Electrical Engineering Capstone Project Examples

ELECTRICAL CAPSTONE EXAMPLE

WIRELESS POWER SUPPLY IN ELECTRIC CARS INTRODUCTION Wireless power transmission is the term referring to the energy transfer of sources to consumers without using conductors or any kind of strong links. It is a general concept that combines the different transfer technologies from the simplest transmission by electromagnetic induction to the complex transmission of light waves using laser beams.

With the advancement of technology we can see that the world around us is changing. There are fewer wires and cables that gradually are replaced by wireless technology: from mobile phones, over wireless and recently wireless car chargers and small home appliances. The simplest form of such transmission is the transmission by electromagnetic induction. An example of such a transmission would be a transformer where the primary and secondary are not physically connected, but the transmission of energy takes place through an electromagnetic field. When transmitting electromagnetic induction, care should be taken at transmitter and receiver positions and their distance, as the transfer efficiency is rapidly decreasing with increasing distance. This type of transmission is used for small distances. In this transmission group is also a resonant transmission that is generally improved by electromagnetic induction, where the primary and secondary coils resonate at the same frequency, which increases the transmission distance and their position does not affect so much the efficiency of the transmission. This allows the transmission to medium distances, from tens of yards to several meters. In contrast, relatively simple wireless transmission technologies use more sophisticated optical energy transfer techniques with the use of laser beams to send energy to a remote receiver where photons are transformed into electrical energy. Effective power transmission over large distances is possible with this type of transmission, but a very complex system or targeting and monitoring mechanism is required to maintain the connection between the two sides if they are not stationary. Also, if an object is found between, the connection is interrupted and damage is possible if it is more powerful.

Therefore, in this type of transmission it is necessary to ensure unobstructed optical visibility. For long distances the transfer is used also transferring the microwaves with the corresponding antennas. This type of transmission has similar problems and benefits as the transfer using laser. Both of these techniques fall into high-electromagnetic radiation transmission and are not conducive to widespread use. Otherwise, the idea of transferring electricity without the use of conductors is more than a century old. At the turn of the 19th

1

ELECTRICAL CAPSTONE EXAMPLE

WIRELESS POWER SUPPLY IN ELECTRIC CARS century, Nikola Tesla studied and experimented in this area. He worked on long-range wireless power transmission to bring hectic energy to every household around the world using the ionosphere. His first patent on wireless power transfer was patented in 1891. The patent referred to a transformer that did not have an iron core but the transmission was carried out by air. Transmission was possible due to the high frequency at which coils were resonated. We can freely say that Nikola Tesla was the initiator of resonant energy transfer.

Wishing to realize his idea, he continues to study and experiment in that direction. In 1897 he patented the first patents relating to Wardenclyffe's Tower or today known as Tesla's Tower.

The idea behind this project is to use a resonant frequency in the space between Earth's crust and ionosphere for power transmission. Tesla's research has come to the conclusion that this frequency is about 8 Hz, which is confirmed more than 50 years later. This frequency is now known as Schumann's constant and is 7.8 Hz. The tower was built in 1901 and it is considered that this was the beginning of the realization of the idea of Nikola Tesla. The project was abandoned in 1906 due to termination of funding. In addition, in order to cover Tesla's debts, the tower was disassembled in 1917 for the purpose of collecting money, so the project was definitely completed. Today, a growing number of small electrical appliances are being used. In everyday life, an interesting idea seems to be that would not include so many wires and cables in that picture. Since these devices surround us, it would be good for them not to radiate and to be completely safe for their environment. That is why it is a very interesting transfer by electromagnetic induction on everyday occasions. In the case of wireless technology by electromagnetic induction, we can soon expect a big leap in production because they can already be shaken at a distance of several decades, with a high percentage of transfer efficiency of over 90%.

An electric car is a car whose electric drive is electric. The electric motor code of the electric car uses its power to store its batteries in the car. The benefits of electric cars compared to gasoline and diesel cars are significant. Electric cars are the most environmentally acceptable alternative to vehicles with classic fuels. The CO2 emission in electric cars is equal to 0. The full transition to an electric drive would have a significant impact on the environment if this difference in the need for electricity was replaced by renewable energy sources. The noise level generated by electric vehicles is negligible in comparison to classic cars, which is, on the one hand, an advantage, and on the other hand poses a problem for pedestrians who are not accustomed to silent vehicles. Furthermore,

2

ELECTRICAL CAPSTONE EXAMPLE

WIRELESS POWER SUPPLY IN ELECTRIC CARS the electric motor that drives them is in principle very simple. It has a high moment since the start. Its speed is easy to regulate and there is no need for a gearbox. The cost of maintaining electric cars is minimal because there is no oil or filter that needs to be changed regularly as with classic vehicles.

The question is why electric cars are so seldom seen on the roads. If we ignore the main reason, the oil lobby and their impact on the whole story, we can point to two basic shortcomings of electric cars. These are the reach and filling times. The extent of most electric cars is about 100-150 km. Really seeing in everyday life most drivers have no need for greater reach. There are also electric car models that are about 400 km long. These cars are considerably harder for larger batteries and are priceless because the price of the battery affects the price of a car. Battery prices are still high, although there is a trend that shows that this year's price drops considerably. Charging time depends on the power of the charger. Chargers that can be plugged into single-phase sockets charge empty batteries for about 5 hours or more. Three-phase socket can be connected to more powerful chargers that shorten it by one hour and half to two. There are also fast charging stations where the batteries can be charged for about half an hour. But those half-hours are considerably longer than a couple of minutes as it takes to squeeze the fuel into the resonator. From this we can conclude that charging time is definitely the biggest shortage of long-distance electric cars, where one without charging cannot reach the destination. The drop in performance at temperature extremes is another shortage of electric cars. The study carried out on several electric vehicles showed a drop in performance at temperature extremes. At a temperature below -7 oC, a drop in performance of up to 57% was noted. Also at a temperature above 40 oC a 33% performance decrease was noted. To prevent such a fall in performance, most manufacturers incorporate into their vehicle heat regulators to ensure that batteries and other components whose performance is influenced by the outside temperature of the hold in the optimum temperature range.

3

ELECTRICAL CAPSTONE EXAMPLE

WIRELESS POWER SUPPLY IN ELECTRIC CARS REFERENCES Kesler, M. (2013). Highly Resonant Wireless Power Transfer: Safe, Efficient, and over Distance. Massachusetts: WiTricity Corporation.

Xing, Y., Ma, E. W. M., Tsui, K. L., & Pecht, M. (2011). Battery Management Systems in Electric and Hybrid Vehicles, Energies, 4, 1840-1857.

Kaiser, R. Optimized Battery-Management System to Improve Storage Lifetime in Renewable Energy Systems. J. Power Sources 2007, 168, 58–65.

4