New optimal scheme for the poly-generation system, integrated with ORC and hydrogen production units, using technical, emergy, and thermo-risk analyses-case study for qeshm power and water co-generation plant

Abstract

The diversity of energy demand in terms of products has led to the upgrading the power plants into multi-generation systems. The Qeshm freshwater and power plant located in Qeshm Island, Iran, has been investigated. The existing plant was integrated with an absorption chiller, solar thermal collector, and RO desalination unit in the previous study. This study has proposed and evaluated a new configuration for this plant. This new scheme consists of power, heating, cooling, freshwater, and hydrogen production units. A PEM electrolyzer and an organic Rankine cycle have been integrated into the previously proposed system to generate hydrogen and more power. In order to evaluate the proposals for the Qeshm freshwater and power plant, the energy, exergy, exergo-economic, exergo-environmental, emergo-economic, emergo-environmental, and exergo-risk (7E) analyses have been performed on the new integrated system. Furthermore, a multi-objective optimization process has been conducted on the proposed system using the multi-objective particle swarm optimization (MOPSO) algorithm to obtain the optimal scheme of the proposed configuration. The results of the thermo-risk analysis indicate that the most hazardous unit of the system is the gas cycle section, with a 91.21% share of the total rate of risk in the site, which equals 11.705 × 10 - 6 i n j u r e d / y e a r . By comparing the results of the previous work and the new proposed integrated plant, the new system’s poly-generation efficiency and net power output have been enhanced by 5.523% and 7.945%, respectively. The new integrated plant can produce two new hydrogen and oxygen products in 0.003 and 0.21 kg/s, respectively. Also, the cost of power produced by the system has been raised only by 0.393 $/MWh or 0.91%, while its environmental impact has been decreased by 0.702 pts/MWh or 3.98%. The total rate of risk of the system will increase due to adding ORC and PEMEC units to the cycle, which is from 10.129 to 11.105 × 10 - 6 i n j u r e d / y e a r . But, from the thermo-risk point of view, the total specific risk of the plant’s products has been reduced from 37.820 to 37.486 × 10 - 8 i n j u r e d / ( y e a r . M W ) . Furthermore, the optimization process results show that implementing the optimization process has improved the objective functions of the proposed integrated plant from technical, monetary, ecological, and risk points of view.