1 UNWIRED CHARGING USING POWER CAST TECHNOLOGY AND ECOUPLED TECHNOLOGYA seminar report submitted to S.P.R. College of Engineering and Technology in Partial Fulfillment of the Requirements for the award of BACHELOR OF TECHNOLOGY IN ELETRICAL & ELECTRONICS ENGINEERING BY S.MANOHAR REDDY Roll No: 08GM1A0225 Under the esteemed guidance of R.NAGESWARA RAO Assistant Professor DEPARTMENT OF ELECTRICAL ENGINEERING S.P.R. COLLEGE OF ENGINEERING & TECHONOLOGY (AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY), ANKUSHAPUR (VIL), GHATKESAR (MDL), RANGA REDDY (DIST). 2012
2 DEPARTMENT OF ELECTRICAL ENGINEERING S.P.R. COLLEGE OF ENGINEERING & TECHNOLOGY (AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY), ANKUSHAPUR (VIL), GHATKESAR (MDL), RANGA REDDY (DIST). CERTIFICATEThis is to certify that this technical seminar report entitled “unwired charging usingpowercast technology and ecoupled technology ” has been submitted by S MANOHARREDDY bearing the Roll No: 08GM1A0225, in partial fulfillment of the requirementsfor the award of degree of Bachelor of Technology in Electrical & ElectronicsEngineering. The result embodied in this project report has not been submitted to any otheruniversity/institution for the award of any degree.Project Guide Head of DepartmentR.NAGESWARA RAO Md. JaffarAssistant Professor Assistant Professor PRINCIPAL P.Yadagiri
3ABSTRACT:This paper consists It seems that these days everyone has a cellular phone. Whetheryours is for businesspurposes or personal use, you need an efficient way of charging the battery in the phone.My mobile have been switched off, my Laptop computer have no charging …….no suchquestions! Can we imagine the life without electrical wires? from now, answer to thisquestion is yes. The methods proposed in the present paper thoughutilizes contrasting technologies for wire less transmission of power namely ‘power casttechnology’ and ‘eCoupled technology’ are presented in the name of “unwired charging”,Which will facilitate to Transfer power without using wires.The efficient low-range power can be transmitted to any device which uses that range ofpower by the technique used in this concept called “power casting”. This technology usesradio frequency waves for carrying power.The efficient mid-range power can be transmitted to any device which uses that range ofpower by the technique used in this concept called “eCoupling”. This technology useselectro magnetic coupling for carrying power. Now a days there is a Rapid development of autonomous electronics like Laptops,Cell-phones, House-hold robots and all the above devices typically rely on chemicalenergy storage(Battery) .As they are becoming daily needs to present generation,Wireless energy transfer would be useful for many applications as above and they needlow-range and mid-range energy. This is the main reason to prepare this concept.
