## 4 Conclusions  
In this article, a simple Rankine organic cycle (SORC) system has been adapted for exhaust heat recovery in a stationary natural gas power generation engine. Initially, a selection methodology was implemented that allowed the selection of three organic fluids according to safety and environmental criteria, as well as critical system conditions. Then, thermodynamic, exergetic, and economic models of the system were developed under certain defined considerations and, finally, under a set of parametric studies taking into account four variables of the system such as pump efficiency, turbine efficiency, pinch condenser, and pinch evaporator, it was possible to observe the influence that these variables exert on the combined power of the system (Wcomb engine plus ORC), exergetic efficiency, specific fuel consumption (\(\Delta\)BSFC), and on the economic indicators (PBP, LCOE, SIC). The main conclusions can be summarized as follows:  
As for the thermo-economic analysis of the SORC system, it was found that the highest rates of exergy destruction occur in the heat transfer units ITC1 (tube and shell exchanger), in the evaporator ITC2 (plate exchanger), and in the condenser ITC3 (plate exchanger). These three system components represented 81.25% of the total destroyed exergy cost of the system. Next was the turbine with a value of 20.16 kW (17.53%), and finally, the pumps represented only 1.22% of the total cost of exergy destroyed from the system. Also, the exergo-economic factor f revealed that the B1 and T1 are the components with the highest values of the system, which implies that the possibility of acquiring more economic ones must be evaluated sacrificing the exergetic efficiency of the equipment. Finally, the sum of the C values \(\dot{\mathrm{C}}_{\mathrm{D}}+\dot{\mathrm{C}}_{\mathrm{L}}+\,Z_{\mathrm{k}}\) was high for ITC1 compared to the other equipment, suggesting a component with potential for improvement from the exergo-economic point of view. From the parametric study, it is concluded that the turbine efficiency significantly affected the energetic and exergetic performance of the system, with respect to the pump efficiency. However, even though the effect of the variation of the efficiency of the pump did not affect, to a great extent, the outputs of the energetic and exergetic indicators, these presented higher values than those reported when the turbine efficiency was varied. The opposite case was evidenced when studying the influence of the pinch condenser and pinch evaporator, where the increase of these variables generated a decrease in power (Wcom), specific fuel consumption (\(\Delta\)BSFC), and exergetic efficiency of the system. In this section, acetone was the working fluid that produced the best results in terms of energy and exergetic efficiency compared to toluene and cyclohexane. As for the costs of exergies destroyed by components, the condenser is the device that presented the highest values when the pump efficiency was varied, registering values in the range of \(3.90\times 10^{-3}\) USD/kWh when the working fluid is toluene, \(1.93\times 10^{-3}\) USD/kWh for acetone, and \(8.08\times 10^{-3}\) USD/kWh for cyclohexane, while the other components did not present a significant variation; so, the acetone was the best working fluid in this configuration. In addition, when the turbine efficiency was increased, a decrease in the cost of destroyed exergy was presented in all components, with toluene being the fluid with the best performance. The influence of the evaporator pinch point increase caused a decrease in the cost of destroyed exergy for the condenser, while for the evaporator and pump 2 (B2), it resulted in an increase, with the toluene in this case study being the fluid that gives the lower values. However, the increase of the evaporator pinch generated an increase in the costs of destroyed exergy that did not exceed 10% in the components, except Pump 2 (B2).