地热井深度对ORC系统热经济性的影响

Effect of Geothermal Well Depth on Thermo-Economic Performance of ORCs

发展地热发电是减少燃煤消耗和污染物排放的重要方向,有机朗肯循环(ORC)是利用中低温地热能发电主要技术之一。地热井深度决定了地热流体温度,进而影响ORC的热力性能,此外钻井成本、生产/回注泵耗功和系统投资亦受地热井深度的影响。本文针对徐家围子三个典型地热井深度(2700m、3200m和4000m),以系统净输出功最大为目标函数优化了异戊烷的蒸发温度,分析了地热井深度对ORC热经济性的影响。结果表明:随着生产井深度的增加,生产/回注泵耗功占比降低,单位功率所需换热面积降低,发电成本降低;生产井深度为4000 m,上网电价为1.2 CNY.(kW·h)^-1时投资回收期约10年。

The use of geothermal energy for power generation is a key approach to reduce the coal consumption and pollutant emissions.Organic Rankine cycle(ORC)is a promising technology for converting the medium-low temperature geothermal energy to electricity.The geothermal fluid temperature is decided by the production well depth which affects the ORC thermodynamic performance,the drilling cost,the production or reinjection pump consumption and the system investment.Mathematical models were established for Xujiaweizi geothermal field with 3 typical production well depths of 2700 m,3200 m and 4000 m.The isopentane evaporation temperatures were optimized to maximize the net power output for various production well depths.The effects of the production well depth on the ORC thermo-economic performance were analyzed.The results show that as the production well depth increases,the proportion of the power consumed by the production and reinjection pumps decreases,the overall heat transfer area per unit power output and the levelized cost of electricity decrease.The system payback period is less than 10 years for production well depth of 4000 m when the on-grid tariff is 1.2 CNY-kWh^-1.