1. Wireless Power Transmission
EE563-Graduate Seminar
Fall Group 5
Alan Chun-yip Yeung
Leanne Cheung
Jeff Samandari
Wehibe Belachew
Tesfa Mael
Jose A. Becerra

2. Presentation Outline 1. Introduction / Background
2. Theory of Wireless Power Trans.
3. Major Research Projects
4. Comparison of Efficiency …
5. Proposed Project/Experiment
6. Conclusion

3. 1. Introduction / Background

4. Outline History/Background Solar Power Satellite
Microwave Power Transmission
Conclusion
Reference:

5. Background, Nikola Tesla
Innovations:
Alternating current
Wireless power transmission experiments at Wardenclyffe
Image: lifeen.html
MSN Encarta, Nikola Tesla,< April 10, 2004)

6. 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)
Image: wardenclyffe.gif
MSN Encarta, Nikola Tesla,< April 10, 2004)

7. 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
Wikipedia, Microwave Power Transmission,< April 10, 2004)

8. 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
David, Leonard, Bright Future for Solar Power Satellites, < April 10, 2004)
Space Power, SPS Timeline,< April 10, 2004)

10. 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)
Cost—$74 billion
Interference
David, Leonard, Bright Future for Solar Power Satellites, < April 10, 2004)
Space Power, SPS Timeline,< April 10, 2004)
US Department of Energy, EREC Brief Solar Power Satellites,< April 10, 2004)

11. 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
ISIS, Highlights in Space 2000, < April 10, 2004)

12. Microwaves Frequency 2.45 GHz microwave beam
Retro directive beam control capability
Power level is well below international safety standard
Nagatomo, Makoto, Conceptual Study of a Solar Power Satellite, SPS 200, < April 10, 2004)

13. Microwave vs. Laser Transmission
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
ISIS, Highlights in Space: 2000, < (accessed April 10, 2004)
Wikipedia, Solar Power Satellite, < April 10, 2004)

14. Rectenna Microwaves are received with about 85% efficiency
“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
Quote:
Wikipedia, Solar Power Satellite, < April 10, 2004)

15. 5,000 MW Receiving Station (Rectenna)
5,000 MW Receiving Station (Rectenna). This station is about a mile and a half long.
image_library.html

16. 2. Theory of Wireless Power Trans.

17. Theory of Operation Electromagnetic Radiation Antenna basics
Phased-array antenna
Diffraction analogy
Energy distribution
Rectenna
Physical limitations & relationships

18. Physics of Wireless Power Transmission
Forms of Electromagnetic radiation
Travel at same speed
F = frequency
C = velocity of light
L =wavelength

19. Dipole Antenna Transmission of power is simpler than TV & Radio
Transmitter: wire half a wavelength
Pushes electrons back and forth
Receiver: wire half a wavelength

20. Antenna Radiation Pattern

21. Phased-array antenna The λs for microwaves are small  dipoles small
Beam focusing: phased-array antenna
Electronically steered by varying the timing or phase
Waves will merge together

22. Phased-Array Antenna

23. Diffraction analogy Light same properties
Laser beam shinning trough a narrow opening & spreads out or diffracts
Bright spot in the center w/fainter spots on the side

24. Diffraction & Microwaves
Waves reinforce at some points and they cancel out at other points (bright and fainter points)
In microwaves: is a scaled up version of diffraction

25. Intensity

26. Main lobe energy Circular central max  Main lobe 84% of energy
Sidelobes surround
No energy  minima

27. Intensity 84% in main lobe

28. Rectenna
Array of dipole antennas known as rectifying antenna or Rectenna
Diameter = Dr

29. Rectenna

30. Physical Limitations
The receiving diameter Dr increases with transmitter receiver separation distance S.
Dr increases if transmitter diameter Dt decreases

31. Physical Limitations

32. 2. Sample Calculations

33. Calculations/Analysis
Frequency, f (Hz)
Intensity, I (watts per square meter)
Wave-Length, L (meters)
Received Main Beam Lope (“spot”) Diameter, Dr (meters or kilometers)
Transmitting Phased Array Diameter, Dt (meters or kilometers)
Example: how to estimate Intensity, I ?

34. Frequency Formula Dt * Dr Frequency, f (Hz) = -------------- (2)
(L * S)
Dt: transmitting phased array diameter
Dr: received main beam lobe (“spot”)
diameter
L: wavelength
S: separation

35. Frequency Analysis
Dt * Dr
If (Frequency, f (Hz) = )  GHz (2)
(L * S)
Then at least, 84% of the energy of the beam will be captured
Note:
This energy is not linear; 42% of the energy is not equivalent to 1.22 GHz.
Equation (2) represent a best case scenario.
Practical antenna sizes may have to be larger if most of the beam is to be captured.
The rectenna will have to be at least as large as Dt, even if (2) says Dr is smaller.

