The Promise and the Challenge of Space Solar Power

1
The Promise and the Challenge of Space Solar
Power

• April 2003
• John C. Mankins
• Chief Technologist, Human Exploration
  Development of Space
• NASA Headquarters
• Washington, DC, USA

2
INTRODUCTION
3
The Official Forecast
4
What Technologies Are We Using?
5
The Issues with Energy
Equity Security
Economy Geology
Environment Climate
Technology
6
A Few Questions About Energy in the 21st Century

• Equity
• What level of inequity in world economics is
  acceptable? What are the consequences and costs
  of poverty in the world?
• Energy and Geology
• When will the production of various fossil fuels
  fail to keep up with increasing demand? Will it
  ever??
• Environment Climate
• What are the long term effects of fossil fuel
  use on the environment and the climate? What are
  the prospective effects of other energy sources
  on the environment and the climate??
• Technology
• What are the technological options for future
  energy sources? What must be done to bring these
  new technologies on line and when will we need
  them??

7
Equity And Population
???
5B6B7B
The current world population is over 6 billion
and increases at a rate of 76,570,430 people
every year. U.S. population has increased 85
percent since 1950, growing from 151 million to
283 million in just fifty years. If present
trends continue, our population will reach 400
million by the year 2050.
1B
8
Environment and ClimateCourses and the
Consequences
But
9
The Impact on Energy ofStabilizing CO2 Levels in
the Atmosphere

• gt 16 TW
• Carbon-Neutral Power Generation Capacity Required
  to Stabilize the atmosphere at 4-times
  pre-industrial CO2 levels

40 TW Carbon-Neutral Power Generation Capacity
Required to Stabilize at 2-times pre-industrial
levels
10
HistorySolar Power Satellites in the 1970s
Invented by Peter Glaser in the late 1960s
11
RECENT WORK
12
Recent DevelopmentsSolar Power Satellites in
the late 1990s
13
Space Solar Power A Complex Network of
Characteristics
Space/Radiation Environment
Transmission Frequency
Marketplace Demand
Delivered Energy Price (/Energy)
Operations Maintenance Cost (/Energy)
Orbital Distance
Beam Steering
Marketplace Flexibility
Installation Cost (/Mass)
Power Level
Power Generation Cost (/Power)
Solar Conversion
Spectrum Management Requirements
Power Management Distribution
End-to-End Efficiency (In/Out)
Hardware Cost (/Mass)
Beam Energy Density Constraints
Thermal Management (Mass/Cost)
Hardware Module Size (Mass/Launch)
SPS Systems Size (Mass/Power)
SPS Systems Specific Masses (Mass/Power)
14
EMERGING SPACE APPLICATIONS
15
Space Solar Power Communications/National
Security Satellite Power Trends
Doubles every 5.5 years!
Spacecraft Power (Watts)
Future National Security Needs SBR on critical
roadmap for gt25kW power needs SBL Increased
power identified as a top enabler NRO gt
100kW SMC/XR (Don Gasner) gt100-200kW
Year
Courtesy of Boeing
16
Space Solar Power Exploration and Commercial
Development
25-50 kW Hybrid Propellant Module
10 kW to 1 MW Lunar Resources
5-10 kW DS-1 Class SEP
1 MW Space Business Park
100 kW International Space Station
5-10 MW Solar Clipper
17
21st Century Space Mission Challenges and SSP
Technology Areas
SPACE SOLAR POWER Technology Roadmap Areas
Solar Power Gen.
Wireless Power Trans
Poer Mgt Dist
Assy, Maint Ops
Platform Systems
ETO Trans Infr
In Space Trans Infr
Structure, Matls Controls
Ground Segment Systems
Environ Safety Factors
Systems Integra- tion
Thermal Mgt Materials

