Abstract:
This dissertation reports about the development of and the application of a simple
spreadsheet-based mathematical model for the sizing, the performance prediction,
and the economic analysis of a PV-Diesel-Battery autonomous power supply system.
The main objective was to find appropriate reliability level required of a mini-grid
system in Lesotho that minimized the Levelized Cost of Energy (LCOE), and at the
same time, supplied a satisfactory energy service. The goal was to determine the costeffective level to set for the energy reliability for mini-grids in Lesotho, such that the
LCOE would not increase disproportionately with the marginal increase in the reliability
level. The method used was to find the reliability at the minimum cost using the elbow
of the graph. The simulation and performance analysis showed that there was an
infinite number of combinations of battery, PV array and diesel generator size required
to achieve a given supply reliability. It was observed that the conditions for minimum
LCOE may not correspond to highest reliability and satisfactory energy service.
