Thermodynoamic analysis of three solar thermal power plants

Abstract

A very important component to achieve sustainable development in the energy sector is the improvement of energy efficiency of widely applied thermodynamic processes. Evaluation and optimization methods of energy processes play a crucial role in fulfilling this goal. A suitable method for the evaluation and optimization of energy conversion systems has been proven to be the exergetic analysis. In this work, three parabolic trough solar thermal power plants are simulated using commercial software, and they are further analyzed and compared using exergetic analysis. The goal is to detect thermodynamic inefficiencies of the three different configurations and propose measures to minimize them. The first simulated solar thermal plant uses a thermal fluid to produce the steam required in a steam generator, the second plant produces the steam directly in the solar field, while the third power plant is used to find trade-offs between the first two alternatives by generating part of the necessary steam using a thermal fluid and part of it in the solar field. The analysis involves the evaluation of the individual components of the power plants, as well as the performance evaluation of the overall structures. When examining the first two simulated plants, we find similar main sources of exergy destruction: the solar field (parabolic trough solar collectors), followed by the steam generator. This shows the importance of an optimal design of these particular components, which could reduce inefficiencies present in the system. Performing a sensitivity analysis using the configuration of the third available power plant we find the best possible combination that minimizes the thermodynamic inefficiencies of the first two alternatives for the generation of steam. The differences in the exergy destruction and exergetic efficiencies of individual components of the three plants are analyzed based on comparable operational conditions. The analysis shows the convenience of using a hybrid configuration where steam is directly generated in the solar field, white it is reheated using a heat transfer fluid.