长沙浅层地热能资源调查与评价

浅层地热能属于清洁能源,其开发利用在我国处于起步阶段。基于大量的野外调查与试验,对长沙浅层地热能开发进行适宜性评价,估算了浅层地热能热容量、可利用资源量以及开发潜力,讨论了其经济、环境效益。实测长沙浅层地温梯度介于0.69℃/100 m~1.98℃/100m,平均为1.40℃/100 m。浅层地热能总热容量约3.34×1014k J/℃,可利用资源量达3.55×1014k J/a。研究区第四系松散岩类沉积物厚度较薄,对浅层地热能储量几乎没有影响。长沙适宜选择地埋管地源热泵系统开发浅层地热能,其适宜区面积占62.6%,较适宜区占33.9%。地埋管地源热泵系统冬、夏季换热功率分别为1.25×107和1.66×107k W,开发潜力分别为(4.22±0.31)×105m2/km2和(3.82±0.17)×105m2/km2。据估算,浅层地热能开发可为长沙节省标准煤1.21×107t/a,减少CO2排放约2.89×107t/a,并减轻大气污染。发展浅层地热能有利于实现节能减排目标,为长沙的可持续发展提供保障。

Survey and Evaluation of Shallow Geothermal Energy in Changsha

Shallow geothermal energy is a kind of clean energy. Development of the energy is still in beginning stage. Based on a number of field surveys and tests in Changsha, the adaptive partition of developing of shallow geothermal resource was evaluated, and the total shallow geothermal capacity, available resource, and potential were studied. Furthermore, environmental and economic benefits from the development were discussed. Changsha is located in a low geothermal gradient area of South China. The average shallow geothermal gradient is 2.41 ℃/100 m in South China. While our results show that the shallow geothermal gradient varies between 0.69 ℃/100 m-1.98 ℃/100 m with an average of 1.40 ℃/100 m in Changsha. The total shallow geothermal capacity and available resource are 3.34×10¹⁴ kJ/℃ and 3.55×10¹⁴ kJ/a respectively. The thin Quaternary sediments (20 m in average) present almost no impacts on the shallow geothermal energy. Besides, sandstone, mudstone, slate, granite and carbonatite distri-bute widely within 200 m underground. Those bedrocks are of high thermal conductivity and bad water yield property. Therefore, it is considered that the ground-source heat pump system of pipe heat exchanger is the appropriate choice to develop shallow geothermal energy in Changsha. The area that best suits for the ground-source heat pump system accounts for 62.6% and the area that better suits accounts for 33.9% for the ground-source heat pump system. The Yuelu Mountain area and the central city are not suitable for the ground-source heat pump system for the bad geological settings. Only the ambient areas of rivers are suitable for ground-source heat pump system of groundwater heat exchanger. Heat exchange power of the heat pump system of pipe heat exchanger is 1.25×10⁷ kW in winter and 1.66×10⁷ kW in summer. At the same time, the geothermal developing potential is (4.22±0.31)×10⁵ m²/km² and (3.82±0.17)×10⁵ m²/km² in winter and summer respectively. The temperature differences used by the ground-source heat pump system are higher in summer than in winter, which is induced the higher heat exchange power and developing potential of shallow geothermal energy in summer. Exploring shallow geothermal energy in Changsha will bring great benefit in economy and environment due to the high available temperature difference and long running term of air conditioner. About 1.21×10⁷ t/a standard coal will be saved by exploring and utilizing the shallow geothermal energy in Changsha. Besides, emission of CO₂ (about 2.89×10⁷ t/a) and air pollutants will also be reduced. Development of shallow geothermal energy is beneficial to achieve the energy conservation and emission reduction target and to succeed in sustainable development of Changsha.