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Electrical Power System

Electrical Power System. By Aziatun Burhan. Overview. Design goal requirements throughout mission operation: Energy source generates enough electrical power Energy storage stores electrical power Power distribution distributes electrical power Power regulation controls electrical power

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Electrical Power System

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  1. Electrical Power System By Aziatun Burhan

  2. Overview Design goal requirements throughout mission operation: • Energy source generates enough electrical power • Energy storage stores electrical power • Power distribution distributes electrical power • Power regulation controls electrical power • For a slide like this enlarge the font to fill the slide or fill space with a picture (check other slides as well)

  3. Power Budget

  4. Mission Power Profile

  5. Trade studies summary • This trade study examines the option of using only non-rechargeable battery vs solar cells+rechargeable battery system as satellite’s power source. To meet NANOsat requirements, a power source that has low mass and small size is desirable for this mission. • Try to make this slide into a couple of bullets rather than sentences

  6. Solar cells vs Battery • Factors that effect trade study: - Total power consumption and power profile during the mission - Mission life of satellite : 24 hours - Mass and area constraints that come from NANOsat requirement * Solar cells can produce lots of power with little increase in total mass * If power consumption is large, the mass and size of non-rechargeable battery could be greater. - Choice of orbit and type of attitude control - Operating environment

  7. Solar cells vs Battery • We choose solar cells as the main power source with rechargeable battery to store energy and to provide power during eclipse - Solar cells+ battery has little increase in mass for larger increase in power consumption - Fewer non rechargeable battery that is qualified for space application

  8. Solar cell vs Battery

  9. Solar cells • Ultra triple junction Gallium Arsenide solar cell • 28.0 % BOL efficiency • 2.31 V, 16.3 mA/cm² ( ~0.96 W/ cell) • 2.3g Customized size: 3.69 cm Area per cell: ~ 25cm² 6.85cm

  10. Solar cells layout & assemblies Sides (A) • 5 identical solar panels • Power source: Direct sunlight, at 45 ° angle • from normal direction of plane • 91 UTJ GaAs solar cells per side • - 13 solar cells per string : 30 V • - 7 strings : 2.85 A • 40.68 Watt minimum per side during • daylight • Dimension : 48 cm x 48 cm • Area: 2275 cm²

  11. Assumption: • 2 sides are exposed in direct sunlight at one time. • Solar flux is at constant value of 1353 W/m^2 • Worst case hot temperature was used to find thermal efficiency for a solar cell , therefore the calculated power output from the a solar panel is the minimum value. • Enlarge the font

  12. Rechargeable Batteries • Saft MPS 176065 Lithium-ion cells • 8 cells in series in a battery box • Capacity: 5.8 Ah • Mean voltage: 3.6 V • Battery mass: 1.4 kg (including casing) • Maximum DOD: 70% for <500 cycles • Charging method: Constant Voltage-constant current + balancing • Space qualified • 2 battery boxes (for redundant operation with one unit failed)

  13. Energy storage requirements: Peak power load: ~90 W Discharge time: 36 min (maximum) Charging time: 0.9 to 1 hour Charge/Discharge cycle / day: 16 Required battery capacity: 2.6 Ah for 75% DOD

  14. Demonstration *will recheck the values this weekend

  15. Power Management & Distribution • SmallSat power management electronics • 28V unregulated; MPPT; Modular & Scalable from 30W to 300W • Consist of 3 main elements: • - Battery Charge Regulator (BCR) • - Power Conditioning Module (PCM) • - Power Distribution Module (PDM)

  16. Power Distribution Design ADCS COMM DC-DC step down converter FCS OBC Power Bus (~28 V) 5V supply line DC-DC Step down converter Payload (Camera) 12 V supply line Thermal control Propulsion Power

  17. Power Distribution • Continuous power per one orbit period: 23.7 W • Maximum power per one orbit period: 89.7 W • Average power per one orbit period: 47 W • Average power during daylight: 42.5 W • Average power during eclipse: 53 W ** non continuous operation

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