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Session: Poster Session and Sponsors Exhibition
Session starts: Thursday 22 September, 14:00

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Teemu Turunen-Saaresti ()
Antti Uusitalo ()
Juha Honkatukia ()
Jaakko Larjola ()

Abstract:
The Organic Rankine Cycle (ORC) consists at least of a turbine, a pump, a condenser and an evaporator. The optimal operation of all process components is important to the efficient performance of the ORC. This is especially true in a case of a small electrical output and a low evaporation temperature processes where initial conditions are not supporting the high efficiency. The turbine efficiency can vary widely and it is affected by many factors e.g. the operation point, size, design and type of the turbine. Also when optimum operation of the turbine is sought, the maximum efficiency of the turbine is obtained using highly laborious and complex techniques. Therefore, it is important to study the necessity of achieving the top efficiency. In this study, the sensitivity of the ORC process to the turbine efficiency is evaluated. The ORC process is designed to produce about 10 kW of electric power and the heat source temperature is about 400 degree of centigrade. The working fluid of the cycle is siloxane, MDM. The effects of the turbine efficiency on the ORC process electric efficiency and on the measure of the ORC process quality are presented in this paper. The electric efficiency of the ORC process is rather insensitive for the turbine efficiency. The change in the electrical efficiency of the process is about 0.2 percent while the isentropic efficiency of the turbine changes one percent. Therefore, benefits improving the turbine efficiency using laborious methods and resulting complex geometry are not economically essential in units where the electric power is small. The financial benefit increasing the turbine isentropic efficiency by 5 percent is 174€ - 347€ per year with the electric price varying from 60€/MWh to 120 €/MWh and 5000 operation hours per year in the unit studied in this article. The financial benefits of the higher turbine efficiency are larger when the unit size is larger but in units with the small electric power the financial benefits are very low. Therefore, the main focus should be paid to the manufacturing costs of the turbine/unit rather than to optimize the turbine efficiency. REFERENCES: [1] J.P. van Buijtenen, J. Larjola, T Turunen-Saaresti, J Honkatukia, H. Esa, J. Backman and A. Reunanen: “Design and validation of a new high expansion ratio radial turbine for ORC application” 5th European conference on Turbomachinery, Prague, March 17-22, 2003 [2] J. Harinck, T. Turunen-Saaresti, P. Colonna, S. Rebay, and J. P. van Buijtenen, “Computational Study of a High-Expansion Ratio Radial Organic Rankine Cycle Turbine Stator”, Journal of Engineering for Gas Turbines and Power, 2010, 132, 054501