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wireless power transmission full report
Post: #1

.doc  WIRELESS POWER TRANSMISSION final report.doc (Size: 906 KB / Downloads: 2523)

In the age of wireless communication and portable music players the demand for powering those devices wirelessly is ever prevalent. The advantages of portability and wireless communication are greatly hindered by the fact that the devices themselves must be plugged into the walls to charge. The next generation in portable devices is a device that receives power wirelessly. The first step in wireless power is providing power to a computer charging pad wirelessly. The market for this device would be businesses with large conference rooms. The device would allow users to plug their phones and computers into the conference room table without large power bricks and cords running everywhere. The pads can conveniently be placed under the table and inside the ceiling so there are no visible wires that could ruin the aesthetic feel of the room. The ease of installation and convenience of this device would make the marketability of this product quite large and if finished could be seen in thousands of conference rooms. If the efficiency of coupling could be increased slightly further, wireless power transmission could become a standard means for charging a mobile device.

Submitted By
SANTOSH KR. VAISH 0619231041
ANKIT SINGH 0619231007

1.1 Objectives
The overall goal of this project is to design and successfully implement a wireless power transmission system to be used in a conference room. The system will work by using resonant coils to transmit power from an AC line in the ceiling to a pad on the table. The pad will output DC voltages in order to charge computers and cell phones. There are several benefits for the use of such a system:
¢ Elimination of cords on the ground that make tripping hazards.
¢ Allows no wire installation and mobility on table.
¢ A necessary step towards consumer wireless power.
The entire interface has the following features:
¢ Feedback control for driving frequency to maximize efficiency.
¢ DC power output for computers and cell phone charging that allows for elimination of large power bricks.
¢ Slight mobility offered for different table heights and positions.
1.2 Specifications
The specifications original specifications from our design proposal are as follows in Error! Reference source not found..
Transmission Efficiency >30 %
Overall Efficiency >25 %
Output Voltage 18 VDC ± 1.8 V
5 VDC ± .5 V
Frequency Within 10 kHz of optimal
Power Abilities Laptop and cell phone
1.3 Block Diagram
The block diagram for the transmission setup is shown in Error! Reference source not found..
Figure 1: Block Diagram
1.4 Block Descriptions
The different blocks shown in the block diagram were implemented separately and then integrated together. Below are descriptions of each block and specifications for each.
1.4.1 DC Source
The DC source takes in the input from the wall voltage which is a 60 Hz sinusoid. Using diodes, the voltage is rectified and passed through a PI filter. The original design specified a 1 % voltage ripple, but this ripple requirement was excessive and difficult to meet at such a low frequency. The final design chosen had a voltage ripple of less than 5 % and was more than suitable.
1.4.2 Full Bridge Inverter
The full bridge inverter is a circuit that uses four switches, a DC source, and a load. The four switches are setup in an H-bridge with the middle being the load. In this case the load is the top coil. Two of the switches are connected from the high side DC source to opposite sides of the coil. The remaining two switches are connected from the low side of the DC source to opposite sides of the coil. High side switches have opposite duty cycles and the low side switches are connected such that the DC source is applied across the load. The result is a square wave being applied across the coil. The switches are MOSFETs that have the capability to carry the max current and can block the full DC voltage.
1.4.3 Gate Drivers
Gate drivers are used to turn on and off the switches. The gate drivers take in a timing signal and output a voltage high enough and with enough current to drive MOSFETs on and off at the same frequency of the timing signal.
1.4.4 PIC Microcontroller
The gate drivers are controlled by a PIC microcontroller. There is feed back into the PIC about how much power is being drawn. The PIC attempts to increase the frequency until the power out of the DC source is at a maximum. This should correspond to the resonant frequency because the increase in input power means there is an increase in output power. The PIC outputs 10 digital logic pins as either high or low. The pins are then converted to a voltage by the Digital to Analog Converter (DAC).
1.4.5 DAC/ VCO
The output of the DAC is a voltage between 0 and 5 V. This voltage is an input to a Voltage Controlled Oscillator (VCO), which produces a square wave that increases in frequency as the input voltage increases. The range of frequencies is determined by a bias voltage and an external capacitor, and is set around our expected resonant frequency.
1.4.6 Current Sensing
The current sensing circuit is used to tell the PIC how much current is being pulled from the DC source. It uses a precision .15 resistor on the output of the DC source and that voltage is feed into an op-amp circuit that produces a voltage proportional to the current. This voltage is designed to be within the range of inputs for the PIC.
1.4.7 Coils and Air Gap
The coils are each made out of 100 turns of 20 AWG magnet wire. They are separated by about 2 m and have a diameter of about 1 m. The power transfer between them is done through resonant magnetic coupling.
1.4.8 Transformer
A transformer is used to scale down the voltage to around 18 V. This is done before the signal is converted to DC because high frequency transformers are small and relatively efficient.
1.4.9 Rectifier and Filter
A similar circuit is used to convert the AC signal from the transformer to a DC signal. Different diodes are used due to the high frequency nature of the signal. Smaller capacitors are used in the filter because the frequency is much higher than the 60 Hz signal filtered the top filter. The capacitors are also ceramic because electrolytic capacitors have a much lower self resonant frequency, after which they begin to behave like inductors.
1.4.10 Buck Converter
A buck converter is used to convert the 18 V for the computer down to 5 V for charging the cell phone. It was ordered to save us the trouble of making our own and its ability to keep the voltage regulated with a large input voltage range.
The overall concept for mutually inductive coils is an idea from an MIT experiment used to transmit power to power a light bulb. The size of the inductors was increased and the number of turns increased due to ideal equations in hopes of lowering resonant frequency and increasing transmission efficiency. PSPICE simulation was done wherever possible to verify design before actual testing.
2.1 DC source

