engleski

Effect of Working Fluid on Organic Rankine Cycle in Geothermal Power Plant with Medium Temperature Geothermal Fluid

Over the past 30-35 years, worldwide electricity production based on geothermal sources has increased significantly: the installed generating capacity has grown from 1300 MW in 1975 to almost 18, 500 MW in 2017. In 1998 the Energy Institute “Hrvoje Požar” prepared a Program of Geothermal Energy Usage in the Republic of Croatia, which shows that in the Republic of Croatia there are some medium temperature geothermal sources (geothermal water) in the range from 90 to 170 ºC, by means of which it is possible to produce electricity in binary plants, either with the Organic Rankine Cycle (ORC) or with the Kalina cycle. However concrete initiatives for the construction of geothermal power plants have only recently been started. In accordance with this authors in previous papers have presented result of an energy-exergy analysis of geothermal resources Velika Ciglena (170 ºC), Lunjkovec-Kutnjak (140 ºC), Babina Greda (125 ºC) and Rečica (120 ºC), in order to determine which cycle is better for the conditions in Croatia. On the basis of analysis results that the ORC is thermodynamically better from the Kalina cycle for temperatures of all cited geothermal sources and cooling air, and considering the problems that all the new technologies encounter in their early phase of application, authors propose the application of binary plants using ORC cycle for all medium temperature geothermal sources in the Republic of Croatia. Researches related to the application of the ORC generally deals with the selection of the working fluid, optimization of the ORC unit and the whole plant and analysis of possible modifications with aim to increase its thermodynamic efficiency or net mechanical power output. Although in the available literature, there are a large number of published research results on the selection of the working fluid, however, every geothermal source is a case for itself with respect to the temperature of geothermal water and the cooling fluid on location (water or air). Therefore, in this paper will be presented the results of analysis of the working fluids effect on thermodynamic and techno–economic characteristics of binary plant with ORC - case study of Geothermal Power Plant Lunjkovec-Kutnjak with temperature of geothermal water 140 ºC. As the working fluid the next refrigerants and hydrocarbons will be analyzed: isopentane (C5H12), isobutene (C4H10), isohexane (C6H14), R114 (C2Cl2F4), R141B (C2H3Cl2F) and R142B (C2H3Cl2F2).

Effect of Working Fluid ; Organic Rankine Cycle ; Geothermal Power Plant ; Medium Temperature Geothermal Fluid

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