The document discusses the history of wireless power transmission from Nikola Tesla's experiments in the late 1800s to current designs for solar power satellites (SPS). An SPS would collect solar power in space and transmit it to Earth via microwave beams to rectennas on the ground. Recent studies propose SPS as a reliable, continuous source of solar power without the limitations of weather-dependent terrestrial solar. However, significant technological and economic challenges around satellite construction, space transportation, and large-scale wireless power transmission remain before SPS could become practical.

1. Wireless Power Transmission for
Solar Power Satellites
By
B.Ravindra Reddy
(MT097109)

2. Outline
 Background
 SolarPower Satellite
 Microwave Power Transmission
 Current Designs
 Conclusion

3. Background
1899-1990

4. Nikola Tesla
 1856-1943
 Innovations:
– Alternating current
– Wireless power
transmission
experiments at
Wardenclyffe

5. 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)

6. 1940’s to Present
 World War II developed 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

7. Brief History of Solar Power
 1940-50’s Development of the Photovoltaic cell
 1958 First US Satellite that used Solar Power
 1970’s Oil embargo brought increased interest
and study

8. Details of the DOE Study
 Construct the satellites in space
– Each SPS would have 400 million solar cells
 Use the Space Shuttle to get pieces to a low
orbit station
 Tow pieces to the assembly point using a
purpose built space tug (similar to space
shuttle)

9. 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.

10. Continued
 Waste heat is radiated back into space
 No air or water pollution is created during
generation

11. Problems
 Issues identified during the DOE study
– Complexity—30 years to complete
– Size—6.5 miles long by 3.3 miles wide
Transmitting antenna ½ mile in
diameter(1 km)

12. Continued
 Cost—prototype would have cost $74 billion
 Microwave transmission
– Interference with other electronic devices
– Health and environmental effects

13. 1980’s to Present
 Japanese continued to study the idea of SPS
throughout the 1980’s
 In 1995 NASA began a Fresh Look Study
– Set up a research, technology, and investment
schedule

14. NASA Fresh Look Report
 SPS could be competitive with other energy
sources and deserves further study
 Research aimed at an SPS system of 250 MW
 Would cost around $10 billion and take 20
years
 National Research Council found the research
worthwhile but under funded to achieve its
goals

15. Possible Designs

17. Deployment Issues
 Costof transporting materials into space
 Construction of satellite
– Space Walks
 Maintenance
– Routine
– Meteor impacts

18. Microwave Power Transmission
How the power gets
to Earth

19. 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

20. Microwave vs. Laser Transmission
 Microwave  Laser
– More developed – Recently developed solid
– High efficiency up to 85% state lasers allow efficient
transfer of power
– Beams is far below the
lethal levels of – Range of 10% to 20%
concentration even for a efficiency within a few
prolonged exposure years
– Cause interference with – Conform to limits on eye
satellite communication and skin damage
industry

21. 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

22. Current Developments

23. Details
 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 a rectenna

24. Power to Mobile Devices
 Ifmicrowave beams carrying power could be
beamed uniformly over the earth they could
power cell phones
 Biggest problem is that the antenna would
have to be 25-30 cm square

25. Issues
 Would require a network of hundreds of
satellites
– Air Force currently track 8500 man made objects in
space, 7% satellites
 Would make telecommunications companies
into power companies

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

27. 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