A novel compressed air and thermochemical energy storage system integrated with two-step ceria chemical looping cycle for hydrogen and sulfur production

A novel compressed air energy and thermochemical energy storage system is holistically integrated with a two-step ceria chemical looping cycle to produce compressed hydrogen, elemental sulfur, and electric power. Unlike conventional methane-based reduction, this process employs hydrogen sulfide as the reducing agent. To implement this concept, the developed integrated energy system is adapted to operate in at least two operational modes (charging thermochemical cycle and discharging thermochemical cycle). Hydrogen sulfide from the industrial waste stream undergoes a two-step ceria chemical looping cycle using an oxygen carrier (OC), CeO 2 /Ce 2 O 3 redox pair. These reduced OC particles (Ce 2 O 3 ) are employed as thermochemical energy storage media to produce additional hydrogen during the discharging mode. The entire system, including both operational modes, is analyzed and modeled in the Aspen Plus software. Several sensitivity analyses, including input feed ratio, temperature, reduced OC flow rates, and oxidized OC flow rate, are conducted to assess the performance of the CeO 2 /Ce 2 O 3 redox pair over hydrogen sulfide. It is found that the charging mode of the thermochemical cycle does not follow stoichiometry, and maximum H 2 production is achieved at an H 2 S/CeO 2 ratio of 0.57. The storage of Ce 2 O 3 particles tends to produce 88.97 % more H 2 during the discharging mode. Both hydrogen and sulfur produced from both operational modes are stored in the tanks with a flow rate of 53.39 kg/day and 3.34 kg/day. The overall performance of the developed system is assessed to be 80.26 % as energy efficiency and 43.11 % as exergy efficiency. • The system is based on CeO 2 /Ce 2 O 3 redox cycle converting H 2 S into H 2 and S. • Reduced oxygen carriers are stored to produce additional H2 during discharging phase. • Air is used to store excess energy during off-peak times and provide power during peak loads. • The charging mode achieves energetic and exergetic efficiencies of 75.51% and 36.36%. • Overall energy and exergy efficiencies of the system are 82.26% and 43.11%.