Compressed carbon dioxide energy storage in salt caverns holds promise for China's hard-to-abate sectors

<p>Compressed Air Energy Storage (CAES) is an effective technology for grid-scale peak shaving, while Carbon Capture Utilization and Storage (CCUS) plays a crucial role in carbon reduction. As China strives to peaking carbon emissions by 2030 and achieve carbon neutrality by <styled-content style-type="number">2060</styled-content> faces significant challenges, especially for the hard-to-abate sectors pose significant challenges. Building on the principles of CAES and CCUS, this paper introduces a novel approach: Compressed Carbon Energy Storage (CCES), , which integrates CAES and CCUS. CCES uses salt caverns to store compressed supercritical CO<sub>2</sub> instead of air. This study explores the feasibility of CCES in salt caverns, addressing stability, tightness, containment, site selection, and capacity potential in China. Key findings include: 1) CCES, an advanced version of CAES, offers doubles the installed capacity compared to traditional CAES by combining the benefits of both CAES and CCUS benefits. 2) CCES salt caverns in typical bedded salt formations can maintain stability and integrity for 100 years. 3) Optimal cavern depths for supercritical CO<sub>2</sub> storage range 800-<styled-content style-type="number">1500</styled-content> m, with a minimum cavern volume of 25 × 10<sup>4</sup> m<sup>3</sup> for a capacity of at least 300 MW. 4) CO<sub>2</sub> storage in salt caverns offers better tightness compared to air, methane (CH<sub>4</sub>), and hydrogen (H<sub>2</sub>), with an interlayer permeability threshold of ≤ 1.0 × 10<sup>–18</sup> m<sup>2</sup> for adequate tightness. 5) Potential CCES sites in China have been identified, with preliminary estimates suggesting a total capacity of 46.62-69.93 GW and theoretical capacity of up to 280 million tons of CO<sub>2</sub> for China’s hard-to-abate sectors.</p>