Conceptual Investigation of Thermoelectric Linings of Tunnels in High-Geothermal Environments

Abstract

High-geothermal environments present significant challenges for tunnel construction and operation while simultaneously offering promising opportunities for renewable energy utilization. In response, this study proposes a novel high-geothermal tunnel thermoelectric generator (HGT-TEG) system, designed to convert geothermal heat into electrical energy. A numerical model was developed to investigate the heat-transfer characteristics and power generation performance of the system. The model was validated through comparison with both on-site measurements and laboratory experiments. A parametric analysis revealed that the thickness of the thermal insulation layer and the spacing of thermoelectric modules (TEMs) are key factors, affecting the power output. Furthermore, the integration of thermal conductive layers significantly enhanced the effective temperature gradients across TEMs, thereby improving the overall system performance. Under geothermal conditions with a surrounding rock temperature around 92°C, an HGT-TEG system, featuring 30 cm spacing between TEMs in a 1 km tunnel segment (8 m wide, 10 m high), generated an estimated 4867 kWh of electricity, annually. The proposed HGT-TEG system represents a viable and sustainable solution for geothermal energy harvesting, contributing to the resilience and sustainability of tunnel infrastructure in geothermally active regions