Wireless Power Transmission

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