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Energies 2016, 9(6), 422; doi:10.3390/en9060422

Working Fluid Stability in Large-Scale Organic Rankine Cycle-Units Using Siloxanes—Long-Term Experiences and Fluid Recycling

Centre for Sustainable Energy Technology Research (, University of Applied Sciences Stuttgart, Schellingstrasse 24, Stuttgart 70174, Germany
BIOP Biomasseoptimierungen GmbH, Parkstrasse 37, Remshalden 73630, Germany
Department of Industrial System and Product Design (TEI), Ghent University, Graaf Karel de Goedelaan 5, Kortrijk 8500, Belgium
This paper is an extended version of our paper published in Erhart, T.; Gölz, J.; Eicker, U.; van den Broek, M. Fluid stability in large scale ORCs using Siloxanes—Long-term experiences and fluid recycling. In Proceedings of the 3rd International Seminar on ORC Power Systems, Brussels, Belgium, 12–14 October 2015; pp. 1313–1322.
These authors contributed equally to this work.
Author to whom correspondence should be addressed.
Academic Editor: Sylvain Quoilin
Received: 28 January 2016 / Revised: 28 April 2016 / Accepted: 9 May 2016 / Published: 31 May 2016
View Full-Text   |   Download PDF [2498 KB, uploaded 31 May 2016]   |  


The results in this work show the influence of long-term operation on the decomposition of working fluids in eight different organic rankine cycle (ORC) power plants (both heat-led and electricity-led) in a range of 900 kW el to 2 MW el . All case study plants are using octamethyltrisiloxane (MDM) as a working fluid; the facilities are between six to 12 years old. Detailed analyses, including the fluid distribution throughout the cycle, are conducted on one system. All presented fluid samples are analyzed via head space gas chromatography mass spectrometry (HS-GC-MS). Besides the siloxane composition, the influence of contaminants, such as mineral oil-based lubricants (and their components), is examined. In most cases, the original working fluid degrades to fractions of siloxanes with a lower boiling point (low boilers) and fractions with a higher boiling point (high boilers). As a consequence of the analyses, a new fluid recycling and management system was designed and tested in one case study plant (Case Study #8). Pre-post comparisons of fluid samples prove the effectiveness of the applied methods. The results show that the recovery of used working fluid offers an alternative to the purchase of fresh fluid, since operating costs can be significantly reduced. For large facilities, the prices for new fluid range from € 15 per liter (in 2006) to € 22 per liter (in 2013), which is a large reinvestment, especially in light of filling volumes of 4000 liters to 7000 liters per unit. Using the aforementioned method, a price of € 8 per liter of recovered MDM can be achieved. View Full-Text
Keywords: organic rankine cycle (ORC); siloxane; working fluid; fluid stability; operational experience; fluid recycling organic rankine cycle (ORC); siloxane; working fluid; fluid stability; operational experience; fluid recycling

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Erhart, T.G.; Gölz, J.; Eicker, U.; van den Broek, M. Working Fluid Stability in Large-Scale Organic Rankine Cycle-Units Using Siloxanes—Long-Term Experiences and Fluid Recycling. Energies 2016, 9, 422.

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