Thermodynamic analysis of waste heat in a combined super-critical CO2 Brayton cycle for power and hydrogen production

Abstract

The current investigation aims to propose a novel cycle to generate power and hydrogen using waste heat. For this purpose, super-critical carbon dioxide Brayton cycle, Organic Rankine Cycle (ORC) and proton exchange membrane (PEM) electrolyser systems are consideredin the cycle. Energy, exergy analyses along with parametric study are performed in the research. The best organic working fluid is selected for ORC based on the obtained results. Zero-dimensional modeling for components is performed and results are presented. Results show that the net power generation is 245.5 MW, thermal efficiency is 40.97 %, exergy efficiency is 56.73 %, and hydrogen and oxygen production is 9.04 kg/h and 74.2 kg/h, respectively. The optimum working pressure ratio and evaporator temperature are calculated. The effect of different working parameters on the system performance is obtained. It is shown that increasing the isentropic efficiency of the main and recompression compressors increases power generation, hydrogen production and system efficiency. Furthermore, increasing the turbine's inlet temperature increases the power generation of the system.