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Space-Based Solar Power

Space-Based Solar Power James Harkins, Dan Livingston, Alex Wong, Aaron Sanders How it works Solar panels on satellite capture light, sends power to earth using microwave wireless power transmission technology

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Space-Based Solar Power

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  1. Space-Based Solar Power James Harkins, Dan Livingston, Alex Wong, Aaron Sanders

  2. 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.

  3. History • Producing electricity in space from sunlight is used by hundreds of satellites in operation today. • In 1968, Dr. Peter Glaser, formerly of NASA, introduced the concept of a solar power satellite system with square miles of solar collectors in high geosynchronous orbit to collect and convert the sun's energy into a microwave beam to transmit energy to large receiving antennas (rectennas) on earth. • In 1999 NASA formed SERT, the Space Solar Power Exploratory Research and Technology program to perform design studies and evaluate feasibility.

  4. Design Ideas • Thrusters must be used to counteract solar winds • The space-based antenna needs to be at least 1 km in diameter, making it far larger than any satellite ever proposed. • Recieveing antenna (an array of wires) must cover 20,000 acres. • Sidebands not worth capturing • Laser alternative to microwave power transmission. Sage-Hall Thrusters

  5. Technology obstacles to overcome • NASA estimates a SSP will need to operate at 1000v or higher, which leads to self-destructive arcing. Current experimentation is at 300 v. • Wireless power transmission only recently became a reality, with small amounts of power over a few feet. • Lots of design work left regarding the high temperature characteristics of the transmitting antenna and the solar array. Example of self destructive arcing Image: http://gltrs.grc.nasa.gov/reports/2000/TM-2000-210210.pdf

  6. Solar Arrays • Weight between 0.5 kg/kW to 10 kg/kW • Lifespan is about 20 years • Exposure to charged particles can reduce the lifespan drastically • Naturally degrades about 1 to 2 percent per year • Efficiency up to 30% • Solar radiation is 5-10 times greater in space

  7. Power • Efficiency of power transmission is about 50% • Microwave transmission will diffract greatly • Total efficiency is about 7% • Power yield from rectenna is about 90 W/m2 • Lasers are an alternative to microwaves • Rectenna will only need to be 180m in diameter

  8. Benefits of SSP

  9. General Benefits • No pollution after construction • No ghg during power generation • Source of energy is free • Large amount of energy potential.

  10. Space Advantages • Less atmosphere for sunlight to penetrate for more power per unit area • Any location on Earth can receive power • Satellite can provide power up to 96% of the time • Solar panels do not take up land on Earth • Lots of space in space • Promote growth of space, solar, and power transmission technology

  11. Problems with SSP • 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 • Would need a complex propulsion system

  12. VERY Expensive Initial Costs • Cost of Lifting Cargo Into Space using Space Shuttle is currently $10000/kg • Reusable Launch Systems looking to reduce this cost are underdeveloped • Space Elevator

  13. 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 + ≠ http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800022396_1980022396.pdf

  14. Very large antennas/rectennas • The distance between the antenna and rectenna will be roughly the distance from Earth to geosynchronous orbit (22,300 miles) • For best efficiency the satellite antenna must be circular between 1 and 1.5 kilometers in diameter • The ground rectenna would need to be elliptical and around 14 kilometers by 10 kilometers http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800022396_1980022396.pdf

  15. Very large antennas/rectennas (cont.) • Anything smaller would result in excessive losses due to sidelobes. • To collect and convert the desired energy the satellite would need between 50 and 100 square kilometers of collector area using standard ~14% efficient monocrystalline silicon solar cells making this much larger than most man-made structures on Earth. • Though not unfeasible, such an enormous undertaking in orbit has never been attempted image: http://www.spacefuture.com/archive/conceptual_study_of_a_solar_power_satellite_sps_2000.shtml Microwave power distribution on the ground surface.

  16. Targets • Launch costs: < $250/kg • Currently: $10,000/kg • Not feasible with chemical rocket technology • Space elevator • SSP array costs: < $1,000/kW • Must be very efficient • Currently: $2.4 million/kW • Ground-based: $5,000/kW • Operation and Maintenance: < $0.01/kWh

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