SEMINAR ON WIRELESS ENERGY TRANSFER www.fakengineer.com What is Wireless Energy Transmission? • Wireless energy transfer or wireless power is the transmission of electrical energy from a power source to an electrical load without interconnecting wires. • Needs-To energize satellites, electronic gadgets -To reach the unreachable places -To use power efficiently lost during transmission TYEPS • There are 3 major types(depending on ranges) – Short range; Electromagnetic induction – Medium range;Coupled Magnetic Resonance – Long range; Electromagnetic Wave Power Transfer Electromagnetic induction • It is of two types – - Electrodynamic induction method or inductive coupling. - Electrostatic induction method or capacitive coupling • This method is restricted to very short range approxmately 1/6 of wavelength Inductive Coupling • Non-resonant coupling-> • Inductive coupling works on the principles of Electromagnetism . • When a current (electricity) passes through a wire, it generates a magnetic field perpendicular to the wire. This effect can be magnified through coiling the wire. When a wire is in proximity to a magnetic field, it generates a current in that wire • Here Z depends on resistance, inductance, and importantly on the value of k which depends on distance. •Hence power transfer efficiency depends on distance • Inductive coupling is used for wireless charging of electronic devices, RadioFrequency Identification (RFID) tags, induction heater Coupled Magnetic Resonances • Resonant induction still uses the same principles as magnetic induction (magnetic fields to transfer current), but it uses resonance to increase the range at which the transfer can efficiently take place. • In this method efficiency can be increased by making Z=r and suitably choosing reactive elements. • Here efficiency can go upto 40%. • This technique can used inside a room to energize different Electrical components. • Magnetic fields interact weakly with biological masses (humans), and energy is only transmitted between resonating objects Example-> Here, the technique wirelessly powers an LCD TV in a prototype demonstrated by Haier Group Co. (Qingdao, China) at CES 2010. Microwave Power Transfer • Microwave Power Transfer (MPT) is a form of wave power transfer that, obviously, sends energy through the air in the form of microwaves (other forms can use lasers and visible light). • MPT has a range miles longer than its inductive counterparts, and it’s being investigated as a way to beam power to space or vice versa Working principle • First, microwaves are converted from DC power, and sent via a large transmitter. On the other end, the are caught” by an even larger receiver and converted to AC power. • Here disk shaped rectifying antenna or “rectenna” is used whose conversion efficiency is more than 95%. • These type of transmission can be helpful to energize satellites, aircrafts and long distance power transfer . Drawbacks-> • microwaves has the difficulty that for most space applications the required aperture sizes are very large due to diffraction limiting antenna directionality. • These sizes can be somewhat decreased by using shorter wavelengths, although short wavelengths may have difficulties with atmospheric absorption and beam blockage by rain or water droplets. • human electromagnetic exposure safety also a matter of concern here. Laser method • In the case of electromagnetic radiation closer to visible region of spectrum (10s of microns to 10s of nm), power can be transmitted by converting electricity into a laser beam that is then pointed at a solar cell receiver. This mechanism is generally known as "powerbeaming" because the power is beamed at a receiver that can convert it to usable electrical energy. • Advantages-> • no radio-frequency interference . • compact size of photovoltaic cell, control of access. • It also provide narrow beam cross section for transmission over long distance. • Disadvantages-> • photovoltaic cells have only 40%-50% conversion efficiency. • this method requires a direct line of sight communication. • Atmospheric absorption causes losses. CONCLUSION• Wireless power solutions today provide hope for additional freedoms in the future, but many hurdles still stand in the way. Magnetic induction, resonant induction, and electromagnetic wave power transmission all have applications that could revolutionize the way we live and use electricity. REFERENCES• 1.C. G. Kim, D. H. Seo, J. S. You, J. H. Park, and B. H. Cho, “Design of a contactless battery charger for cellular phone,” IEEE Trans. Ind. Electron., vol. 48, No. 6, pp. 1238-1247, December 2001. • 2. G. B. Joung and B. H. Cho, “An energy transmission system for an artificial heart using leakage inductance compensation of transcutaneous transformer,” IEEE Trans. Power Electron., vol. 13, pp. 1013-1022, November 1998. • 3. T. Sekitani, M. Takamiya, Y. Noguchi, S. Nakano, Y. Kato, T. Sakurai, and T. Someya, “A large-area wireless powertransmission sheet using printed organic transistors and plastic MEMS switches,” Nature Mater., vol. 6, pp. 413-417, June 2007. • 4. Z. N. Low, R. A. Chinga, R. Tseng, and J. Lin, “Design and test of a high-power high-efficiency loosely coupled planar wireless power transfer system,” IEEE Trans. Ind. Electron., vol. 56, No. 6, pp. 1801-1812, May 2009. • 5. Circuit Analysis of Wireless Power Transfer by “Coupled Magnetic Resonance” F.Z. Shen1, W.Z. Cui2, W. Ma2, J.T. Huangfu1*, L.X. Ran11 Department of Information and Electronic Engineering, Zhejiang University, Hangzhou 310027, China 2Xi’an Institute of Space Radio Technology, Xi’an 710000, China • 6. Circuit Model Based Analysis of a Wireless Energy Transfer System via Coupled Magnetic Resonances Sanghoon Cheon, Yong-Hae Kim, Seung-Youl Kang, Myung Lae Lee, Jong-Moo Lee, and Taehyoung Zyung • 7. IEEE Vehicle Power and Propulsion Conference (VPPC), September 3-5, 2008, Harbin, China 978-1-4244-18497/08/$25.00○C 2008 IEEE Simulation and Experimental Analysis on Wireless Energy Transfer Based on Magnetic resonance.