Review of Technologies and Optimisation Methods for Integrating Renewable Energy Sources and Storage Within the Australian National Energy Market

Renewable energy generators such as Concentrated Solar Thermal (CST), Photovoltaic (PV), wind, wave and tidal power do not always generate power when it is needed, and so there is an increasing need for energy storage. For thermal systems, the storage could be thermal energy storage at the generator or electrical storage at the generator or within the electrical network. With the proliferation of non-scheduled generation from renewable electrical energy sources such as there is an ever present need for enabling scheduled generation via the incorporation of energy storage; either as from directly coupled Thermal Energy Storage (TES) at the source or distributed Electrical Storage Systems (ESS) within the electrical network or grid. The aims of this paper are twofold: to review the existing and emergent storage technologies and to survey the most appropriate optimisation techniques in determining the storage size and the subsequent optimal operation of the system within the context of the Australian National Energy Market (NEM). Firstly, a review for storage technologies is performed to establish sources for indicative characterisations of energy density, storage containment, conversion efficiency, charge/discharge rates and associated costing. The survey of optimisation techniques is partitioned into those methods most appropriate for various time scales. That is, from "whole of year", seasonal, monthly, weekly and daily averaging to those best suited matching the Australian National Energy Market bid timing of five minute dispatch pricing, which is then averaged on the half hour to determine the spot price for trading settlement. The paper concludes with the selection of what we believe to be the most promising research directions to determine the optimal sizing and operation of storage within the grid for scheduled generation from renewable electrical energy sources.