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Christos Tsiklios, Steffen Schneider, Matthias Hermesmann, Thomas Ernst Müller

• This work evaluates the effectiveness of chemical-based solutions for storing large amounts of renewable electricity. Four "Power-to-X-to-Power" pathways are examined, comprising hydrogen, methane, methanol, and ammonia as energy carriers. The pathways are assessed using a model scenario, where they are produced with electricity from an onshore wind farm, stored in suitable facilities, and then reconverted to electricity to meet the energy demand of a chemical site. An energy management and storage capacity estimation tool is used to calculate the annual load coverage resulting from each pathway. All four pathways offer a significant increase in load coverage compared to a scenario without storage solution (56.19%). The hydrogen-based pathway has the highest load coverage (71.88%) and round-trip efficiency (36.93%), followed by the ammonia-based (69.62%, 31.37%), methanol-based (67,85%, 27.00%) and methane-based (67.64%, 26.47%, respectively) pathways. The substantially larger storage capacity required for gaseous energy carriers to ensure a steady supply to the consumer could be a decisive factor. The hydrogen pathway requires a storage volume up to 10.93 times larger than ammonia and 16.87 times larger than methanol. Notably, ammonia and methanol, whose load coverages are only 2.26 and 4.03 percentage points lower than that of hydrogen, offer the possibility of implementing site-specific storage solutions, avoiding potential bottlenecks due to limited pipeline and cavern capacities.