk to health. In addition, the charging stations will be able to use the surplus energy produced by solar panels or wind systems, thus minimizing the impact on the environment.

The system designed by Siemens in cooperation with BMW will be tested and verified in practice over the coming months so that designers will be able to do the required changes and improvements to it. We should also recall that BMW strongly believes in the future of electric vehicles (EVs) and hybrid cars. With respect to this topic, they recently announced the creation of a new brand of models (identified by the letter "i") with the aim to offer the most advanced solutions for future mobility. In 2013 it is expected the launch of the models BMW i3 (a compact city car, also called as "Megacity"), and BMW i8 (a sportcar with a winning design). The BMW i3, visible in the drawing below, will be equipped with an electric motor with rated power of 100kW and aims to have minimal impact on the environment, with extensive use of carbon fiber materials to reduce weight and increase the rigidity of the vehicle.