Design and analysis of a novel integrated hydrogen liquefaction process using the organic Rankine cycle and dual-pressure Brayton cycle

Hydrogen liquefaction is a critical yet energy-intensive process for clean energy transitions, with current systems exhibiting high specific energy consumption (SEC) and low exergy efficiency (EXE). This study proposes an integrated process combining an organic Rankine cycle (ORC) for power generation with the LNG/LN2 precooling and a dual-pressure Brayton cycle. The ORC utilizes LN2 as a heat sink and hydrogen as a heat source, with R170 as the working fluid (WF), to recover waste cold energy and enhance efficiency. The proposed process eliminates the need for an ortho-para hydrogen conversion reactor, reduces helium usage by 2.6 %, and achieves a daily production capacity of 120 t of liquefied hydrogen (LH2). Simulation results demonstrate significant improvements, with a SEC of 6.354 kWh/kgLH2, an EXE of 47.62 %, and a coefficient of performance (COP) of 0.2071, representing a 3.7 % reduction in SEC compared to the reference process. Sensitivity analysis reveals that helium compression pressure is a key factor influencing system performance, particularly in relation to the logarithmic mean temperature difference (LMTD) and heat exchange efficiency during the refrigeration stage. This study highlights the potential of integrating the ORC and Brayton cycles for energy-efficient hydrogen liquefaction, offering a cost-effective solution for large-scale clean energy applications.