Wireless Power Transmission Presented by_ Ali Asghar Fathi Electrical Power Engineering Shomal university of Amol Student No: 901157067 Professor: Mr Tayebi Fall 2012
Wireless Power Transmission Presented by_
Ali Asghar Fathi Electrical Power Engineering
Shomal university of Amol Student No: 901157067 Professor: Mr Tayebi
Fall 2012
Presentation Outline
1. Introduction / Background
2. Theory of Wireless Power Trans.
4. Major Research Projects
5. Comparison of Efficiency …
6. Conclusion
3. Sample Calculations
1. Introduction / Background
Introduction • The demand for energy worldwide has
increasing by 100% or almost doubled in every decade.
• The world’s main source of power is still generated by fossil fuels which is limited
(85% of the total power globally). • Harmful effects of hydrocarbon-based power
sources to environment. • Regional political and religious conflicts can
disrupt world-wide distribution of fossil fuel.
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
Basic Concept
• Solar Power Satellites providing a better way of power generation
• Transmission of power to earth via microwaves
• Collection of power by specially developed antennas (rectennas)
SOLAR POWER SATELLITES
Solar Power Satellite or SPS, is a proposed satellite built in geostationary orbit that uses microwave power transmission to beam power to a very large antenna on Earth where it can be used in place of conventional power sources.
Basic components
• A huge solar collector, typically made of solar cells.
• D.C. to Microwave conversion through magnetron.
• Transmitting antenna sub array on the satellite, aimed at earth.
16
Magnetron Operation
Advantages over Earth based solar power
• More intense sunlight due to absence of air • In geosynchronous orbit, 36,000 km (22,369
miles) an SPS would be illuminated over 99% of the time
• Power can be beamed to any location where it is desired.
• No air or water pollution is created during generation
Specifications
1. Satellite antenna must be between 1 and 1.5 kilometers in diameter and the ground rectenna around 14 kilometers by 10 kilometers .
2. Collector area must be between 50 (19 sq miles) and 150 square kilometers (57 sq miles)
Continued…
4. 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.”
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
How the power gets to Earth?
• Power from the satellite is sent to Earth using a microwave transmitter
• The beamed power is received through “rectenna” located at a place on Earth
Microwave Transmission 1. Frequency 2.45 GHz microwave beam 2. Beamed Power level is well below lethal
levels of concentration even for prolonged exposure
3. High efficiency up to 85% 4. Cause interference with communication
satellites 5. Safety ensured for flying bodies to greater
extent.
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
Basic block diagram
Power captured by rectenna
• The voltage at the terminal of rectenna is equal to the electric field times the effective length.
VT =El • Half of the power captured is scattered
back and half is delivered to the load.
PT = VT2 /4RT
Rectification • The conversion from A.C. to D.C. by means of
rectifying device. • Types of rectification schemes. -half wave -full wave • The expected overall rectification efficiency, ηc=dc output power/rf incident power • The obtained conversion efficiency due to
mismatch, ηc=dc output power/ (rf incident power-rf reflected power)
Full-Wave Vs Half-Wave Rectification • Why full wave
rectification? -Large Vmin -Smaller ripple factor • Full wave rectification
by two diodes. • Diode’s inputs 180
degrees out of phase.
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
Wire mesh reflector
Magic carpet
Rectenna Issues • Size – Miles across
• Location – Aesthetic – Near population center
• Health and environmental side effects – Although claim that microwaves would
be safe, how do you convince people
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
• 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
Antenna Radiation Pattern
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
Phased-Array Antenna
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
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
3. 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 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
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 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)
Wave-Length, L Calculations
• Wave-Length, L (meters) c 300,000,000 meter/sec = ----- = ( -------------------------------- ) = 0.1224 (1) f 2,450,000,000/sec meter c: speed of light f: frequency
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: wave length S: separation Dt: 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: wave length S: separation Dr: 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 (1) L Dt * Dr Frequency, f (Hz) = -------------- Dt (2) (L * S) P Dt Intensity, I (watts/m^²) = ½ ( Pi * -----) * ( --------- ) (3) 4 L * S
Example Calculations
• Intensity, I (watts per square meter)
P Dt = ½ ( Pi * -----) * ( --------- ) (3) 4 L * S
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
4. 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 200-
400 MW
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
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
5. 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
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
• 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.
Continued… • 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.)
Continued… • 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.
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
Continued… • 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
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
• A network of low orbit satellites could provide power to almost any point on Earth continuously because one satellite would always be in range
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.
Thank you