A method to account for transient performance requirements in the design of steam generators for concentrated solar power applications

Concentrating solar power plants are strongly characterized by recurring start-up and shut-down procedures. This imposes new challenges for conventional components such as the steam generator systems, as frequent load variations might lead to high thermal stress cycles, affecting their lifetime negatively. In this context, the header and coil design is a favourable configuration to reduce stresses. This paper introduces a method to design the heat exchangers of the header and coil steam generator type accounting for the dynamic performance, thermal stress sensitivity and impact on the performance of the power plant. Optimal designs were determined by minimizing the cost and total water-side pressure drop of the steam generator and the levelized cost of electricity of the power plant. The steam generator dynamic model was successfully validated using operational data. The results suggest that a steam generator design characterized by a tube outer diameter of 30 mm, high steam generator pressure drop and low investment cost is the optimal solution for the power plant under consideration. A configuration featuring a large number of tube layers is optimal in order to reduce the pressure drop at the superheater while at the same time, guaranteeing acceptable stresses and good transient response.