(A TECHNICAL SEMINAR REPORT)WIRELESS POWER TRANSMISSION AND RECEPTION USING SOLAR POWER SATELLITES AND RECTENNA
INTRODUCTION 1. SOLAR POWER IS - INEXAUSTIBLE(RENEWABLE) ENERGY RESOURCE. 2. We can, in fact directly convert solar energy into electrical energy with the use of solar cells, but sunlight diffuses at night time from the earth. 3. If the need arises for 24 hours power supply, we are helpless. 4. The solution is wireless power transmission from spacethrough a system consisting of SPS (Solar Power Satellite)and RECTENNA (RECtifying anTENNA) by Microwaves.
PRINCILPLE1.Modern techniques enables us to create a platform inspace carrying solar batteries, generators convertingelectric current worked out by them into theElectromagnetic field energy of ten centimeter range(microwaves) and antenna forming electromagneticwave beam2.On the earth, the other antenna (rectenna) receives thebeam and it is converted into electric current again.3.The principal advantage of the space location is itsindependence of weather and day-night cycle and ispollution free.
4.It is shown that a correct choice of the field distribution onthe radiation antenna allows us to increase the wirelesspower transmission efficiency and to lessen its cost(As SpaceSolar Power Stations are costly because of sheer size ofRadiating & Receiving Antennas.).5.Antenna and Rectenna sizes are chosen such that therectenna is situated in the antenna’s Fresnel’s area. 6.This Design has many Advantages from Environmental point of view.
THE WIRELESS POWER TRANSMISSION SYSTEMSSIMULATION
OVERVIEW OF SYSTEM DESIGN*Construction of spacetenna and rectenna to increase theeffectiveness of WPT.I.SPACETENNA:(THE ANTENNA ON SATELLITE)1.Spacetenna is a triangular prism with a length of 800 m and sides of 100 m.2.The main axis lies in the north-south direction, perpendicular to the direction of orbital motion.3. The transmitting antenna on the horizontal under-surface faces the Earth, and the other two sides of the prism carry solar arrays.
4.The faces of the prism are embedded with photovoltaiccells. These Photovoltaic cells would convert sunlight intoelectrical current, which would, in turn, power an onboardmicrowave generator.5. The Microwave thus produced Travels through Atmosphere& is collected by RECTENNAS on Earth.6. The Spacetenna has a square shape whose dimension is 132meters by 132 meters and which is regularly filled with1936 segments of sub array.7. The sub array is considered to be a unit of phase control andalso a square shape whose edges are 3 meters. It contains 1320units of cavity-backed slot antenna element and DC-RFcircuit. Therefore, there will be about 2.6 million antennaelements in the spacetenna.
8.The spacetenna is composed of pilot signal receivingantennas followed by detectors finding out the location ofthe rectenna on the earth, power transmission antennaelements and phase control systems.9. Moreover, the pilot signal frequency and a frequency for theenergy transmission are different from each other.10. Using two kinds of frequency for the power transmissionand the pilot signal prevents each other from interfering andmakes it possible to find out the accurate direction of aspecified rectenna.
II.RECTENNNA :(RECTIFYING ANTENNA)1.A Rectenna can be considered as a base station for a geo-stationary satellite. Microwaves of 2.45 GHz frequency are usedto transmit power from the satellite to the rectenna.2. It consists of a mesh of an array of dipole antennas connectedto diodes to convert the radio frequency energy to DC voltage,which is then converted to regular AC electricity and wired tohomes, factories, etc.3. A simple reflector plane could be added to the mesh toimprove the efficiency to 50%.
Orbit Selection1.A 1100km altitude equatorial orbit will be used. This choiceminimizes the transportation cost and the distance of powertransmission from space.2. If it was in GEO (that is, 35,800 kilometers from Earth)then the transmitting antenna would have to be 40 timeslarger than a LEO one - or else the receiving antenna wouldhave to be 40 times larger.3. So satellite has to orbit above the equator in order to havefrequent transmission opportunities. It transmits up to10Mwatts of radio-frequency power. Ten satellitesplaced evenly around the orbit would require only nineminutes of storage capacity to provide continuous power.
Advantages•Unaffected by day-night cycle, weather or seasons. Optimizedadvances may enable 21 hour power supply per day.•This is an eco-friendly, renewable and maintenance free energyresource unlike the conventional fuels.•As the equipment is positioned in space, it is occupies no landarea and remains unaffected by harsh weather conditions.Rectennas can share land with farms.•The spacetenna could direct energy to any rectenna on earthwithin the range of its steering angle, which could satisfy theenergy requirements of all the equatorial countries.•Waste heat is re-radiated back into space, instead of warming thebiosphere.
Conclusion Synthesizing the wireless power transmission, it can beconcluded that to make the SPS concept commerciallyviable, it becomes a priority to improve its efficiency and thecost per watt. This can be achieved by:1.Placing the Rectenna within the Fresnel area ofthe transmitter. 2. Placing the transmitting antenna in the LEOorbit to reduce installation cost and the distance oftransmission.
3. Using a discontinuous equidistant array with quasiGauss distribution.4. Using a discontinuous non-equidistant array withuniform distribution.BOTTOMLINE: Will be a boon as we are runningout of fossil fuels.