A LowCost Precursor for Laser Space Solar Power Paul Jaffe US Naval Research Laboratory Tanwin Chang Deep Phase Labs Bert Murray Lighthouse Dev Robert Winsor Lighthouse Dev This work ID: 464225
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Slide1
Update on Over the Horizon Wireless Power Transmission (OTH-WPT)
A Low-Cost Precursor for Laser Space Solar Power
Paul Jaffe, U.S. Naval Research Laboratory
Tanwin Chang, Deep Phase
Labs
Bert Murray, Lighthouse Dev
Robert Winsor,
Lighthouse Dev
This work
is dedicated to
the late
New
York Institute of Technology Professor Stephen
BlankSlide2
Overview
Motivation
Laser SSP Concepts
Laser Power Beaming Demonstrations
Wavelength Trades
SSP Concepts with High-Altitude Elements
Proposed Terrestrial DemonstrationSlide3
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 authorSlide4
Selected Laser SSP Concepts
JAXA
Concept, circa
2011
EADS
Astrium
Concept, circa
2010
Two-stage SSP Concept
Tethered aerostat could be used instead of
microwave beam from high altitude platform (HAP)Slide5
Selected Laser Power Beaming Demonstrations
EADS
Astrium
tracking
l
aser to power
r
over, circa 2003
Kinki Univ. & Hamamatsu Photonics Inc. laser power to small helicopter
, circa 2007
Lasermotive
outdoor
l
aser power to UAV, circa 2012
Lighthouse Dev Eye-safe laser demo
http://www.bbc.co.uk/programmes/p00yjt99
5:40, circa 2012Slide6
Comparison of Microwave and Laser Power Transmission for SSP from GEO
Microwave
Laser
Transmit frequency
5.8
GHz
1.4
m
m
Transmit Aperture Diameter In GEO
1 km
2.5 mReceiving Aperture Diameter On or Near Earth3.2 km on earth40 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 platformSlide7
Laser Sources at Ten vs. One micron
10.6 microns
1064
nm
Transmit frequency
~ 30 THz
~ 300 THz
Laser
Technology
CO2
Sealed Gas Laser
Diode Pumped Fiber LaserCost
per watt (COTs)< $100 per Watt
~ $100 per WattDemonstrated Transmitter Conversion Efficiency>
20%
>
30%
Demonstrated
Receiver Conversion Efficiency
TBD
~50%
SWaP
(turn-key
system)< 10 kg / 100 W< 5 Kg / 100 W
Laser
Safety
Challenges
“Eye Safe”
Cornea
is transparentSlide8
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 aerostatSlide9
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
Perhaps leverage existing “directed energy” assetsSlide10
Demonstration ConfigurationSlide11
OTH-WPT Goal & Conclusion
Provide deployable, portable, long range, economical power transmission for civil, commercial,
and
security
applications
Over the Horizon Wireless Power Transmission represents an achievable, low-cost precursor for Space Solar PowerSlide12
BackupSlide13
Ground Location 2
Ground Location 1
Aerostat or Airborne Platform
OTH-WPT Functional Block Diagram
Laser
Adaptive
Optics
Laser Power Converter
Panel
High Voltage
Power
Conversion
Tether
Power Conditioning & Distribution
Power
Supply
(dotted indicates optional element)
Trihedral
Reflector Panel
Beam
Path
Steering
Mirror
Wavefront
Sensor
Control
Electronics
Pilot SignalSlide14
Frequency/Wavelength Comparison for a Terrestrial WPT Link
with 10m Apertures & 100km Range
2.45 GHz
5.8 GHz
34 GHz
94 GHz
1.0
μ
m
1.5
μm“eye safe”Eff. Rx
90.6%†82.7%†
~70%†~37%†
44.7%
44.7%
iii
Eff.
