Techno-economic performance comparison of enhanced geothermal system with typical cycle configurations for combined heating and power

Abstract The hot dry rock contains abundant heat, which can be exploited by enhanced geothermal systems, being one of the most commonly used geothermal power generation solutions. To enhance the power generation efficiency and utilization of geothermal resource, four combined heating and power systems are presented for geothermal fluids temperature ranging from 120 °C to 220 °C and dryness between 0 and 0.9. The operating parameters of four enhanced geothermal systems are respectively optimized, and the system performances are analyzed and compared. The results showed that the system performances as well as the optimal operating conditions varied with the temperature and dryness of the geothermal fluid. The double-flash organic Rankine cycle based combined heating and power system exhibited the highest power generation efficiency under geothermal fluid temperature and dryness coupling. The double-flash organic Rankine cycle based combined heating and power system had the highest techno-economic performance in the practical application, which the levelized cost of electricity was 0.0831 $/kWh and the payback period was 9.43 years. The organic Rankine cycle subsystem using n-Octane showed preferable power generation performance, while using n-Decane showed preferable techno-economic performance. Moreover, the enhanced geothermal system configuration and its operating parameters should match with actual local geothermal fluid conditions and the double-flash organic Rankine cycle based combined heating and power system was recommended in most cases.