36. Frequency Analysis
Such a wide beam can be focused, but only to a minimum size Dr.
For low Earth-orbit power-beaming demonstrations, it is easier to put the smaller antenna in space and the larger antenna on Earth.
Early demonstrations may capture only a small percentage of the total power, in order to keep antenna sizes small.
to light up a 60 watt bulb, thousands of watts may have to be transmitted.
Since costly to launch such a power generating apparatus, the most feasible demonstration project may be Earth-to-space transmission from a large transmitting antenna (such as the Arecibo dish) to a smaller rectenna in space.

37. Intensity, I Formula Intensity, I (watts per square meter) P Dt
= ½ ( Pi * -----) * ( ) (3)
4 L * S
Pi: 3.14…
P: total power transmitted
Dt: transmitted phased array diameter
L: wave length
S: transmitter to receiver distance (separation)

38. Wave-Length, L Calculations
Wave-Length, L (meters)
c 300,000,000 meter/sec
= = ( ) = (1)
f ,450,000,000/sec meter
c: speed of light
f: frequency

39. Received Main Beam Lope Diameter, Dr Calculations
Received Main Beam Lope (“spot”) Diameter, Dr (meters or kilometers)
f * L * S * m * 35,800,000m
= =
Dt m
= 10,700 meter = kilometers
L: wave length
S: separation
Dt: transmitting phased array diameter

40. Transmitting Phased Array Diameter, Dt Calculations
Transmitting Phased Array Diameter, Dt (meters or kilometers)
f * L * S * m * 35,800,000m
= =
Dr ,700 meter
= 1000m = 1 kilometers
L: wave length
S: separation
Dr: received main beam lope (“spot”) diameter

41. Example What is the Intensity, I = ?
Given: f, Dr, and a typical solar power satellite transmitting 5 billion watts from geostationary orbit kilometers high.
Solution: Use the following (1), (2), & (3) C
f =  L (1) L
Dt * Dr
Frequency, f (Hz) =  Dt (2)
(L * S)
P Dt
Intensity, I (watts/m^²) = ½ ( Pi * -----) * ( ) (3)
4 L * S

42. Example Calculations Intensity, I (watts per square meter) P Dt
= ½ ( Pi * -----) * ( ) (3)
4 L * S
w m
= ½ ( Pi * ) * ( )
4m m* 35800,000m
= 205 watts/m^² or milliwatts/cm^²

43. Example Analysis peak beam intensity, Ip = 20.5 milliwatts/cm^²
 This is about twice US industrial standard for human exposure
 This is converted (by rectenna) to electricity by 90% efficiency
Average intensity, Ia  1/3 * 20.5 milliwatts/cm^²

44. Rectangular Transmitting antenna array Calculations
Mathematics slightly different, but the same general principles apply.
Central maximum of the beam contain 82% of the transmitted energy.
Rectangular in shape, but will spread out more along TX array’s short direction than its long direction.
Example: Canada’s Radar sat
rectangular transmitting antenna: 1.5m × 15m
“footprint” on the ground: 7,000m × 50,000m
frequency: GHz
altitude: ,000m
output power: watts
 The power is too spread out at the ground to use in a practical demonstration project.

45. Two more points Use certain transmitting methods
to reduce the level of the sidelobes
to put some of the sidelobe energy into the main lobe
 Price to pay: Larger Rectenna (because main lobe spreads out)
Principal of diffraction also limits the resolution of optical systems:
Lenses
Telescopes

46. 3. Major Research Projects

47. 1979 SPS Reference System concept (GEO)

49. Accomplishments of Solar Power Satellites
1980, 30 kW of microwave power was transmitted to a receiving antenna over one mile
1993, Japan successfully transmitted a 800W microwave beam from a rocket to a free-flying satellite in space.
1998, Microwave to DC conversion efficiency of 82% or higher by the rectenna.

50. NASA’s 1995-1997 Fresh Look Study
MEO (Mid-Earth Orbit)
Sun Tower:
- 6 SPS yields near 24-hr power to sites
- ± 30 degrees Latitude Coverage
- Power services of MW

51. Continued Solar Disc - 1 SPS provides nearly 24-hr power to markets
- Spin-stabilized solar array, de-spun phased array with electronic beam-steering
- Geostationary Earth Orbit
- ± 60 degrees Latitude
Coverage
- Power services of about 5 GW
per SPS -

52. 1999-2000 Space Solar Power (SSP) Exploratory Research and Technology (SERT) program
Exploration and Commercial Development

54. Integral Symmetrical Concentrator

55. NASA’s SSP Strategic Research & Technology Roadmaps

56. SPS 2000

57. Details of SPS 2000
Japan is to build a low cost demonstration of SPS by 2025.
Eight countries along the equator agreed to be the rectenna sites.
10 MW satellite delivering microwave power in the low orbit 1100 km(683 miles)
Will not be in geosynchronous orbit, instead low orbit 1100 km (683 miles)
Much cheaper to put a satellite in low orbit

58. Japan’s Recent Research Efforts
- 2001, Japanese’s Ministry of Economy, Trade and Industry (METI) launched a research program for a solar-powered-generated satellite.
- By 2040, beginning of a SPS operation. The planned satellite will be able to generate 1GW/Sec. (equivalent to the output of a nuclear plant) in a geostationary orbit. The receiving antenna (rectenna) on the ground will be either positioned at desert or sea.

