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Session: Poster session & Sponsor Exhibition
Session starts: Monday 07 October, 14:00

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Stephanie Frick (GFZ Potsdam)
Stefan Kranz (GFZ Potsdam)
Ali Saadat (GFZ Potsdam)

Abstract:
ORC power plants using low temperature heat sources (approx. 100 to 200 °C) are characterized by relatively low conversion efficiencies and high amounts of waste heat. Since low temperature ORC are typically located close to the heat source (e.g. waste heat from industrial processes or low temperature geothermal resources), once-through-cooling typically is not applicable so that wet cooling towers or air-cooled condensers have to be used. The net power output of low temperature ORC power plants is hence significantly depending on the condensation temperature as well as the auxiliary power demand of the cooling equipment. The reason is that both gross power output and auxiliary power demand for the cooling equipment increase with decreasing condensing temperatures. Since geothermal driven ORC power plants - in comparison to other ORC applications - are especially dependent on an improved plant design in order to come up for the technical and financial effort when accessing a deep geothermal reservoir, the optimization of the cooling system is part of geothermal research. Experience from running geothermal power plants as well as the planning of the GFZ geothermal research power plant shows that optimization potential exists for the planning and operation of the cooling system. By means of numerical simulation studies in the software environment DYMOLA/Modelica the influence of changing ambient / cold source conditions on the performance of low temperature ORC power plants with different cooling system set-ups and operation strategies has been studied. Based on the study results, the contribution will present and discuss different aspects of optimizing the design and operation of wet cooling towers and air-cooled condensers. Recommendations how an improved cooling system design could be realized will also be addressed.