1. Nevzat AKKURT Thesis: Investigation of the Criteria for Fluid selection in an Organic Rankine Cycle based on a solar-geothermal hybrid plant Room 1337, ERB M.Sc Student Mechanical Engineering Email: akkurt@wisc.edu Hometown: Ankara, TURKEY

3. Motivation The organic Rankine cycle is a promising way for the conversion of low temperature heat to electricity. Different fluids can be used in organic Rankine cycles for the utilization of additional (solar, geothermal, waste) heat. The suitability of a certain fluid depends on its thermodynamic properties as well as on the conditions at which the solar and geothermal heat are available, therefore it is often unclear if an organic fluid has any advantage compared to inorganic fluids like water.

4. Goals and Objectives Refrigerants such as R134a (which is widely used, nontoxic and nonflammable fluid), high boiling point organic fluids and mixtures of fluids (R141b mixed with RC318) will be investigated as possible working fluids for the different temperature ranges at which the solar-geothermal heat is available. Optimization and dimensioning of the main Organic Rankine cycle components for the utilization of the geothermal source Optimization of the off-design working conditions, when an additional (solar energy) heat source is included. Increase net efficiency for power generation using mixtures of fluids and find the most suitable working fluid.