## 1 Introduction
The working fluid selection can greatly affect economic feasibility of an ORC while the economic performance of ORC system is an important factor affecting its application and development. Moreover, the impact on the environment is also greatly affected by working fluid selection. From a historical perspective, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) dominated organic working fluids from 1931 to the early 1990s. Since the ratification of the Montreal Protocol in 1987 and the Kyoto Protocol in 1997, more and more attention has been paid to the development of environmentally friendly organic working fluids. Therefore, based on environmental concerns, CFC working fluids have been phased out and HCFC working fluids will be phased out by 2040 for developing countries. Hydrofluoroolefins (HFO) working fluids are drawing more and more attention. During the transition period, R123 (HCFC working fluid) [23; 24; 25; 26; 27; 28; 29; 30] and R245 fa (HFC working fluid) [24; 25; 26; 27; 31; 32; 33; 34] are two frequently-used working fluids in ORC. Therefore, the economic analysis of ORC utilizing R123 and R245 fa is of great significance. Especially for developing countries, many ORC systems using R123 or R245 fa as working fluids are in use or in development. One of the first articles focusing on exergoeconomic analyses was carried out by [PERSON] in the 1980s [35]. Afterwards, much research on economic analysis of thermodynamic cycle system has been conducted from different aspects. Different methods and equations have been developed and proposed accordingly. [PERSON] et al. [36] developed an exergy-costing method by assigning a single unit cost to a specific exergy, regardless of the type of exergy stream and state of the stream. Applying the cost-balance equation to each component of a 1000 kW gas turbine cogeneration system, they obtained exergy costs, production cost of electricity, and the lost costs of each component of the system. Based on the Specific Exergy Costing (SPECO) approach, [PERSON] and [PERSON] [37] proposed a systematic and general methodology for defining and calculating exergetic efficiencies and exergy related costs in thermal systems. They introduced some guidelines that can generalize and simplify the definitions of exergetic efficiencies and the costing procedures. Those guidelines significantly reduce the arbitrariness in applications of exergy costing. Using levelized energy cost (LEC) as an economic indictor, [PERSON] et al. [38] conducted a performance comparison and parametric optimization of subcritical ORC and transcritical power cycle system for low-temperature geothermal power generation. They found that, although the thermal efficiency and exergy efficiency of R125 in transcritical cycle is 46.4% and 20% lower than that of R123 in subcritical ORC, it provides 20.7% larger recovery efficiency. The LEC value is relatively low. Moreover, 22032L petroleum is saved and 74,019 kg CO\({}_{2}\) is reduced per year when the LEC value is used as the objective function. [PERSON] and [PERSON] [39] discussed the concepts of exergetic cost and cost accounting methods, and conducted a brief historical overview on the exergoeconomic analysis and optimization of combined heat and power production (CHPP). Compared with conventional energy analysis, these methods can solve problems related to complex energy systems. [PERSON] et al. [40] presented an overview of the technical and economic aspects, as well as the market evolution of the Organic Rankine Cycle (ORC). In their research, because of the lack of any real installations to show the cost, a simple economic analysis has been carried out to find the maximum investment that a project can assume when the return on investment is required in a year. [PERSON] et al. [41] used investment and operation and maintenance (O&M) costs as the indicators to analyze and compare exergoeconomic performance of ORC and Kalina cycles, which are used to exploit low and medium-high temperature heat from two different geothermal sites. [PERSON] et al.