Optimization of solar aided coal-fired power plant layouts using multi-criteria assessment

This paper presents an integration methodology for medium and high temperature solar aided coal-fired power generation systems. A set of preferred integration methods is proposed using analysis of pinch point, exergy and solar share and the application of system simulation methods. These methods can be used for hybrid (solar/fossil) systems screening, pre-assessment and decision-making. Power plant annual performance is analyzed to confirm the validity of the abovementioned methods. The presented methodology has been applied into a 100 + 1000 MWe grade solar tower aided coal-fired power generation plant (STAPG). According to the proposed methodology, the best integration scheme is found for a scenario where high-temperature solar thermal energy is used for steam reheating, while the remaining solar thermal energy is used for feedwater heating providing the maximum utilization of solar energy. The analysis reveals that as much as 214.7 MWe could be generated using solar thermal energy under the best integration scheme. This accounts for 21.3% of total electricity produced, while representing more than twice as much the power produced by an equivalent stand-alone solar tower power plant of the same solar field size. Furthermore, solar-to-electricity efficiency of the hybrid system may reach 36.8%, with power block efficiency of 43.3%, and the coal consumption rate is 203.5 g/kW h. All these parameters are representative of the best scenario amongst the seven integration schemes studied in this paper.