Optimal battery sizing for a grid-tied solar photovoltaic system supplying a residential load: A case study under South African solar irradiance

Abstract

Owing to the global increasing need for clean renewable energy, solar photovoltaic (PV) generation technology has gained more attention. The utilization of a grid-tied solar PV rooftop system may minimize the electricity bills of residential consumers. Battery storage proved to be the most expensive component of a solar PV system. Hence, optimal battery sizing for a grid-tied PV solar system is of fundamental importance to maximize investment returns. This study aims to determine the optimal battery size for the proposed non-interactive grid-tied solar PV-battery system when exposed to South African solar irradiance. The proposed system is investigated for supplying the residential load under the time-of-use (TOU) pricing strategy. Hence, the optimal power flow control model has been developed and utilized to determine the optimal battery size. Optimal power flow management has been achieved through the use MATLAB optimization solver called linprog. Different battery sizes have been analyzed for the selected 4.2-kW solar PV array that supplies a residential load having a peak demand of 4.2-kW. The optimization results indicated that the optimal battery size is 18.3% of the residential load demand, in the context of South African solar irradiance and the TOU tariff scheme. When the selected PV array size matches the peak load demand, the selection of a battery size greater than 18.3% proved to minimize the economic returns as a result of the inflexible electricity cost savings. For PV array size greater than the peak load demand, the optimal battery storage size increases by 11.5% of the daily load energy consumption per kW upsizing.