The DC source was designed with a rectifier and filter circuit. A full bridge rectifier was chosen because they have less ripple than a half bridge rectifier because the frequency is twice as fast. This means the filter has to supply the voltage for only half as long so it has less time to decay. Figure 2 shows the difference in the two rectifiers.
Figure 2: Rectifier Plots
The capacitors were chosen with relatively high values and the design choice was verified in PSPICE with a simulation
2.2 Full-Bridge Inverter and Gate Drivers
The full bridge circuit is a generic circuit. The switches were chosen based on max frequency, current carrying capabilities, and voltage blocking. The speed is important because our switching frequency is several MHz at high voltage and a reasonable amount of current. The gate drivers were chosen because they have the appropriate frequency requirements and are designed to drive MOSFETs, also they have an inverting and non-inverting signals. This means that it can drive all of the MOSFETs.
2.3 PIC, DAC, and VCO
The PIC was chosen because it was readily available, has an analog input for feedback, and it can operate at a speed that is fast enough to control the frequency. The PIC outputs a 10 bit logical signal that is converted to a voltage by a DAC. The DAC was chosen similar to the PIC in that it was readily available, has the ability to convert the digital pins to the analog voltage range needed. C-code already generated for the PIC did not have to be changed with the operation of this new DAC. The output voltage of the DAC is an input to the VCO. The VCO was chosen because of its frequency range.
2.4 Current Sensing
The Transistor part numbers were changed based on what was available in the parts shop. The fact that the circuit had to handle a common mode voltage of around 170 V made the circuit more complicated than normal current sense circuits. The zener diode and the p-type MOSFETs in the design allow the high side voltage to be as high as 500 V, while only making the voltage supply to the op-amp around 62 V and taking care of any common mode voltage problems by referencing to a voltage other than ground.
2.5 Coils and Air Gap
The coils were designed using a series of ideal equations. If the coils are treated as windings around a transformer the reluctance can be calculated using equation(1.1).
Using the dimensions given and the relative permeability of air the reluctance is . The reluctance can be used to find the mutual inductance using equation(1.2).
The resonant frequency is given in equation(1.3).
Therefore, in order to reduce the resonant frequency using the mutual inductance the number of turns should be maximized, the area should be maximized, and the distance between the coils should be minimized. The distance between the coils was varied to observe the effects on coupling due to coil distance but would eventually be set around six feet to simulate the distance between a tabletop and ceiling. A value of 100 turns was chosen because it was a large value, but not large enough to start contributing too much unwanted factors from series resistance and winding capacitance. The diameter was set to 1 meter because it is large value but not too unreasonable of a size for a pad on or under a desk. The actual expected frequency can be calculated by finding the capacitance which is given by equation(1.4).
Substituting in values for (1.3) and (1.4) results in a resonant frequency of 395.814 kHz. This is a very rough value because of losses in the air and non-ideal elements in the circuits. The actual measured natural frequency is around 3.4 MHz when measured using a signal generator with amplitude 20 Vp-p.
2.6 Transformer
The transformer was designed based on the turn ratio needed to scale down the voltage and current requirements to prevent magnetic flux saturation of the core. The saturation magnetic flux is given by(1.5).
The core losses were attempted to be minimized using(1.5). The number of turns was kept to a minimum to prevent losses from series resistance in the windings.
2.7 Rectifier and Filter
The rectifier was chosen using a single diode to prevent loss because there is only current flowing through one diode and the frequency is fast enough that the full-wave is not need. The diode chosen had its frequency verified by looking at [12]. The capacitor was picked such that its resonant frequency is above 6 MHz because it will not act like a capacitor above this frequency. The inductance from the connections dominates the impedance, and a smaller capacitor was chosen than in the top filter because the self resonant frequency is higher. Ceramic capacitors tend to have a lower capacitance than electrolytic capacitors, but in this case the frequency is high enough that a lower capacitance is acceptable.
2.8 Buck Converter
The component was selected because it can handle the power necessary for the cell phone, outputs 5 V, and meets the power requirements for the cell phone.
A series inductor and a capacitor to ground will filter the signal output by the buck converter making it a cleaner signal.
3.1 DC Source
The DC source comprises of a rectifier circuit using 1N1188 diodes and a PI filter.
Figure 3: Wall Voltage to DC Rectifier and Filter (DC Source)
The 1N1188 diodes were chosen because they can carry more than 1 A and can block up to 400 VDC. They were also readily available in the parts shop. The voltage ripple from this circuit is hard to calculate on paper due to the fact that it is a third order filter. The inductor was chosen at a standard part value and verified in PSPICE that it can regulate the current properly.
A PSPICE simulation was run with Dbreak diodes in place of the 1N1188, because there is no PSPICE model available for the 1N1188. The diodes should not noticeably affect the output voltage.
The output signal is connected by switches operating at the speed that the full-bridge inverter is expected to operate at. The purpose of the switches is not to test the full-bridge inverter circuit, but make sure that the output voltage is properly regulated.
