Advanced power cycles and configurations for solar towers: Techno-economical optimization of the decoupled solar combined cycle concept

摘要

Decoupled Solar Combined Cycle (DSCC) schemes are among current research work lines aiming to integrate higher efficiency Power Cycles in CSP solar plants. This particular plant concept combines a Brayton solarized gas turbine as high temperature cycle and a lower temperature steam Rankine cycle. The plant is equipped with a Thermal Energy Storage (TES) system fed by the topping cycle heat rejection, and providing the decoupling functionality to the bottoming steam cycle. Within this concept, open volumetric air receiver and multi-tower solutions have been proposed aiming at smaller solar fields and high temperature receivers resulting in larger solar efficiencies while keeping larger size and efficiency in the bottoming cycle. This work builds on top of the previous studies in which different DSCC plant schemes were analyzed from a technical (performance and energy efficiency) point of view, and undertakes a techno-economic LCOE-based optimization and financial evaluation to the three most promising DSCC configurations using multi-dimensional optimization algorithms. The three plant schemes techno-economically optimized in this work show increasing levels of complexity and performance by implementing additional cut-offs of heat rejection from the original scheme. Despite their technical potential, the optimization results show that the increased complexity of the more efficient cycles can hardly overweigh the increased costs of the system. Only the second analyzed scheme, posing a two temperature levels heat recovery based on two storage fluids, presents a marginally lower LCOE than the original DSCC plant scheme (-0.4%), at the cost of a more complex configuration and critical control constraints. Considering the accuracy of the models, this difference can be neglected and thus the optimized DSCC with a single level heat recovery plant scheme is considered the optimum approach for this type of power plants.