• Human Health and Support

?
Human- Machine Systems
Information Automation
?
Instruments Laboratories
?
?
21 st CENTURY SPACE MISSION Technology
Opportunities / Challenges
Space Transportation
?
Space Power
Space Platforms
?
Surface Systems
?
Systems Studies
18
STRATEGIC RT
19
Space Solar PowerStrategic Research Technology
Roadmap
SPG, PMAD
Technology Development (TRL 4-5)
Down-select Tech. for MSC-1 Candidates
WPT, TMM
Down-select Tech. for MSC-1.5 Candidates
SMC, RAMS
Down-select Tech. for MSC-3 Candidates
Continuing Innovation
Continuing Innovations
Technology Flight Demonstrations -- TFDs (TRL 6-7)
SSP MSC 1.a 100 kW Class In-Space TFD
SSP MSC 1.b lt5 kW Class Surface Demo
MSC 3.5, 4 (2020)
SSP MSC 2 1 MW Class TFD
SSP MSC 3 10 MW Class TFD
Schedule of Milestones
06-08 100KW Space-to-Ground Space-to-Space
SPG/WPT Demo 2008 gt400W/kg Solar Power
Generation (Array Level in the Lab 50 kW Solar
Electric Propulsion/Generation Flight Test
High-efficiency WPT (gt100kW level) in a Test
Bed 2008 Down-select technologies for 1 MW class
TFD 11-13 1 MW Class Space to Space SPG/WPT
Demo 12-13 gt600W/kg Solar Power Generation
(Array Level) 2013 Down-select technologies for
initial 10MW class TFD 2017 gt1000W/kg Solar Power
Generation (Array Level) 16-18 10 MW CLASS
INTEGRATED SSP SYSTEM FLIGHT DEMO
99-00 Complete initial Space Solar Power
Exploratory Research and Technology (SERT)
Program 2001 Identify/refine top 2-3 systems
concepts/architectures for each MSC Demonstration
opportunity refine interim applications 2002/3 Es
tablish/Integrate SSP test beds at participating
organizations 2003 Down-select technologies for
initial 100kW class TFD 2004/5 gt200 W/kg Solar
Power Generation (Array Level) in a Test
Bed High-efficiency WPT (gt10kW level) in a Test
Bed 2005 50 M class structures controls flight
experiments
Strategic Research and Technology Decision Point
Major Technology Development Milestone
Major Technology Flight Demonstration
LEGEND
20
Space Solar Power BackgroundResults of the US
NRC SSP Review (1 of 2)

• During 2000-2001, the Aeronautics and Space
  Engineering Board (ASEB) of the NRC assessed
  the technology investment strategy of the
  Space Solar Power Program to determine its
  technical soundness and contributed to the
  roadmap by
• Critiquing the overall technology investment
  strategy in terms of the plans likely
  effectiveness in meeting the programs technical
  and economic objectives
• Identifying areas of highest technology
  investment necessary to create a competitive
  space-based electric power system
• Identifying opportunities for increased synergy
  with other research and technology efforts
• Providing an independent assessment of the
  adequacy of available resources for achieving the
  plans technology milestones, and
• Recommending changes in the technology investment
  strategy
• Findings?
• SERT program has provided a credible plan for
  making progress toward the goal of providing
  space solar power for commercially competitive
  terrestrial electric power despite rather large
  technical and economic challenges
• Current SSP technology is aimed at technical
  areas with important commercial, civil, and
  military application
• Dedicated NASA team has defined a potentially
  valuable future program
• Current SSP program is operating on minimal
  budget and significantly higher funding and
  program stability will be necessary to attain
  aggressive goals of program
• Funding plans during the first five years
  (leading to first flight test demonstration) are
  reasonable

21
Space Solar Power BackgroundResults of the US
NRC SSP Review (2 of 2)

• Findings? (continued)
• Concern in committee that investment strategy is
  based on modeling efforts and individual mass,
  cost, and performance goals that may guide
  management toward poor investment decisions
• Significant technical breakthroughs necessary to
  achieve final goal of cost-competitive
  terrestrial baseload power
• Ultimate success of terrestrial power
  application critically depends on dramatic
  reductions in cost of transportation from Earth
  to GEO
• Leveraging of technological advances made by
  organizations external to NASA must be done.
• The SSP RT panel also made a series of
  recommenda- tions for improving the management
  and focus of future program efforts, including
• Need to prepare a formal technology plan
• Need for improvements in systems and cost
  modeling, including increased use of expert
  critique and review
• Continued use of technology flight demonstrations
• Early emphasis on environmental, health and
  safety issues
• Key technologies
• Solar Power Generation
• Wireless Power Transmission
• Space Power Management and Distribution
• Assembly, Maintenance and Serving
• In-Space Transportation

