The role of ground conditions on the heat exchange potential of energy walls

Geotechnical structures are being increasingly employed, in Europe as all around the world, to exchange heat with the ground and supply thermal energy for heating and cooling of buildings and de-icing of infrastructure. Most current practical applications are related to energy piles, but embedded retaining walls are now also being adopted. However, analysis and design methods for these new dual use foundations and ground heat exchangers are currently lacking, making it hard to provide estimates of energy availability without recourse to full numerical simulation. This paper helps to fill this gap by using coupled thermo-hydro finite element analysis to develop charts of energy capacity that could be applied at the outline design stage for energy walls. In particular, the influence of ground properties (hydraulic and thermal conductivities), and ground conditions, (groundwater temperature and flow velocity) are investigated with the results showing that the hydrogeological conditions and the temperature difference between the ground source and application temperature are especially important in determining the performance of the energy wall.