Impact of non-uniform temperature distribution on thermal stress behaviour in energy walls

Energy geostructures, such as energy piles and energy walls, serve a dual purpose by providing both structural stability and renewable thermal energy exchange. While their thermo-mechanical behaviour has been widely studied, many investigations simplify the problem by assuming uniform temperature distributions. This assumption fails to capture the realistic, spatially varied temperature fields caused by the flow of heat-transfer fluids within embedded piping networks. These temperature variations give rise to intricate three dimensional thermal stress patterns, which are further shaped by both internal and external boundary conditions. This research addresses the resulting stress responses in energy walls exposed to non-uniform thermal loading under both heating and cooling operations. A comprehensive three-dimensional numerical model, verified using COMSOL Multiphysics, was employed to simulate the effects of spatial temperature differences on stress development. The simulation outcomes highlight the emergence of significant circumferential, radial, and axial stresses driven by thermal gradients and the configuration of mechanical constraints. During heat injection, zones surrounding the heated pipes experienced marked compressive stress, whereas cooling operations led to the formation of tensile stresses, particularly near the piping zones. Elevated tensile stresses were also observed at sensitive regions, such as the interface with surrounding soil and building-facing surfaces. These results underline the critical need for incorporating non-uniform temperature distributions and realistic boundary conditions into the design and evaluation of energy geostructures. Neglecting these aspects can introduce substantial errors in stress predictions, potentially affecting the durability and performance of such systems over time.