A review of contextual frameworks relevant to energy storage on the South African grid

Decision makers in South Africa's power utility require a reliable method to evaluate energy storage systems (ESSs) and its optimal geographical locations. Therefore, a contextual framework is needed to segment and clarify the various aspects of ESSs for the decision maker. To this end, this paper reviews existing contextual frameworks from literature and groups relevant information to clarify the different aspects considered during decision making. Three of the main technology types considered for the South African grid are lithium ion, sodium sulphur and vanadium redox batteries. Two diagrams showing the specifications for different ancillary services are drawn to compare use cases for ESSs. The first diagram shows response time needed for a certain power output per service, while the second outlines the duration of the power need per service. The complexity of optimal energy storage location is also reviewed by examination of available literature. Furthermore, methods of weight factor allocations in contextual frameworks are summarised from literature. Finally, the different software tools required for a detailed analysis of ESSs are discussed. This paper can therefore serve as a starting point to guide decision makers in strategic choices related to ESSs.