This circuit diagram in Figure 4 is what was used to simulate. The switches were used to make the circuit more like the real circuit that would be running in the demo.
As Figure 5 shows, after about 40 ms the voltage is very steady. It has a ripple of less than 1 V. When the circuit in Figure 3 was built, the regulation was not as steady as shown in the simulation of Figure 5 so the capacitance values were changed to 1000 µF.
Figure 4: Simulation Circuit for Rectifier and Filter
Figure 5: Simulation Results
3.2 Full-Bridge Inverter/Gate Drivers
This inverter takes in the voltage from the DC source and through using the PIC and gate drivers, outputs signal in the form of a square wave with a frequency that is controlled by the PIC and is adjusted based on induced current in the coil. The gate drivers are ICs that take in the signal from the VCO and output the right amount of voltage to turn on and off the power MOSFETs in the full-bridge inverter.
3.3 PIC Microcontroller, DAC, and VCO
The DAC requirements were that it had 10 bits, parallel inputs, and transparent output. Finding a part that meet these restrictions was difficult.
Figure 6: DAC and VCO Circuit Diagram
The PIC will control the frequency of the signal that is driving the coil. It will also adjust the frequency based on the current that is sensed through the top coil to get the most power transfer through the coils
Figure 7:PIC Pin Out Diagram
3.4 Current Sensor
A very low resistance resistor will be put in series with the coil. The voltage is then measured across it to determine the current through the coil based on the voltage drop and resistance. The extra parts in this circuit are to protect the op-amp. The op-amp was not rated for 150-170 V common mode voltage, but it was found on the datasheet that this circuit would work [8].
Figure 8: Current Sense Circuit
3.5 Coils
An inductor made with about 100 turns and a diameter of around 1 m. It will also have a current limiting resistor in series to make sure nothing burns up. An inductor like the top coil that will receive the electromagnetic waves transmitted by the top coil and have a current and voltage induced to power the devices. The inductance of either coil was around 27 mH. This was lower than calculated but still relatively high. Preliminary tests were done on the coils to find their resonant frequency. Multiple frequencies were found, including 3.4 MHz, 6 MHz, and one around 9 MHz. The most resonant of these being the 6 MHz signal, but the 3.4 MHz was chosen for the target frequency, due to the fact that it is easier to find parts for and will work nearly as well.
These frequencies were far from the expected frequency. This could be due to a multitude of factors including skin effect of the 20 AWG wire, imperfections in the windings, incorrect permeability numbers, incorrect estimates of capacitance, and fringing among others. The high frequency made the designs a bit more restricted.
3.6 Transformer
The transformer was not made because we were never able to get a voltage on the bottom coil so it was hard to figure out a turn ratio and what the saturation current would be.
3.7 Half Wave Rectifier
A diode that will take the signal induced in the bottom coil and cut off the negative side of the AC, helping to create a DC signal.
Filter: A series 1mH inductor and a capacitor to ground that will filter the signal output by the rectifier making it a smoother signal.
Figure 11: Circuit Diagram for Transformer, Rectifier, and Filter
3.8 DC/DC Buck Converter
A Buck-Converter will step the 18 V for the laptops down to 5 V for a phone. Initial tests found that the regulation by this buck converter is outstanding, changing 1 mV or less through the recommended input voltage range.
The final product is designed to operate off a wall outlet. The only other considerations for cost are placing the bottom coil under the table top. The final design would also need some voltage supplies (5 and ±12).
4.1 Parts
Part Block Quantity
Current Sensing Resistor Current Sensor 1
62 V Zener Diode Current Sensor 1
Operational Amplifier Current Sensor 1
2.7k, 100,
and 2M Resistors 1/4W Current Sensor 1
Current Senor MOSFETS Current Sensor 2
Diodes DC Supply 4
1mH Inductor DC Supply 2
Capacitor 1000uF DC supply 2
20 MHz Oscillator PIC 1
Voltage Controlled Oscillator DAC/VCO 1
Gate Driver Gate drivers 2
Full-Bridge Inverter MOSFETs Full-Bridge Inverter 4
700m Magnet Wire (20AWG) Top and bottom coils 1
Scaffolding Wood Top and bottom coils 1
Transformer Transformer 1
Diode Bottom Filter 1
Capacitor 1uF Bottom Filter 1
Resistor 2.7K Buck Converter 1
Buck Converter Buck Converter 1
Capacitors 100uF, .01uF, and 470Uf Buck Converter 1
100uH Inductor Buck Converter 1
Diode Buck Converter 1
5.1 Accomplishments
¢ Proved that power can be transmitted via resonantly coupled coils (theoretically)
¢ Multiple resonant frequencies found at many coil spacing
¢ PIC able to regulate frequency based on current measured
¢ 60 Hz DC wall voltage filtered with a small voltage ripple
¢ 3 MHz signal able to be filtered with a small voltage ripple
5.2 Uncertainties
¢ MOSFETs were not able to operate fast enough to drive the coils at resonance.
¢ Isolation problems for the inverter.
1. http://en.wikipediawiki/Wireless_energy_transfer.
2. http://www.electricalternativewireless.htm.
3. SIXTH INTERNATIONAL SYMPOSIUM NIKOLA TESLA October 18 “ 20, 2006, Belgrade, SASA, Serbia
4. http://novaspivack.typepadnova_spivacks_...less.html.
5. http://ecoupledapplicationsMain.html
6. http://www.wiredgadgetlab/2009/01/video-wireless/
7. http://www.instructablesid/Wireless-Powe...stances-U/
9. http://www.electronicsinfolineNew/Lights...nsfer.html
1.1 Objectives 1
1.2 Specifications 2
1.3 Block Diagram 2
1.4 Subprojects 3
1.4.1 DC Source 3
1.4.2 Full-Bridge Inverter 3
1.4.3 Gate Drivers 3
1.4.4 PIC 4
1.4.5 DAC/VCO 4
1.4.6 Current Sensing 4
1.4.7 Coils and Air Gap 4
1.4.8 Transformer 4
1.4.9 Rectifier/Filter 5
1.4.10 Buck Converter 5

