Solar Power Satellites and Microwave Power Transmission

1
Solar Power Satellites and Microwave Power
Transmission

• Andrew K. Soubel
• Energy Law Spring 2004
• Chicago-Kent College of Law
• soubel_at_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
1940s 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

• 1940-50s Development of the Photovoltaic cell
• 1958 First US Satellite that used Solar Power
• 1970s Oil embargo brought increased interest and
  study

8
Solar Power from Satellites

• 1968s 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
  1970s, but after prices stabilized idea was
  dropped
• US Department of Energy research program 1978-1981

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, dont 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
• Complexity30 years to complete
• Size6.5 miles long by 3.3 miles wide
• Transmitting antenna ½ mile in diameter(1 km)

13
Continued

• Costprototype would have cost 74 billion
• Microwave transmission
• Interference with other electronic devices
• Health and environmental effects

14
1980s to Present

• Japanese continued to study the idea of SPS
  throughout the 1980s
• 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 kilowatt-class nuclear power
  stations.

18
Possible Designs
19
(No Transcript)
20
(No Transcript)
21
Deployment Issues

• Cost of transporting materials into space
• Construction of satellite
• Space Walks
• Maintenance
• Routine
• Meteor impacts

22
Possible Solutions

• International Space Station
• Presidents 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

36
(No Transcript)
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, dont 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