Screening of adsorbent materials for small-scale compressed CO2 energy storage using pressure swing adsorption

The growing demand for efficient and sustainable energy storage solutions has accelerated the increased interest in novel energy storage technologies such as Compressed CO 2 Energy Storage (CCES). Within this domain, adsorption-coupled configurations are recent and sparse, indicating a field in early development. To date, published studies have evaluated CCES with adsorption beds investigating only one adsorbent: NaX zeolite, known for its high equilibrium capacity, and have employed temperature-swing adsorption despite its added complexity relative to pressure-swing adsorption (PSA). This study replaces the low-pressure CO 2 reservoir with a PSA bed to simplify gas recovery process during discharge. We developed a theoretical thermodynamic cycle analysis of CCES coupled to a material screening using equilibrium isotherm data for families of zeolites and activated carbons. This analysis aims to assess how adsorbent properties influence key metrics: usable CO 2 working capacity (under the specified isothermal process assumptions), energy-to-volume ratio (EVR), and round-trip efficiency (RTE). Storage (adsorption) and discharge (desorption) are modeled under near-ambient isothermal conditions (≈ 298–303 K) across pressure swings ranging from 1 to10 bar during storage and from 0.1 to 1 bar during discharge. Results show that the optimal adsorbent for adsorption-coupled CCES is not necessarily the one with the highest equilibrium loading (e.g. NaX) but the one that maximizes usable working capacity over the specified pressure swing; for above-atmospheric operation, high-silica CHA and Norit RB2 perform best. Quantitatively, EVR ranges from 2 to 10 kWh/m 3 and RTE from 30 to 70 %, contingent on operating conditions. These findings highlight the trade-off between energy density and system simplicity, offering a practical framework to guide adsorbent selection prior to detailed system design and dynamic modeling. • Adsorbent screening is key for compressed CO₂ energy storage optimization. • Absolute and relative gains are used to compare adsorbent performance. • Gas recovery is modeled via pressure swing with sub/super-atmospheric levels. • Dynamic working capacity is critical to system energy performance. • Zeolites and ACs show distinct trends based on material and pressure conditions.