1. Solar Power Satellites and
Microwave Power Transmission
Andrew K. Soubel
Energy Law Spring 2004
Chicago-Kent College of Law
soubel@msn.com

2. Outline
 Background
 Solar
Power Satellite
 Microwave Power Transmission
 Current Designs
 Legal Issues
 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. 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
 Idea
gained momentum during the Oil Crises of
1970’s, but after prices stabilized idea was
dropped
–
US Department of Energy research program 19781981

9. 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)

10. 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
–
Only a few days at spring and fall equinox would the
satellite be in shadow

11. Continued
 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
grid
 No air or water pollution is created during
generation

12. 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)

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

14. 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

15. 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

16. Specifications
 Collector
area must be between 50 (19 sq
miles) and 150 square kilometers (57 sq miles)
 50 Tons of material
– Current rates on the Space Shuttle run
between $3500 and $5000 per pound
– 50 tons (112,000lbs)=$392,000,000

17. Continued
 There
are advantages
 Possible power generation of 5 to 10 gigawatts
–
“If the largest conceivable space power
station were built and operated 24 hours a
day all year round, it could produce the
equivalent output of ten 1 million kilowattclass nuclear power stations.”

18. Possible Designs

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

22. Possible Solutions



International Space
Station
President’s plan for a
return to the moon
Either could be used as
a base for construction
activities

23. Microwave Power Transmission
How the power gets
to Earth

24. 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

25. Microwaves
 Frequency
2.45 GHz microwave beam
 Retro directive beam control capability
 Power level is well below international
safety standard

26. 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

27. 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

28. Rectenna Design
 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

29. 5,000 MW Receiving Station
(Rectenna). This station is about a
mile and a half long.

30. Rectenna Issues
 Size
Miles across
 Location
– Aesthetic
– Near population center
 Health and environmental side effects
– Although claim that microwaves or lasers
would be safe, how do you convince people
–

31. Current Developments

32. SPS 2000

33. 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

34. Continued
 10
–
–
–
MW satellite delivering microwave power
Will not be in geosynchronous orbit, instead
low orbit 1100 km (683 miles)
Much cheaper to put a satellite in low orbit
200 seconds of power on each pass over
rectenna

35. Power to Mobile Devices
 If
microwave 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

37. Low Orbit
 Communications
industry proposing to have
hundreds of satellites in low earth orbit
 These satellites will use microwaves to beam
communications to the ground
 Could also be used to beam power

38. Continued
 Since
a low orbit microwave beam would
spread less, the ground based rectenna could
be smaller
 Would allow collectors on the ground of a few
hundred meters across instead of 10
kilometers
 In low orbit they circle the Earth in about every
90 minutes

39. 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

40. Reliability


Ground based solar 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

41. Legal Issues
 Who
will oversee?
 Environmental Concerns
 International

42. NASA
 Funding
the research
 In charge of space flight for the United States
 Would be launching the satellites and doing
maintenance

43. FCC
 Federal
–
Communications Commission
The FCC was established by the
Communications Act of 1934 and is charged
with regulating interstate and international
communications by radio, television, wire,
satellite and cable.

44. Environmental
 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 for the rectennas is
massive

45. International
 Geosynchronous
satellites would take up large
sections of space
 Interference with communication satellites
 Low orbit satellites would require agreements
about rectenna locations and flight paths

46. 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