Large-scale urban underground hydro-thermal modelling – A case study of the Royal Borough of Kensington and Chelsea, London

Abstract

The urban underground of dense cities is increasingly exploited for various purposes due to the significant rise in urban populations. Past research has shown that underground activities have a significant impact on local subsurface temperatures. However, the resulting spatial variabilities of ground temperature elevations at a cityscale are not well understood. This is due to lack of sufficient information and modelling complexity at such large scales. This paper presents a novel semi 3D finite element approach to evaluate the temperature rise in the ground due to heat sources such as residential basements and train lines across an entire district. This novel modelling approach is capable of capturing the combined influence of underground built environment characteristics, coupled with ground properties on ground temperature elevations at large-scales. It is observed that density and distribution of heat sources are critical parameters in ground temperature evaluation in highly impermeable ground such as London Clay Formation. The extent of ground thermal disturbance, however, is mostly affected by geological and hydrogeological characteristics in permeable ground. The locality of temperature rise and potential ground energy within immediate impermeable ground surrounding heat sources versus significantly large extent of ground thermal disturbance in permeable ground highlights the significant spatial dependency of ground thermal state and geothermal potential at the studied site. Results show that resilient planning of underground developments and sustainable geothermal exploitation in the short and long-term requires large-scale ground thermal modelling using local ground and underground built environment characteristics.

Effect of anthropogenic heat sources in the shallow subsurface at city-scale

“…In the study presented in this paper, the geology of the citycentre of Cardiff, UK is combined with an accurate representation of buildings which have heated basements. This builds on previous work by Bidarmaghz et al [2,5] by accounting for more refined geological variation in and a greater realism in the building distribution. A numerical model is created using the finite element solver COMSOL Multiphysics ® [6] where coupled heat transfer in porous media and fluid flow through the media is considered.…”

“…The numerical semi-3D approach used in this paper was developed by Bidarmaghz et al [5], whereby the 3D geometry of the domain is sub-divided into 2D horizontal planes. Within each plane, heat flow is modelled through conduction in porous media and convection via groundwater flow.…”

Bayesian parameter inference for shallow subsurface modeling using field data and impacts on geothermal planning

“…Detailed information on the numerical modeling methodology, including governing equations, initial and boundary conditions, and a labeled schematic of the model set-up can be found in Supplementary Appendix B. The methodology has been validated against more complex detailed 3D numerical simulations which have, in turn, been validated against both experimental and numerical data (Bidarmaghz and Narsilio, 2018; Bidarmaghz et al, 2020; Makasis et al, 2020).…”

Shallow subsurface heat recycling is a sustainable global space heating alternative

“…Although research on urban heat islands and anthropogenic heat flows has predominantly focused on or above the land surface 3 , 4 , the shallow subsurface also continuously absorbs and stores heat 5 – 10 . Consequently, subsurface temperatures, which are typically measured in shallow groundwater, are elevated under urban heat islands and in most places affected by human activity 11 – 13 . Due to their sheer number and ubiquity, heat lost from buildings and heat from sealed surfaces warmed by solar radiation are the main contributors to large-scale subsurface warming in a stable climate 14 – 17 .…”