30-04-2011, 01:12 PM
Presented by:
RAVINDRA CHANDRA
[attachment=13125]
SOLAR POWER SATELLITES ( SPS )
Innovations:
Alternating current
Wireless power transmission experiments at Wardenclyffe
Wardenclyffe
1899
Able to light lamps over 25 miles away without using wires
High frequency current, of a Tesla coil, could light lamps filled with gas (like neon)
1940’s to Present
World War II - ability to convert energy to microwaves using a magnetron, no method for converting microwaves back to electricity
1964 - William C. Brown demonstrated a rectenna which could convert microwave power to electricity
1968’s - idea for Solar Power Satellites proposed by Peter Glaser
Would use microwaves to transmit power to Earth from Solar Powered Satellites
Solar Power satellite
Space Solar Power System
consists of three parts:
a means of collecting solar power in space, for example via solar cells or a heat engine
a means of transmitting power to earth, for example via microwave or laser
a means of receiving power on earth, for example via a microwave antenna (rectenna)
EFFECIENCY
BLOCK DIAGRAM OF SPS SYSTEM
Solar energy conversion (solar photons to DC current)
Solar panels of the SPS would be placed in geostationary orbit (GEO) at a distance of 36000 km from the Earth’s surface which converts solar energy into DC current .
In an SPS implementation, photovoltaic cells used are different from the pv cells in current terrestrial use
optimized for weight, tolerant of the space radiation environment, anti corrosion
Solar arrays
Weight – 0.5 kg/kw to 10 kg/kw
Life cycle – 20 yrs
Degrades about 1- 2% per yr
Solar radiation is 5- 10 times greater in space
SPS location
GEO
antenna geometry stays constant, and so keeping the antennas lined up is simpler.
continuous power transmission.
LEO/MEO instead of GEO
shorter energy transmission path, lower cost
frequent changes in antenna geometries, i, more power stations needed to receive power continuously
From the Satellite
Solar power from the satellite is sent to Earth using a microwave transmitter
Received at a “rectenna” located on Earth
Recent developments suggest that power could be sent to Earth using a laser
Microwaves
Frequency 2.45 GHz microwave beam
Retro directive beam control capability
Power level is well below international safety standard
On the left: Part of the solar energy is lost on its way through the atmosphere by the effects of reflection and absorption.
On the right: Space-based solar power systems convert sunlight to microwaves outside the atmosphere, avoiding these losses, and the downtime due to Earth's rotation, experienced by surface installations
Microwave vs. Laser Transmission
Microwave
More developed
High efficiency up to 85%
Beams is far below the lethal levels of concentration even for a prolonged exposure
Cause interference with satellite communication industry
Laser
Recently developed solid state lasers allow efficient transfer of power
Range of 10% to 20% efficiency within a few years
Conform to limits on eye and skin damage
Rectenna
“An antenna comprising a mesh of dipoles and diodes for absorbing microwave energy from a transmitter and converting it into electric power.”
Microwaves are received with about 85% efficiency
Around 5km across (3.1 miles)
95% of the beam will fall on the rectenna
5,000 MW Receiving Station (Rectenna). This station is about a mile and a half long.
Theory of Operation
Block diagram
Electromagnetic Radiation
Antenna basics
Phased-array antenna
Diffraction analogy
Energy distribution
Rectenna
Physical limitations & relationships
Block Diagram
Physics of Wireless Power Transmission
Forms of Electromagnetic radiation
Travel at same speed
F = frequency
C = velocity of light
L =wavelength
Dipole Antenna
Transmission of power is simpler than TV & Radio
Transmitter: wire half a wavelength
Pushes electrons back and forth
Receiver: wire half a wavelength
Phased-array antenna
The λs for microwaves are small dipoles small
Beam focusing: phased-array antenna
Electronically steered by varying the timing or phase
Waves will merge together
Phased-Array Antenna
Diffraction analogy
Light same properties
Laser beam shinning trough a narrow opening & spreads out or diffracts
Bright spot in the center w/fainter spots on the side
Diffraction & Microwaves
Waves reinforce at some points and they cancel out at other points (bright and fainter points)
In microwaves: is a scaled up version of diffraction
Intensity
Main lobe energy
Circular central max
Main lobe
84% of energy
Sidelobes surround
No energy minima
Intensity 84% in main lobe
Rectenna
Array of dipole antennas known as rectifying antenna or Rectenna
Diameter = Dr
Rectenna
Physical Limitations
The receiving diameter Dr increases with transmitter receiver separation distance S.
