Transcript Sample Presentation Title - Georgia Institute of Technology

A Gigawatt-Level Solar
Power Satellite Using
Intensified Efficient
Conversion Architecture
Brendan Dessanti
Shaan Shah
Narayanan Komerath
Experimental Aerodynamics and
Concepts Group
School of Aerospace Engineering
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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Outline
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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
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
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Space Power Grid Architecture
Deviations from Traditional Approaches
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• 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
Girasol Converter Satellite Conceptual Design
Conceptual Design of a 1-GW Converter Satellite
What it must do?
• Receive large quantities of directed sunlight, convert, and
beam power as millimeter wave
• Maximize efficiency of conversion
• Minimize heat that must be radiated
• Maximize specific power (power beamed /unit mass)
launch costs
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Gas Turbine vs. Broadband PV Conversion
Potential for Order of Magnitude Improvement Using Gas Turbine
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Gas Turbine vs. Broadband PV Conversion
• Broadband PV scales linearly
• Specific Power of High Intensity PV arrays limited by heat
radiation problem
Why?
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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IηCA
Intensified Efficient Conversion Architecture
1. Primary Brayton Cycle Conversion
2. Optional Narrowband PV Conversion
Attempt to achieve 50% efficiency at ground, thus
each girasol collects 2GW directed sunlight
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Given high Brayton Cycle efficiency and high specific mass
of mechanical to electrical converter
not cost effective to use narrowband PV conversion
Girasols
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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 orbit
2. No atmosphere
3. Temperature in space
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Girasol Turbomachinery
Components:
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1)
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300m Collector
Intensified Feed
Heater
Compressor
Turbine and Generator
Radiator
Phase Array Antenna
Thermodynamic Cycle Analysis
Efficiencies Based on Jet Engine Efficiencies
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Girasol Satellite
Mass Budget and Cycle Analysis
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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
Mirasols
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 Conclusions
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By separating solar spectrum, narrow band PV conversion can extract roughly
14% of total solar power as DC
Narrowband conversion of pre-separated spectrum minimizes active thermal
control requirement
Closed Brayton Cycle can achieve over 80% conversion of remaining solar
spectrum to AC electrical power
Given high Brayton Cycle efficiency and high specific mass of mechanical to
electrical converter, not cost effective to use narrowband PV conversion
Superconducting generators needed to achieve high power per unit mass
needed for mechanical to electric power
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
Future Improvements and refinements could lead to >3.4 kW/kg
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A potentially revolutionary impact
If roadblocks encountered with heat rejection systems, could use spectral
separation and narrowband conversion with PV to increase
specific power
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
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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
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?
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Backup
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Backup
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