Study on Preliminarily Estimating Performance of Elementary Deep Underground Engineering Structures in Future Large-Scale Heat Mining Projects

Abstract

Geothermal energy will become an important part of energy in the future because of its advantages in source stability, sustainability, and potential high utilization ratio. In particular, the development and utilization of deep geothermal energy from HDR have gradually attracted people’s attention. Aiming at solution to the bottleneck of EGS-D, a new EGS-E based on excavation technology is proposed. In this paper, a concise and direct method for estimating the early performance of this disruptive and innovative geothermal development scheme is established as a viable alternative to supercomputing for the subsequent quantitative research of the corresponding relationship between a typical deep engineering structure and its heat extraction efficiency. Firstly, the effects of the fixed temperature at a tunnel wall, the radius of a tunnel, and the rock type on the annual heat extraction rate of the tunnel are studied based on the analytical solution of a one-dimensional radial plane problem of the transient heat conduction through high-temperature surrounding rock to the tunnel wall covering 30 years. Then, three different estimation methods of EGS-E efficiency with comb-shaped and chessboard-shaped underground tunnels, respectively, are studied, and the research ideas for the estimation of the EGS-E system with more complicated cobweb-shaped tunnels are pointed out.