Systematic Nonlinear Sensitivity Analysis of Working Fluid Mixtures for Flexible Solar Rankine Cycles

A systematic method is proposed for the selection of working fluid mixtures in a solar Organic Rankine Cycle (ORC) system in view of operating variability. The method is based on a sensitivity analysis procedure where several operating and design parameters that affect the cycle performance are assessed and investigated through an appropriate sensitivity index, which quantifies their impact on several important system performance indices. The proposed method is applied to 11 mixtures, which were previously identified to present increased energy and exergy performance in solar ORC systems. Among those mixture 70 % 1,1,1-trifluoro-propane / 30 % 1-Fluoromethoxy-propane is found to combine good performance in steady state conditions with reduced sensitivity to variability.