The Net Capacity: An Unambiguous Metric for Evaluating Hydrate-Based Gas Storage

Gas hydrates are increasingly investigated as alternative materials for gas storage, however, using established metrics, their storage performance relative to conventional gas compression is often not immediately apparent. To address this, this study introduces the “net capacity” framework as an unambiguous method for assessing the gas storage performance of hydrate systems relative to this compression baseline. The metric directly shows the gain or loss in terms of capacity by its positive or negative value, respectively. Theoretical net capacity surfaces, showing net capacity as a function of temperature and pressure, were calculated for methane, hydrogen, and carbon dioxide hydrates, including gas hydrate systems with thermodynamic promoters and hydrate formation in porous materials. This analysis enabled the delineation of operational boundaries, i.e., the thermodynamic conditions under which hydrate-based storage offers a capacity gain over compression. A rigorous examination of data from the literature revealed that many experimental studies fall outside these boundaries or fail to achieve net positive capacities due to limited uptake or unfavorable conditions. The proposed net capacity framework provides a practical tool for identifying viable experimental conditions and paves the way for more transparent performance assessment.