22
FUTURE DIRECTIONS
23
But

• Despite our best efforts, we are NOT there yet
• We have a better understanding of the issues and
  the challenges
• We have an extensive database of options and
  alternatives
• We have an strong, peer-reviewed Strategic RT
  road map
• We have made progress on many key technologies
• Except the key area of very low cost access to
  space
• We have NOT yet gotten to clear economic
  viability
• Dont buy stock in an SPS Start-Up Company just
  yet
• What will a viable concept be like? --
  Concept-X

24
A Visionary Idea Concept-XWhat Might It Be
Like?

• Most probably some version of the ISC/Sandwich
  approach
• Use of solar flux redirecting optics (e.g., large
  thin-film mirrors)
• In the RF Case
• Phased array must be very low mass per square
  meter
• All thermal should be local
• All PMAD should be localwith no converters
• Diameter of transmitter should be large, but send
  beam to multiple ground sites
• Reducing size of ground station
• Find some way to avoid using a full 101 Gaussian
  distribution
• Solar-pumped laser based concepts may also
  prove promising, but are not yet sufficiently
  mature to allow the definition of a Concept-Y

25
A Visionary Idea Concept-XWhat Might It Be
Like?

• Ambitious Goals must be achieved
• Sandwich or ISC -like Optics (lt 10 of total
  system mass)
• PV Energy Conversion
• Efficiency gt 50
• RF transmitter
• 5 km diameter at 2.45 GHz (or another
  frequencychoice is not critical)
• Efficiency gt 80
• RF Power Output per square-meter 500 W
• Total Power Output gt10 GW
• Ground Rectenna
• 10-20 stations at lt 2 km diameter each (and _at_lt
  500 MW output)
• Cost per Receiving Station lt 2/W

26
A Visionary Idea Concept-XWhat Should We Seek
to Achieve?
4 kg/m2
5 kg/m2
6 kg/m2
3 kg/m2
10
GOALS 2-5/Watt Installed 50 PV Conversion
Eff. 500W/m2 RF Output
8
2 kg/m2
Total Cost of Power (/kWh)
6
4
1 kg/m2
2
500
1000
1500
2000
2500
3000
Total Specific Cost to Installation (,kg)
Including cost of Money, H/W, Launch, etc.
27
SSP Research and TechnologySome Key Directions

• Continuing advances in / applications of
  intelligent systems and robotics -- pursuing the
  goals of self-assembly, large and self-sufficient
  communities of systems, etc.
• Including modular/distributed avionics -- e.g.,
  wireless network avionics (massively redundant)
• Higher strength-to-weight materials and
  structural concepts applicable in the space
  environment
• Both thin film / deployable and rigid structure /
  assembled
• Higher temperature solid state devices of various
  types, including PV cells, FET amplifiers, phase
  shifters, etc.
• MEMS / µ-device thermal management, etc.
• Various Options, including
• Laser wireless power transmission (electric and
  solar-pumped)
• High-voltage and/or HTc power management and
  distribution
• Others
• PLUS
• Very low cost space transportation

28
BUT, WHAT ABOUT??
29
Terrestrial Solar Power?

• There must be terrestrial solar
• For baseload power, however, the challenges
  facing ground solar power are in many
  ways harder than those for space-based
  systems
• The total solar energy available at a
  typical site on the Earths surface
  is much less than in space
• Moreover, the energy available varies
  widely seasonally and daily
• Baseload using ground solar requires
  substantial over-capacity and costly large-scale
  energy storage or global distribution networks

Solar Energy Available at a Typical Location in
the U.K.
BASIC TRADE WPT Space Transport Versus Ground
Solar Energy Storage
30
Low Cost Space Launch?

• Diverse concepts promise Earth-to-orbit (ETO)
  transport at 200/kg or less
• National Policy is already pursuing this goal for
  civilian, military and commercial reasons
• Moreover, lower the cost of space transportation
  depends on new technology, new systems and new
  markets
• Additional areas needing technology development?
• In space transportation
• SSP helps
• Low cost space hardware manufacturing

Challenging Technology and a Classic
Chicken-and-the Egg Problem
31
the Safety of Power Beaming?

