科研之友
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摘要
Geothermal heating can effectively alleviate the haze weather in northern China. Hot dry rocks have abundant geothermal energy reserves but their commercial exploitation is limited due to high cost, inefficient technology of crack distribution and resulting induced seismicity. Due to the limitations of resource properties and environment, their scale of development is also small. In most areas, the water output of geothermal single well is low, or recharge is difficult owing to the constraint of geologic structure and resource endowment, resulting in an uneconomic exploitation. Deep borehole heat exchanger (DBHE) is an effective way to exploit geothermal energy with low water output or difficult injection. However, its performance is difficult to improve because of poor thermal conductivity of rocks, thus leading to a longer cost recovery time. To enhance heat output, enhanced deep borehole heat exchanger (EDBHE) is proposed in this study. It functions by actively controlling composite filler to flow into leakage formation by adjusting its density, viscosity and back pressure during the drilling process with the aim of improving the thermal conductivity of rocks. The research result shows that the extracted thermal output from the single EDBHE well is 1002.34 kW, which is 2.36 times that of the DBHE (424.45 kW) well. The extracted thermal output for double EDBHE wells reaches a remarkable 27501.61 kW with an annual attenuation rate of 0.95%. EDBHE significantly improves the performance of geothermal well with low water output and effectively enhances the potential of geothermal heating.
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单位中国科学院; 中国科学院大学