2.1 DC Source 6
2.2 Full-Bridge Inverter/Gate Drivers 6
2.3 PIC, DAC, and VCO 7
2.4 Current Sensing 7
2.5 Coils and Air Gap 7
2.6 Transformer 8
2.7 Rectifier and Filter 9
2.8 Buck Converter 9
3.1 DC Source 10
3.2 Full-Bridge Inverter/Gate Drivers 11
3.3 PIC, DAC, and VCO 12
3.4 Current Sensing 13
3.5 Coils and Air Gap 13
3.6 Transformer 14
3.7 Rectifier and Filter 14
3.8 Buck Converter 14
4.1 Parts 15
5.1 Accomplishments 16
5.2 Uncertainties 16
Post: #2
Hi Guys,

It seems you have done a great in this project, but you lack many thing in it,
i am also work in the same project, really you have been in wrong track out totally,
the block diagram is really good but missed out many thing in it.

Work hard for it and understand the base first, you will not get any material for the subject but search on Google you can find many basic concept of your project.
first thing is that you are working with wrong frequency, only this much hint i can give,
u have to wait for come period then i will give the demo for my project currently its now
on prototype.

Best of Luck for Project, need any basic information then you can ask me.

Post: #3
thanks for pointing out the mistakes in the report. We will try to rectify them. Also thanks for lending a helping hand to anyone working on the project.
Post: #4
hi, the project is very intresting so i'm thinking to do something like this so can u guide me futher with correct circuits with reports for the WIRELESS POWER TRANSMISSION...
Post: #5
hi every one find my demo for wireless power, lamp glow of 5 watts & mobile charging.


Post: #6
Thanks for that!
Post: #7
i want wireless projects
Post: #8
plz provide me full report
Post: #9

.pdf  FINAL Wireless Power Study-Final R1.pdf (Size: 672.33 KB / Downloads: 435)
Lunar Wireless Power Transfer Feasibility Study

Prof. Zoya Popovic, University of Colorado, Boulder
David R. Beckett, Scott R. Anderson, Diana Mann, Stuart Walker, Independent Consultants
Sheldon Fried, Ph.D., National Security Technologies, LLC

Abstract –

This study examines the feasibility of a multi-kilowatt wireless radio frequency (RF)
power system to transfer power between lunar base facilities. Initial analyses, show that wireless
power transfer (WPT) systems can be more efficient and less expensive than traditional wired
approaches for certain lunar and terrestrial applications. The study includes evaluations of the
fundamental limitations of lunar WPT systems, the interrelationships of possible operational
parameters, and a baseline design approach for a notionial system that could be used in the near
future to power remote facilities at a lunar base. Our notional system includes state-of-the-art
photovoltaics (PVs), high-efficiency microwave transmitters, low-mass large-aperture high-power
transmit antennas, high-efficiency large-area rectenna receiving arrays, and reconfigurable DC
combining circuitry.
Post: #10
presented by:
Aarthi V.G..

