Conceptual design of two novel hydrogen liquefaction processes using a multistage active magnetic refrigeration system

Abstract

Hydrogen is a promising clean energy carrier. However, its transportation in liquid form faces many challenges because the conventional liquefaction processes for hydrogen are highly inefficient and expensive. Moreover, due to the rising environmental concerns and low energy efficiency of compressor refrigeration technologies, active magnetic regenerator refrigeration technique (AMR) can be used as an alternative. This study presents a novel conceptual design for two hydrogen liquefaction (LH2) processes where the precooling section consists of AMR instead of the traditional compressors technology. The aim is to reduce the specific energy consumption and increase the exergy efficiency of the process while utilizing an AMR pre-cooling section for better environmental safety. Although, the process is considered small scale for LH2 production, it is infact the highest reported capacity for AMR processes. Hence, a comprehensive economic analysis is performed to analyze the costs involved within the processes. The results indicate that the proposed AMR processes provide ∼5.9–15.4% energy savings (SEC 4.15 kWh/kg for process 1 and 8.73 kWh/kg for process 2) as compared to the mixed refrigerants (MR) pre-cooling based processes (SEC 4.41 kWh/kgLH2 for conventional process 1 and 10.32 kWh/kgLH2 for conventional process 2). The Coefficient of performance (COP) of the proposed processes has values of 0.191 and 0.143, which are ∼6.3% and 18.2% more than the conventional processes 1 and 2. Compared to conventional MR processes 1 and 2, the exergy efficiency of process 1 increases by 10.55%, while that of process 2 increases by 18.2%. The economic analysis shows that LH2 can be produced with a competent levelized cost of product (LCOP) ranging between 1.31 and 1.75 US$/kg LH2.