Near‑isothermal compressed‑air energy storage in aquifers: simulation‑based performance assessment and techno‑economic optimisation under geological uncertainties

Abstract

Compressed air energy storage (CAES) is a promising energy storage technology for balancing the intermittency of renewable energy such as wind and solar. Aquifers are more advantageous as storage media for CAES since they are more widespread. In this thesis, an integrated simulation-based framework is developed for assessing the performance of near-isothermal CAES (I-CAES) in aquifers under geological uncertainties and is applied to the Gippsland Basin in Australia as a case study. The results show the round-trip efficiency of I-CAES in aquifers to be significantly higher than that of existing diabatic CAES plants, without the need of consuming fossil fuels to reheat the expanded air under most of geological conditions. The geological and well parameters, as well as surface plants are found to influence the performance of the system. As a result of the study, the overall storage potential in the Gippsland Basin is found to be enough to support daily electricity consumption for a city of 5 million population. A techno-economic analysis-based multi-objective optimisation framework is also developed to design I-CAES in aquifers, considering the trade-offs between performance and cost-effectiveness. The results indicate that the levelized cost of electricity (LCOE) of the proposed I-CAES system can be significantly lower than other existing energy storage systems. The multi-objective optimisation analysis provides optimal solutions for CAES grid size and air flow rate to maximise the round-trip efficiency and overall output power while minimising LCOE.