Wireless Power Transmission Using Microwaves Nikhil B

International Journal of Engineering Innovation & Research Volume 1, Issue 2, ISSN : 2277 – 5668

Wireless Power Transmission Using Microwaves Nikhil B. Dhake Arati A. Dandavate Dhole Patil College of Engineering, Wagholi, Pune. Dhole Patil College of Engineering, Wagholi, Pune. (University of Pune) (University of Pune) [email protected] [email protected]

Abstract— In this paper, we present the concept of wireless and ionospheric plasmas. In the MINIX experiment, they power transmission to cut the clutter or lead to clean sources used cooker-type 800W-2.45GHz magnetron for of electricity. It will eradicate the hazardous usage of microwave transmitter. New wave-wave-particle electrical wires which involve lot of confusion in particularly interaction phenomenons were observed in the MINIX. organizing them. The plan is transmitting power as Plasma theory and computer experiments supported the microwaves from one place to another in order to reduce the use of clumsy wires & distribution losses. This paper will give observations [7][8]. The world’s first fuel free airplane the idea about impact on human beings, advantages, powered by microwave energy from ground was reported disadvantages, & applications of wireless power in 1987 at Canada. This system is called SHARP transmission. (Stationary High – Altitude Relay Platform) [9]. In 2003, Dryden Flight Research Centre of NASA demonstrated a Key Words— Microwave Power transmission (MPT), laser powered model airplane indoors. In 2004 Japan Nikola Tesla, Rectenna, Wireless Power transmission (WPT). proposed wireless charging of electric motor vehicles by Microwave Power Transmission. Powercast, a new company introduced wireless power transfer technology I. INTRODUCTION using RF energy at the 2007 Consumer Electronics Show [10]. In 2007 a physics research group, led by Prof. Marin Wireless Power Transmission is not new to the world, Soljacic, at the Massachusetts Institute of technology Nikola Tesla is the one who first Conceived the idea (MIT) demonstrated wireless powering of a 60W light Wireless Power Transmission and demonstrated “the bulb with 40% efficiency at a 2m (7ft) distance using two transmission of electrical energy without wires" that 60cm-diameter coils [11]. Intel reproduced the MIT depends upon electrical conductivity as early as 1891[1]. group's experiment by wirelessly powering a light bulb He further culminated his efforts in a major breakthrough with 75% efficiency at a shorter distance in 2008 [12]. in 1899 at Colorado Springs by transmitting 100 million volts of high-frequency electric power wirelessly over a II. NEED FOR WIRELESS POWER distance of 26 miles at which he lit up a bank of 200 light TRANSMISSION bulbs and ran one electric motor! With this souped up version of his Tesla coil, Tesla claimed that only 5% of the transmitted energy was lost in the process. [43]. One of the major issue in power system is the losses The wireless transmission of energy is common in much occurs during the transmission and distribution of of the world. Radio waves are energy, and people use electrical power. As the demand increases day by day, the them to send and receive cell phone, TV, radio and Wi- power generation increases and the power loss is also Fi signals every day. The radio waves spread in all increased. The major amount of power loss occurs during directions until they reach antennae that are tuned to the transmission and distribution. The percentage of loss of right frequency. A similar method for transferring power during transmission and distribution is electrical power would be both inefficient and dangerous. approximated as 26%. The main reason for power loss During the world war II, W. C. Brown started the first during transmission and distribution is the resistance of microwave power transmission (MPT) research and wires used for grid. According to the World Resources development in 1960s based on the development of the Institute (WRI), India’s electricity grid has the highest microwave tubes. First of all, he developed a rectifying transmission and distribution losses in the world – a antenna, for receiving and rectifying microwaves Called whopping 27%. Numbers published by various Indian rectenna. The efficiency of the first rectifying antenna government agencies put that number at 30%, 40% and (rectenna) developed in 1963 was 50 % at output 4WDC greater than 40%. This is attributed to technical losses and 40% at output 7WDC, respectively [3]. P. E. Glaser (grid’s inefficiencies) and theft [2]. proposed a Solar Power Satellite (SPS) in 1968, based on The above discussed problem can be solved by choose the Brown’s work, [4]. In 1980s, Japanese scientists an alternative option for power transmission which could progressed the MPT technologies and research[5][6]. In provide much higher efficiency, low transmission cost and 1983 and 1993, Hiroshi Matsumoto’s team carried out the avoid power theft. Microwave Power Transmission is one first MPT experiment in space. The rocket experiment of the promising technologies and may be the righteous were called MINIX (Microwave Ionosphere Nonlinear alternative for efficient power transmission. Interaction experiment) in 1983 and ISY-METS (International Space Year – Microwave Energy Transmission in Space) in 1993, respectively. They focused nonlinear interaction between intense microwave

