| Title | Modeling and Analysis of Sub- and Supercritical Binary Rankine Cycles for Low- to Mid-Temperature Geothermal Resources |
|---|---|
| Authors | Augustine, Chad; Field, Randall; DiPippo, Ronald; Gigliucci, Gianluca; Fastelli, Irene; Tester, Jeff |
| Year | 2009 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Power Cycles; Binary; Supercritical; Air-Cooled Condenser |
| Abstract | A binary cycle power plant uses the thermal energy from a geofluid to heat a secondary (working) fluid in a Rankine cycle to produce electricity. The choice of working fluid in the cycle and the determination of optimum operating conditions to maximize power production depend on the temperature of the given geothermal resource. The goal of this study was to evaluate different working fluids for use in binary Rankine cycles to find the best ones as a function of resource temperature. Binary Rankine cycles using a range of working fluids, including conventional organic fluids, refrigerants, and novel working fluids, were modeled using Aspen simulation software. Both sub- and supercritical cycles were considered. The impact of parasitic power losses from air-cooled condensers was assessed. The optimum cycle conditions for each working fluid were determined for geofluids ranging from 100-200 oC at 10 oC intervals based on the cycle utilization efficiency, and the best candidates were identified for both sub- and supercritical cases. The study found that even though the best working fluid at each temperature interval differed for the two cases, the supercritical Rankine cycle always had a higher utilization efficiency than subcritical cycles at each geofluid temperature considered. |