Survey and Evaluation of Shallow Geothermal Energy in Changsha

LONG Xi-ting, YUAN Rui-qiang, PI Jian-gao, SUN Xi-liang, LIU Chang-ming

JOURNAL OF NATURAL RESOURCES ›› 2016, Vol. 31 ›› Issue (1) : 163-176.

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JOURNAL OF NATURAL RESOURCES ›› 2016, Vol. 31 ›› Issue (1) : 163-176. DOI: 10.11849/zrzyxb.20141143
Resource Evaluation

Survey and Evaluation of Shallow Geothermal Energy in Changsha

  • LONG Xi-ting1, YUAN Rui-qiang2, PI Jian-gao1, SUN Xi-liang1, LIU Chang-ming1
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Abstract

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.

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LONG Xi-ting, YUAN Rui-qiang, PI Jian-gao, SUN Xi-liang, LIU Chang-ming. Survey and Evaluation of Shallow Geothermal Energy in Changsha[J]. JOURNAL OF NATURAL RESOURCES, 2016, 31(1): 163-176 https://doi.org/10.11849/zrzyxb.20141143

Funding

National Natural Science Foundation of China, No; 41301033; Geothermal Survey Project of China Geological Survey, No; 1212011120168
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