| Abstract |
Due to limited fossil fuels supply and their negative impact on environment, utilization of renewable energy resources attracts more attention among researchers every day. Geothermal power generation is the most reliable renewable energy resource. Geothermal power plants have the highest capacity factor among other renewable power generation technologies. Unlike solar radiation and wind energy it is not fluctuating during each day and different times of the year. Introducing technologies with higher energy conversion efficiency or improving existing power generation stations would make geothermal power plant more competitive with conventional fossil fired power plants for base load power supply. Considering relative simplicity and reliability of single flash plants, they are often the first type of plants installed in a newly developed field [1]. But, hot brine coming out of separator (that is re-injected to the reservoir) has high working potential and can be used for further power generation. Using combined flash-binary cycles is an effective way of capturing this available energy and increasing power output of the system. One of the most important design parameters in a combined flash-binary power system is selection of secondary working fluid. Because each geothermal field is unique and different from others, selection of secondary fluid must be done with respect to incoming brine from the field. In this paper we will analysis the combined flash-binary power cycles from energy and exergy point of view. For different brine temperatures optimum performance and most appropriate working fluid will be presented. Binary working fluids R-32, R-125, HC 270 and R-22 (as wet fluids), R-21, R-142b, R-134a (as isentropic fluids) and R-601, R-600 and FC-4-1-12 (as dry fluids) will be considered as secondary fluid selections for each case. |