Experimental Investigation of Energy Extraction Power from Heated Granite

Geothermal energy has emerged as a promising renewable energy source due to its low carbon footprint and high energy output. However, the efficiency and economic viability of geothermal energy harvesting largely depend on the heat extraction power from the subsurface. Here we carried out a series of water flow experiments through a drilled borehole in hot granite to determine the heat extraction power. The outflow temperature higher than the inflow temperature demonstrates successful heat extraction from the hot granite. The experimental results show that the heat extraction power generally increased with a greater flow rate and a higher surrounding temperature. The flow rate and surrounding temperature have an indirect influence on the heat extraction power due to the non-isothermal nature of water flow. The findings provide insights into the design and optimization of geothermal energy harvesting systems, and further numerical studies are needed to investigate the non-linear variation of heat extraction power.