1. Millimeter Wave Space Power Grid Architecture 2011
Nicholas Picon
Brendan Dessanti
Shaan Shah
Richard Zappulla
Narayanan Komerath
Experimental Aerodynamics and Concepts Group
School of Aerospace Engineering

2. Conference Papers from Our Team
B. Dessanti, R. Zappulla, N. Picon, N. Komerath, “Design of a Millimeter Waveguide Satellite for Space Power Grid”
N. Komerath, B. Dessanti, S. Shah, “A Gigawatt-Level Solar Power Satellite Using Intensified Efficient Conversion Architecture”
N. Komerath, B. Dessanti, S. Shah, R. Zappulla, N. Picon, “Millimeter Wave Space Power Grid Architecture 2011”

3. Outline Introduction Space Solar Power Background
The Space Power Grid Architecture
Aerostats
Proposed US-India Demonstration as a First Step
System Assumptions and Parameter Choices
Technical and Economic Results Analysis
Conclusions

4. Introduction The Dream of Space-Based Solar Power (SSP):
Deliver cheap, limitless, clean, quiet electric power to the world
Factors Driving Cost and Difficulty of SSP
Magnitude of the Problem – Cost to First Power
Specific Power – The power that must be generated per unit mass placed in orbit
Relationship between orbit height, beam frequency, and receiver size
Launch Costs – Cost to place mass in orbit

5. Space Solar Power Background
Space-Based Solar Power is an old dream
Arthur C. Clarke – 1945 – benefits of GEO
Peter Glaser – 1968 – Patent for GEO based SSP arch.
NASA/DOE Study – Late 1970s
NASA “Fresh Look” Study – 1997
NASA SERT – 1999
Proposed JAXA LEO Demo
Etc….
Recurring Conclusion:
No Technical Show Stoppers
Significant Improvements Needed
for Economic Viability
New Scientist Magazine SSP Illustration

6. Space Solar Power Background: Traditional Approaches
Geosynchronous Earth Orbit (36000km altitude)
Pros: No dynamic beam pointing necessary
Cons: Distance drives spacecraft size, immense launch costs, no evolutionary approach possible, requires large initial investment
Microwave Beaming
Pros: Atmospheric transmission efficiency, low technology risk
Cons: Transmitter/Receiver Size
Photovoltaic Panels for Collection
Pros: low technology risk
Cons: Specific Power, Linear Scaling

7. SSP Architecture Analysis: Viability Parameter
How much improvement do we need?
Prospect of Breakeven: k ~1
P: price of space-generated power in (e.g. $0.2/KWHe)
h: efficiency of converted power transmission to the ground. (e.g. 50%)
s: (KWe/Kg): Technology of conversion, giving mass needed per kilowatt of electric power generated in space. (e.g., 1 KWe/kg)
c: Launch cost in $ per kg to Low Earth Orbit. (e.g., $2500/kg)
Technical barriers: h, s
Parameter
Present
Needed
P, US$/ KWHe
0.2 h
?? (0.1?)
0.5
c, $/kg to LEO
$2K - $15K
<$2.5K
s, Kwe/Kg in space
<0.1
>1
Ground receiver diameter
~ 100km
<1km

8. Space Power Grid Architecture
The Bottom Line: According to our analysis, a roughly 100x improvement in viability is needed for SSP to become a reality
Is this possible?
“Flash Drive” Argument (mass production collapses cost)
Our approach:
Trade the launch cost risk of GEO-based systems for technology risks associated with SPG

9. Space Power Grid Architecture Deviations from Traditional Approaches
Use Primary Brayton Cycle Turbomachine Conversion of highly concentrated sunlight (InCA: Intensified Conversion)
Specific Power, s
Separate the collection of sunlight in high orbit from conversion in low orbit
Antenna Diameter
Millimeter Wave Beaming at 220GHz
Use Tethered Aerostats
Efficiency Through Atmosphere
Power Exchange with terrestrial renewable energy
Cost to First Power Barrier

