Sustainable process modeling and holistic 4E assessment of an innovative CHP plant with renewable hydrogen production based on multi-heat recovery and PEM electrolyzer

This article presents an integrated system that combines heat and power output by recovering waste heat from a gas turbine. Additionally, it includes a proton exchange membrane electrolyzer that generates pure hydrogen. The heat recovery encompasses the integration of an organic Rankine cycle for the generation of hot water, the optimization of the organic Rankine cycle segment through the incorporation of a Kalina cycle, and the transformation of the waste heat from the Kalina cycle into electric power within the organic Rankine cycle by employing R-141b as the working fluid. Additionally, the excess hot water and electricity produced have been converted into hydrogen. This novel procedure involves the utilization of two organic Rankine cycle systems employing distinct working fluids. The primary aim is to employ octane as the working fluid to generate electricity and facilitate enhanced energy integration. The system underwent thorough examination and assessment, considering energy, exergy, economic, and environmental variables. Additionally, a sensitivity analyses of the operational parameters was performed. In addition, the thermodynamic performance of the process has been analyzed in three different scenarios: single generation, combined heat and power, and combined heat, power, and hydrogen. The findings revealed that the process attains an energy efficiency of 64.99 %, an exergy efficiency of 57.47 %, and an electrical efficiency of 41.93 %. The environmental assessment concluded that the proposed approach can decrease targeted CO2 emissions by 39.83 % in comparison to the situation when a single product is produced. Furthermore, this reduction is much greater (50.17 %) when compared to a similar structure that relies on biomass fuel. Economically, the total plant cost rate has been computed at 2867 $/h, with the exergy unit cost for this innovative process amounting to 29.63 $/GJ. The sensitivity study reveals that raising the inlet air temperature to the burner to a maximum of 870 ℃ leads to a notable improvement in energy efficiency, reaching 72.4 %, and exergy efficiency, reaching 62 %. This new system, with its advanced thermal integration and multi-heat recovery, presents a highly efficient and environmentally friendly solution for energy and hydrogen production.