Emissions of greenhouse gases (GHGs) are one of the main problems of using fossil energy sources such as coal and natural gas. Thus, decarbonization of the energy sector, i.e., the increased use of the lower carbon intensity and carbon-free energy sources and technologies, such as solar and wind, is needed to meet increasing energy demand and reduce emissions. Although the Sun’s energy falling on Earth has the capacity of being the largest source of electricity by the mid-century, efficiency, intermittency, and cost are the challenges for the solar and other renewable energy technologies. Concentrating solar power tower (CSP-T) technology is one of the technologies for converting solar energy to electric energy (electricity). In a CSP-T plant, the large number of mirrors or lenses is used to concentrate incoming solar energy to a small area. Thus, solar energy is first converted to the thermal energy in the solar receiver, and then to the mechanical and electrical energy in a plant power block. This study focuses on the CSP-T technology integrated with power cycles such as Rankine and Brayton. Selection of the power cycles, working fluids, and heat rejection systems was analyzed in this research study with the objective to improve conversion (mirror-to-electric generator) efficiency and reduce the cost. The selection of the best working fluid for a power cycle is traditionally performed by conducting a large number of parametric calculations over a range of cycle operating parameters for a number of candidate working fluids. A novel and systematic multi-step method was developed in this study for the selection of the best working fluid(s) for the commonly considered power cycles and specified (selected) cycle operating conditions (maximum temperature and pressure, and heat rejection temperature). The best working fluid gives the highest thermal efficiency, or the highest net power output of the power cycle. The power cycle modeling and design analysis were performed by employing EBSILON Professional Version 11 (EPV-11) software. Thermo-physical and environmental properties of the working fluids, and construction and operating cost of the CSP-T plant were the main criteria considered in the working fluid and power cycle selection procedure. To alleviate the negative effects of dry cooling in arid areas, where most CSP-T plans are (and will be) built, a direct air-cooled cooling tower (CT) with the "cold energy" thermal storage system (CE-TES), and a closed-loop hybrid-cooled CT are proposed. The effects of both cooling methods on cycle performance (net power output and electricity generation) were analyzed and compared.