4E analysis and optimization of onboard ORC-CCS system based on cold-heat-electricity-carbon conversion

To achieve green shipping, an efficient conversion method of cold-heat-electricity-carbon for LNG-fueled ship is proposed. The combined ORC-CCS (Organic Rankine Cycle-Carbon Capture Storage) system is established for fulfilling onboard carbon capture with zero-energy increasement. Two configurations, namely, SORC-CCS (Series ORC-CCS) and PORC-CCS (Parallel ORC-CCS) are compared. The combustion flue gas of the main engine provides CO₂ desorption heat. The LNG cold energy is used by ORC unit, and the low-grade LNG cold energy is utilized in the CO₂ liquefaction unit. The simulation model of ORC-CCS system is developed in Aspen HYSYS. The ORC working medium are optimally determined to be R1270/R600 and R1270/R290 for SORC-CCS and PORC-CCS, respectively. Afterwards, the energy, exergy, economy and environment (4E) analysis are performed under basic working conditions. Furthermore, the multi-objective optimization of the ORC-CCS system is carried out. The results demonstrate that both SORC-CCS and PORC-CCS could realize onboard CO₂ capture with zero-energy consumption. The multi-objective optimization indicates that the SORC-CCS performs better than the PORC-CCS with the efficiency η_en,sys*η_ex,sys of 6.43%, the avoid CO₂ emission of 34.69%, and carbon capture cost of 62.38 $/t CO₂, respectively. This work provides references for the design of onboard low consumption carbon capture and multi-energy conversion systems.