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/PowerPoints/Wireless%20Power%20Transmission%20-%20Soubel.ppt

Background, Nikola Tesla 1856-1943 Innovations: Alternating current Wireless power transmission experiments at Wardenclyffe Image: www.mercury.gr/tesla/ lifeen.html MSN Encarta, Nikola Tesla,<http://encarta.msn.com/encyclopedia_761567992_1____3/Tesla_Nikola.html#s3>(accessed April 10, 2004)

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: www.tfcbooks.com/images/teslafaq/ wardenclyffe.gif MSN Encarta, Nikola Tesla,<http://encarta.msn.com/encyclopedia_761567992_1____3/Tesla_Nikola.html#s3>(accessed April 10, 2004)

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,<http://www.fact-index.com/m/mi/microwave_power_transmission.html>(accessed April 10, 2004)

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 David, Leonard, Bright Future for Solar Power Satellites, <http://www.space.com/businesstechnology/technology/solar_power_sats_011017-1.html>(accessed April 10, 2004) Space Power, SPS Timeline,<http://www.spacefuture.com/power/timeline.shtml>(accessed April 10, 2004)

http://www.ssi.org/assets/images/SPS_summary.jpg

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, <http://www.space.com/businesstechnology/technology/solar_power_sats_011017-1.html>(accessed April 10, 2004) Space Power, SPS Timeline,<http://www.spacefuture.com/power/timeline.shtml>(accessed April 10, 2004) US Department of Energy, EREC Brief Solar Power Satellites,<http://www.eere.energy.gov/consumerinfo/refbriefs/l123.html>(accessed April 10, 2004)

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, <http://www.oosa.unvienna.org/isis/highlights2000/sect6b.html>(accessed April 10, 2004)

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, <http://www.spacefuture.com/pr/archive/conceptual_study_of_a_solar_power_satellite_sps_2000.shtml>(accessed April 10, 2004)

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, <http://www.oosa.unvienna.org/isis/highlights2000/sect6b.html> (accessed April 10, 2004) Wikipedia, Solar Power Satellite, <http://www.fact-index.com/s/so/solar_power_satellite.html>(accessed April 10, 2004)

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: http://www.spacetalent.com/cgi/glossary.cgi?gl=term&term=Rectenna Wikipedia, Solar Power Satellite, <http://www.fact-index.com/s/so/solar_power_satellite.html>(accessed April 10, 2004)

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

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 http://imnh.isu.edu/digitalatlas/clima/atmosph/images/waves.jpg

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: phased-array 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 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 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

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 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 - 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 small-scale experiment, and to use this experiment as a “probe” to explore the potential problems of transmitting power from space to earth

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

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

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

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

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 “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_know_about_wireless_power_transmission.shtml “Solar Power Satellites and Microwave Power Transmission” http://www.kentlaw.edu/classes/fbosselm/Spring2004/PowerPoints/Wireless%20Power%20Transmission%20-%20Soubel.ppt 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