4E analysis for a novel cryogenic hydrogen liquefaction process using various refrigerants: Energy, exergy, economic, and environment

Hydrogen liquefaction process (HLP) is a principal technology to overcome energy storage and transportation problems and to meet the demand for an eco-friendly energy source. This study proposes three conceptual designs of HLPs with various refrigerant cycles. The specific energy consumption (SEC) of HLP could be reduced by various refrigerants. Three different refrigerants (liquid air (LA)), liquified natural gas (LNG), and mixed refrigerants (MR)) were compared to the conventional LN₂-based HLP to verify 4E (efficiency, exergy, economics, and environmental) of each process based on their thermodynamic properties. From the results, we found that the process performance, economics, and environmental effects of the LNG-based hydrogen liquefaction process (LNG-HLP) were the best. In particular, the LNG-HLP, which uses the cold energy of LNG, required less refrigerant than LN₂, thereby reducing the energy consumed by major compressors. It had an SEC of 11.04 KWh/kg-LH₂ and capital, operating cost, and CO₂ emissions of the LNG-HLP process were considerably lower by 5.5 %, 6.2 %, and 12.2 % (unit kg CO_2eq/kg LH₂), respectively, compared to the conventional process. To propose better economic or environmental scenarios to stakeholders and governments, in this study, the HLP and hydrogen production processes were expanded to include CO₂ emission calculation and carried out analysis for levelized cost of hydrogen contribution rate to electricity production types by country.