Techno-economic Performance of Combined Heat and Power (CHP) for EGS with Different Cycle Configurations

Abstract

As a kind of geothermal resource, hot dry rock (HDR) has huge reserves in the earth's crust, and its power generation technology has simple structure and low input cost compared with the traditional power generation technology. Therefore, this study selects four combined heat and power (CHP) systems based on: single-stage flash (SF), double-stage flash (DF), single-stage flash ORC (SFORC) and double-stage flash ORC (DFORC). The power generation efficiency and CHP efficiency were selected as the target parameters. Considering that the geothermal fluid is in the gas-liquid mixed state at the wellhead, so the dryness has a crucial influence on the system performance, and the suitable CHP configuration for different dryness of geothermal fluids has been screened out. The results show that the efficiency of the CHP is 49.7%~67.5% higher than that of the stand alone power generation system, but the power generation efficiency is relatively reduced by 15.7%~16.8%. When the heat source temperature is 150℃ and the dryness is changed from 0.1 to 0.9, the power generation efficiency of the CHP system based on DF, SFORC and DFORC is higher than that of the SF-based CHP system, while the CHP efficiency of the SF-based CHP system is higher than that of the other three systems. The DF-based CHP system has the highest levelized cost of electricity (LCOE) and the best economic performance when the dryness is greater than 0.3. The SF-based CHP system can achieve optimal economic performance when the dryness is less than 0.3.