Abstract
Energy geo-structures are a promising application of shallow geothermal energy technologies utilising underground structures primarily build for stability to also convert them to ground heat exchangers and make thermal energy provision their secondary function. One type of energy geo-structures that has received little attention is energy soldier pile walls. This work adopts advanced numerical modelling approaches to investigate the thermal performance of these energy walls and important parameters affecting this performance including the soldier pile depth, spacing, pipe length and thermal load. The results indicate that both the soldier pile depth and spacing can impact the thermal performance with higher values being desirable. Non-linear/logarithmic performance trendlines have been identified. The scenario of activating less piles overall to increase their (thermal) spacing is also investigated, showing a decrease in the thermal performance but noting that in certain cases this decrease could be acceptable compared to the capital cost savings of activating less piles. The pipe configuration is found to result in relatively insignificant returns after utilising more than about 3 U-loops connected in series, suggesting the potential suitability of an easy to adopt rule-of-thumb for these structures.(C) 2021 The Author(s). Published by Elsevier Ltd.