Exploiting seafloor hydrothermal energy through optimized closed-loop heat extraction

The Seafloor hydrothermal offer abundant renewable thermal energy. However, the complexity of geology and hydrothermal reactions makes harnessing this energy a significant challenge. This paper proposes a novel closed-loop thermal energy extraction system specifically designed for seafloor hydrothermal environments. This system incorporates high-porosity metal foam as backfill material, a design that seeks to uphold structural integrity in marine settings while potentially enhancing heat exchange efficiency. We've constructed an experimental platform that marries fracture porous media flow analysis with heat transfer measurements, simulating the layout and operation of heat pipes in heterogeneous geological environments. Furthermore, we've developed numerical simulations and computational models customized to hydrothermal conditions, focusing on optimizing key parameters of heat pipe design, such as backfill layer parameters, depth, and fluid flow rate. Our experimental results indicate that fractures and large porosities can increase local heat transfer rates by approximately 42 %. Utilizing high-porosity metal foam as the backfill material, with a thickness 1.1 times the diameter of the heat pipe, can boost heat exchange efficiency by up to 26.71 %. Under optimal conditions (flow rate 0.6 kg/s, drilling depth 200 m), our mathematical model estimates a heat exchange rate of 216.72 kJ/s, potentially generating approximately 75.85 kW. h of electricity per heat pipe. In conclusion, this study sheds new light on the utilization of seafloor hydrothermal energy, fostering the development and application of marine renewable energy.