S-Ethane Brayton Power Conversion Systems for Concentrated Solar Power Plant

The objective of this investigation is the comparison between supercritical ethane (s-ethane, C₂H₆) and supercritical carbon dioxide (s-CO₂) Brayton power cycles for line-focusing concentrated solar power plants (CSP). In this study, CSP are analyzed with linear solar collectors (parabolic trough (PTC) or linear Fresnel (LF)), direct molten salt (MS), or direct steam generation (DSG) as heat transfer fluids (HTF), and four supercritical Brayton power cycles configurations: simple Brayton cycle (SB), recompression cycle (RC), partial cooling with recompression cycle (PCRC), and recompression with main compression intercooling cycle (RCMCI). All Brayton power cycles were assessed with two working fluids: s-CO₂ and s-ethane. As a main result, we confirmed that s-ethane Brayton power cycles provide better net plant performance than s-CO₂ cycles for turbine inlet temperatures (TITs) from 300 °C to 550 °C. As an example, the s-ethane RCMCI plant configuration net efficiency is ∼42.11% for TIT = 400 °C, and with s-CO₂ the plant performance is ∼40%. The CSP Brayton power plants were also compared with another state-of-the-art CSP with DSG in linear solar collectors and a subcritical water Rankine power cycle with direct reheating (DRH), and a maximum plant performance between ∼40% and 41% (TIT = 550 °C).