Dr increases if transmitter diameter Dt decreases
Physical Limitations
Calculations/Analysis
Frequency, f (Hz)
Intensity, I (watts per square meter)
Wave-Length, L (meters)
Received Main Beam Lope (“spot”) Diameter, Dr (meters or kilometers)
Transmitting Phased Array Diameter, Dt (meters or kilometers)
Example: how to estimate Intensity, I ?
Frequency Formula Dt * Dr
Frequency, f (Hz) = -------------- (2)
(L * S)
Dt: transmitting phased array diameter
Dr: received main beam lobe (“spot”)
diameter
L: wavelength
S: separation
Frequency Analysis
Dt * Dr
If (Frequency, f (Hz) = ----------- ) 2.44 GHz (2)
(L * S)
Then at least, 84% of the energy of the beam will be captured
Note:
This energy is not linear; 42% of the energy is not equivalent to 1.22 GHz.
Equation (2) represent a best case scenario.
Practical antenna sizes may have to be larger if most of the beam is to be captured.
The rectenna will have to be at least as large as Dt, even if (2) says Dr is smaller.
Frequency Analysis
Such a wide beam can be focused, but only to a minimum size Dr.
For low Earth-orbit power-beaming demonstrations, it is easier to put the smaller antenna in space and the larger antenna on Earth.
Early demonstrations may capture only a small percentage of the total power, in order to keep antenna sizes small.
to light up a 60 watt bulb, thousands of watts may have to be transmitted.
Since costly to launch such a power generating apparatus, the most feasible demonstration project may be Earth-to-space transmission from a large transmitting antenna (such as the Arecibo dish) to a smaller rectenna in space.
Intensity, I Formula
Intensity, I (watts per square meter)
P Dt
= ½ ( Pi * -----) * ( --------- ) (3)
4 L * S
Pi: 3.14…
P: total power transmitted
Dt: transmitted phased array diameter
L: wave length
S: transmitter to receiver distance (separation)
Wave-Length, L Calculations
Wave-Length, L (meters)
c 300,000,000 meter/sec
= ----- = ( -------------------------------- ) = 0.1224 (1)
f 2,450,000,000/sec meter
c: speed of light
f: frequency
Received Main Beam Lope Diameter, Dr Calculations
Received Main Beam Lope (“spot”) Diameter, Dr (meters or kilometers)
f * L * S 2.44 * 0.12224m * 35,800,000m
= -------------- = --------------------------------------------
Dt 1000m
= 10,700 meter = 10.7 kilometers
L: wave length
S: separation
Dt: transmitting phased array diameter
Transmitting Phased Array Diameter, Dt Calculations
Transmitting Phased Array Diameter, Dt (meters or kilometers)
f * L * S 2.44 * 0.12224m * 35,800,000m
= -------------- = ----------------------------------------------
Dr 10,700 meter
= 1000m = 1 kilometers
L: wave length
S: separation
Dr: received main beam lope (“spot”) diameter
Example
What is the Intensity, I = ?
Given: f, Dr, and a typical solar power satellite transmitting 5 billion watts from geostationary orbit 35800 kilometers high.
Solution: Use the following (1), (2), & (3)
C
f = ----- L (1)
L
Dt * Dr
Frequency, f (Hz) = -------------- Dt (2)
(L * S)
P Dt
Intensity, I (watts/m^²) = ½ ( Pi * -----) * ( --------- ) (3)
4 L * S
Example Calculations
Intensity, I (watts per square meter)
P Dt
= ½ ( Pi * -----) * ( --------- ) (3)
4 L * S
2287485.869w 1000m
= ½ ( Pi * ---------------------------) * ( ----------------------------------- )
4m 0.1224m* 35800,000m
= 205 watts/m^² or 20.5 milliwatts/cm^²
Example Analysis
peak beam intensity, Ip = 20.5 milliwatts/cm^²
This is about twice US industrial standard for human exposure
This is converted (by rectenna) to electricity by 90% efficiency
Average intensity, Ia 1/3 * 20.5 milliwatts/cm^²
Rectangular Transmitting antenna array Calculations
Mathematics slightly different, but the same general principles apply.
