Wireless Power TransmissionAn Obscure History and a Bright Future?

Presented by Andrew Bomber March 9, 2005

Dr. Andres La Rosa (PH 464 Applied Optics)

Tesla and the WardenclyffeTower

Tesla lit an incandescent lamps by current induced in a local loop consisting of a single wire forming a square of fifty feet on each side, which includes the lamps, and which was at a distance of one hundred feet from the primary circuit energized by the oscillator (Century Magazine, June 1900). The building of a global wireless energy distribution system called the Wardenclyffe Tower was started almost a century ago by Tesla but was abandoned because of lack of funds. (1)

Brown invents the RectennaBrown invented a “rectenna” in the early 1960s and demonstrated a “practical” application for it by inventing a microwave-powered helicopter in 1964.But why transmit power with radio waves? Surely not for Parlor tricks.

Why Wireless Power Transmission

To transport power over an impossible or impractical barrier for traditional wire transmission.

Solar Power Satellite to Earth Terminal.Desert Solar Power Farm to Civilization.Earth Terminal To Space Probe.Power Supply to remote Relay Site

Rapid Deployment of Temporary Disaster Relief or Military Assets.

Why Increased interest now

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Energy demands will soon out-pace fossil fuel production and many societies are un-accepting of nuclear energy making renewable energy very attractive.

One solution to the coming power shortage . . .

Solar Power Satellites (SPS)

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Solar Power Satellites

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Efficiency of a MPT system

“The highest record (84%) of microwave-to-dc conversion efficiency was achieved in the demonstration of MPT in 1975 at the JPL Goldstone Facility. Power was successfully transferred from the large parabolic transmitting antenna dish to the distant rectenna site over a distance of 1.6 km. The dc output was 30 kW.” [2]

(5)

Efficiency of a MPT system

“The highest record (84%) of microwave-to-dc conversion efficiency was achieved in the demonstration of MPT in 1975 at the JPL Goldstone Facility. Power was successfully transferred from the large parabolic transmitting antenna dish to the distant rectenna site over a distance of 1.6 km. The dc output was 30 kW.” [2]

[5]

Solar Power SatellitesMagnetron will likely be transmission wave generating device.Its Frequency not precisely controllable but it’s efficient. That’s why it’s used in microwave ovens not communication systems.(9)

Solar Power SatellitesBasic RectennaArray. E-field of microwave create voltage across diodes and thus also generates current.~85%to99% efficient (i.e. incident RF/DC power)

Summing Current

E-Field

(-) (+)

Solar Power SatellitesRectenna Array size would be large so that energy density would only be 25% of sun light at Earth's surface.A Pilot beam directs the Satellite’s transmission

Tracking Signal

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Atmospheric OpacityOptical Would be preferable to Microwave if there was more efficient means of generation and collection(10)

Single Junction PV Cells

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PV Cell InefficiencyMulti junction PV Cell take advantage of varying band gaps of semiconductor devices.Si Band gap ~ 1.1 eVFsi = 1.1eV/4.13x10-15 eV-s =265.977 THz -> 1.13umhv – Eg = 0 generation of Electron Hole Pair (EHP) which creates Current.hv – Eg > 0 lost as heat hv-Eg < 0 lost as uncpatured light (i.e. Transmitted through material).

hv > Eghv < Eg

hv = Eg

Heat

Multi-Junction PV CellMulti-juctiontion PV cells match light to bandgap so less energy is lost in heat.

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Multi-Junction PV Cells

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Sources1. Wikipedia. (Updated: March 19, 2006) “Wireless energy transfer” Wikimedia

Foundation, Inc. http://en.wikipedia.org/wiki/Wireless_energy_transfer2. Cynthia Boyko & Stu McCormick. (Updated: February 6, 2001). by

Friends of CRC, http://www.friendsofcrc.ca/Projects/SHARP/sharp.html3. T21 World Global Trends (Accessed March 23, 2006).

http://www.t21.ca/energy/index.htm.4. Matsumoto, Hiroshi. “Research on Solar Power Satellites and Microwave Power

Transmission in Japan”. IEEE Microwave Magazine. December 2002. pp. 36 – 45. 5. William C. Brown and a E. Eugene Eves. “Beamed Microwave Power Transmission

and its Application to Space” IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL 40. NO 6. JUNE 1992. pp. 1239-1250.

6. U.S. Department of Energy National Center for Photovoltaics (NCPV). “The Basic Physics and Design of III-V Multijunction Solar Cells “http://www.nrel.gov/ncpv/pdfs/11_20_dga_basics_9-13.pdf

7. Rines, Glen. “Highly Efficient Fiber Lasers for Wireless Power Transmission” NASA SBIR 2004 Solicitation http://sbir.gsfc.nasa.gov/SBIR/abstracts/04/sbir/phase1/SBIR-04-1-X2.03-9461.html

8. Berland, B. “Photovoltaic Technologies Beyond the Horizon: Optical Rectenna Solar Cell”. ITN Energy Systems (February 2003) http://www.nrel.gov/docs/fy03osti/33263.pdf

9. Wikipedia. (Updated: March 19, 2006) “Cavity Magnetron” Wikimedia Foundation, Inc. http://en.wikipedia.org/wiki/Magnetron

10. Ulaby, FAWWAZ T. Fundamentals of Applied Electromagnetics. 2004 edition. Copyright 2004 Prentice Hall. Upper Saddle River, NJ. p 20.

11. http://www.mtt.org/awards/images/rmd-2a.jpg