Energy performance enhancement of solar thermal power plants by solar parabolic trough collectors and evacuated tube collectors‐based preheating units.

Summary: Solar steam power plant is the dominant technology in the category of solar thermal power systems. In steam power cycles, there is usually a couple of steam lines, extracted from medium‐pressure and low‐pressure turbines, to preheat the working fluid before the boiler. This although leads to an increase in the energy efficiency of the cycle, reduces the contribution of the turbine proportionally. Therefore, finding an alternative method of preheating the working fluid would be effective in further enhancement of the efficiency of the system. In this study, the feasibility of using solar collectors for the preheating process in a solar steam power plant is investigated. For this, parabolic trough solar collectors and evacuated tube solar collectors based on a wide range of different scenarios and configurations are employed. The plant is designed, sized and thermodynamically analyzed for a case study in Saudi Arabia where there is a large solar irradiation potential over the year. The results of the simulations show that, among all the considered scenarios, a power cycle aided by a set of parabolic trough collectors as the preheating unit is the best choice technically. This configuration leads to about 23% increased power generation rate and 6.5% efficiency enhancement compared to the conventional design of the plant. Highlights: Performance enhancement of solar steam power plant in Saudi Arabia is investigated.Replacement of feed water heating via turbine extraction by solar thermal systems is proposed.Solar parabolic trough and evacuated tube collectors are considered as potential solutions.Six different scenarios are investigated to cover all the possibilities.The best solution among all the investigated scenario is introduced. In this study solar thermal units in different arrangements and configurations come into service to provide feedwater heating in conventional solar steam power plants. This results in a stronger effectiveness of solar energy in the system and a considerable improvement of the cycle efficiency. Comparison of different designs in terms of thermal effectiveness makes it clear which type of collector in which arrangement is the best choice. [ABSTRACT FROM AUTHOR]