Conceptualization and evaluation of the exploration and utilization of low/medium-temperature geothermal energy: a case study of the Guangdong-Hong Kong-Macao Greater Bay Area

Geothermal energy is one of the most promising renewable energies due to its high load factor. This work is devoted to presenting the conceptualizations and research advances made at Shenzhen University on the exploration and utilization of low/medium-temperature geothermal energy based on the geothermal resource potential and characteristics of the Guangdong-Hong Kong-Macao Greater Bay Area. The results indicate that the geological structure and lithology of this area are conducive to the formation of geothermal conditions. The geothermal flow and geothermal gradient in this area are higher than the average values in southern China. The total hydrothermal resources and hot dry rock geothermal resources amount to 1.8 x 10(17) kJ and 4.0 x 10(17) kJ, respectively. To enhance the permeability of geothermal reservoirs, especially hot dry rock reservoirs, the volumetric fracturing technique, which is based on three-dimensional fracture mechanics, and the fatigue pneumatic fracturing technique are proposed to stimulate geothermal reservoirs. The advances in theoretical and experimental research and some noteworthy future research topics on volumetric fracturing and fatigue pneumatic fracturing techniques are summarized. To increase the efficiency of low/medium-temperature geothermal power generation, conceptualizations of magnetic levitation power generation technology and thermovoltaic power generation technology for geothermal power generation are proposed. This study may provide new insights into geothermal exploration and low/medium-temperature geothermal power generation.