Hydrothermal interactions in energy walls

Energy geostructures: Theory and application

“…Charts allowing to estimate the thermal power that can be extracted or injected from energy geostructures are available for energy piles [e.g., 36,1], energy walls [e.g., 37,38] and energy tunnels [e.g., 39,1,40]. These charts account for site characteristics that include the pipe configuration, the effective thermal conductivity of the ground, the presence, significance and direction of groundwater flow, and the presence and significance of the airflow in underground built environments.…”

“…The advent of relatively sophisticated and accessible numerical software currently facilitates the modeling of the pipes embedded in energy geostructures that significantly characterize their geothermal operation and the associated heat and mass transfers. Through this capability, pipes can be modeled as linear elements [e.g., [101][102][103][104]39,105,106,37,[107][108][109]38] or heat sources [e.g., 110,12,100], but also as actual three-dimensional ducts [e.g., 54]. The hypotheses involved in the previous approaches can lead to predictions that may be more or less adherent to the actual thermo-hydraulic conditions occurring within the pipes.…”

“…Therefore, heat transfer with only the ground or also with the underground built environments may be relevant to achieve and simulate. Typical boundary conditions for the interface(s) between energy geostructures and underground built environments include adiabatic [e.g., 115], prescribed temperature [e.g., 106,116-120], or convection boundary conditions [e.g., 109,38,40]. The immediate presence of such conditions on the boundary of energy geostructures can involve completely different energy, geotechnical and structural performances.…”

“…11: Examples of thermal boundary conditions applied to numerical models of (a) energy piles (modified after Batini et al. [101]), (b) energy tunnels (modified after Cousin et al [109]) and (c) energy walls (modified after Zannin et al [38]).…”

Thermal design and full-scale thermal response test on Energy Walls

“…Moreover, the seepage effect is interacting with the power extraction/injection rate of the heat exchangers: the seepage moves the heat in the flow direction, the soil temperature varies along the y direction, interacting with the power extraction/injection of subsequent pipe loops. On one side, a higher groundwater flow velocity guarantees a higher heat exchange, but at the same time hydraulically-induced thermal interactions among consequent pipe loops take place, affecting the thermal behaviour of consequent heat exchanger loops [7].…”