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.
Dedeoglu et al. (Wed,) studied this question.