Power Analyses

Power Budget

Solar Array Sizing

Power Simulations

A series of dynamic power simulations were done using Simulink to further verify the design parameters for the power subsystem. This simulation will further be integrated with the AODCS simulations to provide more detailed results for the performance of the satellite, discover worst case scenarios, and plan ahead for low power cases. 

Under normal operation conditions, the power simulator shows that the battery will charge to 100% and during eclipses, the state of charge drops to around 92%, and goes back to 100% right after getting back to the sun. 

This was true for sun angles up to 45°, after which the spacecraft will enter a power negative state that depletes the batteries. 

In power negative cases, the fall of battery's state of charge results into autonomous switching of the power mode to low-power, survival, and critical hold mode. In the lower power modes, the spacecraft will consume less power, which in result, will help with storing more energy in the batteries. 

One of these worst cases were simulated with the approximate sun angle of 80°. Results below show how the switching of the power mode to critical hold helped preserving more energy and increasing the battery's state of charge. 

Given that the LiFePO4 batteries that we use are always kept within their operating specs and are not going to go through depth of discharges more than 15%, we're anticipating negligible degradation of the capacity through the lifetime of the satellite