Search for optimum renewable mix for Australian off-grid power generation

Highlights: • Hybrid renewable energy systems offer cost effective electricity for off-grid areas. • Combined use of solar thermal, PV and diesel generators yields lowest energy costs. • Concentrating solar thermal presents lower cost baseload power than PV-battery. • PV and diesel generators are necessary supplements to concentrating solar thermal. • Supercritical CO₂ power cycles offer cost and efficiency advantages. -- Abstract: The electrification of remote locations that lack grid-connectivity is a global challenge. In Australia, off-grid communities and mining sites that are not connected to the electrical grid meet their electricity demand primarily through diesel generator systems. The economic and environmental ramifications associated with diesel generators can be minimised using hybrid renewable energy technologies. This study aims to identify the optimal combination of technologies in a hybrid system consisting of concentrating solar thermal (CST), solar photovoltaic (PV), battery storage and diesel generators. Optimisation is carried out through an economic analysis based on minimisation of the levelised cost of energy (LCOE). The CST system considered here utilises a supercritical CO₂ power cycle, which presents increased suitability for small scales (<10 MW). The efficiencies and costs of the CST system are closely related to the turbine inlet temperature. In this work, three temperatures are explored to identify the optimal case. The results indicate that the optimal system consists of CST (650 °C) as the primary source of baseload power, with PV and diesel generation serving as supplementary sources. These systems present significant reductions in LCOE and emissions compared to the diesel base case, and therefore offer a promising solution for remote electricity.