EWM-TOPSIS comprehensive evaluation for renewable energy long-distance transportation carriers: Based on thermodynamic and economic analyses

To enable the long-distance transportation of renewable energy, a system model was developed for four promising chemical energy carriers: hydrogen, methane, ammonia, and iron. A comprehensive evaluation model based on the entropy weight and TOPSIS methods was applied to assess the advantages and disadvantages of these carriers in terms of thermodynamic performance, economic feasibility, and environmental impact. The calculations reveal that the iron system achieves the highest energy storage efficiency (53.61 %) and exergy efficiency (55.17 %). Although the ammonia system has the highest exergy efficiency (56.77 %), it incurs a high-electricity generation cost of 77.54 $/MWh, mainly due to significant energy consumption in the reactor, with a small portion allocated for emission treatment. Similarly, the methane system has a cost of 81.63 $/MWh. In comparison, the cost for the iron system is 60.01 $/MWh. The final performance scores for the methane, iron, hydrogen and ammonia systems were 0.946, 0.675, 0.655, and 0.401 respectively. As an energy carrier, iron still presents substantial research opportunities, particularly in terms of technological maturity and transportation costs. This study provides a comprehensive multi-criteria evaluation of renewable energy carriers for long-distance storage and transportation, offering a thorough examination of the feasibility of these carriers in facilitating energy decarbonization.