TRIO-CINEMA 1 UCB, 2/08/2010 Solar Array Kevin Jenkins Mechanical Engineering Space Sciences...

TRIO-CINEMA 1 UCB, 2/08/2010

Solar ArrayKevin Jenkins

Mechanical Engineering

Space Sciences Laboratory

University of California, Berkeley


Solar Cell Agenda

AGENDAOverview

Requirements

Design

Test Results

Development Plan

Issues


Overview

Panels made from TASC cells will be placed on the outside of the satellite, as shown


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


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


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


Design

Alternative:Clydespace Panel

Advantages/Disadvantages:

Clyde Array

TASC Array

Cost - +

Risk(Assembly and Coverglass)

+ -

Education Value - +

Magnetic Cleanliness

- +


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


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.


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


Assembly Testing

Infra-red thermometer to control for possible variation of cell power under different temperatures

Ambient lighting controlled for


Electrical Testing

Re-tested cells show good repeatability


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


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.

TRIO-CINEMA 1 UCB, 2/08/2010 Solar Array Kevin Jenkins Mechanical Engineering Space Sciences...

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