Energy quay walls: Performance analysis and optimisation

Energy Quay Walls (EQWs) are innovative energy geostructures with the unique capability to exchange heat with both soil and open water. Although previous laboratory testing demonstrated a promising energy efficiency for this type of system, its novelty necessitated thorough research to advance comprehension of its thermal behaviour and optimise energy efficiency. This paper conducts an in-depth examination of EQWs, employing numerical models validated against real data from a full scale test in Delft, The Netherlands. Two Finite Element numerical models were developed to (i) reconstruct the undisturbed (i.e. pregeothermal activation) temperature profile within the soil and (ii) conduct a comprehensive (3D) analysis of heat exchange processes in an EQW application (i.e. during geothermal activation), calibrating relevant parameters with field test data, providing valuable insights into its energy efficiency. Following validation, the geothermal activation model was employed to assess the impact of the flow regime within the heat exchanger pipes and the velocity of the open water on the energy efficiency of the EQW system. Additionally, the contributions of soil, water, and air to the energy gain are investigated. The results indicate that the primary source of energy gain is from open water, and the dominance of this contribution is further increased by the presence of turbulent flow within the heat exchanger pipes. However, the soil can play a key role in short term energy delivery. Furthermore, this study emphasises the importance of the open water movement, revealing a 48% reduction in energy extraction for fully stationary water scenarios.