“…Their results revealed the significant influence of underground structures on groundwater temperature. A recent proof-of-concept numerical study of a London Borough showed ground temperature elevations range between 1-5.5°C as a result of continuous heat losses from basements to the ground (Bidarmaghz et al 2018). The extent of temperature elevation in the surrounding ground (vertical and horizontal) was found to vary significantly as a function of local geological variations, the thickness of the permeable layer, the groundwater regime and velocity around underground structures.…”
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.
“…Their results revealed the significant influence of underground structures on groundwater temperature. A recent proof-of-concept numerical study of a London Borough showed ground temperature elevations range between 1-5.5°C as a result of continuous heat losses from basements to the ground (Bidarmaghz et al 2018). The extent of temperature elevation in the surrounding ground (vertical and horizontal) was found to vary significantly as a function of local geological variations, the thickness of the permeable layer, the groundwater regime and velocity around underground structures.…”
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.
“…3 ), all using the same set of input parameters. The exact geometries and parameters used to generate the dataset as well as expanded analyses on this topic can be found in [1] . Fig.…”
Section: Experimental Design Materials and Methodsmentioning
confidence: 99%
“…Value of the data The data were generated using complex and computationally expensive numerical methods (requiring several months to be completed) and can be of use to researchers that are interested in modelling the heat transfer process in shallow geothermal systems. The data allow researchers to further expand on the analyses presented in [1] and/or use other statistical tools in investigating this effect. The range of input parameters used to generate the data allow researchers to investigate different aspects of this technology and the importance of these parameters.…”
mentioning
confidence: 99%
“…The data allow researchers to further expand on the analyses presented in [1] and/or use other statistical tools in investigating this effect.…”
The dataset in this article is related to shallow geothermal energy systems, which efficiently provide renewable heating and cooling to buildings, and specifically to the performance of the vertical ground heat exchangers (GHE) embedded in the ground. GHEs incorporate pipes with a circulating (carrier) fluid, exchanging heat between the ground and the building. The data show the average and inlet temperatures of the carrier fluid circulating in the pipes embedded in the GHEs (which directly relate to the performance of these systems). These temperatures were generated using detailed finite element modelling and comprise part of the daily output of various one-year simulations, accounting for numerous design parameters (including different pipe geometries) and ground conditions. An expanded explanation of the data as well as comprehensive analyses on how they were used can be found in the article titled “Ground-source heat pump systems: the effect of variable pipe separation in ground heat exchangers” (Makasis N, Narsilio GA, Bidarmaghz A, Johnston IW, 2018) [1].
“…Independently of the other parameters, this configuration would result in a low borehole thermal resistance. In reality, as discussed by Makasis et al [22], vertical pipes inside a borehole are seldomly perfectly aligned, and the separation distance often varies with depth. Makasis et al, however, also explain how often the use of spacers placed at regular intervals ensures a higher level of confidence in a commonly made assumption around which most analytical and numerical work on vertical pipe separation is based, that is, that pipes are equally spaced along the entire depth of the borehole.…”
Section: Effect Of Shank-space On System Performancementioning
One parameter that may affect the performance of a ground source heat pump is the shank-space, the center-to-center distance between the two branches of a vertical U-tube used in a ground heat exchanger. A 3D steady-state computational fluid dynamics (CFD) model of a U-tube ground heat exchanger was used to investigate the influence of varying shank-space on the thermal performance of two isolated vertical shallow U-tubes, one 20 m deep and the other 40 m deep, given that most existing research focuses on systems making use of deeper boreholes. The models adopt an innovative approach, whereby the U-junction at the bottom of the U-tube is eliminated, thus facilitating the computational process. The results obtained show that, although the temperature drop across the U-tube varies for different shank-spaces and is lowest and highest for the closest and the widest shank-spaces, respectively, this temperature drop is not linear with increases in shank-space, and the thermal performance improvement drastically diminishes with increasing shank-space. This indicates that, for shallow U-tubes, the temperature drop is more dependent on the length of the pipework.
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