Solar Arrays

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Solar Arrays

• Shannon R. Wheatley

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Outline

• History and Background
• How a solar cell works
• Solar Arrays on the International Space Station
  (ISS)
• Beta Gimbal Assembly

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History

• Discovered in early 1940 by Russell Ohl, a
  researcher at Bell Telephone Laboratories.
• The first solar cells were launched into space on
  the US satellite Vanguard I
• Solar arrays have appeared on past space stations
  such as Skylab and Mir.

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Solar Cell
Photons from the sun enter the silicon Energy is
given to electrons from the photons Electrons
then flow to the holes located in the n-type The
flow can be directed through an electrical load
thus producing electricity
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International Space Station Solar Arrays
Final Configuration

• Current configuration

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ISS Solar Array Specifications

• One solar blanket has 16,400 cells
• Bypass diodes are located every 8 cells
• Final configuration 262,400 cells available for
  producing power
• Total area of 27,000 square feet approximately
  half an acre
• Each solar blanket has 82 active panels.
• 41 strings
• Each string is wired in parallel to produce the
  required power output.
• Primary power (150-160V DC)
• Secondary power (124.5 /- 1.5 V DC)

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One Solar Array
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On the Dark Side

• Primary power storage is provided by nickel
  hydrogen battery assemblies
• During the eclipse, a portion of the stored
  battery power is discharged to supply the ISS
  loads.
• Stored power is not limited to the dark portion
  of the orbit.
• If the power generation function were to fail,
  the batteries could supply power for one complete
  orbit following a period of orbital eclipses with
  a reduced ISS power consumption rate

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Beta Gimbal Assembly

• Deployed by either
• Mission Control Center Houston
• Space Shuttle Early Portable Computer System
• Manually with Extravehicular Activity (EVA)
  hand-tools.

The mast may retain only about 10 percent of its
strength if it is not fully deployed, depending
on were it stops.
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Beta Gimbal Orientation

• 360 degree continuous rotations
• Currently the solar array wing is only able to
  rotate about its long axis but future missions
  will supply equipment to adjust about the axis
  perpendicular to the long axis

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Beta Gimbal Modes

• Autotrack Mode
• Directed Position Mode
• Manual Free Mode
• Blind Mode

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Key Points

• Solar cells produce power by using the sun
• Solar Array is a combination of solar cells
• ISS
• Currently 4 Solar Arrays
• Completion 16 Solar Arrays
• Nickel hydrogen battery assemblies
• Beta Gimbal Assembly

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Questions?