III. ARCHITECTURE OF MICROWAVE A. Microwave Generator POWER TRANSMISSION The microwave transmitting devices are classified as Microwave Vacuum Tubes (magnetron, klystron, The pioneer in wireless power transmission technology, Travelling Wave Tube (TWT), and Microwave Power William C. Brown, has designed, developed a unit and Module (MPM)) and Semiconductor Microwave demonstrated to show how power can be transferred transmitters. The highest efficiency over 90% is achieved through free space by microwaves. The concept of at 2.45 GHz among all the frequencies [14]. Wireless Power Transmission System can be explained a. Magnetron with functional block diagram as shown in Fig1. In the It was W. C. Brown who invented a voltage controlled transmission side, the microwave power source generates oscillator with a cooker-type magnetron in a phase locked microwave power and the output power is controlled by loop[15]. He could control and stabilize a phase of electronic control circuits. The wave guide ferrite microwave emitted from cooker-type magnetron. It is circulator which protects the microwave source from however confirmed that spurious emissions from the reflected power is connected with the microwave power cooker-type magnetron with a stable DC power supply is source through the Coax – Waveguide Adaptor. The tuner low enough and this can be applied to the MPT matches the impedance between the transmitting antenna system[16]. and the microwave source. The attenuated signals will be b. Semiconductor Amplifier then separated based on the direction of signal propagation Because of advance of mobile phone network, after by Directional Coupler. The transmitting antenna radiates 1980s, semiconductor device played the major in the power uniformly through free space to the rectenna. In microwave world instead of the microwave tubes. The the receiving side, a rectenna receives the transmitted semiconductor device is expected to expand microwave power and converts the microwave power into DC power. applications, for instance, phased array and Active The impedance matching circuit and filter is provided to integrated antenna (AIA), because of its manageability setting the output impedance of a signal source equal to and mass productivity. Some microwave power transfer the rectifying circuit. The rectifying circuit consists of (MPT) experiments were carried out in Japan with phased Schottky barrier diodes converts the received microwave array of semiconductor amplifiers, after 1990s, [17]. Due power into DC power.[13]. to the nature of small-size, thinness, lightness and multi- functions in AIA, a power transmission part of the spacetenna (space antenna) can be realized in thin structure. Prof. Kawasaki’s group has developed some AIA system for the MPT application [18]. In present, new materials are developed fore the semiconductor device to increased output power and efficiency. They are called wide-band gap devices such as SiC and GaN. The wideband gap devices can make over hundreds watt amplifier with one chip. In recent days, there are some development of microwave amplifiers with SiC MESFET [19][20] or GaN HEMT[21][22]. A weight of the semiconductor amplifier is more than that of the microwave tube when we compare the weight by power-weight ratio (kg/kW), the microwave tube can generate/amplify higher power microwave than that by the semiconductor amplifier. Kyoto University’s group have developed a light weight phase controlled magnetron called COMET, Compact Microwave Energy Transmitter with a power-weight ratio below 25g/W[23]. The COMET includes a DC/DC converter, a control circuit of the phase controlled magnetron with 5.8 GHz, a heat radiation Fig.1. Functional Block Diagram of Wireless Power circuit, a wave guide, and an antenna. The power-weight Transmission ratio of the COMET is lightest weight in all microwave generators and amplifiers. TWTA for satellite use has lighter power weight ratio: 220W at 2.45GHz at 2.65 kg OMPONENTS OF PT YSTEM IV. C W S (the TWTA weighs 1.5kg, the power supply weighs 1.15kg). 130W at 5.8 GHz at 2.15 kg (the TWTA weighs The Primary components of Wireless Power 0.8kg, the power supply weighs 1.35kg). Hence, they can Transmission are Microwave Generator, Transmitting deliver 12g/W and 16.5g/W, respectively [24]. Since antenna and Receiving antenna (Rectenna). The output microwave power is very small, semiconductor components are described as follows. amplifiers have heavy power-weight ratio, though it may seem that they are light in weight. Heat reduction is most

