08-16-2017, 10:59 PM
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Andrew K. Soubel
Energy Law Spring 2004
Outline
Background
Solar Power Satellite
Microwave Power Transmission
Current Designs
Legal Issues
Conclusion
Nikola Tesla
1856-1943
Innovations:
Alternating current
Wireless power transmission experiments at Wardenclyffe
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)
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
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
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 1978-1981
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)
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
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
Problems
Issues identified during the DOE study
Complexity 30 years to complete
Size 6.5 miles long by 3.3 miles wide
Transmitting antenna mile in diameter(1 km)
Cost prototype would have cost $74 billion
Microwave transmission
Interference with other electronic devices
Health and environmental effects
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
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
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
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.
Deployment Issues
Cost of transporting materials into space
Construction of satellite
Space Walks
Maintenance
Routine
Meteor impacts
Possible Solutions
International Space Station
President s plan for a return to the moon
Either could be used as a base for construction activities
Microwave Power Transmission
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
Microwaves
Frequency 2.45 GHz microwave beam
Retro directive beam control capability
Power level is well below international safety standard
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
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
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
Current Developments
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
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
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
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
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
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
Legal Issues
Who will oversee?
Environmental Concerns
International
NASA
Funding the research
In charge of space flight for the United States
Would be launching the satellites and doing maintenance
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.
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
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
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