Conventional and advanced exergy analysis of a solid waste powered organic rankine cycle

The increase in population and urbanization rate and the decrease in raw-material due to the effects of industrialization and technological developments throughout the world made it inevitable to turn to alternative energy sources to fossil-fuels. However, wastes which are formed in parallel with the increasing propensity to consume, have reached a level threatening human and environmental health due to their quantity and harmful-substances. In this study, energy and exergy analysis was carried out for different working fluids of the cogeneration (Combined Heat and Power; CHP) system based on the Organic-Rankine-Cycle (ORC), which uses the energy obtained by burning solid wastes to generate heat and electricity. First of all, a research has been made on the characteristics, working principles and components of ORC-technologies in the literature. At the same time, application areas of the system, thermal energy sources and working fluid selection criteria were examined. Municipal wastes with different calorific values for Bartın province were evaluated by characterization method. Results obtained TUIK 2018 municipal waste statistics have been integrated into existing data for Bartın province and thermal energy has been found to be transferred to the system working fluid by incineration of wastes. In the mathematical model of ORC/CHP system created in the Engineering-Equation-Solver (EES) program, the amount of energy produced when the steam obtained as a result of the incinerating of municipal-solid-waste (MSW) is used only for electricity generation or for electricity and heating purposes is calculated. In order to determine the optimum working fluid for the system, mass, energy, and exergy analyzes resulting from combustion were performed for each component. Thermodynamic values obtained from different organic fluids(Isopentane, R141b, R123, Methanol, n-pentane, n-octane, n-heptane, R718) with dry, isentropic and wet properties were used in the analysis. In the energy and exergy balance equations of mathematical model, the first and second laws of thermodynamics are used. Thermal and exergy efficiencies, net work output and exergy-destruction-rates were analyzed analytically in three different energy production projections and operating conditions determined for each fluid as a function of evaporator pressure, interval pressure and condenser pressure, and graphical comparison was made using the Origin program. In order to determine the actual development potential of the system and the interactions of components with each other, advanced exergy analysis was applied together with conventional exergy analysis. In the performance of advanced exergy analysis, R141b was chosen as the working fluid and the exergy destruction occurring in the components and the system for three operating conditions was determined to be avoidable with unavoidable and the endogenous with exogenous parts. In the first case, ORC thermal and exergy efficiency were calculated as 15.12% and 33.82%, respectively. In the second case, ORC, process and CHP thermal efficiencies of the system were calculated as 10.98%, 59.92% and 70.9%, respectively. ORC, process and CHP exergy efficiencies were 24.56%, 12.3% and 36.86%. In the third case of the system, ORC, process and CHP thermal efficiencies were 9.361%, 70.89% and 80.25%, respectively. ORC, process and CHP exergy efficiencies were 20.94%, 16.83% and 37.77% respectively.