Central maximum of the beam contain 82% of the transmitted energy.
Rectangular in shape, but will spread out more along TX array’s short direction than its long direction.
Example: Canada’s Radar sat
rectangular transmitting antenna: 1.5m × 15m
“footprint” on the ground: 7,000m × 50,000m
frequency: 5.3 GHz
altitude: 800,000m
output power: 5000 watts
The power is too spread out at the ground to use in a practical demonstration project.
Two more points
Use certain transmitting methods
to reduce the level of the sidelobes
to put some of the sidelobe energy into the main lobe
Price to pay: Larger Rectenna (because main lobe spreads out)
Principal of diffraction also limits the resolution of optical systems:
Lenses
Telescopes
1979 SPS Reference System concept (GEO)
Accomplishments of Solar Power Satellites
1980, 30 kW of microwave power was transmitted to a receiving antenna over one mile
1993, Japan successfully transmitted a 800W microwave beam from a rocket to a free-flying satellite in space.
1998, Microwave to DC conversion efficiency of 82% or higher by the rectenna.
SPS 2000
Details of SPS 2000
Japan is to build a low cost demonstration of SPS by 2025.
Eight countries along the equator agreed to be the rectenna sites.
10 MW satellite delivering microwave power in the low orbit 1100 km(683 miles)
Will not be in geosynchronous orbit, instead low orbit 1100 km (683 miles)
Much cheaper to put a satellite in low orbit
Advantages over Earth-based solar power
More intense sunlight
In geosynchronous orbit, 36,000 km (22,369 miles) an SPS would be illuminated over 99% of the time
No need for costly storage devices for when the sun is not in view
Waste heat is radiated back into space
Power can be beamed to the location where it is needed, don’t have to invest in as large a gri
Cont.
No air or water pollution is created during generation
Ground based solar only works during clear days, and must have storage for night. Thus it is More reliable than ground based solar power
Vision on Future Development
Conclusion
More reliable than ground based solar power
In order for SPS to become a reality it several things have to happen:
Government support
Cheaper launch prices
Involvement of the private sector
RAVINDRA CHANDRA
[attachment=13125]
SOLAR POWER SATELLITES ( SPS )
Innovations:
Alternating current
Wireless power transmission experiments at Wardenclyffe
Wardenclyffe
1899
Able to light lamps over 25 miles away without using wires
High frequency current, of a Tesla coil, could light lamps filled with gas (like neon)
1940’s to Present
World War II - ability to convert energy to microwaves using a magnetron, no method for converting microwaves back to electricity
1964 - William C. Brown demonstrated a rectenna which could convert microwave power to electricity
1968’s - idea for Solar Power Satellites proposed by Peter Glaser
Would use microwaves to transmit power to Earth from Solar Powered Satellites
Solar Power satellite
Space Solar Power System
consists of three parts:
a means of collecting solar power in space, for example via solar cells or a heat engine
a means of transmitting power to earth, for example via microwave or laser
a means of receiving power on earth, for example via a microwave antenna (rectenna)
EFFECIENCY
BLOCK DIAGRAM OF SPS SYSTEM
Solar energy conversion (solar photons to DC current)
Solar panels of the SPS would be placed in geostationary orbit (GEO) at a distance of 36000 km from the Earth’s surface which converts solar energy into DC current .
In an SPS implementation, photovoltaic cells used are different from the pv cells in current terrestrial use
optimized for weight, tolerant of the space radiation environment, anti corrosion
Solar arrays
Weight – 0.5 kg/kw to 10 kg/kw
Life cycle – 20 yrs
Degrades about 1- 2% per yr
Solar radiation is 5- 10 times greater in space
SPS location
GEO
antenna geometry stays constant, and so keeping the antennas lined up is simpler.
continuous power transmission.
LEO/MEO instead of GEO
shorter energy transmission path, lower cost
frequent changes in antenna geometries, i, more power stations needed to receive power continuously
From the Satellite
Solar power from the satellite is sent to Earth using a microwave transmitter
Received at a “rectenna” located on Earth
Recent developments suggest that power could be sent to Earth using a laser
Microwaves
Frequency 2.45 GHz microwave beam
Retro directive beam control capability
Power level is well below international safety standard
On the left: Part of the solar energy is lost on its way through the atmosphere by the effects of reflection and absorption.
