ABSTRACT
In order to overcome the shortcomings of the existing enhanced geothermal systems (EGSs)， this chapter proposes a novel hot dry rock (HDR) geothermal energy extraction method for excavation-based EGS (EGS-E). For the EGS-E, it uses mining technology to form tunnel systems with specific structures in HDR, thus completing the construction of geothermal reservoirs that can be further exploited. The EGS-E geothermal reservoir consists of a shaft system, a tunnel system, a piping system, a drive system and other supporting structures. The EGS-E uses a two-stage heat exchange system of “fluid-rock (tunnel heat exchange subsystem) and fluid-fluid (pipe heat exchange subsystem).” The EGS-E has the following advantages over existing methods: customizable and large-scale volume of geothermal reservoirs, stable flow rate of working fluid, high-temperature working fluid, adjustable heat extraction rate, less energy consumption, good safety and environmental friendliness, and controllable financial risk. As with almost all new technologies for HDR exploitation, EGS-E also faces many problems; the biggest problem is how to carry out construction under the existing technology.
