Preliminary design, thermodynamic analysis and optimization of a novel carbon dioxide based combined power, cooling and distillate water system

The problems of power difficulty, hot weather, and distillate water shortage on the island platform have seriously affected people's production and life. Constructing a multi-energy supply system is an effective method to solve the above problems. Hence, a novel system combined power, cooling and distillate water system is proposed in this paper. The proposed system includes supercritical carbon dioxide recompression Brayton cycle, absorption refrigeration cycle, and multi-effect desalination. According to the energy, mass, and salt balance, the thermodynamic model is established. With the application of the control variate method, the influences of five key variables on the proposed system performance are analyzed. Parametric analysis results reveal that the decrease of compressor pressure ratio or the increase of turbine inlet temperature and heat-end temperature difference in generator contributes to the design thermodynamic performance. In addition, the performance of the proposed system and the stand-alone supercritical carbon dioxide recompression Brayton cycle is compared under the base design case. The proposed system can gain improvements by 4.02% for exergy efficiency and 52.51% for energy utilization factor in comparison with the stand-alone supercritical carbon dioxide recompression Brayton cycle. At the same time, the proposed system can generate 101.8 MW of cooling capacity and 25334 m3/day of distillate water production. Furthermore, objective optimization using a genetic algorithm is carried out to obtain the optimal design performance for the proposed system and stand-alone supercritical carbon dioxide recompression Brayton cycle. The energy utilization factor and exergy efficiency of the proposed system are 49.83% higher and 3.49% higher than those of supercritical carbon dioxide recompression Brayton cycle under the optimal conditions. Finally, this study can provide a new idea for improving the design and performance of power, cooling and distillate water combined system for island platforms.