## 4 Discussion and Conclusions  
In this study, information is obtained about modelling and performance improvement of the geothermal binary geothermal power plant (GPP) with air-cooled organic Rankine cycle (ORC). As a case study, the exergy analysis according to the Second Law of Thermodynamics is applied to the Sinem GPP, operating currently and belonging to Maren Maras Electricity Generation Inc. with data collected from the system under operating conditions. Meanwhile, a model is developed to simulate fully and accurately the GPP in terms of thermodynamics. Using the artificial bee colony (ABC) method, the developed model is optimized for thermodynamic performance. With the ABC method, 12 cases are chosen for optimization conditions. Thus, the performance of the power plant can be predicted with reasonable accuracy and at the same time, the physical process to be used to improve the performance of the power plant can be better understood. Firstly, exergy analysis is performed for the GPP. The largest exergy losses from the power plant occur during re-injection of the geofluid, and then from the condenser, evaporator and pumps. Of the total 53.8 MW exergy input rate into the system, 23.7% is spent for re-injection, 0.5% for release of NCG into nature and 75.8% is exergy rate destroyed by the components of the GPP. According to exergy analysis, the total exergy production of the GPP is 21 MW and the exergy efficiency is 54.52%, after removing parasitic loads. The results of exergy analysis shown that the highest exergy destruction rate occurs in the condensers. The components with the highest exergy destruction rate are ranked as CON 2, VAP 2, CON 1, PU 1, PU 2 and separators. Their percentages are 4.6%, 4.6%, 3.7%, 3.6% and 3.6%, of the total exergy input rate, respectively. This order also determines the components requiring priority improvement. In this study, a mathematical model fully simulating Sinem GPP accurately and thermodynamically is developed. This model is completed with the MATLAB program, which can rapidly incorporate thermodynamic flow properties from the COOLPROP program. The model uses an iterative method while attempting to estimate the outputs corresponding to component inputs  
Figure 17: Improvement potentials of the components according to exergy input of the actual system. in the system. This model is used to estimate the true potential of improvement or interactions between components. Fixed values in the model are changed in an attempt to make the model adapt to new conditions. Thus, the model gains dynamism. This model can adapt to environmental temperature and variations in temperature, pressure and flow parameters in all line numbers in the system. However, variations in temperature parameters strongly affect the ORC cycle, it may lead to insolvability. Variable selection and optimization intervals (upper and lower limits) are determined to maximize exergy efficiency of the Sinem GPP with the ABC optimization method. Thus, 12 cases are created with the optimization conditions (Cases 1-12). These cases all maximized exergy efficiency at the GPP. However, the best performance is obtained from Case 4 relating to the 2 turbines and Case 12 relating to the condensers. Case 7 simulates the real system exactly. As the real Sinem GPP is designed in accordance with parameters relating to geofluid, exergy efficiency of the geothermal brine line did not cause much effect. As the output pressure of the turbines used to produce electricity increased, the condensers began to experience problems (and as a result the fans) and changes in the number of fans ensuring ORC affected the net electrical power generated. The net power generated in Case 4 is 16% larger than that of the real system. This increase is equivalent to electricity production of more than 3 MW. In Case 12 relating to condensers, this value is 14%. Thus, the most important components requiring care in the design and operation of Sinem GPP are turbines and condensers.