Medium voltage consumers’ cost evaluation connected to a micro-grid PV system

Abstract

The increase in the deployment of photovoltaic systems has brought a change to the national grid and directly influences the energy charges applied by the utilities. Different types of tariffs are applied to consumers for electrical energy. These tariffs differ according to the level of voltages that are supplied to the customers. The low voltage applies to household customers and some small businesses, while the medium voltage grid supplies the industries using voltages higher than that of low voltages. In South Africa, the medium voltage grid-tied solar photovoltaic customers can operate a network that generates up to 100MW of power from their solar systems without a licence. However, the tariffs that apply to such customers are the same as those who do not have solar systems since operating without a licence does not permit feeding power back to the grid. Many industries use medium voltages, and it is crucial to evaluate the cost-effective tariffs for medium voltages with a solar system. This paper uses consumption data to verify the type of tariffs that result in lower energy charges. It was found that the large power user tariffs result in higher energy charges than the time of use tariffs during holidays and weekends and vice versa during weekdays. However, the paper concludes that the time of use tariffs can lower energy costs if applied in a grid-tied solar system with battery storage, provided that the batteries supply power during peak hours.