Heat Transfer Fluid Life Time Analysis of Diphenyl Oxide/Biphenyl Grades for Concentrated Solar Power Plants

To gain a better understanding of how purity affects fluid degradation in concentrated solar power (CSP) plants, commercially available eutectic diphenyl oxide/ biphenyl heat transfer fluids were tested for their thermal stability at different temperatures and for their chlorine content. A model for thermal degradation of the eutectic diphenyl oxide/ biphenylfluids in a parabolic trough CSP plant was built based on laboratory testing results and average fluid analysis results from operating CSP plants. Fluid degradation was compared between high quality product at 99.9% purity such as DOWTHERM™ AHeat Transfer Fluid and commercially available products with purities around 99.5%. A range of 1.7-2.4 times more degradation was determined for 99.5% purity fluids compared to the 99.9% quality for the operating conditions in a CSP plant. More frequent degradation separation operations are needed for lower 99.5% purity fluids, which ultimately means extra operating cost. In addition to that, the additional new fluid refills needed over a 25 years of operation is $2/kg.DOWTHERM™ is a trademark of The Dow Chemical Company.