Tx
62%
ξ
82%
iv
73%
25%53%i
64%
Atmospheric
Attenuation
Negligible
Negligible
Negligible
Negligible
>50%
ii
<10%
ii
Safe power density
limit
v
1mW/cm
2
1mW/cm
2
1mW/cm
2
1mW/cm
2
0.09W/cm
2
0.08W/cm
2Regulatory
challenges WifiBluetooth
MinimalPossible FAA issue
Possible FAA issuesYesYes
Total Efficiency at 100 km*1%
4%16%6%23.7%
28.6%*with a transmitter radius of 10 m and a receiver radius of 10 m, 100km range
†Receiver Efficiencies: Durgin; Valenta (2014) Harvesting Wireless Powerξ http://www.microwavejournal.com/articles/9441-a-compact-high-power-2-45-ghz-microwave-generator
χ Assuming a Gaussian Distribution, 10dB, and 21 receiver elements i McCormic School of Engineering and Applied Science ii http://people.bu.edu/clemens/mimir/atmospheric_transmission.htmliii Dimroth
, F, Wafer Bonded four junction GaInP/GaAs//GaInAsP/GaInAs concentrator solar cells with 44.7% efficiency, Progress in Photovoltaics (2014)Iv McSpadden
, James, Design and Experiments of a High-Conversion-Efficiency 5.8 GHz Rectenna (1998)v ICNIRP . "On Limits of Exposure to Incoherent Visible and Infrared Radiation." 2013. Report.
Green = BetterYellow = OkayRed = WorseAdapted from a chart created by Mickey Da Silva for DHSSlide15
Range as a function of air platform
height, (km),
(atmospheric attenuation effects not included)
Slide16
Estimated Transmission coeff., T(
L,h
), at
λ= 1.06 μ
m as a function of air platform height (h km) and
horizontal beaming distance (L km)Slide17
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
TransmitterSlide18
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.Slide19
Airborne Reflector Configuration
Advantages:
One airship
No tethers/power cables
Disadvantages:
Atmospheric attenuation both directions
Potential laser radiation hazardSlide20
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
TransmitterSlide21
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
TetherSlide22
Beam at Altitude Configuration
Advantages:
Minimizes atmospheric attenuation
Very long range, potentially > 1000 km
Power easily sent to multiple locations
Little or no radiation hazard
Disadvantages:
Two airships
Requires tethers/power cablesSlide23
Design Challenges
Airborne/field deployable high power lasers
Beam pointing, tracking, retro-directivity
Compensating for atmospheric effects
Mirrors for high power lasers
Laser power conversionLaser 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.Slide24
Hardware Sources
High power lasers:
IPG Photonics
Teradiode
Beam Control:
Lighthouse Development
Adaptive Optics / Northrop Grumman
Boeing
Lasermotive
Aerostats:
ILC DoverT-comLaser energy conversion:
Spectrolab JX CrystalsSlide25
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 or longer, eye-safe) Slide26
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.Slide27
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/Slide28
St: stratus, Sc: stratocumulus, Nb: nimbostratus; Ac: altocumulus, As: altostratus; Ci: cirrus, Cs: cirrostratus, Cc: cirrocumulus; Cu: cumulus, Cb: cumulonimbus.Slide29
Density of Air vs. Altitude
http://www.aerospaceweb.org/question/atmosphere/q0046b.shtml
http://www.braeunig.us/space/atmos.htm Slide30
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
Star
²
Tower
LEMVSlide31
Tethered Aerostat with ground stationSlide32
Tether propertiesSlide33
Aerostats, widely used, U.S. mfg. items.Slide34
Air Platform Technical Issues
Strong winds and lightning at operational altitudes and possible interference of the aerostat with aviation.
These problems are common to other high altitude aerostats used for surveillance purposes, which survive 90 mph winds, have lightning protection and carry warning systems to avoid collision with air traffic.
Powered stabilization will be studied.Slide35
OTH-WPT Portability
OTH-WPT would be highly portable and relatively economical
Aerostat and ground system could be moved with relative ease
Portability of great importance in providing power to remote areas on an emergency basis and to theaters of operation that are rapidly changing
Hard-wired power lines or fuel trucking are often not feasible or are very expensive to remote areas Slide36
Future Material
Historically relevant work:
Fischer
AFRL Directed Energy demo to crane suspended mirror
Graphical range comparison showing advantage of aerostat over tower
Geometric advantage
Reduced atmospheric attenuation advantage
Actual FOB example case, AFG?
