South African renewable energy hybrid power system storage needs, challenges and opportunities

Renewable Energy Systems (RESs) are becoming an increasingly favoured source of clean power. However due to the intermittent and unpredictable nature of renewable resources, energy storage needs to be used to ensure that the load is met by the supply at all times. There are many possible options for energy storage, of which the most popular and technologically mature option is batteries. Two main technical issues related to integrating batteries with RES are firstly, sizing the batteries optimally so as to minimise operating costs of the overall system and secondly, developing a battery controller to schedule the charging and discharging cycles of the battery in order to ensure uninterrupted supply to the loads within specified voltage and frequency limits. The authors are conducting research on developing a battery management and control system for a RES which would address the above mentioned issues as built-in functionalities. The paper reviews different types of batteries, possible problem areas, modelling and simulation methods needed for battery performance analysis and design of battery controllers.