Application of Silicone Based Heat Transfer Fluids in Parabolic Trough Collectors

Despite leaning toward a lower LCOE [1], a higher operation temperature and less degradation products over time [2], silicone-based heat transfer fluids (HTF) have not yet been used in a commercial Parabolic Trough Collector power plant. In this work, a summary of the proof-of-concept process for the new HELISOL® line of silicone-based HTFs developed by Wacker Chemie AG is presented. Three generations of polydimethylsiloxane (PDMS) HTFs, HELISOL® 5A [3], HELISOL® XA and HELISOL® XLP, were successively operated for a loop scale demonstration at temperatures between 425 °C and 450 °C for 480 hours each at Plataforma Solar de Almeria (Spain). Prior to said qualification activities, the PROMETEO parabolic-troughs test facility, with a mirror surface of 1300 m², has been upgraded to withstand temperatures up to 450 °C. For each of the tests the plant was completely drained, cleaned and filled with 7 to 8 m³ of the corresponding HELISOL® grade. HTF degradation and gas formation were determined, plant performances monitored, and operational behaviour and incidents documented while elaborating a guideline on the application of silicone-based HTFs in parabolic trough solar fields [4], which was the basis for developing and proposing an international standard in the IEC context.<br/><br/><b><i>DISCLAIMER</i></b><br/>Authors acknowledges the funding received from the German government to the projects Si-CO (03EE5063A), SING (03EE5047A and 03EE5047B), SIMON (0324216A and 0324216C), SITEF (0325846A and 0325846B) and Si-HTF (0325453A and 0325453C). Authors also acknowledges the funding received from the Spanish government to the project Si-CO (PCI2020-120704-2/AEI/10.13039/501100011033) and projects SIMON (PCIN-2017-009) and SITEF (PCIN-2014-083). And finally, all authors acknowledge the funding received from SolarPACES to the international projects SiHTF-Guideline and SiHTF-Preparation of a Standard.<br/><br/><b>REFERENCES</b><br/>[1] Abschlussbericht zum Verbundvorhaben SIMON-Silicone Fluid Maintenance and Operation. (n.d.)<br/>[2] Jung, C., Dersch, J., Nietsch, A., & Senholdt, M. (2015). Technological Perspectives of Silicone Heat Transfer Fluids for Concentrated Solar Power. <i>Energy Procedia</i>, <i>69</i>, 663–671. https://doi.org/10.1016/j.egypro.2015.03.076<br/>[3] Hilgert, C., Jung, C., Wasserfuhr, C., Leon, J., & Valenzuela, L. (2019). Qualification of silicone based HTF for parabolic trough collector applications. <i>AIP Conference Proceedings</i>, 2126, 080003. https://doi.org/10.1063/1.5117598<br/>[4] Guidelines Silicone-Based Heat Transfer Fluids (SiHTF) in Line Focusing Concentrating Solar Power Applications Version 1.0. (2021). Available online in https://www.solarpaces.org/silicone-based-heat-transfer-fluids-guidelines/<br/>[5] Jung, C. & Senholdt, M. (2020). Comparative study on hydrogen issues of biphenyl/diphenyl oxide and polydimethylsiloxane heat transfer fluids. <i>AIP Conference Proceedings</i>, 2303, 150009. https://doi.org/10.1063/5.0028894