Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (1): 185-193.DOI: 10.13745/j.esf.2020.1.20

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Overview of enhanced geothermal system (EGS) based on excavation in China

KANG Fangchao(), TANG Chun’an*()   

  1. 1. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116023, China
    2. Deep Underground Engineering Research Center, Dalian University of Technology, Dalian 116023, China
  • Received:2019-06-01 Revised:2019-10-12 Online:2020-01-20 Published:2020-01-20
  • Contact: TANG Chun’an

Abstract:

Geothermal energy is a permanent, renewable, inexhaustible and clean energy stored in regosol, fluid and magmatic bodies in the Earth’s crust. Its exploitation and utilization, mainly hot dry rock (HDR), may become a meaningful way to solve the future energy crisis. The enhanced geothermal system (EGS) is the primary method used in the exploitation of HDR up till the present time. Because of the complexity of geological environment and dependency of hydraulic measures on natural fissures, most of EGS projects have many technical shortcomings, such as insufficient thermal storage volume and heat transfer area, low working fluid flow rate, low terminal temperature and induced earthquake risk, making large-scale commercialization of DHR unachievable. The prospects of the enhanced geothermal system based on excavation technology (EGS-E) inspired us to find breakthroughs overcoming the technical difficulties and limitations of EGS. In this paper, we discussed EGS-E in great detail on its operation fundamentals, engineering principles and technical advantages based on a conceptual model. By adopting mining technologies, such as excavation, blasting and caving, EGS-E can significantly overcome geological environmental restrictions on thermal storage quality to form a unique fracturing system of geothermal reservoir as well as a special thermal energy exchange system. It has the advantages of building up customized thermal storage, forming sufficient heat transfer areas, maintaining stable working fluid flow rate and temperature, and reducing earthquake risks, thus provides a brand-new scheme for the commercialization of HDR geothermal energy.

Key words: geothermal energy, hot dry rock, deep geothermal exploitation, enhanced geothermal system

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