SPANDEX

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SPANDEX

• FRR

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Mission Goal We aim to measure solar panel
efficiency as a function of altitude. We would
like to determine if the lower temperature and
thinner air of the upper atmosphere have an
effect on the efficiency and power output of a PV
cell. Science Objectives We seek to determine the
efficiency of the solar cell, discover what
effect varying temperatures have on the
efficiency, and to discover if the Suns
radiation in the upper atmosphere has a different
effect from the radiation in the lower
atmosphere. Technical Objectives We will
construct a well-insulated box, voltmeter, and
MPP (maximum power point) tracker. We also want
to keep the payload level at all times.
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Background and Requirements
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Background and Requirements
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Background and Requirements

• P out V2 / R
• Efficiency P out / P in
• Area of cell 106.25 cm2
• The solar cell data sheet claims that the cell
  should put out 1.55 watts at 25 degrees Celsius
  with an irradiance of 1000 W/m2 shining directly
  on it
• We expect a max of 1.84 W at -60 degrees Celsius
  with the sun at 21 degrees from its normal with
  an irradiance measurement of 1000 W/m2.
• We expect a min of 0.08 W at 80 degrees Celsius
  with an irradiance measurement of 625 W/m2 with
  the sun at 64.8 degrees from the normal on a
  cloudy day.

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Mechanical Structure
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Mechanical Structure
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Electronics
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Flight Software
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Ground Software
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Thermistors
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Testing
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Results
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Results
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Results
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Results
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Results
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Results
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Results
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Analysis

• Error for the power 8.5
• Based on the cells spectral response, we
  predicted that the ratio of efficiency below the
  clouds to efficiency beneath the clouds would be
  4/5. We found that the actual ratio of average
  efficiencies is 6.997 to 7.793 (11 difference).

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Conclusion

• The max efficiency was 11.1 and occurred at
  11.12215 km
• Because this max occurred near the tropopause
  where both the external and operating
  temperatures reached a min, and because we found
  no correlation between power in and efficiency,
  we conclude that efficiency increases as
  temperature decreases, but not necessarily as
  irradiance increases
• We could improve our experiment by using solar
  panels that produce higher voltages and by
  attaching our own pyranometer to our payload
  instead of relying on outside data

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Special Thanks

• Instructors
• Dr. Greg Guzik
• Mr. Brad Ellison
• Mr. Jim Giammanco
• Dr. John Wefel
• Absent Teammates
• Joe Thompson
• Bob Thompson
• Other Help
• Thomas Stoffel (NREL)
• CSBF
• Jeff the engineer