.docx  41053605-Wireless-Power-Transfer-New (1).docx (Size: 353.93 KB / Downloads: 355)
Wireless power transfer

Imagine a future in which wireless power transfer is feasible: cell phones, household robots, mp3 players, laptop computers and other portable electronics capable of charging themselves without ever being plugged in, freeing us from that final, ubiquitous power wire. Some of these devices might not even need their bulky batteries to operate.
Wireless energy transfer or wireless power transmissionis the process that takes place in any system where electrical energy is transmitted from a power source to an electrical load without interconnecting wires. Wireless transmission is useful in cases where instantaneous or continuous energy transfer is needed but interconnecting wires are inconvenient, hazardous, or impossible.
Wireless energy transfer is different from wireless transmission of information, such as radio, where the signal-to-noise ratio or the percentage of power received becomes critical only if it is too low to recover the signal successfully. With wireless energy transfer efficiency is the more important parameter.
The most common form of wireless power transmission is carried out using induction, followed by electro dynamic induction. Other present-day technologies for wireless power include those based upon microwaves and lasers.
Transmission of electrical energy from one object to another without the use of wires is called wireless transmission. Consider two self resonating copper coil of same resonating frequency with a diameter 20 inches each.
One copper wire is connected to the power source(transmitter), while the other copper wire is connected to the device(receiver).
Near field is Wireless transmission techniques over distances comparable to, or a few times the diameter of the device(s), and up to around a quarter of the wavelengths used. Near field energy itself is non radiative, but some radiative losses will occur. In addition there are usually resistive losses. Near field transfer is usually magnetic (inductive), but electric (capacitive) energy transfer can also occur.
Main article: Inductive coupling
The action of an electrical transformer is the simplest instance of wireless energy transfer. The primary and secondary circuits of a transformer are not directly connected. The transfer of energy takes place by electromagnetic coupling through a process known as mutual induction. (An added benefit is the capability to step the primary voltage either up or down.) The battery charger of a mobile phone or the transformers on the street are examples of how this principle can be used. Induction cookers and many electric toothbrushes are also powered by this technique.
The main drawback to induction, however, is the short range. The receiver must be very close to the transmitter or induction unit in order to inductively couple with It.
Electro dynamic induction
The "electro dynamic inductive effect" or "resonant inductive coupling" has key implications in solving the main problem associated with non-resonant inductive coupling for wireless energy transfer; specifically, the dependence of efficiency on transmission distance. Electromagnetic induction works on the principle of a primary coil generating a predominantly magnetic field and a secondary coil being within that field so a current is induced in the secondary. This results in a relatively short range because most of the magnetic field misses the secondary. Over greater distances the induction method is inefficient and wastes much of the transmitted energy.
The application of resonance improves the situation somewhat, moderately improving the efficiency by "tunneling" the magnetic field to a receiver coil that resonates at the same frequency. When resonant coupling is used the two inductors are tuned to a mutual frequency and the input current is modified from a sinusoidal into a non-sinusoidal rectangular or transient waveform so as to more aggressively drive the system. In this way significant power may be transmitted over a range of many meters. Unlike the multiple-layer windings typical of non-resonant transformers, such transmitting and receiving coils are usually single layer solenoids or flat spirals with series capacitors, which, in combination, allow the receiving element to be tuned to the transmitter frequency and reduce losses.
A common use of the technology is for powering contactless smartcards, and proposed systems exist to power and recharge laptops and cell phones.
Post: #11

