Advanced exergy analysis of an integrated solid waste fueled cogeneration system based on organic Rankine Cycle for different working fluids

Abstract

In this study, the performance evaluation of an ORC-based solid waste-powered cogeneration system was carried out using conventional and advanced exergy analysis methods. Eight different working fluids including dry (isopentane, n-pentane, n-octane, n-heptane), isentropic (R141b, R123), and wet (methanol, water) types were selected for the evaluation. The total capacity of the heat source was determined with the data obtained from the assessment of municipal solid wastes with different calorific values by the characterization method. Energy and exergy analyses were carried out for each component to examine the effect of selected cycle parameters, including evaporator pressure, intermediate pressure, and condenser pressure, and determine the optimum working fluid for the system. The exergy destruction in the components was split into avoidable/unavoidable and endogenous/exogenous parts in the advanced exergy analysis to identify the improvement potentials and the interaction between the components. The thermal and exergy efficiency values reach the highest values of 81.36 % and 40.76 %, respectively. R141b performs as the best working fluid, while the lowest performance is obtained from water. About 121.3 kW of power generation and 918.2 kW of process heat were obtained from the ORC-CHP system using R141b at 1400 kPa evaporator pressure. Conventional exergy analysis states that the evap-orator, process heater, and turbine are the most critical components, accounting for 67.94 %, 19 %, and 4.92 % of the total exergy destruction rate, respectively. The advanced exergy analysis shows that the priority should be on the turbine having the largest share of the avoidable part. The avoidable part, which accounts for 14.5 % of the total exergy destruction, can be reduced by system improvements.