4 INTRODUCTION:In our day-to-day life we use laptop computers, cell phones, digital cameras, voicerecorder, portable printer, MP3players all plays a significant role. But the majorlimitation is that they have to be charged regularly which is possible only by connectingthe device to the supply through electrical Wires. More often it looks like snakes ……cables, cables…..and more cables… as shown
5 But this dream of wire less charging might be possible very soon, by means oftechnology explained below. Unless this concept is not implemented we can’t reallycall the world as really wire free world. This is because although wireless mantra is aold concept over the world we still need electric wires and chemical batteries forpurpose of charging and transmitting power.TECHNOLOGY:Power casting technology: The Basic Idea: If we walk a few meters from where we are standing now we will probably becutting across at least a dozen radio waves zipping invisibly across our room that ishow common they are…. So common that we barely spare time to even think aboutthem seriously! Radio frequencies are foundational for most devices we use today right from TVsand radios to mobile phones. But we ever think of how powerful the radio frequenciesare? The simple example that makes radio frequency identification (RFID) superior tobarcodes is that they can store more data, they can be read and written to, they can bere-used etc., but what makes all this possible? How is RFID chip able to survive on itsown, woven into some product or person, isolated from the rest of civilization? It isbecause the chip is able to charge itself through the radio waves transmitted by thetransceiver when reading or writing. Basically this is a simple example of the energycarrying property of radio waves
6 Then why cannot RF (Radio Frequency) be used to power devices? If we have a Base station that draws power from a power line and keepstransmitting it as radio waves and all our mobile devices have receivers that canreceive these radio waves and convert them into DC current, that’s pretty much a wireless powering system. That is one base station can charge quite number of devices-provided they all have the receivers built into them this is precisely how the powercast system worksTECHNOLOGY BEHIND THE POWER: The mess of wires, those power strips overloaded with transformers and maddeninggadget connectors half a nanometer from perfection may all soon be a thing of thepast.The power cast wireless power platform consists of a transmitter called ‘power caster’and a receiver called ‘power harvester’. The ‘power caster’ can double the effectiverange, compared to normal RF transmitters and a power harvester can harvest up to70% of the theoretical maximum power with in the range and convert it into dccurrent for the device to use. The power harvester is a chip about half the size of anordinary battery used for charging and must be accompanied by a small antennawhose size varies according to the frequency of transmitted power. It can fit quitecomfortably into the battery compartment of most devices, and many devices coulduse the case itself as the antenna. Of course small tweaks in the circuitry of the devicewill be needed to connect the power harvester to it. The power harvester is available in various models for multiple frequency ranges,voltage requirements sizes and so on. The design can fully customized according tothe requirements. Any device fitted with a power harvester gets charged automaticallywhenever it is with in the range of power caster and any number of ‘power harvestingdevices’ can be placed within the range of single power caster. This does not give riseto problems like cancellation and interference because power caster neither causes noris affected by such problems. In-fact, the power harvesters actually outwit noises bymaking use of them.
7POTENTIAL POWER HARVESTERS: All the devices cannot be powered using power cast system only devices that workon AA, AAA batteries or cell batteries can make use of this wire less power system.Power cast is designed to power devices with very low power. Sensor networks,hearing aids, headsets etc., are ideally suited for this technology basically any devicewhich requires small battery (to be recharged) are requires very little power for directpowering (such as Light Emitting Diode LED) is suitable for taking advantage ofpower cast technology. Power cast technology is designed to provide milli watts ofpower to devices with in an effective range of the transmitter. Radio waves are in fact energy. They are already used to send and receive cellphone, television, radio, and ‘Wi-Fi’ signals every day. Those waves spread out in alldirections until they reach an antenna that is tuned to the appropriate frequency.Power casts wireless power platform uses a "Power caster" transmitter circuit runningon conventional current to broadcast a low-power radio signal at a predeterminedfrequency. The smaller "Power harvester" receiver circuit which can be embedded inany low-power device then uses that energy to recharge or can even replace thedevices battery. The Power cast solution is able to maximize power transfer by using a muchbroader area of the RF spectrum, the 900-MHz band. While not necessarily areplacement for a conventional charger, the technology will be able to "trickle charge"a variety of electronics over a period of time so that their energy is never fullydepleted. As with a traditional AM/FM radio, the closer one is to the tower transmitting thesignal, the better the reception. Power casts wireless platform operates using a similarprinciple. The wireless power platform can harvest a few milli watts of energy withina meter of the source, in this case the transmitter. That is enough energy to charge asingle depleted cell phone battery about half way overnight. The solution will also beideal for devices with small batteries such as watches, hearing aids, wirelesskeyboards and mice, and game controllers, all of which could be continuouslycharged. But there are limits to the charging capabilities the Power cast platform.Larger devices will not be able to make use of this ‘power cast’ technology solution
8simply because they require too much power. In fact, the size limit for now seems tobe at the cell phone level for effective charging.eCoupled technology:The Basic Idea: The basic concept behind this is Magnetic Resonance. Two resonant objects of thesame resonant frequency tend to exchange energy efficiently, while dissipatingrelatively little energy in extraneous off-resonant objects. In systems of coupledresonances, there is often a general “Strongly Coupled” regime of operation. If onecan operate in that regime in a given system, the energy transfer is expected to be veryefficient. Midrange power transfer implemented in this way can be nearly omnidirectional and efficient, irrespective of the geometry of the surrounding space, withlow interference and losses into environmental objects. The above considerationsapply irrespective of the physical nature of the resonances. Magnetic resonances are particularly suitable for everyday applicationsbecause most of the common materials do not interact with Magnetic Fields, sointeractions with Environmental objects are suppressed even further. We were able toidentify the strongly coupled regime in the system of two coupled magneticresonances by exploring Non-radiative (near-field) magnetic resonant induction atMegahertz frequencies.
