Energy Quay Walls (EQWs) are innovative energy geostructures which exchange thermal energy with both soil and open water while providing a structural function. A full-scale EQW with thermally activated sheet piles was tested, measuring 8.4 m in length along a 1.75m deep canal, with the sheet piles embedded 13m into the underlying soil. Two different length heat exchangers were used: shallow (3 m length) loops primarily extracting thermal energy from the open water, and deep (15 m length) loops extracting energy also from the soil. The shallow loops demonstrated a high heat extraction rate per activated surface area (∼200 W/m2 at 8 °C water temperature, compared with ∼60 W/m2 for the deep loops), with their performance closely linked to the open water temperature. The shallow loops did not require time to restore surrounding temperatures, indicating stable long-term performance, yet can extract the least energy at the coldest time periods. In contrast, the deeper loops exhibit greater stability across varying open water temperatures and achieve the highest total energy extraction per quay wall length (∼900 W/m at 8 °C water temperature, compared with ∼600 W/m for the shallow loops). Realistic operation of the deep loops lowered the soil temperature by ∼2 °C.

Energy quay walls (EQWs) are an innovative type of energy geostructure (EG), capable of exchanging thermal energy with both soil and open water. In this work, a validated 3D finite element numerical model is employed to conduct a parametric analysis aimed at identifying the most important design- and site-dependent parameters for optimising EQW energy performance. The Taguchi Experimental Design statistical method is employed to explore the parameter space for two types of heat exchanger loops used in EQW installations: loops incorporated into the structural elements and add-on panels. The most influential design parameter on the energy performance is shown to be the number of U-loops, which can significantly improve the energy yield (up to ∼50%). The effects of reduced inlet temperature (up to ∼35%), enlarged pipe cross-sectional area (up to ∼26%) and increased heat exchanger fluid velocity (up to ∼20%) are also significant for the EQW thermal performance. Among site-specific factors, the presence of a deep water body (up to ∼100%) with high temperature (up to ∼62%) is confirmed essential for achieving high energetic performance, while a high open water flow velocity (up to ∼32%) and elevated soil thermal conductivity (up to ∼23%) are influential in the short-term thermal output.