Simultaneous Design Optimization of Binary CO2-Mixture-Based Power Cycles for Concentrated Solar Power Applications

Abstract This paper introduces a novel approach for optimizing binary CO2-mixture-based both condensing and non-condensing power cycles for high-temperature CSP applications, featuring a simple recuperative layout. It synchronously optimizes cycle design parameters, dopant selection, and working fluid composition. Scenarios investigated include two maximum cycle temperatures: 550°C for conventional solar power towers and 700°C for advanced systems, across three design dry bulb temperatures: 30°C, 35°C, and 40°C. Investigated dopants include SO2, C6F6, TiCl4, a non-organic dopant (NOD), and C2H3N. The multi-objective optimization focuses on thermal efficiency and specific work, while the suggested methodology allows for the expansion of the dopant list, to include any interesting dopant as long as their thermophysical properties are captured in 3D look-up tables using accurate Equation of State (EoS) and binary interaction parameters (BIP). Results show that including specific work as an optimization objective enhances cost effectiveness by minimizing power block costs, and helps to select optimized designs while retaining high efficiencies. Additionally, considering ΔT as an objective could further reduce potential thermal energy storage (TES) costs, increasing the cost competitiveness of CO2-mixture-based cycles to increase their chances in market entry.