.doc  243.doc (Size: 291 KB / Downloads: 249)
Abstract -.The technology for wireless power transfer (WPT) is in the forefront of electronic development. Applications involving microwaves, solar cells, lasers, and resonance of electromagnetic waves have had the most recent success with WPT. The main function of wireless power transfer is to allow electrical devices to be continuously charged and lose the constraint of a power cord. Although the idea is only a theory and not widely implemented yet, extensive research dating back to the 1850’s has led to the conclusion that WPT is possible.
The three main systems used for WPT are microwaves, resonance, and solar cells. Microwaves would be used to send electromagnetic radiation from a power source to a receiver in an electrical device. The concept of resonance causes electromagnetic radiation at certain frequencies to cause an object to vibrate. This vibration can allow energy to be transmitted between the two vibrating sources. Solar cells, ideally, would use a satellite in space to capture the suns energy and send the energy back to Earth. This concept would help to solve the major energy crisis currently concerning most of the world. These ideas would work perfectly in theory, but converting the radio frequencies into electrical power and electrical power to radio frequencies are two main problems that are withholding this idea to become reality.
This paper will explore the technological applications of microwaves, resonance, and solar cells in WPT and explain the basic technique of transmitting power wirelessly. It will also include problems encountered during experimentation and recent advances in the field. The paper will also include the futuristic applications of WPT and its ability to solve the energy crisis.
The Beginning Of WPT
Electricity by today’s standards is considered an essential to life. Electricity has been the fuel for technological development since its first applications dating back to the late 16th century. This marvellous phenomenon, however, comes with a price. The cost of making electricity is harmful to the environment. The Energy Information Administration’s records show that nearly 50% of all electrical plants are high polluting coal plants. Major changes in the environment have occurred over the last 30 years that are detrimental to the future of this planet. If this path is left unchanged, scientists have predicted that certain parts of the world could be uninhabitable by 2050. The solution is to reduce greenhouse gas emissions into earth’s atmosphere through alternative power generation. One sustainable technology leading this charge is wireless power transfer (WPT).
The concept of WPT has been around since the mid 17th century. WPT is exactly what the name states; to transfer electrical power from a source to a device without the aid of wires. The founder of AC electricity, Nikola Tesla, was first to conduct experiments dealing with WPT. His initial experiment of lighting gas discharge lamps from over 25 miles away, wirelessly, was a success. His idea came from the notion that earth itself is a conductor that can carry a charge throughout the entire surface. Although his idea of a world system of WPT could never be properly funded, his initial research sparked the scientific world into a whole new theory of power generation. While Tesla’s experiments were not creating electricity, but just transferring it, his ideas can be applied to solve our energy crisis. His experiments sparked new ideas such as applications involving microwaves, lasers, resonance and solar cells. Each application has its respective drawbacks but also has the potential to aid this planet in its dying need for an alternative to creating power.
Today, portable technology is a part of every day life. Most commonly used devices no longer need to draw power from the supply continuously. But from portability emerges another challenge: energy. Almost all portable devices are battery powered, meaning that eventually, they all must be recharged–using the wired chargers currently being used. Now instead of plugging in a cell phone, PDA, digital camera, voice recorder, mp3 player or laptop to recharge it, it could receive its power wirelessly–quite literally, “out of thin air”.
How Does WPT Work
Wireless power transfer is a varied and complicated process. There is more than one system that works to complete the process. Three more scientifically sound ideas are space solar cells, lasers, and resonating electro-magnetic waves. While each process varies in the way the energy is collected and used, the mechanisms of converting from RF energy to DC energy and vise versa are the same for all WPT systems.
The process of converting DC to RF starts with the power- that power to be transmitted is first tapped from the main power grid at about 50Hz AC. The voltage is then reduced to a viable load for rectifying into DC.
The energy then is supplied to an oscillator-fed magnetron and electrons are emitted from the central terminal. A positively charged anode surrounds the inner cathode to attract the electrons. Due to the current flowing through the magnetron the, the magnetic field produced causes the electrons to experience the cyclotron effect.
The circling electrons pass resonating cavities of the magnetron and create a pulsating magnetic field which constitute an electromagnetic radiation in microwave frequency range. The voltage coming out of the rectifier that connects the AC grid to the magnetron controls the magnetron anode DC voltage.
Since the anode is attracting the electrons into it (the cyclotron effect), the DC voltage that is supplied to it will determine the strength of the magnetic field. The stronger the magnetic field the greater the force on the electrons through the resonating cavities. Although frequency of the radiation can be adjusted by varying the inductance or capacitances of the resonant cavities, the experimental transmitting frequencies with the highest success rate are 2.45GHz and 5.8GHz.
The process of ‘catching’ the energy for it to be used in the conversion back to DC has different obstacles than the process of transmission. A problem with transmitting RF energy long distances is that it will lose its strength due to free space propagation. In order to compensate for this loss, antennas are connected in arrays. One such device called the energy harvesting circuit, patented by University of Pittsburgh’s Dr. Marlin Mickle, consists of multiple antennae each tuned to a different portion of the frequency spectrum. This increases the RF energy absorbed thus increasing the efficiency of the transmission. A series-parallel assembly of Scohttky diodes (rectenna) are then used at the receiving end to convert the microwave power back into DC. These diodes contain a low standing power rating but RF qualities enabling it to rectify the incoming microwaves into usable energy.
Using resonating electromagnetic waves is the system that will most likely be seen in the near future in applications that demand less than 10m of transmission. When two objects vibrate at the same frequency, they create larger amplitude together, rather than standing alone. If an antenna resonating with a particular frequency is brought within a few meters of a receiving antenna resonating at the same frequency, then the energy can be ‘tunneled’ through space and into the receiving antenna to be rectified. The quantum phenomenon of tunneling allows the energy to travel through space without being propagated. In a sense, the energy being tunneled is able to cross the potential gap between the two antennae without losing any energy. This resonating causes electromagnetic waves to vibrate through space. The energy is then used to recharge a battery inside the device. Since no energy is lost during the transfer, any surrounding circuitry is not harmed.
Solar power is a truly unlimited energy supply. Using the resonating electromagnetic waves system in coordination with outer space solar cells, takes wireless power transfer to a new scale. In geosynchronous orbits, solar satellites would be illuminated by the sun’s rays 99% of the time. A constant transmission of energy from the satellites down to earth would prove that there would be no need for costly storage devices to hold excess energy. The theory includes massive outer space panels attached to these satellites that would continuously absorb the suns rays. The energy would be beamed back to Earth using the electromagnetic wave system. Wasted heat cause from the absorption and transmission can be radiated right back into space, eliminating the potential for overheating. This has been looked into extensively, especially for the reasons of the energy problems in the world today. Particular problems however occur when trying to implement a WPT system able to sustain such a demand as currently needed. Besides the cost and complexity to build such a large scale system, a recent study by the DOE shows that the solar collectors would cover many square miles just in space. The receiving collectors on earth would cover close to 50 square miles. Despite the setbacks, this form of WPT is receiving currently the most attention in the science world due to the fact that it can transmit energy at close to 85% efficiency.
The use of lasers to transfer energy is a much different process from those above. This process involves transferring energy from a source to a receiver by beaming a laser to an object with a solar cell receiver. This idea is possible but is highly inefficient. The laser would need a direct line of sight to the object it is charging. Also, converting electricity to a laser and back to electricity causes a loss of energy. Energy from the laser is absorbed into the atmosphere also causes a loss of energy. In theory the system would work, but it is not an efficient form of wireless power transfer and would not be worth the trouble that the system would cause.
WPT Today
WPT is becoming a world renowned idea and is in a position to change the society in countless ways. Each country is doing its part to contribute to the cause. Over the past 50 years countries such as the United States, Canada, France, Russia and Japan have brought feasible and scientifically sound ideas to this field .
Currently in the U.S., Dr Joseph Hawkins and William Brown are experimenting with a fully operational microwave powered helicopter that was publicly demonstrated in 1995 at a conference for WPT in Japan. Applying similar concepts as their helicopter project, the team has developed the concept of ESPAM, or electronically steerable phased array module. Proposed applications of such systems include power transfer from ground to air or ground to space through the use of microwaves. This could provide power to long-haul space flights, orbiting spacecraft and orbiting facilities.
France is in the forefront of European research on WPT. With France being dependent on relatively low polluting nuclear energy, the idea of having an additional cleaner source of power sparked the interests of many scientists. The most recent project is to extend utility grade power (~100kW) across a three km ravine on Reunion Island using WPT, where utility cable would be hazardous to the environment. Although this does not demonstrate a space to ground application, the concepts of transmitting and converting RF energy is independent of the distance needed to travel. On top of thier research, France also hosts world summit meetings to discuss space solar power, every two years.
Russian Professor Vladimir Vanke has made the most significant contribution to solving the hurdles of WPT. In order for microwaves to be used as electricity, the radiant energy needs to be converted into DC power. Vanke solved this problem with the invention of the cyclotron wave converter.
Post: #12
why wireless power transfer is not possible by ultasound?(i.e. by using piezoelectric materials we can convert electric energy to wave energy and then again convert it into electric energy)
Post: #13

