NUMERICAL ANALYSIS OF GEOTHERMAL TUNNELS

Abstract

Geothermal energy is a good alternative of fossil fuels and its usage is the most innovative and useful technology that contributes to environmental protection and provides substantial energy, long term cost savings and minimized maintenance. Geothermal energy can be extracted or injected to the earth through tunnels, where tunnels acts as a heat exchanger, in which absorber pipes are fitted, which are circulated with heat transfer liquid. In cities, tunnels provide access for rail, road and utilities. They can also be used as ground heat exchanger for GSHP (Ground Source Heat Pump) systems. Tunnels dug underground use geothermal power to bring our home temperature to earth temperature, i.e helps in heating and cooling. The concept for the thermal tunnel utilizes the temperature difference between the ground and inlet temperature, via compression (heating) or expansion (cooling), to generate building heating or cooling. The system is reversible and operated at best efficiency between seasons. Response of the tunnel as a element has to be recorded and studied. ABAQUS is finite element software (FEM) used for the analysis. Study deals with the simulation of geothermal tunnels using ABAQUS, involving heat transfer analysis and coupled thermo-mechanical analysis using a 3-D model. The model has been analysed for finding out thermal stresses, temperature and displacements on concrete lining, embedded pipes and the soil in which tunnel is being constructed. Results are generated in the form of various plots after running the analysis for a duration of 8 years.