## 1 Introduction  
Solar energy has played an important role in sustainability. The main routes to harvest solar energy are by concentrating solar thermal power (CSP) and solar photovoltaics (PV) [1]. There is a lot of research on PV, including economics and environmental performance [2, 3]. Compared with the PV generation, CSP has certain advantages in the power generation scale. At present, multiple kinds of CSP technology, including the parabolic trough collector (PTC) [4], the linear Fresnel reflector [5], and the solar power tower (SPT) [6] have been reported. Among them, parabolic trough (PT) can be considered the most mature technology for CSP plants due to projects conducted by the United States [7] and Spain [8]. At present, the Rankine cycle is the most common power generation cycle in CSP technology, which uses parabolic trough collectors, while organic working fluids and water are commonly adopted. However, these forms of power generation face barriers, including the use of working fluids that are easy to aggravate global warming, and high investment costs [9]. The performance of the Organic Rankine Cycle (ORC) is limited by chemical degradation and auto-ignition at high temperatures [10]. Thus, ORC is a better power cycle choice only when the temperature of the heat source is lower than 300 \({}^{\circ}\)C, according to the research data of some literatures [11]. In addition, the thermal characteristics of steam lead to the use of multi-stage turbines and complex power plants, which will undoubtedly increase the costs. Supercritical carbon dioxide (S-CO\({}_{2}\)) has been identified as an attractive working fluid with lots of advantages [12]. Firstly, CO\({}_{2}\) is inexpensive, non-toxic, nontoxic, inert, abundant, and easy to reach critical point (7.38 MPa, 304.25 K) [13]. The low compressibility, viscosity, and the high density of S-CO\({}_{2}\) can be helpful to achieve high efficiency and compact mechanical structures in the power cycles [14; 15]. Finally, compared with the Rankine cycle, it can save when it comes to the cost of several valves and condensers, because of the little phase change in the S-CO\({}_{2}\) power cycle. Hence, more attention has been paid to the application of the S-CO\({}_{2}\) Brayton cycle, especially in the fields of waste-heat recovery [12], nuclear power generation [16], and CSP [17; 18]. Nowadays, most research on the application of SCO\({}_{2}\) in CSP technology are SPT, which can take advantage of the higher working temperatures [19]. [PERSON] et al. [20] discussed the thermodynamic assessment of three S-CO\({}_{2}\) cycles with turbine inlet temperatures up to 800 \({}^{\circ}\)C. Recompression with Main Compression Intercooling (RMCI) configuration was considered as the optimal loop structure in the study, which reached electric efficiency of 24.5% under the design condition. [PERSON] et al. [21] compared the efficiencies of different S-CO\({}_{2}\) Brayton cycle layouts coupled with SPT. The partial-cooling and inter-cooling cycle with reheating could achieve efficiency of 50%. [PERSON] et al. [22] also carried out the energy and exergy analysis for different S-CO\({}_{2}\) cycle layouts using SPT. However, SPT is not a mature technology, and the plants using SPT have limitation of large floor space. Therefore, it should be considered to use S-CO\({}_{2}\) cycles with PTC. The above conclusions are made in the case of heat source temperatures above 500 \({}^{\circ}\)C (even above 600 \({}^{\circ}\)C). However, CSP using conventional PTC at maximum temperatures, in the range between 350 \({}^{\circ}\)C and 400 \({}^{\circ}\)C, is common technology. Hence, it is still necessary for the comparative study of S-CO\({}_{2}\) cycles coupled with PTC. In fact, some researchers have carried out the research of S-CO\({}_{2}\) cycles coupled with PTC [23; 24]. However, their research is based on the performance of the system, and there are few comparative studies on the economy between different types of cycles.