## 1 Introduction  
In recent decades, the rapid increase in the world's population, the social, economic, and industrial growth as well as urbanization, have significantly amplified the energy needs, the utilization of fossil fuels, and greenhouse gas emissions [1]. These facts have affected negatively not only the natural environment and the atmosphere, but they also can cause health problems for human beings; therefore, the international community has decided to act via international environmental policies such as the Kyoto Protocol (1997), and the Paris agreement (2015). These agreements focus on the avoidance of environmental damage and global warming, as well as the replacement of non-renewable energy sources [2]. Human needs can be covered through cleaner, more sustainable, and energy-efficient ways [1], using renewable energy sources such as biomass, wind, or solar [3]. Solar energy is an environmentally friendly source with very high potential. Many different technologies and devices have been developed to exploit solar irradiation into electricity or thermal energy. Photovoltaic (PV) cells can transform solar energy directly into electricity, while solar thermal collectors produce useful heat. Solar collectors can be utilized for small-scale applications, such as space and water heating, as well as in large-scale installations, to provide industrial heat or drive power plants [4]. The most developed and utilized solar technology is the parabolic trough collector (PTC). A PTC exploits solar beam irradiation and includes a parabolic mirror, as well as a tubular receiver, in which the heat transfer medium absorbs heat and its temperature increases. In parallel, the collectors track the Sun during the day and are incorporated with thermal energy storage (TES) units, to improve their efficiency. Moreover, PTCs operate at low- and medium-temperature levels, with values up to 400 \({}^{\circ}\)C; therefore, these devices can be used for industrial heating applications and can properly feed electricity generation systems [5], such as organic Rankine cycles (ORC), or Brayton cycles [6]. First of all, [PERSON] et al. [7] investigated a solar-powered ORC unit, which consisted of a PTC field, as well as a hot, and cold TES tank. In the case of using toluene as a working medium, the most proper performance was achieved, as the overall efficiency was enhanced by 24.8%, in comparison with another study in the literature. The thermal and exergy efficiencies were also increased by 11.3% and 10.8%, respectively, for the case of using a supercritical ORC, compared with the corresponding subcritical cycle. In addition, [PERSON] and [PERSON] [8] studied an ORC plant fed by PTCs, which was supposed to be installed in a low-solar radiation zone. A hot and cold storage tank was also integrated. Six eco-friendly organic refrigerants, as well as water steam, were investigated. According to the results of dynamic analysis, the optimum and the most economically viable design was the case of the water-steam cycle, when the net present value was calculated at USD 9.012 \(\times\) 10\({}^{6}\). The maximum rates of energy and exergy performance were determined as 11.05% and 11.86%, respectively. Moreover, configurations based on the combination of a steam Rankine cycle and an ORC were analyzed in publications. For example, [PERSON] et al. [9] investigated a PTC-based power generation unit that included a two-stage steam Rankine cycle and an ORC as a bottoming cycle. Molten salt was used as a heat transfer and storage fluid in the incorporated tank. The configuration was optimized via the particle swarm optimization (PSO) algorithm considering the maximum exergy efficiency and the minimum levelized cost of electricity (LCOE). At the optimum scenario, the overall exergy efficiency, and the levelized cost of electricity were found at 63.89% and 0.1529 USD/kWh, respectively. Furthermore, [PERSON] et al.