9Experimental Design: Our experimental scheme consists of two Self-resonant coils. One coil (sourcecoil) is coupled inductively to an oscillating circuit; the other (device coil) is coupledinductively to a resistive load. Self-resonant coils rely on the interplay betweendistributed inductance and distributed capacitance to achieve resonance. The coils are made of an electrically conducting wire of total length ‘l’ andcross-sectional radius ‘a’, wound into a helix of ‘n’ turns, radius ‘r’, and height ‘h’.There is no exact solution for a finite helix in the literature, and even in the case ofinfinitely long coils, the solutions rely on assumptions that are inadequate for thissystem. So here the method implemented is simple Quasi-static model to find theparameters. Those are in Electro Magnetic equations.Efficiency of the System: The efficiency of the system is nothing but the ratio of output power to inputpower. The output power is nothing but the device power rating and input power issum of the power dissipated by source, power loss due to decay and output power. Efficiency=Pw / (Ps+Pd+Pw) The experiment done in 7th June, 2007 by the Massachusetts Institute ofTechnology, Cambridge gives the result that in order to get 60W approximate poweris the output useful power with 40% efficiency. They resonated the circuit at ≈9.9MHz so that they developed the power is transmitted up to 8 times greater than theradius of the coil used.
10ADVANTAGES OF ABOVE TECHNOLOGIES: • The need for batteries and numerous redundant adaptors which consists of toxic substances like nickel, cadmium, mercury are reduced. This reduces the electronic waste. • There is no need for alkaline batteries which are to be recharged regularly. • Complexity and risk of electric shorts reduces as we are not using any electrical wires. • Unaffected by the day night cycle, weather or seasons. • This is an eco friendly and the system poses no health hazards what so ever as the power limits. • It is a boon for the devices which use low-range and mid-range powerCOMPARISON BETWEEN ABOVE TECHNOLOGIES: • Power cast technology is suitable for only low range power, while eCoupled technology is suitable for both low-range and mid-range powers • Power cast technology is effective even though the distance between transmitter and receiver is high but major limitation of eCoupled technology is air gap should be low. • As eCoupled technology is based on magnetic resonance it could be easily effected by presence of Ferro magnetic materials in its path. • In eCoupled technology as the device is close to the charging source it is able to provide more power than while charging using RF. • Inductive method gives higher power at shorter distances but power cast system though gives low range power it transmits even at longer distances. • In eCoupled technology the resonance condition should be satisfied, if any medium error is there possibility of power transfer is affected, while as power cast system uses radio waves it is independent of medium around it. • In power cast technology any number of power harvesting devices can be placed with in the range of single power caster. It is not possible in case of eCoupled technology
11CONCLUSION:-From the above discussion we can conclude that no technology can be perfectly ideal bymaking use of best ideas in the technologies and working in conjunction with them wecan achieve wireless power transmission very sooner. This reduces the risk of usingelectrical cables and redundant adaptors. Each of the above system has its own pros andcons and one needs to decide based on one’s needs. This is the Christmas tree which is lighted based on power transmission by radio frequency waves using power cast technology. It can be placed anywhere in the range of transmitter.