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Over the Horizon Wireless Power Transmission (OTH-WPT)
A Low Cost Precursor for Space Solar Power
Stephen Blank, IBE Systems & NYIT
Paul Jaffe, NRL
Overview
• Background
– Laser SSP Concepts
– Laser Power Beaming Demonstrations
– SSP Concepts with High-Altitude Elements
• Proposed Terrestrial Demonstration
– Configurations
– Challenges
Selected Laser SSP Concepts
Aerospace Corp. Laser Concept, circa 2002
JAXA Concept, circa 2011
EADS Astrium Concept, circa 2010
Selected Laser Power Beaming Demonstrations
EADS Astrium tracking laser to power rover, circa 2003
Kinki Univ. & Hamamatsu Photonics Inc. laser power to small helicopter, circa 2007
Lasermotive outdoor laser power to UAV, circa 2012
Comparison of Microwave and Laser Power Transmission for SSP from GEO
Microwave Laser
Transmit frequency 5.8 GHz 1.4 mm
Transmit Aperture Diameter In GEO 1 km 2.5 m
Receiving Aperture Diameter On or Near Earth
3.2 km on earth 40 m
Demonstrated Transmitter Conversion Efficiency
~80% ~30%
Demonstrated Receiver Conversion Efficiency
~90% ~50%
Vulnerability to Weather Probably negligible Not negligible*
Spectrum Allocation Challenges Likely to be high ?
International Political Challenges ? Likely to be high*
*this problem may be reduced or eliminated by using a high altitude receiving platform
Selected High Altitude Receiving Platform SSP Concepts
C.A. Schafer, D. Gray, "Transmission media appropriate laser-microwave solar power satellite system", Acta Astronautica 79 (2012) 140–156
S. Blank, S. Leete, P. Jaffe, “Feasibility Study of Space Based Solar Power to Tethered Aerostat Systems”, IEEE Aerospace Conf 2013
Space to Tethered Aerostat SSP
• Beaming from space to a high altitude tethered aerostat avoids main effects of atmospheric attenuation
• Potentially allows use of “eye-safe” laser transmit frequency which results in far smaller apertures vs. microwave for: transmit antenna in GEO and receive aperture on the aerostat
Demonstration Motivation
• The high cost of getting to space has been an obstacle to demonstration implementations
• Over the Horizon Wireless Power Transmission, OTH-WPT, is proposed as a low cost precursor to SSP that does not require access to space
“...large-scale demonstration of power beaming is a necessary step to the development
of solar power satellites.” – Geoffrey Landis, scientist and author
Demonstration Configuration
Ground Location 2
Ground Location 1
Aerostat or Airborne
Platform
Demonstration Configuration Functional Block Diagram
Laser
Laser Power Converter Panel
Power Conditioning
& Distribution Power Supply
Trihedral Reflector Panel
Beam Path
Steering Mirror
Detector
Pilot Signal
Control Electronics
Tether
Demonstration Configuration Range
Range as a function of air platform height (km)
2 4 6 8 100
100
200
300
r h( )
h
Power Down Tether
Converter Panels
Notes: Airship altitudes above troposphere
Demonstration Configuration • Advantages:
• Atmospheric attenuation one direction only •Power easily sent to multiple locations
• Disadvantages: • Requires tether • Potential radiation hazard
Transmitter
Airborne Reflector Configuration • Advantages:
• One airship • No tethers
• Disadvantages: • Atmospheric attenuation both directions • Potential radiation hazard
Transmitter
Reflector
Converter Panels
Note: Tether could be used with airship if desired.
Power Beam Down Configuration • Advantages:
• Atmospheric attenuation one direction only • Power easily sent to multiple locations • Easier logistics at receiving site
• Disadvantages: • Requires tether • Potential radiation hazard
Power Up
Tether
Converter Panels
Transmitter
Beam at Altitude Configuration • Advantages:
• Minimizes atmospheric attenuation • Very long range, potentially > 1000 km • Power easily sent to multiple locations
• Disadvantages: • Two airships • Requires tethers
Transmitter
Power Down Tether
Converter Panels
Notes: Airship altitudes above troposphere Power
Up Tether
Design Challenges
• Airborne/field deployable high power lasers • Beam pointing, tracking, retro-directivity • Compensating for atmospheric effects • Mirrors for high power lasers • Laser power conversion • Laser radiation safety • Air platform: high altitude, long duration* • Tether: light weight, low resistance, high voltage • Air traffic control * Aerostats currently operate at 4-5 km with up to 90
mph wind survivability.
Hardware Sources • High power lasers:
– IPG Photonics
– Teradiode
• Beam Control:
– Adaptive Optics / Northrop Grumman
– Boeing
– Lasermotive
– Lighthouse Development
• Aerostats:
– ILC Dover
– T-com
• Laser energy conversion:
– Spectrolab
– JX Crystals
OTH-WPT Goal & Conclusion
• Provide deployable, portable, long range, economical power transmission for security, commercial, and civil applications
• Over the Horizon Wireless Power Transmission represents an achievable, low-cost precursor for Space Solar Power
Thank You
• Stephen Blank, PhD, IBE Systems Corp. and New York Institute of Technology, [email protected] , [email protected]
• Paul Jaffe, NRL, [email protected]
Backup
Lighter Than Air (LTA)
56K
PTDS 74K
TARS 420K Zeppelin
ABC A60
HALE-D
SkyTug
ISIS
Aerostats High Altitude Airships
4.2M TowTech
Heavy Lift
Lightship
HAA
MA-3
GNSS 40K to 80K
StarTower
LEMV
ILC Dover Proprietary Information
Technical Issues
• The amount of loss along the tether during the transmission of the electrical power to the ground is an important technical issue.
• This loss can be reduced through the use of a low resistivity conductor and the choice of a high voltage for transmission.
Technical Issues
• Clouds can occur at operational altitudes.
• Statistical analysis of meteorological data show that the probability of occurrence decreases with altitude and is not statically significant at altitudes above 6 km.
• ref: i) Chilbolton Observatory, UK
ii) Cloudnet, 2007, http://www.cloud-net.org/
What is Proposed?
• Long Range Wireless Power Beaming using a ground-based high-power laser and a high-altitude receiving platform
• 100s of km range
• Delivery of 100s of kW electric power
• Many other configurations are possible to meet variety of range, power, weather and tactical needs
Tethered Aerostat with ground station
Tether properties
Aerostats, widely used, U.S. mfg. items.
Power Down Tether
Converter Panels
Notes: Airship altitudes above troposphere
Demonstration Configuration • Advantages:
• Atmospheric attenuation one direction only •Power easily sent to multiple locations
• Disadvantages: • Requires tether • Potential radiation hazard
Transmitter
Radiation Safety
• Interlocking intrusion control
• Beam pointing positive control
• Power density limitations
• Wavelength choice to minimize potential radiation hazard to personnel, animals and equipment, (1.5 mm, eye-safe)