59. Japan’s Roadmaps for SPS Development

60. References
presentations_pdf/OOSIssuesOverview_Oda.pdf
PowerPoints/Wireless%20Power%20Transmission%20-%20Soubel.ppt
solar_power_new_architectures_concepts_and_technologies.shtml
Lin, James C., “Space solar power stations, wireless power transmissions, and biological implications”, IEEE microwave magazine, March, 2002

61. 4. Comparisons Among Other Power Sources

62. Efficiency and Costs Space Solar Power (Wireless Power Transmission)
Ground Based Solar Power
Nuclear Energy
Fossil Fuel

63. 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

64. Cont. 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
Ground based solar only works during clear days, and must have storage for night. Thus it is More reliable than ground based solar power

65. Advantages over Nuclear Power
There are advantages…
Possible power generation of 5 to 10 gig watts
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.

66. Cont…
Nuclear power doesn't pollute the atmosphere like fossil fuels. But it does produce waste. This stays radioactive for thousands of years and is very dangerous. At the moment most stations bury their waste deep underground, at sea or send it to other countries. (Britain, for example, accepts and buries nuclear waste from several countries.)

67. Cont… One of the disadvantage of Nuclear
On April 26, 1986 the worst catastrophe in nuclear history occurred in the station at Chernobyl, Ukraine.
Due to the failure of one of reactor, two people died immediately from the explosion and 29 from radiation. About 200 others became seriously ill from the radiation; some of them later died. It was estimated that eight years after the  accident 8,000 people had died from diseases due to radiation (about 7,000 of them from the Chernobyl cleanup crew). Doctors think that about 10,000 others will die from cancer. The most frightening fact is that children who were not born when the catastrophe occurred inherited diseases from their parents.
Source  by Vessela Daskalova

68. Advantages over Fossil Fuel
Fossil fuels won't last forever (next 50yrs)
It is not renewable
The ability to match supply to demand may already have run out, especially for oil
Fossil Fuel fired electric power plants in the US emits about 2 billion tons of greenhouse gas CO2 in to air every year. This courses climate change in the future via greenhouse effect.

69. Cost Cost—prototype would have cost $74 billion
“According to Kyle Datta the Oil Factor,” which predicts that oil could hit $100 a barrel by 2010.

70. Disadvantages
If microwave beams carrying power could be beamed uniformly over the earth. They could power Mobile Devices Eg. cell phones
Microwave transmission
Interference with other electronic devices
Health and environmental effects

71. Cont… 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 and also Implementation Complexity

72. Initial conceptual looks at a mega-engineering project as shown in this Boeing design. New technologies point to more efficient, less expensive space solar power systems. Credit: Boeing/Space Studies Institute

73. Early and simple schematic of how a space solar power satellite would beam energy to electrical power grid on Earth. Credit: Space Studies Institute

74. Sustainable energy
To meet the final goal of providing sustainable energy for future growth and protection of the environment, the design and technology for space solar power should be evaluated by the criteria of availability of resources, energy economy (payback time) and waste production such as carbon-dioxide through all the processes required for production of SPS . Power from space should be competitive with other energy sources in this respect. We also need a space solar future if our children are to live in an intact environment. They will be grateful to us

75. 5. Proposed Project/Experiment

76. Goal of the Proposal
Obtain $10,000 grant from EPA to fund our research

77. Proposed Project
Transmit power from AC outlet to a remote circuit wirelessly
to demonstrate the capability of the technology,
to explore the problems we'll face in a small-scale experiment, and
to use this experiment as a “probe” to explore the potential problems of transmitting power from space to earth

78. Benefits
For graduate and undergraduate students to research and study about wireless power transmission
Demonstration tool for a potential laboratory course
Potential commercialization of the proposed project

79. Block Diagram of Proposed Experiment—1
Transmitting Side:
AC Power
Outlet
Power
Conversion
Microwave
Transmitter
This is the AC power supply
This converts the AC power to a microwave power signal
This transmits the microwave power signal

80. Block Diagram of Proposed Experiment—2
Receiving Side:
Rectenna
Power
Conversion
Power
Regulator
Remote
Device
This converts the microwave power signal to DC power signal
This regulates DC voltage level
Remote Device uses this DC power the same way it uses a battery

81. Vision on Future Development
Local
Regional
Orbital
Ability to transmit power within a laboratory
Ability to transmit
power from a
local power
plant to local households
Ability to transmit power
from a
geostationary
satellite to a specific
reception site

82. 6. Conclusion

83. Conclusion
This idea worth to invest in since this technology brings in virtually unlimited power from the sun.
This also benefits the intercontinental power providers.
Absolutely environmentally friendly since it is emission-free.

84. Reference
“A Few Things you occasionally wanted to know about wireless power transmission.” Potter, Seth.
“Solar Power Satellites and Microwave Power Transmission”
PowerPoints/Wireless%20Power%20Transmission%20-%20Soubel.ppt
solar_power_new_architectures_concepts_and_technologies.shtml
Lin, James C., “Space solar power stations, wireless power transmissions, and biological implications”, IEEE microwave magazine, March, 2002