Design and simulation of an effective backup power supply for academic institutions in Nigeria: A case study of NDA postgraduate school

Abstract

This research work is aimed to mitigate the adverse effect of numerous portable generators used in academic environments due to the unstable power supply experienced in Nigeria. Data for the study on the existing backup, availability hours from the national grid, and load demand for the area of study were obtained from the residents of the campus, facility managers, and Kaduna Distribution Company as the grid supplier from August 2017 to December 2020. The average load of the campus was obtained to be 80kW. These were used as a baseline to obtain the required size and quantity of material to generate the backup power needed. A total ampere-hour requirement of the battery to be used was obtained to be 4,278.07Ah considering the average battery depth of discharge of 80%. This resulted in a total number of cells required to be 134 considering a battery with a 200Ah rating and a nominal voltage rating of 48V. A solar photovoltaic (PV) system rating of 166.4kW is required to sufficiently charge the battery bank and also serve the load. This amounts to a minimum of 5 panels per string connected in series and 34 number panels per string connected in parallel based on which the total number of panels required summed up to 666. The inverter rating for the load was obtained to be 150 kVA with a total load of 100 kVA, an efficiency of 80%, and an average future expansion of 20 %. A diesel generator rating of 100kVA with a starting kVA rating of 113.64kVA is required to efficiently serve the load considering future expansion of 1.1 and operating efficiency of 80 %. These obtained parameters were simulated using MATLAB/Simulink to test the feasibility of the backup systems. The generation cost of each backup was calculated based on which solar PV with battery bank has an initial energy generation cost of 81.9 ₦/kWh and a future energy generation cost of 0.27 ₦/kWh while diesel generator has an initial energy generation cost of 1602.04 ₦/kWh and a future energy generation cost of 8.07 ₦/kWh as such, PV has the least energy cost and more economical for the academic environment.