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Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design Power Systems Design -I Power System Design Considerations Power System Requirements Power Sources Power Storage Power Distribution Power Control Introduction to Space Systems and Spacecraft Design Space Systems Design 2 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 3 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 4 Power Systems Design -I Primary Introduction to Space Systems and Spacecraft Design Space Systems Design Secondary 5 Power Systems Design -I Electrical Power Battery Storage Primary – non rechargeable batteries Secondary – rechargeable batteries Introduction to Space Systems and Spacecraft Design Space Systems Design 6 Power Systems Design -I Operating regimes of spacecraft power sources Introduction to Space Systems and Spacecraft Design Space Systems Design 7 Power Systems Design -I Not Rechargeable Energy Storage Introduction to Space Systems and Spacecraft Design Space Systems Design 8 Power Systems Design -I Not Rechargeable Not Rechargeable Introduction to Space Systems and Spacecraft Design Space Systems Design 9 Power Systems Design -I Not Rechargeable Not Good Introduction to Space Systems and Spacecraft Design Space Systems Design 10 Power Systems Design -I Rechargeable Old Technology Introduction to Space Systems and Spacecraft Design Space Systems Design 11 Power Systems Design -I Rechargeable Old Technology Introduction to Space Systems and Spacecraft Design Space Systems Design 12 Power Systems Design -I Rechargeable Old Technology Introduction to Space Systems and Spacecraft Design Space Systems Design 13 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design Rechargeable 14 Power Systems Design -I Rechargeable New Technology Introduction to Space Systems and Spacecraft Design Space Systems Design 15 Power Systems Design -I 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) stored energy of battery, equal to A-hr capacity times average discharge voltage. Watt-hour capacity = Charge rate = Average discharge voltage = Introduction to Space Systems and Spacecraft Design Space Systems Design rate at which battery can accept charge (measured in A) number of cells in series times cell discharge voltage (1.25 v for most commonly used cells) 16 Power Systems Design -I 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 Introduction to Space Systems and Spacecraft Design Space Systems Design 17 Power Systems Design -I Battery selection: Introduction to Space Systems and Spacecraft Design Space Systems Design 18 Power Systems Design -I Considerations for power calculations Two batteries in series. Introduction to Space Systems and Spacecraft Design Space Systems Design 19 Power Systems Design -I Considerations for power calculations Two batteries in parallel. Introduction to Space Systems and Spacecraft Design Space Systems Design 20 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design Rechargeable 21 Power Systems Design -I Operating regimes of spacecraft power sources Introduction to Space Systems and Spacecraft Design Space Systems Design 22 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 23 Power Systems Design -I New Technology Introduction to Space Systems and Spacecraft Design Space Systems Design 24 Power Systems Design -I Solar cell response Peak sun irradiance Sun spectral irradiance Introduction to Space Systems and Spacecraft Design Space Systems Design 25 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 26 Power Systems Design -I Dual Junction Cell Efficiency Added by second junction Introduction to Space Systems and Spacecraft Design Space Systems Design 27 Power Systems Design -I Use of the Sun’s Spectrum Introduction to Space Systems and Spacecraft Design Space Systems Design 28 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 29 Power Systems Design -I Triple Junction Cell Efficiency Added by second junction Added by third junction Introduction to Space Systems and Spacecraft Design Space Systems Design 30 Power Systems Design -I Good Efficiency Introduction to Space Systems and Spacecraft Design Space Systems Design Reduce Efficiency 31 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 32 Power Systems Design -I Max Cell Current when short circuit Max Cell Voltage when open circuit Introduction to Space Systems and Spacecraft Design Space Systems Design 33 Power Systems Design -I Peak Power Introduction to Space Systems and Spacecraft Design Space Systems Design 34 Power Systems Design -I Solar Cell Strings String of cells Parallel strings to cover panel Add cell voltages to get string voltage Introduction to Space Systems and Spacecraft Design Space Systems Design 35 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 36 Power Systems Design -I Shadowing Kills all power Introduction to Space Systems and Spacecraft Design Space Systems Design Power Systems Design -I Close sw to Close sw to crowbar • Use of NiCd batteries required reconditioning crowbar battery second battery • Reconditioning not required for Li Ion batteries. Reconditioning battery system Introduction to Space Systems and Spacecraft Design Space Systems Design 38 Power Systems Design -I How much Battery Charge Left? Discharging causes heating Charging causes heating Introduction to Space Systems and Spacecraft Design Space Systems Design 39 Power Systems Design -I Some Solar Notes Introduction to Space Systems and Spacecraft Design Space Systems Design 40 Power Systems Design -I Approx Cosine Sun Introduction to Space Systems and Spacecraft Design Space Systems Design 41 41 Power Systems Design -I Satellite Orbit Parallel Sun Rays Eclipse Sun Earth Introduction to Space Systems and Spacecraft Design Space Systems Design 42 Power Systems Design -I Gravity Gradient Stabilized Sun Introduction to Space Systems and Spacecraft Design Space Systems Design 43 Power Systems Design -I Passive Magnetic Stabilized N S N S S N N Sun S Introduction to Space Systems and Spacecraft Design Space Systems Design 44 Power Systems Design -I Inertially Stabilized Sun Introduction to Space Systems and Spacecraft Design Space Systems Design 45 Power Systems Design -I Power Systems Design I or EPS Charge Control Solar Panels - source Subsystem Voltage DC/DC Voltage Bus Voltage Subsystem DC/DC Batteries Introduction to Space Systems and Spacecraft Design Space Systems Design 46 Power Systems Design -I Radios • Fixed voltage busses (5v, -5v, 7v, 3.3v, 12v, etc.) • Quieter – generates less noise on voltage bus Introduction to Space Systems and Spacecraft Design Space Systems Design 47 Power Systems Design -I • DC/DC Converter/Regulators • Regulate 2 Li Ion batteries - ~7.2v 5v Requires less circuitry, more efficient to regulate down • “Buck Up” 1 Li Ion battery - ~3.6v 5v Requires more circuitry, less efficient to “buck up” voltage. Introduction to Space Systems and Spacecraft Design Space Systems Design 48 Power Systems Design -I Could be caused by arcing due to spacecraft charging Failure in subsystem that causes a short Feedback on voltage bus from some components Multiple return paths for current to battery – don’t use grounded frame Power cycling required to reset components that have latch up due to radiation Introduction to Space Systems and Spacecraft Design Space Systems Design 49 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 50 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 51 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 52 Power Systems Design -I What type of solar panel system does it take to generate 47.5 watts peak and 27.8 watts average? Introduction to Space Systems and Spacecraft Design Space Systems Design 53 Power Systems Design -I Introduction to Space Systems and Spacecraft Design Space Systems Design 54 Power Systems Design -I Questions? Introduction to Space Systems and Spacecraft Design Space Systems Design 55