• There is a continuing concern regarding the
  health safety issues associated electromagnetic
  radiation
• These must be treated seriously
• At microwave frequencies, the only known physical
  effect on living tissue is thermal heating
• The US Standard Limit for microwave exposure
  is 100 W/m2, for 6 minutes
• For SSP, power densities would vary greatly
  across an incoming beam a 2.45 GHz, 5 GW beam
  would have densities of
• Beam Center 230 W/m2
• Rectenna edge 10 W/m2
• Fence edge 1 W/m2
• Studies conducted in the late 1970s found that
  for exposure levels up to 500 W/m2 for 30 min.,
  there was no discernable effect on honey bee test
  subjects (3000 subjects, over 2 trials)
• Further research in 2001-2002 indicates no effect
  on plants outside the fence
• Further research required to ensure that any
  possible health factors associated to SSP/WPT
  (people and animals) were within acceptable limits

32
SUMMARY
33
Summary

• Space solar power appears to be a
  technically-viable option capable of delivering
  large (gt100s GW) essentially carbon-free
  electrical power globally
• No issues with any areas of fundamental physics
• Significant advances have been made since the
  1970s
• Concepts
• Technology
• Infrastructure
• Technology developments needed in a number of
  areas
• Materials, structures, devices, autonomy,
  robotics, others
• Strategic RT road maps for SSP have been
  developed and reviewed by the National Research
  Council
• SSP technology aimed at technical areas with
  important commercial, civil, and military
  application
• a potentially valuable future program
• significantly higher funding and program
  stability necessary
• Funding plans during the first five years
  (leading to first flight test demonstration) are
  reasonable

34
Back Up Charts
35
Recent SSP Concepts

• A variety of space solar power satellite (SSPS)
  concepts have been examined during the past
  several years
• One goal in these studies as been to balance the
  need for a robust solution to the longer-term
  challenge of power from space for terrestrial
  markets with the nearer-term need to demonstrate
  SSPS

Integrated Symmetrical Concentrator
SunTower
Abacus-Reflector
36
5.8 GHz GEO WIRELESS POWER TRANSMISSION SYSTEM
DESIGN EXAMPLE
BEAM SAFETY SUBSYSTEM
Source PMAD
Polarization Mismatch
DC Power Distribution
Dt 500m Dr 7500 m ? 0.0517 m R 36,000
km ?? 1.583 ?b 0.9182 Edge Taper -10.02
dB Peak/Ave P.D. 2.35
0.999 /- 2 deg
Waste Heat Removal
Rectenna Aperture Scan Loss
0.999 -0.0 dB max
DC-RF Power Conversion Efficiency
Rectenna Element Failures
0.90 -0.458 dB
0.99 -1
EMC Diplexing Filters
Beam Coupling Efficiency
Rectenna Aperture Efficiency
0.794 -1 dB
0.95
Subarray Aperture Efficiency
0.918
EMC Filtering
0.95 -0.706 dB
0.891 -0.5 dB
Waste Heat Removal
Subarray Failures
Rectenna RF-DC Power Conversion Efficiency
0.96 2 Random Failures
0.933
Amplitude Errors Taper Quantization
Propagation Impairments
0.86
0.986 10-Step /- 1 dB
DC Power Collection
Phase Errors
Clear Air -0.05 dB 0.9885 4mm/hr Rain _at_ 0.01
dB/km X 2.5 km -0.025 dB 0.994
0. 97 10 deg rms
Load PMAD
Electronic Beam Steering Scan Loss
0..977 -0.1 dB max
Transmitter Monitor Control System
Rectenna Monitor Control System
0.395 Overall WPT Efficiency
981016rmd
37
Wireless Power TransmissionEffects on Fauna
Honey Bee Testing