.ppt  presentation_WPT.ppt (Size: 1.57 MB / Downloads: 279)
Basic Idea:
Wireless Power Transmission is based on the simple concept of transmitting power without wires i.e. , transmitting power as microwaves from one place to another.
Basically known as Microwave power Transmission.
MPT is most interesting because microwave devices offer the highest efficiency of conversion between DC-electricity and microwave power.
Wireless Power Transmission:
Nikola Tesla ,”Father of Wireless”, was the one who first conceived the idea of WPT and demonstrated the transmission of electrical energy without wires.
In 1893,Tesla demonstrated the illumination of vacuum bulbs without using wires in Chicago.
Functional Block Diagram of WPT:

In the transmission side , the microwave power source generates microwave power and the output power is controlled by electronic control circuits.
The waveguide circulator which protects the microwave source from reflected power is connected with the microwave power source through the coax- waveguide adaptor.
The tuner matches the impedence between the transmitting antenna and the microwave source .
The transmitting antenna radiates the power uniformly through free space to the rectenna .
Components of WPT:-
The primary components of Wireless power transmission are- Microwave Generator
Transmitting Antenna
Receiving Antenna(Rectenna)
The microwave transmitting devices are classified as Microwave Vacuum Tubes(magnetrons).
Magnetron is widely used for experimentation of WPT
The microwave transmission often uses 2.45Ghz or 5.8Ghz frequency.
A microwave tube in which electrons generated from a heated cathode are affected by magnetic and electric fields in such a way as to produce microwave radiation .
The anode of a magnetron is fabricated into a cylindrical solid copper block.
The cathode and filament are at the center of the tube and are supported by the filament leads.
The electric and magnetic fields interact to exert force upon the electrons.
Components of WPT….

