COUPLED WATER-TEMPERATURE FLOW IN SOIL-BOREHOLE THERMAL STORAGE SYSTEMS

This study will focus on the coupled flow of water and heat in the unsaturated soil within a soil-borehole thermal storage system in the vadose zone. The soil-borehole thermal storage system functions by injecting heat collected from solar thermal panels into an array of vertical boreholes containing closed-loop geothermal heat exchangers. The goal of installing the soil-borehole thermal storage system in the vadose zone is to evaluate the potential for enhanced heat exchange from phase change phenomena in the unsaturated soil, as well as the lower thermal conductivity of the unsaturated soil surrounding the storage system. Results from physical modeling tests performed in the laboratory as well as the results from COMSOL simulations will be presented. The results of these analyses confirm that heat injection leads to vaporization of water from the water table, which rises through the soil profile and condenses at a near-surface hydrualic barrier.