important problem in space. All lost power converts to C. Rectenna heat. We need special heat reduction system in space. If we use high efficient microwave transmitters, we can reduce weight of heat reduction system. We should aim for over 80 % efficiency for the microwave transmitter, which must include all loss in phase shifters, isolators, antennas, power circuits. Especially, the SPS is a power station in space, therefore, heat reduction will be a serious problem [25]. B. Transmitting Antenna

Fig. 3. Schematic rectenna system.

In the early of 1960s, the concept of rectifying antenna (rectenna), the name ‘rectenna’ and the rectenna was conceived by W.C. Brown of Raytheon Company [31]. A rectenna is a rectifying antenna, a special type of antenna that is used to directly convert microwave energy into DC electricity. Its elements are usually arranged in a multi element phased array with a mesh pattern reflector element to make it directional.[33]. The rectenna is consists of antenna, rectifying circuit with a low pass filter between the antenna and rectifying diode. The rectenna termed as rectifying antenna, is combination of an antenna and a nonlinear rectifying element (Schottky diode, IMPATT diode…etc.) where the two elements are integrated into a Fig. 2. Waveguide Slot Antenna single circuit. The schematic of a rectenna system is shown in Fig. 3 [32]. Such a system is capable to receive The most popular type of transmitting antenna are the and detect microwave power and converts the RF power slotted wave guide antenna, microstrip patch antenna, and into dc voltage at high frequencies (THz). Rectennas are parabolic dish antenna [26]. The slotted waveguide highly efficient at converting microwave energy to antenna is ideal for power transmission because of its high electricity. In laboratory environments, efficiencies of aperture efficiency (> 95%) and high power handling over 85%[34]. capability.[27]. Rectifying antennae are usually made of an array of The front view of the slotted wave guide antenna is as dipole antennae, which have positive and negative poles. shown in Fig 2 [28]. The slots on the waveguide will These antennae connect to semiconductor diodes. Here's assumed to have a narrow width. Increasing the width what happens: increases the Bandwidth, each slot could be independently 1. Microwaves, which are part of the fed with a voltage source across the slot. The position, shape and orientation of the slots will determine how (or electromagnetic spectrum, reach the dipole if) they radiate. In addition, the shape of the waveguide antennae. and frequency of operation will play a major role. If the 2. The antennae collect the microwave energy and slots are displaced from the centerline, the x-directed transmit it to the diodes. current will not be zero and will need to travel around the slot. Hence, radiation will occur. The distance from the 3. The diodes act like switches that are open or edge will determine the magnitude of the current. As a closed as well as turnstiles that let electrons flow result, the power that the slot radiates can be altered by in only one direction. They direct the electrons to moving the slots closer or farther from the edge. In this the rectenna's circuitry. manner, a phased array can be designed with varying excitation to each element. Antenna arrays made up of 4. The circuitry routes the electrons to the parts and hundreds or even thousand elements are often slotted systems that need them.[37]. waveguides similar to those described above.[29][30]. The rectenna will be used as an array for high power MPT because one rectenna element rectifies a few W only. Fig4 shows the Large Rectenna Array Used for ground to ground experiment in Goldstone in 1975[35].

