Wireless Power Transmission for Solar Power Satellites

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Wireless Power Transmission for Solar Power
Satellites

• By
• B.Ravindra Reddy
• (MT097109)

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Outline

• Background
• Solar Power Satellite
• Microwave Power Transmission
• Current Designs
• Conclusion

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Background

• 1899-1990

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Nikola Tesla

• 1856-1943
• Innovations
• Alternating current
• Wireless power transmission experiments at
  Wardenclyffe

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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)

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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

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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

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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)

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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.

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Continued

• Waste heat is radiated back into space
• No air or water pollution is created during
  generation

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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)

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Continued

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

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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

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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

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Possible Designs
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Deployment Issues

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

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Microwave Power Transmission

• How the power gets to Earth

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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

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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

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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

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Current Developments
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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

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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

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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

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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

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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