trio-cinema 1 ucb, 2/08/2010 solar array kevin jenkins mechanical engineering space sciences...
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TRIO-CINEMA 1 UCB, 2/08/2010
Solar ArrayKevin Jenkins
Mechanical Engineering
Space Sciences Laboratory
University of California, Berkeley
TRIO-CINEMA 2 UCB, 2/08/2010
Solar Cell Agenda
AGENDAOverview
Requirements
Design
Test Results
Development Plan
Issues
TRIO-CINEMA 3 UCB, 2/08/2010
Overview
Panels made from TASC cells will be placed on the outside of the satellite, as shown
TRIO-CINEMA 4 UCB, 2/08/2010
Requirements
Level 3 Solar Arrays
SAR-01 Number of Panels1U panels on +X, -X, +Z, -Z faces. 3x1U panels on +Y and -Y faces
SAR-02 Panel SizeEach Panel covers a ~8x8cm area with ATJ cells with >80% packing factor
SAR-03 Cells Cells shall be 27% efficient or better (prior to any losses)SAR-04 Strings Array strings shall be 2-6 (TBR) cells in length
SAR-05 Blocking
Blocking diodes and/or FETs shall be sued to prevent back-biasing shadowed cells. Blocking may be done on a per string or per panel basis - TBR
SAR-06 Cover Glass
If the cells come without cover glass, some additional radiation shielding will be needed to get the cells to last at least 1 year with no more than 10% radiation losses.
SAR-07 Backwiring
Cells shall be wired to minimize the generated magnetic torque by limiting the area of the current loop and inverting string geometry so strings cancel each-other. An illuminated panel shall generate no more than 1E-3Am2
SAR-08 Mass Panels shall weigh ~37g each
TRIO-CINEMA 5 UCB, 2/08/2010
Full PCB wiring view:
•Holds 24 cells
•2 cells per string
•1 Blocking diode per string of 2 cells
•Wired to minimize magnetic field generated:
•Current flows in small loops•Flows in different directions on different layers
Design
TRIO-CINEMA 6 UCB, 2/08/2010
Design
•Cells will be arranged as shown•Each solar cell will have a temperature sensor on it to ensure predictable performance
•Tabs arranged as shown to accommodate screw holes•They will be placed differently on different panels
•This one is for the 3x1U side
TRIO-CINEMA 7 UCB, 2/08/2010
Design
Alternative:Clydespace Panel
Advantages/Disadvantages:
Clyde Array
TASC Array
Cost - +
Risk(Assembly and Coverglass)
+ -
Education Value - +
Magnetic Cleanliness
- +
TRIO-CINEMA 8 UCB, 2/08/2010
Design
TASC Cells do not have a protective coverglass•An encapsulant may be used instead
•Material is called CV10-2500 •Silicone Based, by Nusil•Low-outgassing (TML=.05%)•Optically clear•Radiation darkening still uncertain
TRIO-CINEMA 9 UCB, 2/08/2010
Design
•Scotchweld 1838 epoxy will hold cells on PCB during assembly•More will be applied after for structural support•Contacts between cell and PCB will be made with solder.
TRIO-CINEMA 10 UCB, 2/08/2010
Assembly Testing
Assembly Procedure Testing:• Reflow oven effectively melts
solder between cell and substrate
• Epoxy holds well under heat, keeps cell in place
• Further testing awaits PCB• Solder adheres better to
PCB• No way yet to test electrical
performance for this design
TRIO-CINEMA 11 UCB, 2/08/2010
Assembly Testing
Infra-red thermometer to control for possible variation of cell power under different temperatures
Ambient lighting controlled for
TRIO-CINEMA 12 UCB, 2/08/2010
Electrical Testing
Re-tested cells show good repeatability
TRIO-CINEMA 13 UCB, 2/08/2010
Development Plans
Development• ETU panel will be assembled February 2010
• PCB will be fabricated
• Reflow procedure will be revised, taking into account any issues with new prototype
• Testing of panel will occur March 2010• As weather improves, electrical tests will be conducted with actual sunlight
to achieve full-spectrum
• Fabrication of flight panels will take place summer 2010
TRIO-CINEMA 14 UCB, 2/08/2010
Issues
Solar Cells• Waiting on PCB to do more testing on assembly procedure
• Need to make sure that solder will not creep too much at higher temperatures
• We will research alternative solders, possibly containing silver for heat tolerance
• We’re not sure yet what type of temperature sensor will be used with the cells.
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