Modeling and analysis of process configurations for hybrid concentrated solar power and conventional steam power plants

Availability and flexibility of variable renewable energy production can be increased without thermal energy storages by integrating intermittent energy production with load following energy production. This paper focuses on modeling, analysis and comparison of three hybrid configurations for concentrated solar power and conventional steam power plants. The configurations include feedwater preheating, cold reheat line and high pressure turbine concepts, in which linear Fresnel collector solar field with direct steam generation is applied to generate steam parallel with the steam boiler. The modeling is conducted using dynamic simulation software Apros®, which enables investigation of the system operation under varying process conditions. In particular, the focus is on the comparison of thermal load balance and interdependencies of the subsystems. In addition, the focus is on increasing the solar contribution, as the solar share is low in current commercial concepts. As a main conclusion, the more solar steam is fed to the system, the more different turbine sections and heat surfaces of the steam boiler are imbalanced, which leads to challenging system design. In addition, the maximum fuel and emission savings are not only determined by the achievable solar share, but also by the hybrid process design. The design of the hybrid system has to be optimized and modified according to the configuration in order to achieve higher peak solar share and fuel and emission savings than 20% achieved in this study.