Performance and feasibility assessment of near-isothermal compressed air energy storage in aquifers

Intermittent renewable energy sources such as wind and solar energy require large-scale energy storage systems to balance electricity production and demand. Near-isothermal compressed air energy storage (I-CAES) in aquifers can be a choice for large-scale energy storage with minimal greenhouse gas emissions. Since there is no existing commercial I-CAES in aquifers and field tests are limited, a numerical investigation is often the only pathway for assessing the technical feasibility and performance while addressing the challenges related to geological uncertainties. The novelty of this study lies in the development of a new framework for assessing the performance of I-CAES based on a coupled surface plant-wellbore-reservoir 3D model in conjunction with machine learning and uncertainty analysis. After conducting a geostatistical analysis with adopting the existing geological database, the feasibility of the I-CAES in aquifer is investigated using Gippsland Basin in Southeastern Australia as a case study. With the proposed framework, this study not only reveals the physical characteristics of a full process of the I-CAES but also assesses its feasibility under geological uncertainties. Results show that the round-trip efficiency of the I-CAES system can reach up to 67 % in highly permeable regions with no need of fuel combustion. It is also found that aquifer depth and permeability are the most significant geological factors affecting the output power and round-trip efficiency. The uncertainty analysis indicates that the daily storage potential in Gippsland Basin is found to range from 0.88 to 1.48 TWh with a corresponding probability of from 90 % to 10 %, which is equivalent to 116 %–181 % of the daily Australian electricity consumption in 2023. It is also demonstrated that there is no need of reheating expanded air with the proposed near-isothermal machinery, which is significantly advantageous than the conventional diabatic-CAES. • A framework for assessing I-CAES performance in deep aquifers is developed. • The uncertainty within the geologic formation is included in the framework. • High permeable deep aquifers have long-term large storage and efficiency. • The best round-trip efficiency of 67 % is higher than 50 % of the existing D-CAES. • Potential storage capacity in Gippsland Basin ranges from 0.88 to 1.48 TWh.