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Solar array design

Solar array design. Life in the Atacama Design Review December 19, 2003 J. Teza Carnegie Mellon University. Solar Panel - requirements. Provide energy through day of mission (full sun) plus charge battery for night operation Light weight Robust Low wind profile Easily removable

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Solar array design

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  1. Solar array design Life in the Atacama Design ReviewDecember 19, 2003 J. TezaCarnegie Mellon University Carnegie Mellon

  2. Solar Panel - requirements • Provide energy through day of mission (full sun) plus charge battery for night operation • Light weight • Robust • Low wind profile • Easily removable • Transportation, safety, access • Minimum shadowing Carnegie Mellon

  3. Solar Panel - design • Emcore ATJ cells • Efficiency > 23% • Panel area: less than 2.5 m2 • Modular • Ease of assembly / disassembly • Simplify design and fabrication • Spares • Orientation • Fixed – simplicity, can’t demonstrate gain of pointed panel offsets complexity and losses of actuation • Horizontal – simplicity, symmetry, lower wind profile • Can this design provide sufficient power? Carnegie Mellon

  4. Simulation • Schedule load over typical mission day • Simulate insolation for location and time • Matlab simulation of sun position, airmass attenuation, integrated over wavelength • Compared insolation against SBDART and Atacama 03 field data (error < 6% for insolation > 300 W/m2) • Model system energy • cell efficiency (empirical) • panel area • MPPT efficiency Carnegie Mellon

  5. Simulation – activity schedule Carnegie Mellon

  6. Simulation – Atacama – 2 m2 panel Date: 9/1/04 Date: 9/30/04 Insolation vs. time Panel Power vs. time Battery Energy vs. time Carnegie Mellon

  7. Simulation – Atacama – 2.5 m2 panel Date: 9/1/04 Date: 9/30/04 Insolation vs time Panel Power vs time Battery Energy vs time Carnegie Mellon

  8. Simulation – Atacama - Results Load energy / day : 2794 Wh Carnegie Mellon

  9. Solar panel – configurations Carnegie Mellon

  10. Solar panel – design strawman • 6 modules • 160 cells / module • dimensions: 58 cm x 85 cm • 20 cells per string yielding 46 volts at MPP • 8 cells parallel yield 2.8 A Iscmax at 1000 W/m2 • Panel • effective area 2.5 m2 • geometric area 2.62 m2 • Power from panel • 1000 W/m2 and 23.4% efficiency • 97.5 W / module • 585 W total • Weight estimate: 8 kg total • (including cell encapsulation, lamination and wiring) Carnegie Mellon

  11. Solar panel – issues • Schedule • design finalization • diode procurement • fabrication • Spares • Testing • Pittsburgh sun in spring insufficient • Arizona testing before shipment limited Carnegie Mellon

  12. Solar – power trackers • Purpose • Electrically couple solar array to battery / DC bus • Operate at or near maximum power point of solar array • Vendors • Brusa / Solectria – analog, complex, geared for lead acid • AERL – buck converter with temperature dependent model of panel IV characteristic (not a true MPPT), simple • Biel – digital controlled, efficient, solar race technology • Others – typically not suitable for this application • Consumer; designed for lead acid (Morningstar) • Reliability, do not support Li technologies, not flexible • Industrial; designed for lead acid (Trace) • Over built - do not support Li technologies Carnegie Mellon

  13. Solar power point tracker – Biel MPPT • Biel School of Engineering and Science (Switzerland) • NG Maximum Power Point Tracker • Boost converter • Tracks maximum power point • Power capacity 800 W • Can bus interface • Issues – reliability, support, programming • Cost $780 Carnegie Mellon

  14. Action items • Solar array • Finalize design • Procure bypass diodes • Fabrication detailing • Power tracker • Finalize solar panels and power system parameters • Procure Carnegie Mellon

  15. Solar power point tracker – Biel MPPT Carnegie Mellon

  16. Solar power point tracker – Biel MPPT Carnegie Mellon

  17. Insolation – Atacama 03 field data Carnegie Mellon

  18. Insolation – Atacama 03 field data Carnegie Mellon

  19. Insolation – Atacama 03 field data Carnegie Mellon

  20. Insolation – Atacama 03 field data - summary • Average available energy per day: 6335 Wh/m2/day • Std dev: 212 Wh/m2/day Carnegie Mellon

  21. Solar panel – cell response Carnegie Mellon

  22. Solar panel – Cells • InGaP/GaAs/Ge cell with Si bypass diode • Cell dimensions: 4 cm x 6.9 cm (nominal) • Cell area, effective : 26.6 cm2 • Cell area, geometric: 27.3 cm2 Carnegie Mellon

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