1. Space Power Satellites & Microwave Power Transmission
Presented By : Nikhil A Kothari
Next Generation Future Energy

2. Outline Introduction Concept of SPS Solar Power Satellite
Key Technologies being evaluated
Microwave Power Transmission
Rectannas
Conclusion

3. Introduction
The space solar power satellite (SSPS or SPS) that will transmit energy from space to the Earth has a potential to become an alternative energy sources even though there are many technical and other hurdles to realize it.
Dr. P. E. Glaser first introduced a concept of the solar power satellite in Since then, many concepts of the solar power satellites were studied.
NASA and DOE (Department of Energy) of U.S.A. conducted feasibility study of the proposed SPS in 1970’s.
The proposed SPS has the solar array of 5km by 10km wide and a microwave antenna of 1km diameter.
The on-ground rectifying antennas (Rectenna) of 10km by 13km in oval axis will produce 5GW of electrical power on ground.
In 1968 PE Glaser 1st introduced to Space Power Solar Transmision.

4. Concept
A solar-energy collector : convert solar energy into dc Electric Power.
A dc-to-microwave converter :coverts dc electric power to microwave.
A large antenna array : To beam the microwave power to ground.
Rectanna : To convert it back to dc electric power.
A solar-energy collector : convert solar energy into dc Electric Power.
A dc-to-microwave converter :coverts dc electric power to microwave.
A large antenna array : To beam the microwave power to ground.
Rectanna : To convert it back to dc electric power.

5. Solar Power from Satellites
1968’s idea for Solar Power Satellites proposed by Peter Glaser
Would use microwaves to transmit power to Earth from Solar Powered Satellites.
Inventor of this Concept in early 1968

6. How it works
Solar panels on satellite capture light, sends power to earth using microwave wireless power transmission technology
Signal sent from receiving antenna on earth (green) allows satellite to pinpoint it’s microwave beam.

7. Different SPS designs
Different Concept Model presented by different countries.

8. Microwave Power Transmission
Power Received from sun at outer edge of atmosphere 1360W/m^2.

9. Microwave Concerns ≠ +
At the earth's surface, the microwave beam has a maximum intensity in the center of 23 mW/cm2 (less than l/4 the solar constant) and an intensity of less than 1 mW/cm2 outside of the rectenna fenceline
Retrodirective phased array antenna/rectenna
Any animal flying through the beam would have not only a low intensity beam strike them, it would also be for only a split second, not long enough to do any real damage
-Passengers in an airplane would be completely protected by the beam because of the plane’s outer casing
-Retrodirective phased array antenna/rectenna:
the way this works is a pilot microwave beam is emitted by the rectenna (on the ground) at a certain frequency. When the satellite gets it in space, it checks to verify that it is indeed the correct frequency and then fire back along the same path. Therefore, if anything were to disrupt the “pilot” microwave beam, the whole process would automatically shut off so a bird or a plane or any human would suffer no harm.

10. Factors to look at Frequency 2.45 GHz microwave beam
Retro directive beam control capability
Transmitting antenna
The output power (beamed to the earth)
Maximum power flux density
Power level is well below international safety standard
Why only 2.45Ghz to 5Ghz frequency is used :

11. Microwave vs. Laser Transmission
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

12. 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

13. Rectenna Design Wire mesh reflector
Currently there are two different design 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 carpet
Material pegged to the ground

14. 5,000 MW Receiving Station (Rectenna)
5,000 MW Receiving Station (Rectenna). This station is about a mile and a half long.

15. Reliability
Ground based solar Array only works during clear days, and must have storage for night
Power can be beamed to the location where it is needed, don’t have to invest in as large a grid
A network of low orbit satellites could provide power to almost any point on Earth continuously because one satellite would always be in range

16. Environmental Possible health hazards Location
Effects of long term exposure
Exposure is equal to the amount that people receive from cell phones and microwaves
Location
The size of construction for the rectennas is massive

17. Pros Any location on Earth can receive power
Satellite can provide power up to 96% of the time
Power can be beamed to the location where it is needed,
don’t have to invest in as large a grid
Solar panels do not take up land on Earth
Lots of space in space
Waste heat is radiated back into space
No air or water pollution is created during generation

18. Cons VERY expensive initial cost Microwave/lasers may be harmful?
Cosmic rays can deteriorate panels
Maintenance Problems
Very large receiving antennas on earth
Solar winds could kick it off course
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 satellite be in shadow

19. Conclusions 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

20. Famous Ever Green Words “Where there is Will there is way so do not give up in difficult times.”
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