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Wireless Power Transmission
EE563-Graduate Seminar
Fall 2004
Group 5
Alan Chun-yip Yeung
Leanne Cheung
Jeff Samandari
Wehibe Belachew
Tesfa Mael
Jose A. Becerra
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
1. Introduction / Background
Outline
•
•
•
•
History/Background
Solar Power Satellite
Microwave Power Transmission
Conclusion
Reference:
http://www.kentlaw.edu/classes/fbosselm/Spring2004/Power
Points/Wireless%20Power%20Transmission%20%20Soubel.ppt
Background, 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
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
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
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
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
5,000 MW Receiving Station
(Rectenna). This station is about a
mile and a half long.
2. Theory of Wireless Power Trans.
Theory of Operation
•
•
•
•
•
•
•
Electromagnetic Radiation
Antenna basics
Phased-array antenna
Diffraction analogy
Energy distribution
Rectenna
Physical limitations & relationships
Physics of Wireless Power
Transmission
•http://imnh.isu.edu/digitalatlas/clima/atmosph/images/waves.jpg
• Forms of
Electromagnetic
radiation
• Travel at same speed
• F = frequency
• C = velocity of light
• L =wavelength
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
http://www.zorg.org/radio/dipole_antenna.shtml
Antenna Radiation Pattern
http://www.astromag.co.uk/portable/dipole.gif
Phased-array antenna
• The λs for microwaves
are small  dipoles small
• Beam focusing: phasedarray antenna
• Electronically steered by
varying the timing or
phase
• Waves will merge
together
http://www.mcs.harris.com/oceannet/features/antenna.html
Phased-Array Antenna
http://www.cea.com.au/products/phasedarray/i2_ceafar.html
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
http://planetquest.jpl.nasa.gov/technology/diffraction.html
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
Intensity
Main lobe energy
•
•
•
•
•
Circular central max
 Main lobe
84% of energy
Sidelobes surround
No energy  minima
Intensity 84% in main lobe
Rectenna
• Array of dipole
antennas known as
rectifying antenna or
Rectenna
• Diameter = Dr
Rectenna
Physical Limitations
• The receiving diameter Dr increases with
transmitter receiver separation distance S.
• Dr increases if transmitter diameter Dt
decreases
Physical Limitations
2. Sample Calculations
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 ?
Frequency
Dt * Dr
• Frequency, f (Hz) = -------------(L * S)
Formula
(2)
Dt: transmitting phased array diameter
Dr: received main beam lobe (“spot”)
L:
S:
diameter
wavelength
separation
Frequency
Analysis
Dt * Dr
If
(Frequency, f (Hz) = ----------- )  2.44 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.
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.
Intensity, I
• Intensity, I (watts per square meter)
P
Dt
= ½ ( Pi * -----) * ( --------- )
4
L*S
Pi:
P:
Dt:
L:
S:
Formula
(3)
3.14…
total power transmitted
transmitted phased array diameter
wave length
transmitter to receiver distance (separation)
Wave-Length, L
Calculations
• Wave-Length, L (meters)
c
300,000,000 meter/sec
= ----- = ( -------------------------------- ) = 0.1224
f
2,450,000,000/sec
c:
speed of light
f:
frequency
meter
(1)
Received Main Beam Lope Diameter, Dr
Calculations
• Received Main Beam Lope (“spot”) Diameter, Dr
(meters or kilometers)
f*L*S
2.44 * 0.12224m * 35,800,000m
= -------------- = -------------------------------------------Dt
1000m
= 10,700 meter = 10.7 kilometers
L:
S:
Dt:
wave length
separation
transmitting phased array diameter
Transmitting Phased Array Diameter, Dt
Calculations
• Transmitting Phased Array Diameter, Dt (meters or
kilometers)
f*L*S
2.44 * 0.12224m * 35,800,000m
= -------------- = ---------------------------------------------Dr
10,700 meter
= 1000m = 1 kilometers
L:
S:
Dr:
wave length
separation
received main beam lope (“spot”) diameter
Example
What is the Intensity, I = ?
Given: f, Dr, and a typical solar power satellite transmitting 5
billion watts from geostationary orbit 35800 kilometers
high.
