Microwave power transmission

1. Phased Array used in
Japanese Field MPT
experiment

2. Solar power from the satellite is sent to
Earth using a microwave transmitter
Received at a “rectenna” located on
Earth
Recent developments suggestthat power
could be sent to Earth using a laser

3. Frequency 2.45 GHz microwave beam
Retro directive beamcontrol capability
Power level is well below international
safety standard

5. Microwave
• More developed
• High efficiency up to 85%
• Beams is far below the
lethal levels of
concentration even fora
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 afew
years
• Conformto limits on eye
and skin damage

6. “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

9. Size
• Miles across
Location
• Aesthetic
• Near population center
Health and environmental side effects

10. 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 arectenna
10 M W 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

11. 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

13. Who willoversee?
Environmental Concerns
International

14. Possible health hazards
• Effects of long termexposure
• Exposure is equal to the amount that people
receive from cell phones and microwaves
Location
• The size of construction for the rectennas is
massive

15. Geosynchronoussatellites would take up
large sections ofspace
Interference with communication
satellites
Low orbit satellites would require
agreements about rectenna locations and
flight paths

16. More reliable than ground based solar
power
In order for SPS to become a reality it
several thingshave to happen:
• Government support
• Cheaper launch prices
• Involvement of the privatesector