Microwave Power Transmission Microwave Power Transmission Components For The SPSComponents For The SPS

N.VIJAYA SURESH,N.VIJAYA SURESH,GEC – 0609,GEC – 0609,M-TECH,SECOND SEMISTER,M-TECH,SECOND SEMISTER,MICROWAVE ENGINEERING,MICROWAVE ENGINEERING,I.T – B.H.U,VARANASI.I.T – B.H.U,VARANASI.

INTRODUCTION :INTRODUCTION :

The concept of SPS was proposed by The concept of SPS was proposed by P.E.GlaserP.E.Glaser in1968. in1968.

The solar energy in the space can be converted to the electrical energy.The solar energy in the space can be converted to the electrical energy.

This electrical energy can be transmitted to the earth by using the This electrical energy can be transmitted to the earth by using the microwaves.microwaves.

..

Need of satellite power stationsNeed of satellite power stations

Demand of electrical power. Demand of electrical power.

Pollution due to the present methods.Pollution due to the present methods.

Principle of satellite power stationPrinciple of satellite power station

Two symmetrically arranged solar collectors are used to Two symmetrically arranged solar collectors are used to convert solar energy directly to electrical energy.convert solar energy directly to electrical energy.

The electricity is then fed to microwave generators The electricity is then fed to microwave generators incorporated in a transmitting antenna located between the incorporated in a transmitting antenna located between the two solar collectorstwo solar collectors

The antenna accurately directs the microwave beam to a The antenna accurately directs the microwave beam to a receiving antenna on Earth where the microwave energy is receiving antenna on Earth where the microwave energy is efficiently and safely converted back to electricityefficiently and safely converted back to electricity..

Earth surface

Microwave link

Solar energy

to DC DC to Microwave

energy

Solar Power Satellite

Rectifier

Rectenna

Rx. antenna

Geo stationary orbit

Sun

Dc to Ac converterLOAD

Figure 1- Principle Block Diagram of Solar Power Station

Tx. antenna

Main considerations of spsMain considerations of sps

1. The efficient conversion of DC power into microwave 1. The efficient conversion of DC power into microwave power. power.

2. The antenna technology of forming a narrow, efficient beam 2. The antenna technology of forming a narrow, efficient beam of microwaves & efficiently absorbing that beam on the of microwaves & efficiently absorbing that beam on the earth’s surface.earth’s surface.

3. The conversion of the microwave power back into DC power 3. The conversion of the microwave power back into DC power at the earth’s surface.at the earth’s surface.

Elements of microwave power transmissionElements of microwave power transmission

MICROWAVE MICROWAVE

BEAM LINKBEAM LINK

Elements of microwave power transmission systemElements of microwave power transmission system

DC POWER CONVERSION

TO MICROWAVE

POWER

COLLECTION AND

CONVERSIONTO

DC POWER

Technologies involvedTechnologies involved

1. 1. Solar photovoltaic cell:Solar photovoltaic cell: This device transforms the sun’s This device transforms the sun’s energy directly into electrical power.energy directly into electrical power.

2. 2. Our space capability:Our space capability: which permits transfer of the solar which permits transfer of the solar photovoltaic cells to space.photovoltaic cells to space.

3. 3. Power transmission:Power transmission: microwave beams are used for the microwave beams are used for the efficient transmission of electrical power.This technology efficient transmission of electrical power.This technology allows the electrical power generated in space to be allows the electrical power generated in space to be coupled to the earth.coupled to the earth.

Components involved in the transmission systemComponents involved in the transmission system

1.Solar Photovoltaic Cell.1.Solar Photovoltaic Cell.

2.Microwave Generator.2.Microwave Generator.

3.Transmitting antenna.3.Transmitting antenna.

4.Rectenna. 4.Rectenna.

Solar Photovoltaic cellSolar Photovoltaic cell

Single crystal, silicon solar cells can be used.Single crystal, silicon solar cells can be used.

These solar cells have already reached efficiencies of 16%.These solar cells have already reached efficiencies of 16%.

A solar cell array can be produced from 50–micron thick A solar cell array can be produced from 50–micron thick silicon wafer.silicon wafer.

Solar radiation damage will cause a logarithmic decay of Solar radiation damage will cause a logarithmic decay of solar cell effectiveness.solar cell effectiveness.

Microwave GeneratorMicrowave Generator

1.1. The microwave generator design is based on the principle The microwave generator design is based on the principle of a cross-field device.of a cross-field device.