The slotted waveguide antenna and parabolic dish antenna are the most popular type of transmitting antenna.
The Rectenna consisits of antenna , rectifying circuit with a low pass filter between the antenna and rectifying diode.
Wireless Power Reception through Rectenna…
Brief introduction of Schottky Barrier Diode
Rectenna Issues..
Size- Miles across
Location- Near population centre
Health and environmental side effects- Although claim that microwaves would be safe , how do you convince people
Wireless Charging of Mobile phones using microwaves
The basic addition to the mobile phone is going to be the rectenna and a sensor.
The Microwave signal is transmitted from the transmitter using special kind of antennas called slotted wave guide antenna at a frequency is 2.45 GHz.
The transmitting Base station is equipped with a Microwave transmitter such as the powerful Magnetron.
Sensor acts as a switch for triggering the rectenna circuitry.
WPT system completely eliminates the existing high tension power transmission line cables , towers and substations .
The cost of transmission and and distribution become less.
The power could be transmitted to the places where the wired transmission is not possible.
Loss of transmission is negligible in WPT and therefore the efficiency is much higher than the wired transmission.
The capital cost for practical implementation of WPT seems to be very high.
The other disadvantage of the concept is interference of microwave with present communication systems.
Generating power by satellites with giant solar arrays in earth orbit and transmitting the power as microwaves to the earth known as Solar Power Satellites.
Fuel free airplanes , fuel free electric vehicles , fuel free rockets etc.
Mobile charging by using additional elements such as rectenna and sensor.
The concept of Wireless Power Transmission Via microwaves offers greater possibilities for transmitting power with negligible losses and ease of transmission than any other invention or discovery heretofore made
We can expect with certitude that in years next few years ,wonders will be wrought by its applications if the conditions are favourable.
Post: #14
In this paper, we present the concept of transmitting power without
using wires i.e., transmitting power as microwaves from one place
to another is in order to reduce the transmission and distribution
losses. This concept is known as Microwave Power transmission
(MPT). We also discussed the technological developments in
Wireless Power Transmission (WPT). The advantages,
disadvantages, biological impacts and applications of WPT are
also presented.
Key Words
Microwave Power transmission (MPT), Nikola Tesla, Rectenna,
Solar Power Satellites (SPS), Wireless Power transmission (WPT).
One of the major issue in power system is the losses occurs during
the transmission and distribution of electrical power. As the
demand increases day by day, the power generation increases and
the power loss is also increased. The major amount of power loss
occurs during transmission and distribution. The percentage of loss
of power during transmission and distribution is approximated as
26%. The main reason for power loss during transmission and
distribution is the resistance of wires used for grid. The efficiency
of power transmission can be improved to certain level by using
high strength composite over head conductors and underground
cables that use high temperature super conductor. But, the
transmission is still inefficient. According to the World Resources
Institute (WRI), India’s electricity grid has the highest
transmission and distribution losses in the world – a whopping
27%. Numbers published by various Indian government agencies
put that number at 30%, 40% and greater than 40%. This is
attributed to technical losses (grid’s inefficiencies) and theft [1].
Any problem can be solved by state–of-the-art technology. The
above discussed problem can be solved by choose an alternative
option for power transmission which could provide much higher
efficiency, low transmission cost and avoid power theft.
Microwave Power Transmission is one of the promising
technologies and may be the righteous alternative for efficient
power transmission.
Nikola Tesla he is who invented radio and shown us he is indeed
the “Father of Wireless”. Nikola Tesla is the one who first
the idea Wireless Power Transmission and demonstrated “the
transmission of electrical energy without wires" that depends upon
electrical conductivity as early as 1891[2]. In 1893, Tesla
demonstrated the illumination of vacuum bulbs without using
wires for power transmission at the World Columbian Exposition
in Chicago. The Wardenclyffe tower shown in Figure 1 was
designed and constructed by Tesla mainly for wireless
transmission of electrical power rather than telegraphy [3].
Figure1.The 187-foot Wardenclyffe Tower
(Tesla Tower)
In 1904, an airship ship motor of 0.1 horsepower is driven by
transmitting power through space from a distance of least 100 feet
[4]. In 1961, Brown published the first paper proposing microwave
energy for power transmission, and in 1964 he demonstrated a
microwave-powered model helicopter that received all the power
needed for flight from a microwave beam at 2.45 GHz [5] from
the range of 2.4GHz – 2.5 GHz frequency band which

Download full report
Post: #15

.ppt  navya presentation.ppt (Size: 776 KB / Downloads: 170)
Recent trends in science and technology
Introduction to How Wirelessspower Works

Resonance and Wireless Power
The MIT wireless power project uses a curved coil and capacitive plates.
Research at MIT indicates that induction can take place a little differently if the electromagnetic fields around the coils resonate at the same frequency. The theory uses a curved coil of wire as an inductor. A capacitance plate, which can hold a charge, attaches to each end of the coil. As electricity travels through this coil, the coil begins to resonate. Its resonant frequency is a product of the inductance of the coil and the capacitance of the plates.
Long-distance Wireless Power
Whether or not it incorporates resonance, induction generally sends power over relatively short distances. But some plans for wireless power involve moving electricity over a span of miles. A few proposals even involve sending power to the Earth from space.
In the 1980s, Canada's Communications Research Centre created a small airplane that could run off power beamed from the Earth. The unmanned plane, called the Stationary High Altitude Relay Platform (SHARP), was designed as a communications relay. Rather flying from point to point, the SHARP could fly in circles two kilometers in diameter at an altitude of about 13 miles (21 kilometers). Most importantly, the aircraft could fly for months at a time.
While scientists have built working prototypes of aircraft that run on wireless power, larger-scale applications, like power stations on the moon, are still theoretical. As the Earth's population continues to grow, however, the demand for electricity could outpace the ability to produce it and move it around. Eventually, wireless power may become a necessity rather than just an interesting idea.

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