Transcript Space Based Solar Power - SEI

Space Engineering Research Center
Texas Engineering Experiment Station, Texas A&M University
Space Engineering Institute (SEI)
Space Based Solar Power
By: Bryan Babbitt, Nate Broughton, Will Dixon,
Stephanie Hasskarl, Travis LaCour, Veronica
Medrano, Joseph Noska, and Mindy Watts
NASA Mentor: Dr. G. D. Arndt
TAMU Mentor: Dr. Frank Little
Project Goal
• Develop a design for a sandwich solar power
satellite module with retrodirective wireless
power transmission system for inclusion in
Japanese LEO to earth solar power satellite
demonstration
• Demonstrate software-controlled
retrodirective wireless power transmission
system
Module System
Sandwich Design
Photovoltaic
Cells
•Energy Storage &
Power Conversion
•Retrodirective
Control logic
•Thermal
Management
Antenna Array
Fall 2009 Goals
• Perform case studies for the preliminary
design concept with software tools such as
Satellite Tool Kit and Thermal Desktop
• Determine hardware components for:
– Solar energy collection
– Power system
– Transmission system
– Antenna
STK / Photovoltaic Cells
• Chose 35° angle of inclination circular orbit, based on orbits
of other Japanese satellites of similar size.
• Chose a single crystal Si photovoltaic cell that has an efficiency
of 17%
• We modeled the top surface of our satellite ( 1 m^2) at this
orbit and found:
– Found that the average energy acquired for every month is 126X10^6
Joules — ~3X10^6 Joules per test transmission
• Determined experiment dates and times for beaming to
College Station
– Satellite passes within 45° of normal
– Maximum transmission length of 170 seconds
– Eclipse requirement limits transmission times, but is still feasible.
STK Image of Reception Cones
Power Transmission and Antenna
• Power Transmission
– Determined a 40 km reception area required to achieve a beam coupling
efficiency of 90%
– Estimated a transmitting power of 2kW necessary for minimum ground
pattern detection signal of 0.1nW
– Identified hardware components for transmitter subsytem
• Microstrip Patch Antenna
– Maximum 450 element phased array
– Capable of achieving 2kW transmitting power
– Required area of elements is small enough to fit in the allowable area of
3/4 m^2 without the possibility of inducing side lobes
– Polarization and power handling capability meets SPS requirements
– Inexpensive and uncomplicated to manufacture
Transmitting Antenna
•Corporate Feeding
Employs uniform amplification and phase shift to a 3x3 element subarray
•5880 Duroid Substrate and copper rectangular patches
Satellite Bus and Electronics
28V Bus
Terma Array
Power
Regulation
Module
Silicon Solar
Array
Terma
Battery C/D
Regulation
Module
Saft
MPS176065
Li-ion Battery
Power
Transmission
System (Solid
State
Amplifiers)
IRF E-Series
DC-DC
Converter
Misc.
Components of
Retro Directive
Control and
Housekeeping
•The Saft MPS battery has a nominal energy of 480 Wh and an end of charge voltage of 32.8 V
•DC-DC Converter, Regulation modules and battery have an efficiency of over 90%
•Less than 6 Kg. for DC-DC Converter, Regulation modules and battery
Thermal Management
• Goal is to ensure that equipment is kept within designated
temperature ranges (-20°C to 60°)
• Hot Case: Transmitting produces about 3 kW of heat
– Plan to transmit during eclipse
– Use loop heat pipes to transfer heat to radiator on bottom of satellite
– Use thermal storage with phase change material
• Cold Case: Shaded by earth and not transmitting
– Use thermal energy stored from transmission time to heat electronics
– Use resistance heaters if additional heat is needed
Thermal Desktop Image
Transient Temperature Response
60
Temperature (°C)
50
Heating of electronics
during transmission with
assumed mass of
20 kg and assumed
radiator size of 0.25 m2.
40
30
20
10
0
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
Time (min)
50
45
Cooling of electronics
after transmission, with
assumed mass of 20 kg
and assumed radiator
size of 0.25m2.
Temperature (°C)
40
35
30
25
20
15
10
5
0
0.00
20.00
40.00
60.00
Time (min)
80.00
100.00
Retrodirective System
• Hardware Retrodirective Control Method
– Researched control technique that uses a 2nd harmonic transceiver to
double and conjugate received pilot beam
– Requires that a receiving antenna be nested within the transmitting
antenna array
– Requires a pilot signal of 2.9 GHz
• Software Retrodirective Control Method
– Use logic to establish conjugate phase of received pilot signal
– Use logic to implement phase conjugation and redirect transmit beam
in the direction of the received pilot signal.
– Preliminary design and required components have been identified
– Method requires same antenna configuration as hardware method
– Frequencies of pilot signal less limited
Retrodirective System
Summary
• Determined solar energy data for a 35° inclination orbit
• Determined power level of 2 kW required for transmitting
detectable signal
• Plan to transmit during eclipse to meet thermal
requirements
• Selected hardware components that meet power
requirements
• Developed design of electronics hardware
• Developed preliminary design of satellite, but final design is
to be determined with further analysis
• Gained knowledge of Thermal Desktop and can model
accurately thermal behavior of satellite when it is updated.
Plan for Spring 2010
• Integrate systems into a unified design
• Conduct trade studies for different system
configurations.
• Maximize photovoltaic and antenna area
while allowing sufficient space for radiators.
• Perform test demonstration of retrodirective
system