Solution: Use the following (1), (2), & (3)
C
f = ----L
 L
Dt * Dr
Frequency, f (Hz) = -------------(L * S)
(1)
 Dt
P
Dt
Intensity, I (watts/m^²) = ½ ( Pi * -----) * ( --------- )
4
L*S
(2)
(3)
Example
Calculations
• Intensity, I (watts per square meter)
P
Dt
= ½ ( Pi * -----) * ( --------- )
4
L*S
(3)
2287485.869w
1000m
= ½ ( Pi * ---------------------------) * ( ----------------------------------- )
4m
0.1224m* 35800,000m
= 205 watts/m^² or
20.5 milliwatts/cm^²
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
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:
5.3 GHz
altitude:
800,000m
output power:
5000 watts
 The power is too spread out at the ground to use in a practical
demonstration project.
Two more points
1. 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)
2. Principal of diffraction also limits the resolution of
optical systems:
– Lenses
– Telescopes
3. Major Research Projects
1979 SPS Reference System concept
(GEO)
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.
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 200400 MW
Continued
• Solar Disc
- 1 SPS provides nearly 24hr
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
1999-2000 Space Solar Power (SSP)
Exploratory Research and Technology
(SERT) program
• Exploration and Commercial Development
Integral Symmetrical Concentrator
NASA’s SSP Strategic Research &
Technology Roadmaps
SPS 2000
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
Japan’s Recent Research Efforts
•
Japan
- 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.
Japan’s Roadmaps for SPS
Development
References
•
www.on-orbit-servicing.com/pdf/OOS2004_
presentations_pdf/OOSIssuesOverview_Oda.pdf
•
•
•
www.kentlaw.edu/classes/fbosselm/Spring2004/
PowerPoints/Wireless%20Power%20Transmission%20-%20Soubel.ppt
www.spacefuture.com/.../a_fresh_look_at_space_
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
4. Comparisons Among Other Power
Sources
Efficiency and Costs
•Space Solar Power (Wireless Power
Transmission)
•Ground Based Solar Power
•Nuclear Energy
•Fossil Fuel
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
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
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.
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.)
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 http://oii.org/html/story.html by Vessela
Daskalova
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.
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.
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
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
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
Early and simple schematic of how a space solar power satellite would beam
energy to electrical power grid on Earth. Credit: Space Studies Institute
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
5. Proposed Project/Experiment
Goal of the Proposal
• Obtain $10,000 grant from EPA to fund our
research
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 smallscale experiment, and
– to use this experiment as a “probe” to explore
the potential problems of transmitting power
from space to earth
Benefits
1) For graduate and undergraduate
students to research and study about
wireless power transmission
2) Demonstration tool for a potential
laboratory course
3) Potential commercialization of the
proposed project
Block Diagram of Proposed
Experiment—1
Transmitting
Side:
AC Power
Outlet
This is the
AC power
supply
Power
Conversion
This converts
the AC power to
a microwave
power signal
Microwave
Transmitter
This
transmits
the
microwave
power
signal
Block Diagram of Proposed
Experiment—2
Receiving
Side:
Rectenna
Power
Conversion
This converts the
microwave power signal to
DC power signal
Power
Regulator
This
regulates
DC voltage
level
Remote
Device
Remote
Device uses
this DC
power the
same way it
uses a
battery
Vision on Future Development
Local
Ability to
transmit power
within a
laboratory
Regional
Ability to
transmit
power from
a
local power
plant to local
households
Orbital
Ability to
transmit power
from a
geostationary
satellite to a
specific
reception site
6. Conclusion
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.
Reference
1)
“A Few Things you occasionally wanted to know about wireless power
transmission.” Potter, Seth.
http://www.spacefuture.com/archive/a_few_things_you_occasionally_wanted_to_k
now_about_wireless_power_transmission.shtml
2)
“Solar Power Satellites and Microwave Power Transmission”
http://www.kentlaw.edu/classes/fbosselm/Spring2004/PowerPoints/Wireless%20P
ower%20Transmission%20-%20Soubel.ppt
3)
www.on-orbit-
servicing.com/pdf/OOS2004_presentations_pdf/OOSIssuesOverview_Oda.pdf
4)
www.kentlaw.edu/classes/fbosselm/Spring2004/
PowerPoints/Wireless%20Power%20Transmission%20-%20Soubel.ppt
5)
www.spacefuture.com/.../a_fresh_look_at_space_
solar_power_new_architectures_concepts_and_technologies.shtml
6)
Lin, James C., “Space solar power stations, wireless power transmissions, and
biological implications”, IEEE microwave magazine, March, 2002