Techno-economic modeling and assessment of a binary power plant for the utilization of two-phase geothermal fluids

Abstract

This paper presents an original design of a binary power plant for the utilization of two-phase geothermal fluids from liquid-dominated fields. The proposed plant concept includes an innovative design aspect based on an additional evaporator for the condensation of previously separated geothermal steam. The model of the proposed system is implemented, and a parametric study conducted through simulations to measure the effect of different process and component design variables on thermodynamic performance. Three dry organic fluids, n-pentane, isopentane, and n-butane, were selected for the thermodynamic analysis. A comparative study was also undertaken to determine whether the proposed system could improve upon the specific power output and economic performance of a single-flash system and a flash-binary system under the same geothermal resource conditions. A maximum net power output of 13.59 MW was achieved using n-pentane as the working fluid for a turbine inlet temperature of 175 ◦C, a wellhead pressure of 13 bar, and an approach temperature difference in the dry cooler of 16 K. The results of the comparative study showed that the proposed system offers both thermodynamic and techno-economic benefits over other geothermal energy systems. Although capital expenditure for the proposed design is 5.6% higher than that for the single-flash system, a more than doubled specific power output ensures a better economic performance. Additionally, the proposed design shows a specific power output improvement of up to 25.6% compared to the flash-binary system while capital expenditure is 19.2% lower.