2.2. The cathode & anode of the microwave generator are The cathode & anode of the microwave generator are designed to reject waste heat to space with extended designed to reject waste heat to space with extended surface radiators.surface radiators.

3.3. The output of an individual microwave generator can The output of an individual microwave generator can range from 2 – 5 kilowatts. range from 2 – 5 kilowatts.

Transmitting antennaTransmitting antenna

The main considerations are efficiency, mass, methods for The main considerations are efficiency, mass, methods for radiating waste heat, life of components etc.radiating waste heat, life of components etc.

A series of microwave generators are combined to in a sub A series of microwave generators are combined to in a sub array which forms part of the transmitting antenna.array which forms part of the transmitting antenna.

Each sub array is provided with an automatic phasing Each sub array is provided with an automatic phasing system.system.

The sub arrays are assembled in a slotted waveguide, The sub arrays are assembled in a slotted waveguide, phased-array transmitting antenna.phased-array transmitting antenna.

Solar Photovoltaic

array

SUN

MAG.DIR.AMP.

Magnetron directional amplifier Magnetron directional amplifier modules with solar arraymodules with solar array

Phased Array AntennaPhased Array Antenna

MAG.DIR.AMP.

MAG.DIR.AMP.

Cont…..Cont…..

A master phase control actuated by a pilot signal from A master phase control actuated by a pilot signal from rectenna is used for regulate the transmission.rectenna is used for regulate the transmission.

Amplitude control:Amplitude control: The amplitude of the microwave output is compare with a The amplitude of the microwave output is compare with a

reference amplitude.reference amplitude.

The resulting error signal is fed to a closed loop control The resulting error signal is fed to a closed loop control system.system.

The magnetic field across the magnetron is varied so that The magnetic field across the magnetron is varied so that the power out put is changed.the power out put is changed.

HOW THE PHASE AND THE AMPLITUDE OF THE MAGNETRON HOW THE PHASE AND THE AMPLITUDE OF THE MAGNETRON DIRECTIONAL AMPLIFIER OUTPUT ARE CONTROLLEDDIRECTIONAL AMPLIFIER OUTPUT ARE CONTROLLED

Cont…Cont…

Phase Control:Phase Control: The phase of the output is simultaneously tracked by a The phase of the output is simultaneously tracked by a

reference phase.reference phase.

The error signal actuates some form of phase shifting The error signal actuates some form of phase shifting device at the input of the magnetron.device at the input of the magnetron.

To compensate the phase shift, the operating conditions of To compensate the phase shift, the operating conditions of the magnetron are changed.the magnetron are changed.

ASSEMBLY ARCHITECTURE FOR MAGNETRON ASSEMBLY ARCHITECTURE FOR MAGNETRON DIRECTIONAL AMPLIFIER IN ANTENNA SUBARRAYDIRECTIONAL AMPLIFIER IN ANTENNA SUBARRAY

RectennaRectenna

The special device which simultaneously collects the The special device which simultaneously collects the microwave energy and converts it back into DC power is microwave energy and converts it back into DC power is called the rectenna.called the rectenna.

It must be environmentally protected, compatible with the It must be environmentally protected, compatible with the collection system and economical to construct. collection system and economical to construct.

It’s maximum combined collection and rectification It’s maximum combined collection and rectification efficiency is close to 90%.efficiency is close to 90%.

In its simple form the rectenna consists of a collection of In its simple form the rectenna consists of a collection of rectenna elements.rectenna elements.

Cont…Cont…

The rectenna itself consists of a two-level structure.The rectenna itself consists of a two-level structure.

The back level is a open mesh metal screen and the front The back level is a open mesh metal screen and the front level consists of many half wave dipoles, their associated level consists of many half wave dipoles, their associated rectifier circuitry, and DC bus lines.rectifier circuitry, and DC bus lines.

The power absorbed by the half wave dipoles are first fed to The power absorbed by the half wave dipoles are first fed to the low pass filter for enhancing the efficiency.the low pass filter for enhancing the efficiency.

Then passes into a simple half wave rectifier circuit.Then passes into a simple half wave rectifier circuit.

