Thermodynamic, economic, and environmental performance comparison of typical geothermal power generation systems driven by hot dry rock

Abstract

Hot dry rock has attracted broad attention due to its relatively high temperature and abundant resources. To match the power generation system suitable for low dryness hot dry rock geothermal fluid, this paper constructed four power generation systems: single stage flash system, double stage flash system, single stage flash combined organic Rankine cycle system and double stage flash combined organic Rankine cycle system. In the range of dryness 0∼0.3 and temperature 150∼200 °C, the matching characteristics between four power generation systems and geothermal fluids in hot dry rock with low dryness were studied. Taking the optimal net power output and exergy efficiency as objective functions, the performance of the four systems was optimized. In addition, the economic performance and environmental benefits of the system are compared. The results show that the temperature of hot dry rock geothermal fluid is positively correlated with the power generation performance, economic performance and environmental benefits of the four systems. In terms of power generation performance, the double stage flash combined organic Rankine cycle system has the best matching characteristics with geothermal fluids. For economic performance, double stage flash combined organic Rankine cycle system and double stage flash system have the highest matching degree when dryness is less than 0.1 and greater than 0.1, respectively. The environmental benefit of double stage flash combined organic Rankine cycle system is superior to the other three systems.

Keywords

• Hot dry rock
• Enhanced geothermal system
• Thermodynamic
• Economic
• Environmental performance
• Organic Rankine cycle