Fully-burdened cost of fuel vs. laser
eff
etc.Power density & receiver area explanationSlide37
Electromagnetic Waves
http://www.rfcafe.com/references/electrical/ew-radar-handbook/images/imgh51.gif
High Frequencies Blocked
Low Frequencies AdmittedSlide38
10.6 Micron Conversion Options
Useful
photovoltaics
do not exist at 10.6 microns due to the inefficiency of generating power from a small band-gap material
Heat engines are a potential solution, but not ideal at 10.6 microns due to the relatively large spot size of the transmitted beam
Microscopic antennas with diode rectification:
Rectennas
, or “
Nantennas
” Slide39
Nantennas
Combination of a lithographically produced bowtie antenna with geometric (ballistic) diode
Depiction adapted from Joshi, S.;
Zixu
Zhu; Grover, S.;
Moddel
, G., "Infrared optical response of geometric diode
rectenna
solar cells," Photovoltaic Specialists Conference (PVSC), 2012 38th IEEE , vol., no., pp.002976,002978, 3-8 June 2012Slide40
WPT Considerations for Most Contexts
Tradeoff between
Tx
/Rx area and power density depending on safety requirements, available collection area
Factors affecting availability: atmospheric conditions, source reliability, susceptibility to single-point failures
Regulatory, safety, and incumbent user issues
Cost & utility vs. alternativesSlide41
WPT Modality: Space-to-Space
Applications
Fractionate spacecraft
Enable power for very low orbit or low-profile spacecraft
Notes
Must have compelling advantage over widely available 1400W/m
2
sunlight, such as minimizing drag
Could make “safe/hold” mode challenging if no battery or PV backup
Potential laser advantage since no atmospheric attenuation and minimal eye safety concernsSlide42
WPT Modality: Space-to-air/sea/ground
Applications
Classic space solar power applications
Disaster response power
Space launch
See applications from NRL SBSP report next slide
Notes
Ability to send power to locations within a huge global area may present a compelling advantage
Power would be quickly
redirectable
without grid losses or extant infrastructureEconomic case challenging to makeSlide43
From NRLSBSP report, prospective,
military power beaming scenarios
OutlineSlide44
WPT Modality: Ground-to-air/space
Applications
UAV dwell extension/power augmentation
Element of disaster response/battlefield power transmission network
Space launch
Enable power for very low orbit spacecraft
Notes
Extended UAV operations without power beaming already demonstratedSlide45
WPT Modality: Sea/
ground-to-sea/ground
Applications
Ship to shore power beaming, vice versa
Power for sensors in denied areas
Power to/from/between FOBs/COPs with towers or aerostats
Notes
Potential to use beam expansion with existing directed energy assets to reduce power density to “safe” levelsSlide46
BackupSlide47
2008-09-30
SBSP
47
Finding 3, Military operations scenarios:
SBSP systems employing microwave power transmission at frequencies below 10 GHz are most suited for a limited number of bases and installations where the large area required for efficient power reception would be available.
For applications requiring smaller apertures, millimeter wave or laser power transmission may be preferable, though tradeoffs between safety, increased atmospheric attenuation, and received power density must be addressed carefully.
Direct power transmission to individual end users, vehicles or very small, widely scattered nodes does not currently appear practical, primarily because of the large inefficiencies and the possible risks of providing what amounts to a “natural resource”.
Backup alternatives should be considered for installations in the event of failure, compromise, or military action as an SBSP system may present the problem of a single point of failure.
NRL SBSP Study Group Summary
FindingsSlide48
2008-09-30
SBSP
48
Finding 3, SBSP Military Operations Scenarios
Background Chart (1 of 2)
Forward Operating Base Power
Possible, but likely only applicable to fairly large installations.
Bistatic radar illuminator
Possible.
Provide power to a remote location for synthfuel production
Possible, but requires considerable infrastructure, feedstock, and forces that could exploit the products.Power for distributed sensor networkUnlikely. Power densities, inefficiencies of widespread isolated receivers, and possible enemy exploitation of “natural resource” are problematic.
