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Transcript of Wireless power transmission soubel
Solar Power Satellites and Microwave Power Transmission
Andrew K. Soubel
Energy Law Spring 2004
Chicago-Kent College of [email protected]
Outline
Background Solar Power Satellite Microwave Power Transmission Current Designs Legal Issues Conclusion
Background
1899-1990
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 ½ mile in diameter(1 km)
Continued
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
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.”
Possible Designs
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
How the power gets to Earth
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 beamRetro directive beam control capabilityPower level is well below international
safety standard
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
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 groundVisually transparent so that it would not
interfere with plant life– Magic carpet
Material pegged to the ground
5,000 MW Receiving Station (Rectenna). This station is about a mile and a half long.
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
SPS 2000
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
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
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
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
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
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
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