On the right: Space-based solar power systems convert sunlight to microwaves outside the atmosphere, avoiding these losses, and the downtime due to Earth's rotation, experienced by surface installations
Microwave vs. Laser Transmission
Microwave
More developed
High efficiency up to 85%
Beams is far below the lethal levels of concentration even for a prolonged exposure
Cause interference with satellite communication industry
Laser
Recently developed solid state lasers allow efficient transfer of power
Range of 10% to 20% efficiency within a few years
Conform to limits on eye and skin damage
Rectenna
“An antenna comprising a mesh of dipoles and diodes for absorbing microwave energy from a transmitter and converting it into electric power.”
Microwaves are received with about 85% efficiency
Around 5km across (3.1 miles)
95% of the beam will fall on the rectenna
5,000 MW Receiving Station (Rectenna). This station is about a mile and a half long.
Theory of Operation
Block diagram
Electromagnetic Radiation
Antenna basics
Phased-array antenna
Diffraction analogy
Energy distribution
Rectenna
Physical limitations & relationships
Block Diagram
Physics of Wireless Power Transmission
Forms of Electromagnetic radiation
Travel at same speed
F = frequency
C = velocity of light
L =wavelength
Dipole Antenna
Transmission of power is simpler than TV & Radio
Transmitter: wire half a wavelength
Pushes electrons back and forth
Receiver: wire half a wavelength
Phased-array antenna
The λs for microwaves are small dipoles small
Beam focusing: phased-array antenna
Electronically steered by varying the timing or phase
Waves will merge together
Phased-Array Antenna
Diffraction analogy
Light same properties
Laser beam shinning trough a narrow opening & spreads out or diffracts
Bright spot in the center w/fainter spots on the side
Diffraction & Microwaves
Waves reinforce at some points and they cancel out at other points (bright and fainter points)
In microwaves: is a scaled up version of diffraction
Intensity
Main lobe energy
Circular central max
Main lobe
84% of energy
Sidelobes surround
No energy minima
Intensity 84% in main lobe
Rectenna
Array of dipole antennas known as rectifying antenna or Rectenna
Diameter = Dr
Rectenna
Physical Limitations
The receiving diameter Dr increases with transmitter receiver separation distance S.
Dr increases if transmitter diameter Dt decreases
Physical Limitations
Calculations/Analysis
Frequency, f (Hz)
Intensity, I (watts per square meter)
Wave-Length, L (meters)
Received Main Beam Lope (“spot”) Diameter, Dr (meters or kilometers)
Transmitting Phased Array Diameter, Dt (meters or kilometers)
Example: how to estimate Intensity, I ?
Frequency Formula Dt * Dr
Frequency, f (Hz) = -------------- (2)
(L * S)
Dt: transmitting phased array diameter
Dr: received main beam lobe (“spot”)
diameter
L: wavelength
S: separation
Frequency Analysis
Dt * Dr
If (Frequency, f (Hz) = ----------- ) 2.44 GHz (2)
(L * S)
Then at least, 84% of the energy of the beam will be captured
Note:
This energy is not linear; 42% of the energy is not equivalent to 1.22 GHz.
Equation (2) represent a best case scenario.
Practical antenna sizes may have to be larger if most of the beam is to be captured.
The rectenna will have to be at least as large as Dt, even if (2) says Dr is smaller.
Frequency Analysis
Such a wide beam can be focused, but only to a minimum size Dr.
For low Earth-orbit power-beaming demonstrations, it is easier to put the smaller antenna in space and the larger antenna on Earth.
Early demonstrations may capture only a small percentage of the total power, in order to keep antenna sizes small.
to light up a 60 watt bulb, thousands of watts may have to be transmitted.
Since costly to launch such a power generating apparatus, the most feasible demonstration project may be Earth-to-space transmission from a large transmitting antenna (such as the Arecibo dish) to a smaller rectenna in space.
