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Wireless Power Transmission

Using Solar Power Satellites (SPS)

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One type of harnessing solar power

Solar energy is collected by using PV cells

Transmitted to earth as Microwaves

Again converted back into electrical energy

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What is Beamed (wireless) Power Transmission??

Power is transmitted through space

Invented by Nikola Tesla in 19th century

Extension to three dimensional networks from two

dimensional networks

Energy can be transmitted through clouds, rain etc

without sufficient lossmakes the system highly efficientwww.final-yearproject.com |

http://troubleshoot4free.com/fyp/


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Three types of WPT

Microwave based WPT

Laser based WPT

Hybrid microwave-laser WPT



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Microwave V/S Laser

MicrowaveMore developed

High efficiency up to 85%

Beams are far below than lethal levels of concentrationeven for a prolonged exposure

Cause interference with communication industrywww.final-yearproject.com |



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Microwave V/S Laser

Laser Recently developed solid state lasers allow

efficient transfer of power

Range of 10% to 20% efficiency with in a few years

Conform to limits on eye and skin damage



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Micro Waves

Wavelength is measured in centimeters

Travel with the same velocity of light

Can penetrates haze, cloud, rain, snow and cloudsGood

for transmitting information from one place to another

Longer microwaves used in Microwave Ovens and Shorter

microwaves used for radar like applications



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How can we produce Microwaves??

DC power can be converted into microwave by using

Magnetron

Uses interaction of electrical and magnetic fields to

produce oscillations of high power

Employs radial electric field, axial magnetic field,

anode structure and cylindrical cathode



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Operation

Two permanent magnets Produces constant magnetic field Electrons produces its own magnetic field

On one side of the electron path magnetic fields gets added up

and on the other side effective magnetic field gets reduced

Electrons trajectory bends towards weakened

direction Circular motionAnode interacts with electrons which produces an alternating

current of high frequency in the cavities

Antenna connected to the anode and is coupled with the

wave-guide (a hollow metal enclosure into which antenna

transmits wave energywww.final-yearproject.com |



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Solar Power Satellite (SPS)

Idea was proposedby Peter E Glaser in

1968

Would use

microwaves to transmitpower to earth

Idea gained

momentum during oil

crisis in 1970, butafter prices stabilized

idea was dropped



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Consists of three parts

A huge solar collector, typically made up of solar cells

A microwave antenna aimed at the earth

A antenna occupying a large area on earth to collect the power



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Placed in geosynchronous orbit SPS illuminated 99% ofthe time

Only moving part is Transmitter antenna which tracks

ground based receiving antenna called Rectenna

Transmitter antenna connected to solar array by two

rotary joints with slip rings

Each SPS will have 400 million solar cells

Waste heat is re-radiated to space reduce globalwarming

Conversion efficiency is 54%www.final-yearproject.com |



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BEAM

FORMI

NG

ANTEN

NA

FREESPACE

TRANSMISSION

DC TO

MICROW

AVE

CONVERS

ION

RECEPTI

ON

CONVERS

ION TO

DC

Power output is around 10 giga watts which is

approximately equal to the power output of 10 nuclear

power stations

Pollution free



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Spacetenna

An antenna onboard the satellite

Antenna in the form of an array

Each array consists of magnetron elements and

directional amplifiers that supplies microwave power to

slotted wave guide

ability to match transmission line impedance (source

impedance) and load (atmosphere 377 ohm)

If impedance match is correct, the energy being transferred

will be radiated in to the atmospherewww.final-yearproject.com |http://troubleshoot4free.com/fyp/


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Power Generation Module



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Array module

110 sub arrays

1320 solar cell units

45 array modules

Each array produces 180 A at 1 kv

Wing summing bus line collects power from each array

Wing summing bus line connected to central bus line which

are interfaced with spacetennawww.final-yearproject.com |http://troubleshoot4free.com/fyp/


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Rectenna

Rectifying Antenna power collecting harmonic filtering rectification into DC power

An antenna comprising a mesh of dipoles and diodes for

absorbing microwave energy from a transmitter and converting

it into DC power

Microwaves are received with about 85% efficiency

Around 5 km across (3.1 miles)www.final-yearproject.com |



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Rectenna Design

Currently there are two different types being looked at:

Wire mesh reflector Built on a rigid frame above the ground Visually transparent so that it would not interfere

with plant life

Magic carpetMaterial pegged to the ground



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Advantages over ground based system:

More intense sunlight

In geosynchronous orbit (36000 km), SPS would be illuminated

99% of the time

No need for costly storage devices for when the sun is not in view

only a few days at spring and fall equinox would the satellitebe in shadow

Waste heat is radiated back to the space

Power can be beamed to the location where it is needed, dont

have to invest in as a large grid



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Problems???

Complexity30 years to complete

Size6.5 miles long by 3.3 miles wide

Transmitting antenna mile in diameter (1 km)

CostPrototype would have cost $74 billion

Microwave transmission

interface with other electronic devices health and environmental effects



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Environmental problems???

Possible health hazards

Effects of long term exposure Exposure is equal to the amount that people receive

from cell phones and microwaves

Location

The size of construction of rectenna is massive



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Developments

US Department of Energy Research Program 1978-1981

Japanese continued to study the idea throughout the 1980s

In 1995, NASA began a fresh look study

set up a research, technology, and investment schedule research aimed at an SPS system of 250MW



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Current Developments

SPS 2000 Project in development in Japan

Goal is to build a low cost demonstration model by 2025

8 countries along the equator have agreed to be the site

of rectenna

10MW satellite delivering microwave power

will not be geosynchronous orbit, instead low orbit 1100 km

ground based rectenna could be smallerA 2.45 GHz microwave frequency is used for transmission



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Power to Mobile Devices

If microwave beam carrying power could be beamed to

earth uniformly, they could power cell phones

Biggest problem is that the antenna would have to be

25-30 cm2

Would require a network of hundreds of satellites



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References:

1. P.E.Glaser, Power from the sun: Its future, Science,

vol. 162, 957-961, 1968

2. G.A.Landis, An Evolutionary path to SPS, Space Power,

vol. 9, No.4 pp. 365-371, 1990

3. www.nasatech.com

4. www.spacefuture.com



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