Morehead State University Morehead, KY Prof. Bob Twiggs RJTwiggs@gmail

1. Power Systems Design - 1 Morehead State University Morehead, KY Prof. Bob Twiggs RJTwiggs@gmail.com

2. Power Systems Design - 1 Power System Design Considerations System Requirements Sources Storage Distribution Control 2 SSE -122

3. Power Systems Design - 1 3 SSE -122

4. Power Systems Design - 1 4 SSE -122

5. Power Systems Design - 1 Operating regimes of spacecraft power sources 5 SSE -122

6. Power Systems Design - 1 Operating regimes of spacecraft power sources 6 SSE -122

7. Power Systems Design - 1 7 SSE -122

8. Power Systems Design - 1 New Technology 8 SSE -122

9. Power Systems Design - 1 Sun spectral irradiance Solar cell response Peak sun irradiance 9 SSE -122

10. Power Systems Design - 1 10 SSE -122

11. Power Systems Design - 1 Dual Junction Cell Added by second junction Efficiency 11 SSE -122

12. Power Systems Design - 1 Use of the Sun’s Spectrum 12 SSE -122

13. Power Systems Design - 1 13 SSE -122

14. Power Systems Design - 1 Triple Junction Cell Efficiency Added by second junction Added by third junction 14 SSE -122

15. Power Systems Design - 1 Good Efficiency Reduce Efficiency 15 SSE -122

16. Power Systems Design - 1 16 SSE -122

17. Power Systems Design –I Ended 10/21/10 Max Cell Current when short circuit Max Cell Voltage when open circuit 17 SSE -122

18. Power Systems Design - 1 Peak Power 18 SSE -122

19. Power Systems Design - 1 Solar Cell Strings Parallel strings to cover panel String of cells Add cell voltages to get string voltage 19 SSE -122

20. Power Systems Design - 1 20 SSE -122

21. Power Systems Design - 1 Shadowing Kills all power SSE -122

22. Power Systems Design - 1 Some Solar Notes 22 SSE -122

23. Power Systems Design - 1 Approx Cosine Sun 23 SSE -122

24. Power Systems Design - 1 Satellite Orbit Parallel Sun Rays Eclipse Sun Earth 24 SSE -122

25. Power Systems Design - 1 Gravity Gradient Stabilized Sun SSE -122

26. Power Systems Design - 1 Passive Magnetic Stabilized S S S S S S S S S S S S S S N N N N N N N N N N N N N N N Sun S 26 SSE -122

27. Power Systems Design - 1 Inertially Stabilized Sun 27 SSE -122

28. Power Systems Design - 1 Questions? 28 SSE -122

29. Power Systems Design - 2 Morehead State University Morehead, KY Prof. Bob Twiggs RJTwiggs@gmail.com

30. Power Systems Design - 2 Power System Design Considerations System Requirements Sources Storage Distribution Control 30 SSE -122

31. Power Systems Design - 2 31 SSE -122

32. Power Systems Design - 2 32 SSE -122

33. Power Systems Design - 2 Primary Secondary 33 SSE -122

34. Power Systems Design - 2 Electrical Power Battery Storage • Primary – non rechargeable batteries • Secondary – rechargeable batteries 34 SSE -122

35. Power Systems Design - 2 Not Rechargeable Energy Storage 35 SSE -122

36. Power Systems Design - 2 Not Rechargeable Not Rechargeable 36 SSE -122

37. Power Systems Design - 2 Not Rechargeable Not Good 37 SSE -122

38. Power Systems Design - 2 Rechargeable Old Technology 38 SSE -122

39. Power Systems Design - 2 Rechargeable Old Technology 39 SSE -122

40. Power Systems Design - 2 Rechargeable Old Technology 40 SSE -122

41. Power Systems Design - 2 Rechargeable 41 SSE -122

42. Power Systems Design - 2 Rechargeable New Technology 42 SSE -122

43. Power Systems Design - 2 • Use of NiCd batteries required reconditioning • Reconditioning not required for Li Ion batteries. Close sw to crowbar second battery Close sw to crowbar battery Reconditioning battery system 43 SSE -122

44. Power Systems Design - 2 How much Battery Charge Left? Discharging causes heating Charging causes heating 44 SSE -122

45. Power Systems Design - 2 Batteries Most common form of electrical storage for spacecraft Battery terms: Ampere-hour capacity = total capacity of a battery (e.g. 40 A for 1 hr = 40 A-hr Depth of discharge (DOD) = percentage of battery capacity used in discharge (75% DOD means 25% capacity remaining. DOD usually limited for long cycle life) Watt-hour capacity = stored energy of battery, equal to A-hr capacity times average discharge voltage. Charge rate = rate at which battery can accept charge (measured in A) Average discharge voltage = number of cells in series times cell discharge voltage (1.25 v for most commonly used cells) 45 SSE -122

46. Power Systems Design - 2 Considerations for power calculations We have a battery that has a power capacity of: 1000mA (1000mAHrs)@ 1.2v It can supply 1000mA for 1 hour or 500mA for 2 hours or 250mA for 4 hours @ a voltage of 1.2 v. Power rating of 1000mA x 1.2 v = 1.2 watt hours 46 SSE -122

47. Power Systems Design - 2 Battery selection: 47 SSE -122

48. Power Systems Design - 2 Considerations for power calculations Two batteries in series. 48 SSE -122

49. Power Systems Design - 2 Considerations for power calculations Two batteries in parallel. 49 SSE -122

50. Power Systems Design - 2 Rechargeable 50 SSE -122