Energy, exergy, economic and environmental assessments on a simple hydrogen liquefaction process under variable working conditions

• A novel efficient hydrogen liquefaction process with simple structure is proposed. • Analysis under variable working conditions is conducted for application guidance. • Annual performance is studied globally, with corresponding concentration optimized. • Economic and environmental superiorities are achieved versus existing studies. • The influence of pressure drops on system performance is found insignificant. As a promising clean energy carrier, hydrogen can help reduce the dependence on fossil fuels for a cleaner future. Nevertheless, its large-scale utilization remains challenged by the considerable energy consumption and costs of liquefaction. Although several energy-efficient process concepts have been proposed, their practical implementation is restricted by system complexity and insufficient evaluation under variable working conditions. To address this gap, a novel hydrogen liquefaction process with simple structure is proposed, which is simulated based on Aspen HYSYS and optimized by genetic algorithm. A specific energy consumption of 5. 412 kW∙h/kg is achieved, representing reductions of over 26. 0% versus other simple-structured systems. The annual energy performance factor is investigated to evaluate system performance under variable working conditions, yielding an average of 5. 200 kW∙h/kg globally. Benefiting from great temperature matching in heat exchangers, an exergy efficiency of 54. 9% is achieved. A specific liquefaction cost of 0. 69 /kg is obtained in Beijing, with lower cost than most of existing studies. A global average specific CO 2 emission of 3. 245 kg/kg is found, corresponding to a reduction of 29. 3% versus the reference. The influence of pressure drops is also investigated, with SEC deviations of less than 9. 0% found. Cryogenic pressures impact energy performance most, and an overall system uncertainty of 6. 1% is found. The findings highlight a simple and efficient hydrogen liquefaction process that lowers both cost and environmental risk, while offering comprehensive evaluations to support industrial implementation. This work contributes to the widespread application of hydrogen energy, promoting the progress of carbon neutrality.