DESIGN OF ELECTRICAL POWER SUBSYSTEM OF A LOW EARTH ORBIT SATELLITE

Abstract

A satellite electrical power subsystem is a satellite subsystem that provides energy used by other subsystems and components of the satellite. It is made up of power generation unit (solar cells), power storage unit (batteries), power regulation unit (charge controller) and power distribution unit (switches, fuses and converters). The aim of this work is to design an electrical power subsystem for a low earth orbit satellite. The design employed mathematical computation using four different solar cells namely: silicon, Gallium Arsenide, Indium phosphide and multi-junction solar cells. Gallium Arsenide solar cells, alongside three different battery types; Nickel cadmium (NiCd), Nickel Hydrogen (NiH) and Lithium-ion (Li-on) batteries are used to determine various parameters of the electrical power subsystem. It was observed that multi-junction Gallium Arsenide solar cell is most preferred because of its higher efficiency, higher beginning – of - life power (for effective charging of batteries and other components operation during the day time) and end – of - life power for de-orbiting the satellite into graveyard orbit at the end of its life span as well as making power available onboard the satellite for some years should re-boosting or re-fueling of dying and dead satellite become a reality. The lithium-ion battery is most preferred because of its least mass compared to others in this design, and because of its higher specific energy which allows it to be able to store more energy than the other. It was also observed that the higher solar cell annual percentage degradation, the lower the end-of-life power of the satellite. The results also showed that temperature and solar radiation have effects on the power generation unit of the satellite. It was then concluded that multi-junction Gallium Arsenide solar cell has higher efficiency, beginning of life power, end of life power as well as less area compared to other solar cells, hence recommended.