Assessment of various hydrogen storage options and electrofuels for smart energy systems

This study aims to evaluate the performance of hydrogen storage both in physical forms and as chemical hydrogen carriers via electrofuels (e-fuels), and to compare their hydrogen storage capacities and overall energy conversion efficiencies with direct hydrogen storage options within power-to-X systems. Thermodynamically, the analysis considers CO 2 captured via direct air capture and green hydrogen produced through electrochemical water splitting in a renewable electricity-driven electrolyzer. The analysis is performed based on the 3S (source-system-service) approach. The study specifically investigates the power-to-methanol, power-to-ethanol, power-to-methane, and power-toammonia pathways. In terms of physical storage, compressed, cryo-compressed, and liquefied hydrogen are evaluated and compared with electrofuels such as e-methane (e-CNG, e-LNG) and other synthesized fuels. For electrofuel paths, the energy requirement to deliver 1 kg of hydrogen stored within the carrier is lowest for e-ammonia at 69.4 kWh/kg H 2 , which makes it the closest alternative to direct hydrogen storage, followed by e-methanol with 121.3 kWh per kg of hydrogen delivered. Consequently, e-ammonia is identified as the most promising hydrogen storage medium among the considered. Finally, compared to direct electrification paths, hydrogen-based renewable energy carriers, particularly electrofuels as an indirect electrification option, require nearly 3 to 9 times higher renewable energy input. • Novel e-fuel paths for e-ammonia, e-methanol, e-ethanol, e-methane are developed. • Thermodynamic assessment is performed using energy and exergy efficiencies. • e-ammonia is identified as most efficient for hydrogen delivery performance. • Indirect electrification via e-fuels requires higher renewable energy input.