The maximum rectenna array in the world is that used for stations between the generating station and a ground to ground experiment in Goldstone by JPL, consumers and would facilitate the USA, in 1975[36]. interconnection of electrical generation plants on a global scale. 3. The cost of transmission and distribution would become less and the cost of electrical energy for the consumer would be reduced also. 4. It has more freedom of choice of both receiver and transmitters. Even mobile transmitters and receivers can be chosen for the WPT system. 5. Loss of transmission is negligible level in the Wireless Power Transmission; therefore, the efficiency of this method is very much higher than the wired transmission. 6. The power failure due to short circuit and fault on cables would never exist in the transmission. 7. Power theft would be not possible at all. 8. Wireless charging would also possible. laptops and cell phones might never need any wires at all. 9. Vehicles would be driven using WPT, no need of fuel. Fig. 4. Rectenna array B. Disadvantages 1. Cost for practical implementation of WPT seems V. BIOLOGICAL EFFECT OF MICROWAVES to be very high. The slightly over 1million dollar Goldstone test in 1975 A general public perception that microwaves are delivered 34 kW at 1.6 km. The costs of the test in Hawaii harmful has been a major obstacle for the acceptance of in 2008, where just under 1 million dollar and delivered 20 power transmission with microwaves. The scientific Watts over 148 kilometers.[40]. research indicates that heating of humans exposed to the The very short range (1- l0m), preliminary radiation and effect of microwave radiation on birds (fried demonstrations of W at low power levels (< kW) were bird effect) is the only known effect.[40]. However this in general quite costly, however, the cost estimates are can happen in a highly intense area, in an area around and coming down for larger power levels and longer ranges. above the rectenna, access would need to be carefully Given the economic disparity andbeam safety controlled to ensure environmental safety and health concerns, it is doubtful that short range WPT standards are maintained. Under normal operating applications involving beams that are near tangent to conditions, the SPS microwave downlink will need to be the Earth’s surface will ever be useful for electric monitored continuously to ensure the tightly tuned phased- power transmission as compared to wired power delivery. array techniques and beam control are functioning However, this does not preclude research and correctly[46]. development tests and demonstrations of WPT from Studies in this domain repeatedly proves that the point to point on the Earth’s surface, where economic microwave radiation level would be never higher than the competition is not the prime consideration[45]. dose received while opening the microwave oven door, 2. Interference of microwave with present meaning it is slightly higher than the emissions created by communication systems is difficult. cellular telephones[38]. Cellular telephones operate with It is assumed that typical SPS systems will use power densities at or below the ANSI/IEEE exposure frequency bands around 2.45 GHz or 5.8 GHz. These standards [39]. Thus public exposure to WPT fields would bands are already allocated in the ITU-R Radio also be below existing safety guidelines. Regulations to a number of radio services, and are also designated for ISM (industry, science, and medical) VI. ADVANTAGES & DISADVANTAGES OF applications such as microwave ovens and wireless LAN . WPT It is mandatory that unwanted emissions, such as carrier noise, harmonics, and spurious and out-of-band emissions A. Advantages of the microwave power transmission beams, are 1. The power could be transmitted to the places suppressed sufficiently to avoid interference with other where the wired transmission is not possible. radio services and applications, in accordance with the 2. Wireless Power Transmission system would ITU-R Radio Regulations.[46]. completely eliminate the existing high-tension power transmission line cables, towers and sub

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AUTHOR’S PROFILE

Nikhil B. Dhake born in Jalgaon District, India on 5th November 1989 is a student at Dhole Patil College of Engineering, Pune, affiliated to the University of Pune. He is in final year of Information Technology and will be granted the degree of Bachelor of Engineering in July, 2012. He has published three Articles in International Journal & also presented various papers at National level.

Mrs. Arati A. Dandvate (B.E (E&CE), M.E(CSE), Ph.D.(CSE Pursuing)) working as HOD(Computer Engg Dept) having 12 years of teaching experience and 2 years IT experience. She has number of national level conferences and paper presentations in her credit.