• In the late 1970s, research was performed to
  determine what, if any, the effects of microwave
  wireless power transmission might be on honey
  bees
• Exposure
• 2.45 GHz, CW
• Varying power levels
• 5 colonies of bees were involved
• 10 Bees / treatment
• 12 treatments
• 5 days
• Total 3000 Bees
• Entire Study Repeated Twice
• No statistically significant effects were observed

TREATMENT (mW/cm2)
MEAN NUMBER OF BEES PER 10 BE GROUP
Returned to Apiary
Return to Wrong Hive in Apiary
Died After Treatment
Not Accounted For
8.5
0.4
0.3
1.0
25
8.7
0.4
0.3
1.0
SHAM
8.3
0.5
0.5
0.9
50
8.6
0.6
0.3
0.9
SHAM
8.5
0.4
0.5
1.0
Laboratory Controls
38
What are the Choices?A Diverse of Mix of
Scenarios/Issues/Opportunities
Adv. Fission
Fusion
Fission
Plus new technologies to make existing energy use
per unit GDP more efficient this factor is
already folded into various models.
Nuclear Energy
Hydro- Electric
Geo- Thermal
Fossil Fuels
Solar Energy
Wind
Coal
Biomass
Ground Solar
Natural Gas
Space Solar
Oil
But
39
What Are the Choices?Some Limits and Issues
Adv. Fission ?
Fusion ???
Not All Choices are Equivalent
Fission ?
Environment Technology Issues
Nuclear Energy
Hydro- Electric
Geo- Thermal
Fossil Fuels Carbon Sequestration
Solar Energy
Wind ??
Coal
Environment Climate Issues
Biomass ???
Ground SOLAR
Natural Gas
Space Solar ??
Oil
Technology Issues
Small Players
40
Equity And Population
41
Potential IssuesPermanently Low Fossil Fuel
Prices?

• There is no consensus view concerning the future
  of fossil fuels
• However, an increasing number of geologists are
  predicting that during the next 10-20 years,
  global oil production will fall behind global oil
  demand
• Similar forecasts have been made for natural gas
• The likely result, given continuing increases in
  demand, could be sharp increases in the price of
  fossil fuels

Reference Scientific American (March 1998 ) by
Colin J. Campbell and Jean H. Laherrère
PREDICTED PEAK IN WORLD OIL PRODUCTION SOURCE

PEAK DATE F. Bernabe, ENI SpA
(1998) 2000-2005 C. Campbell and J. Laherrére,
Petroconsultants (1998) 2000-2010 J. MacKenzie,
World Resources Institute (1996) 2007-2014 OECD's
International Energy Agency (1998) 2010-2020 J.
Edwards, University of Colorado, Boulder
(1997) 2020 DoE's Energy Information
Administration (1998) gt2020 W. Fisher U of
Texas, Austin (1998) 2030-2040
How Much Is EnergyResearch DevelopmentWorth
As Insurance?
42
NSF-NASA Joint Workshop

• In April 2000, during the SERT Program, NASA and
  the National Science Foundation (NSF)
  co-sponsored a workshop on revolutionary robotics
  and SSP
• Goal Identify major cost uncertainties and
  possibilities for cost reduction through
  high-risk RD
• The workshop explored the potential for future
  NSF-supported work related to
• Rational risk-management planning of RD
• Computational intelligence for robotics
• Microwave technology
• Power grid management and devices
• Results can be found at
• robotics.use.edu/workshops/ssp2000/index.html

43
Large-Scale Renewable Energy ProjectsThe 3
Gorges Dam Example

• Project Three Gorges Dam
• Location Yangtze River, China
• Sponsors
• China International Investors
• Concept
• Ultra-large hydro-power dam project to provide
  power for megacity Chongquing (15M people)
• Twenty-six 700MW generators in a single dam
• Construction 1995 to 2014 5 _at_ 40,000 workers
• Studies 1978 to 1994
• 607ft high, 7054ft long, 44-times larger than
  Great Pyramid
• Impact
• 418 mi2 reservoir
• 104 towns 100 archaeological sites to be
  flooded, 175 species threatened 1.2M people
  displaced (with 51 loss in productivity in
  farming (mountain vs. near river)
• Power Output 18,000 MW
• Note Equals 50,000,000 tons/year of coal
• Cost 70,000 M (approx. 4 per watt)