Power to Individual End UsersUnlikely. Similar problems to the above, with the added concerns of extreme precision beam control and possibly unsafe power densities.Slide49
2008-09-30
SBSP
49
Space solar power to non-terrestrial targets
Satellite to satellite power transmission
Possible, but poses significant system design problems, and may not compare favorably to direct power collection.
Space to UAV for dwell extension
Small, moving target challenges wireless power beam control; multi-day solar UAV flights may render this application irrelevant.
Terrestrial Wireless Power Beaming Applications Apart from SBSP
Ship to shore power beaming
Possible, requires refinement of wireless power beaming technologies.
Ground to UAV for dwell extensionSame issues as “Space to UAV”Finding 3, SBSP Military Operations ScenariosBackground Chart (2 of 2)Slide50
2008-09-30
SBSP
50
NRL SBSP Study – Revisit Efficacy of SBSP
Recommendations from “Space-Based Solar Power
As an Opportunity for Strategic Security”,
National Space Security Office Phase 0 Report (Oct 2007)
(Areas of possible NRL contribution)
Recommendation #1
: The U.S. Government should organize effectively to allow for the development of SBSP and conclude analyses to resolve remaining unknowns.
Recommendation #2:
U.S. Government should retire a major portion of the technical risk for business development.
Recommendation #3:
The U.S. Government should create a facilitating policy, regulatory, and legal environment for the development of SBSP.
Recommendation #4:
The U.S. Government should become an early demonstrator/adopter/customer of SBSP and incentivize its development.Slide51
Terrestrial Power Beaming
Sending energy wirelessly may offer utility for military, disaster recovery, or grid-infrastructure deficient areas
Laser and mm-wave allow smaller transmit and receive apertures vs. microwave
Safety and cost are key considerations
Using an aerostat or other airborne platform for the power transmitter or receiver can greatly enhance the range
Successful terrestrial power beaming could pave the way for space solar powerSlide52
Escape Dynamics mm-wave Power Beaming for Space Launch
Building their own
gyrotrons
Demonstrated higher than chemical
Isp
in July 2015Slide53
06 October 2013
A collaboration between Lighthouse, LLC and Eritek, Inc.
Eye-Safe Laser Power Beaming Demo at the University of Maryland
This effort demonstrated the ability to remotely power devices using an (unaided) eye-safe laser beam
Range of demonstration was much shorter than possible
Demonstrated range of 240 meters
Range of up to 2km would have been feasible
This technology offers unique capabilities not found elsewhere in industry:
1000 times smaller area hazard zone for high-power applications
30 times more power than most competing eye-safe systems
FAA compliant (no special permits needed) for nominal eye-safe beams (not true of some competing technologies)
There is a stigma that laser power beaming is terribly dangerous and exotic – we want to change that!
The fact is that this technology is safe and actually costs less than alternative power management schemes for some applicationsSuch as remote controlled vehicles for unattended sensors
SLIDE CONTENT FROM BERT MURRAY, LIGHTHOUSE DEVSlide54
06 October 2013
A collaboration between Lighthouse, LLC and Eritek, Inc.
Components of the Demo
Transmitter:
10 Watts @ 1550nm
Power can be higher
With safety wear, training
125mm aperture
Beam Divergence less than 100urad
Can be focused
Bore-sighted with visible laser
633nm, 5mW50mm beam diameterUsed to assist aimingRifle-scope viewing aid
Assists pointing during daylight conditions
Receiver:Fresnel ConcentratorGaSb
Photovoltaic
0.35V per cell
6 in series
Max 1.5 watts output
Voltage conditioners
Convert voltage, current
Supply 3.3V
Powered Equipment
Bright-white LED
Transistor Radio
Small motor
Raw output can charge single-cell batteries
SLIDE CONTENT FROM BERT MURRAY, LIGHTHOUSE DEVSlide55
Thank You
Paul Jaffe, NRL, paul.jaffe@nrl.navy.mil
Tanwin Chang,
Deep Phase Labs, tanwin.chang@deepphase.com
Bert Murray, Lighthouse Development,
hcm1955@gmail.com