A Gigawatt-Level Solar Power Satellite Using Intensified Efficient
Conversion Architecture
A Gigawatt-Level Solar Power Satellite Using Intensified Efficient
Conversion ArchitectureBrendan Dessanti
Shaan ShahNarayanan Komerath
Experimental Aerodynamics and Concepts Group
School of Aerospace Engineering
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Conference Papers from Our Team 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”
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OutlineOutline
• The Space Power Grid Architecture• Girasol Converter Satellite Conceptual Design• Gas Turbine Comparison with Broadband PV• Girasol Satellite Mass Summary and Design Conclusions• Mirasol Reflector Satellites • Girasol Effect on Architecture Analysis• Conclusions
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Space Power Grid ArchitectureSpace 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/MEOfor conversion
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Space Power Grid ArchitectureDeviations from Traditional Approaches
Space Power Grid ArchitectureDeviations 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 Antenna Diameter
• Use Tethered Aerostats Efficiency Through Atmosphere
• Power Exchange with terrestrial renewable energy Cost to First Power Barrier
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Girasol Converter Satellite Conceptual DesignGirasol Converter Satellite Conceptual Design
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Gas Turbine vs. Broadband PV ConversionGas Turbine vs. Broadband PV Conversion
Potential for Order of Magnitude Improvement Using Gas Turbine
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Gas Turbine vs. Broadband PV ConversionGas Turbine vs. Broadband PV Conversion
• Broadband PV scales linearly• Specific Power of High Intensity PV arrays limited by heat
radiation problemWhy? Sun Intensity = Heat That Must Be Radiated = ATCS Mass
Fundamental Broadband PV issue:Broadband energy must penetrate a solid surface layer before photons can drive electrons through the semiconductor array
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IηCAIntensified Efficient Conversion Architecture
IηCAIntensified Efficient Conversion Architecture
1. Primary Brayton Cycle Conversion2. Optional Narrowband PV Conversion
Attempt to achieve 50% efficiency at ground, thus each girasol collects 2GW directed sunlight
Given high Brayton Cycle efficiency and high specific mass of mechanical to electrical converter not cost effective to use narrowband PV conversion
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GirasolsGirasols
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Closed Helium Brayton Cycle Closed Helium Brayton Cycle
Helium • High and Constant Specific Heat• High Thermal Conductivity• Low Mass Flow Rate Required
Closed Helium Brayton Cycle Operating In Space• Starting Point: Intercooled Helium Brayton Cycle Liquid
Fluoride Nuclear Power Plant Cycle (DOE - ORNL)• Eight 125MW Sections – Dimensions similar to jet engines• Alloys exist that can meet 3650K Operating Temperature• Advantages over terrestrial jet engines:
1. Predictability of orbit2. No atmosphere3. Temperature in space
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Girasol TurbomachineryGirasol Turbomachinery
1) 300m Collector2) Intensified Feed3) Heater4) Compressor5) Turbine and Generator6) Radiator7) Phase Array Antenna
Components:
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Thermodynamic Cycle AnalysisThermodynamic Cycle Analysis
Efficiencies Based on Jet Engine Efficiencies
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Girasol Satellite Mass Budget and Cycle Analysis
Girasol Satellite Mass Budget and Cycle Analysis
Element Mass, kg Percent
Collector 3,534 0.92
Cooling Sys. 168,000 44.0
Brayton Cycle 20,000 3.91
AC Generator 50,000 9.79
Cryogenics 20,000 3.91
220 GHz Amp. 17,000 3.00
Antennae 20,000 3.53
Propulsion 170,300 30.0
Misc. 30,930 5.45
Structure 56,700 10.0
Total Girasol 567,000
Total Mirasol 53,000
Total Mass 620,000
3650K He Gas Turbine Cycle Analysis
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MirasolsMirasols
High Altitude (GEO or Near GEO), Ultralight Reflector Satellites direct sunlight to girasols• Utilize technology similar to solar sails• Optical linking between mirasols/girasols• Sunlight wavelengths on order of μm
very little beam divergence, even over large distances
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Girasol Satellite Design ConclusionsGirasol Satellite Design Conclusions
1. By separating solar spectrum, narrow band PV conversion can extract roughly 14% of total solar power as DC
2. Narrowband conversion of pre-separated spectrum minimizes active thermal control requirement
3. Closed Brayton Cycle can achieve over 80% conversion of remaining solar spectrum to AC electrical power
4. Given high Brayton Cycle efficiency and high specific mass of mechanical to electrical converter, not cost effective to use narrowband PV conversion
5. Superconducting generators needed to achieve high power per unit mass needed for mechanical to electric power
6. IηCA Architecture with Brayton Cycle converter and superconducting AC generator offers specific power >1.6 kW/kg vs. <0.2 kW/kg for PV architectures
7. Future Improvements and refinements could lead to >3.4 kW/kg– A potentially revolutionary impact
8. If roadblocks encountered with heat rejection systems, could use spectral separation and narrowband conversion with PV to increase specific power
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Technical and Economic Results Analysis:Breakeven vs. Selling Price
Technical and Economic Results Analysis:Breakeven vs. Selling Price
Baseline: SPG Architecture presented at March 2011 IEEE Aero ConfIηCA: Current architecture including Iηca Concept
For Given Price of Power, Significant Improvement in Viability
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Technical and Economic Results Analysis:Girasol Effect on NPV Trough
Technical and Economic Results Analysis:Girasol Effect on NPV Trough
Amount of Investment Required Reduced Significantly from Baseline
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Conclusions:Girasol Effect on Architecture Summary
Conclusions:Girasol Effect on Architecture Summary
1. Girasol Brayton Cycle IηCA offers far better efficiency and specific power, and shorter technology path, than previously considered direct conversion options
2. Girasol Brayton Cycle IηCA greatly improves SSP viablity
3. IηCA can achieve breakeven by Year 31, with NPV trough <$3T, at $0.11/kWh
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Questions?Questions?
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