10. Space Power Grid Architecture
Relationship between beam distance, frequency, and receiver diameter:

11. Beam Distance and Frequency Comparison
Assume equal receiver size (100m), equal antenna specific mass (0.05 kg/m^2), assume equal beam capture (84%):
Parameter
GEO,
5.8 GHz
2000km alt.,
220 GHz
Reduction
Beam Distance, R
35,786 km
2,000 km
17.9x
Wavelength, λ
51.7 mm
1.36 mm
37.9x
Transmitter Diameter
45.2 km
66.5 m
679x
Antenna Area
1.60e9 m^2
3478 m^2
460633x
Antenna Mass
8.01e7 kg
174 kg

12. Space Power Grid Architecture
Phase I
Constellation of LEO/MEO Waveguide Relay Sats
Establish Space as a Dynamic Power Grid
Phase II
1 GW Converter Satellites – “Girasols”
Gas Turbine Conversion at LEO/MEO
Phase III
High Altitude Ultra-light Solar
Reflector Satellites – “Mirasols”
Direct unconverted sunlight to LEO/MEO
for conversion

13. Aerostat System
Millimeter Wave Beaming Poor Through Rain and Fog

14. Aerostat System
Possible Solution: Use Tethered Aerostats

15. Proposed US-India Demonstration
A demonstration model for terrestrial power exchange between the US and India was designed to illustrate the benefit and feasibility of the Space Power Grid concept
The two countries were chosen based on the US and India’s high energy production and usage and because of the new Indian-US collaboration as prompted by President Obama and Prime Minister Singh
Model highlights the possibility of selling energy to the partner country at non-peak usage times

16. US-India Demonstration

17. US-India Demonstration
6 Satellite – 2 Facility System
Designed to provide 24 hr. access beaming capability between Mumbai, India and Las Cruces, NM
Satellites at fixed angles in relation to one another, simplifying the problem of satellite to satellite beaming

18. System Assumptions and Parameter Choices
Key Assumption: Launch Cost
Current Launch Cost Rate: >$10,000/kg
Other Architectures argue for $ /kg
Our calculations assume reasonable reductions

19. Systems Architecture Economic Analysis
Breakeven Point: when NPV=0 at specified ROI (6%) from Phase I startup
Baseline SPG System (March 2011) vs. Current Architecture
Using system assumptions in previous slide
5 year dev. period before 1st Satellite Launch
Attempt to reach 4TW of power capacity
Attempt to demonstrate Phase 1 breakeven
within 17 years
Constraint to demonstrate total architecture breakeven within 50 years relaxed
In March 2011, Phase 2 assumed to start after Phase 1, in this paper we investigate beginning Year 12
Ramp rate constrained by infrastructure building limitations

20. Technical and Economic Results Analysis: Breakeven vs. Selling Price
Baseline: SPG Architecture presented at March 2011 IEEE Aero Conf
IηCA: Current architecture including Iηca Concept
For Given Price of Power, Significant Improvement in Viability

21. Technical and Economic Results Analysis: NPV Trough
Phase 1
Full Architecture
Amount of Investment Required Reduced Significantly from Baseline

22. Architecture Analysis Summary and Conclusions
Technical Risk and Uncertainties in Mass and Efficiency in developing mmwave conversion and beaming are main risks to SSP development. Phase 1 SPG addresses these before large 1 GW converters launched.
Phase I Waveguide Satellite and Phase II Girasol Mass Estimates Come in Under Previous Estimates used in SPG architecture reduced uncertainty.
Overlapping Development of Phase I and Phase 2 is considered to reduce deployment time of large scale SSP
Updated architecture can achieve breakeven by Year 31, with NPV trough <$3T, at $0.11/kWh
At given ramp rate, SSP can reach > 5.6 TW by Year 50
Assumes value of unity for k viability parameter

23. Questions?

24. Backup

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