Two level structure of RECTENNATwo level structure of RECTENNA

Separate rectenna elements with their DC output Separate rectenna elements with their DC output connected in parallelconnected in parallel

RECTENNA ELEMENTRECTENNA ELEMENT

Statistics on RECTENNAStatistics on RECTENNA

Wavelength 10 cmWavelength 10 cm Rectenna diameter 7.4 kilometersRectenna diameter 7.4 kilometers Total area 43 * 10^6 square metersTotal area 43 * 10^6 square meters Total no of rectenna elements 1.23 * 10^10Total no of rectenna elements 1.23 * 10^10 Rectenna element density 284/square meterRectenna element density 284/square meter Average power densityAverage power density

10,000 megawatts DC 232 watt/square meter10,000 megawatts DC 232 watt/square meter

5,000 megawatts DC 116 watt/square meter5,000 megawatts DC 116 watt/square meter Maximum power per elementMaximum power per element

10,000 megawatts DC 3.0 watt10,000 megawatts DC 3.0 watt

5,000 megawatts DC 1.5 watt5,000 megawatts DC 1.5 watt Cost per kilowatt of DC o/pCost per kilowatt of DC o/p

10,000 megawatts DC $50.00/watt10,000 megawatts DC $50.00/watt

Salient features of a 10 GW SPSSalient features of a 10 GW SPS

SPACE STATION SPACE STATION

Dimensions of the space station up to 10*20 KmDimensions of the space station up to 10*20 Km

Gross weight up to 86*(10)^6kgGross weight up to 86*(10)^6kg

LIFE 30 years LIFE 30 years (indefinite, if replacement of (indefinite, if replacement of damaged photovoltaic cells) damaged photovoltaic cells)

Requirement of the microwave power transmission systemRequirement of the microwave power transmission system

High power 3.15 * 10^9 wattHigh power 3.15 * 10^9 watt High efficiency 68%High efficiency 68% Transmission distance 22,300 milesTransmission distance 22,300 miles Frequency 2 – 4 GHzFrequency 2 – 4 GHz Long life 30 years.Long life 30 years. Light weight in space < 2 lb/kwLight weight in space < 2 lb/kw Narrow beam 3 * 10^-4 radiansNarrow beam 3 * 10^-4 radians Pointing accuracy 2.8 * 10^- 6 radiansPointing accuracy 2.8 * 10^- 6 radians Acceptable cost < $ 200/kwAcceptable cost < $ 200/kw Minimum radio frequency interference.Minimum radio frequency interference. Passive radiation of all waste power.Passive radiation of all waste power.

Why we put them in space instead of earthWhy we put them in space instead of earth

# Independence of weather and the day-night cycle # Independence of weather and the day-night cycle

# # A satellite in GEO receives ten times as much incident solar energy as a A satellite in GEO receives ten times as much incident solar energy as a ground based location.ground based location.

## The absence of such deleterious Earth-surface conditions as rain, hail, The absence of such deleterious Earth-surface conditions as rain, hail, snow, atmospheric contamination and corrosion, wind, storms and snow, atmospheric contamination and corrosion, wind, storms and earthquakes. earthquakes.

## The ability to dissipate waste heat in space instead of in the Earth’s The ability to dissipate waste heat in space instead of in the Earth’s biospherebiosphere

Disadvantage of using the space locationDisadvantage of using the space location

# # Increase in the cost Increase in the cost

# # The potential environmental impact associated with placing the necessary The potential environmental impact associated with placing the necessary hardware in space. hardware in space.

# # Due to the need to transmit the collected Due to the need to transmit the collected powerpower through the Earth’s through the Earth’s atmosphere, which raises further questions of cost and possible atmosphere, which raises further questions of cost and possible environmental impact. environmental impact.

# # Other concerns include international, military, and societal considerations, Other concerns include international, military, and societal considerations, including possible competition with including possible competition with satellitesatellite communication systems for communication systems for geostationary orbit locations and transmission bands.geostationary orbit locations and transmission bands.

CONCLUSIONCONCLUSION

The cost for the construction and operation of an SPS The cost for the construction and operation of an SPS

using today’s technology is an order of magnitude or higher using today’s technology is an order of magnitude or higher

than economically practicable. But SPS is turning into an than economically practicable. But SPS is turning into an

increasingly viable candidate as a future energy source to increasingly viable candidate as a future energy source to

compete with other sustainable energy candidates to meet compete with other sustainable energy candidates to meet

the goal of providing sustainable energy for future growth the goal of providing sustainable energy for future growth

and protection of the environment. In addition, new and protection of the environment. In addition, new

business models that structure SPS as an Industrial business models that structure SPS as an Industrial

commodity, where the solar power from space is delivered commodity, where the solar power from space is delivered

on demand to earth-bound rectenna sites, could move the on demand to earth-bound rectenna sites, could move the

concept much further along in 15 - 25 years.concept much further along in 15 - 25 years.

THANK YOUTHANK YOU