Intensity, I Formula
Intensity, I (watts per square meter)
P Dt
= ½ ( Pi * -----) * ( --------- ) (3)
4 L * S
Pi: 3.14…
P: total power transmitted
Dt: transmitted phased array diameter
L: wave length
S: transmitter to receiver distance (separation)
Wave-Length, L Calculations
Wave-Length, L (meters)
c 300,000,000 meter/sec
= ----- = ( -------------------------------- ) = 0.1224 (1)
f 2,450,000,000/sec meter
c: speed of light
f: frequency
Received Main Beam Lope Diameter, Dr Calculations
Received Main Beam Lope (“spot”) Diameter, Dr (meters or kilometers)
f * L * S 2.44 * 0.12224m * 35,800,000m
= -------------- = --------------------------------------------
Dt 1000m
= 10,700 meter = 10.7 kilometers
L: wave length
S: separation
Dt: transmitting phased array diameter
Transmitting Phased Array Diameter, Dt Calculations
Transmitting Phased Array Diameter, Dt (meters or kilometers)
f * L * S 2.44 * 0.12224m * 35,800,000m
= -------------- = ----------------------------------------------
Dr 10,700 meter
= 1000m = 1 kilometers
L: wave length
S: separation
Dr: received main beam lope (“spot”) diameter
Example
What is the Intensity, I = ?
Given: f, Dr, and a typical solar power satellite transmitting 5 billion watts from geostationary orbit 35800 kilometers high.
Solution: Use the following (1), (2), & (3)
C
f = ----- L (1)
L
Dt * Dr
Frequency, f (Hz) = -------------- Dt (2)
(L * S)
P Dt
Intensity, I (watts/m^²) = ½ ( Pi * -----) * ( --------- ) (3)
4 L * S
Example Calculations
Intensity, I (watts per square meter)
P Dt
= ½ ( Pi * -----) * ( --------- ) (3)
4 L * S
2287485.869w 1000m
= ½ ( Pi * ---------------------------) * ( ----------------------------------- )
4m 0.1224m* 35800,000m
= 205 watts/m^² or 20.5 milliwatts/cm^²
Example Analysis
peak beam intensity, Ip = 20.5 milliwatts/cm^²
This is about twice US industrial standard for human exposure
This is converted (by rectenna) to electricity by 90% efficiency
Average intensity, Ia 1/3 * 20.5 milliwatts/cm^²
Rectangular Transmitting antenna array Calculations
Mathematics slightly different, but the same general principles apply.
Central maximum of the beam contain 82% of the transmitted energy.
Rectangular in shape, but will spread out more along TX array’s short direction than its long direction.
Example: Canada’s Radar sat
rectangular transmitting antenna: 1.5m × 15m
“footprint” on the ground: 7,000m × 50,000m
frequency: 5.3 GHz
altitude: 800,000m
output power: 5000 watts
The power is too spread out at the ground to use in a practical demonstration project.
Two more points
Use certain transmitting methods
to reduce the level of the sidelobes
to put some of the sidelobe energy into the main lobe
Price to pay: Larger Rectenna (because main lobe spreads out)
Principal of diffraction also limits the resolution of optical systems:
Lenses
Telescopes
1979 SPS Reference System concept (GEO)
Accomplishments of Solar Power Satellites
1980, 30 kW of microwave power was transmitted to a receiving antenna over one mile
1993, Japan successfully transmitted a 800W microwave beam from a rocket to a free-flying satellite in space.
1998, Microwave to DC conversion efficiency of 82% or higher by the rectenna.
SPS 2000
Details of SPS 2000
Japan is to build a low cost demonstration of SPS by 2025.
Eight countries along the equator agreed to be the rectenna sites.
10 MW satellite delivering microwave power in the low orbit 1100 km(683 miles)
Will not be in geosynchronous orbit, instead low orbit 1100 km (683 miles)
Much cheaper to put a satellite in low orbit
Advantages over Earth-based solar power
More intense sunlight
In geosynchronous orbit, 36,000 km (22,369 miles) an SPS would be illuminated over 99% of the time
No need for costly storage devices for when the sun is not in view
Waste heat is radiated back into space
Power can be beamed to the location where it is needed, don’t have to invest in as large a gri
Cont.
No air or water pollution is created during generation
Ground based solar only works during clear days, and must have storage for night. Thus it is More reliable than ground based solar power
Vision on Future Development
Conclusion
More reliable than ground based solar power
In order for SPS to become a reality it several things have to happen:
Government support
Cheaper launch prices
Involvement of the private sector
