Abstract
In this paper, mixtures of CO2 and SF6 were evaluated as working fluids for geothermal plants based on property measurements, molecular dynamics modeling, thermodynamic cycle analysis, and materials compatibility assessment. The CO2 - SF6 was evaluated for a reservoir temperature of 160 oC. Increasing the efficiency for these low reservoir sources will increase the options available for geothermal energy utilization in more sites across the country. The properties for the mixtures were obtained either from thermodynamic property measurements and molecular dynamics simulations. Optimum compositions of the CO2 - SF6 were identified for a well reservoir temperature and a given water-cooling condition. Concerning the global warming potential, it was estimated that the equivalent CO2 emissions per 1kWh for a Rankine cycle operating with 100% SF6 would be approximately of 7.6% than those for a coal-fired power plant.
