Numerical Analysis of Seasonal Heat Storage Systems of Alternative Geothermal Energy Pile Foundations

Sinnathamby, Gowthaman; Gustavsson, Henry; Korkiala-Tanttu, Leena; Cervera, Carles Perez

doi:10.1061/(asce)ey.1943-7897.0000236

Cited by 6 publications

(4 citation statements)

References 10 publications

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“…Numerical methods are common in ground heat exchanger research (e.g Fan et al, 2008, Zanchini et al, 2012 and allow consideration of many more configurations that can be addressed in practical experiments. However, most models are produced to consider specific case studies (e.g Knellwolf et al, 2011, Dupray et al, 2014, Sinnathamby, 2014 and do not take the opportunity to study the important general problem of optimisation guidance for designers. Distinct from previous work this study allows the relative importance of the design key parameters to be compared so that practical recommendations can be made regarding where designers should focus their efforts to increase the energy efficiency of their energy piles scheme.…”

Section: Introductionmentioning

confidence: 99%

Influences on the thermal efficiency of energy piles

Cecinato

Loveridge

2015

Energy

142

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Energy piles have recently emerged as a viable alternative to borehole heat exchangers, but their energy efficiency has so far seen little research. In this work, a finite element numerical model is developed for the accurate 3D analysis of transient diffusive and convective heat exchange phenomena taking place in geothermal structures. The model is validated by reproducing both the outcome of a thermal response test carried out on a test pile, and the average response of the linear heat source analytical solution. Then, the model is employed to carry out a parametric analysis to identify the key factors in maximising the pile energy efficiency. It is shown that the most influential design parameter is the number of pipes, which can be more conveniently increased, within a reasonable range, compared to increasing the pile dimensions. The influence of changing pile length, concrete conductivity, pile diameter and concrete cover are also discussed in light of their energetic implications. Counter to engineering intuition, the fluid flow rate does not emerge as important in energy efficiency, provided it is sufficient to ensure turbulent flow. The model presented in this paper can be easily adapted to the detailed study of other types of geothermal structures.

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Section: Introductionmentioning

confidence: 99%

Influences on the thermal efficiency of energy piles

Cecinato

Loveridge

2015

Energy

142

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“…Therefore, two-dimensional analyses were performed in order to reproduce all the cases outlined in Table 1. In each of these simulations, the extraction rate 2 [ / 2 ] applied to the plane sources was the one commonly employed in the literature, which guarantees that the same energy per metre is exchanged with the ground (Dupray et al 2014;Sinnathamby et al, 2015):…”

Section: Valuesmentioning

confidence: 99%

“…Pothiraksanon et al, 2010). The frequently employed practice of simply dividing the heat extraction rate of the individual vertical heat exchanger ( ) by their out-of-plane spacing ( ) (Dupray et al 2014;Sinnathamby et al, 2015) is shown to lead to inaccurate estimates of temperature changes in the ground. Indeed, analyses presented herein demonstrate that this approach tends to overestimate the temperature field around a group of VHEs, especially with a low number of heat exchangers and a small spacing (less then 10m).…”

Section: Introductionmentioning

confidence: 99%

A new approach to estimating temperature fields around a group of vertical ground heat exchangers in two-dimensional analyses

2018

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Vertical ground heat exchangers (VHEs), in the form of either Borehole Heat Exchanger (BHE) or thermo-active piles, are increasingly being deployed to provide low cost and sustainable heating and cooling to buildings. These are often installed within densely built urban environments, where adjacent foundation systems and underground structures can be affected by soil temperature changes induced by the heat exchangers. Therefore, they need to be considered in the geotechnical design of such structures, which typically involves carrying out two dimensional finite element plane strain analyses in order to assess their stability and performance. In such a scenario, it is common to model a line of heat exchangers as a planar source with one infinite dimension and a heat flux rate calculated by dividing the design extraction rate of a single heat exchanger by their spacing in the out-of-plane direction. This study shows that this approach largely overestimates the generated temperature field and proposes a simplified but accurate procedure to estimate the required heat flux to be applied to the planar heat sources in a 2D analysis. For this purpose, a correction factor, Full-size image (<1 K), is introduced which is shown to depend on geometric parameters and thermal ground properties

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“…While more recent studies focused on the environmental impact of SUHIs (e.g Müller et al [6], Bonte et al [14], Brielmann et al [15]), others have studied their associated geothermal potential (e.g., Allen et al [16], Arola and Korkka-Niemi [17], Sinnathamby et al [18]). Zhu et al [19], Zhang et al [20] for instance evaluated this potential in several cities including London, Prague, Cologne, Winnipeg and Beijing.…”

Section: Introductionmentioning

confidence: 99%

Increased temperature in Urban ground as source of sustainable energy

Rivera¹,

Benz²,

Blum³

et al. 2016

Int. J. EQ

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Densely urbanized areas are characterized by special microclimatic conditions with typically elevated temperatures in comparison with the rural surrounding. This phenomenon is known as the urban heat island (UHI) effect, but not restricted exclusively to the atmosphere. We also find significant warming of the urban subsurface and shallow groundwater bodies. Here, main sources of heat are elevated ground surface temperatures, direct thermal exploitation of aquifers and heat losses from buildings and other infrastructure. By measuring the shallow groundwater temperature in several European cities, we identify that heat sources and associated transport processes interact at multiple spatial and temporal scales. The intensity of a subsurface UHI can reach the values of above 4 K in city centres with hotspots featuring temperatures up to +20°C. In comparison with atmospheric UHIs, subsurface UHIs represent long-term accumulations of heat in a relatively sluggish environment. This potentially impairs urban groundwater quality and permanently influences subsurface ecosystems. From another point of view, however, these thermal anomalies can also be seen as hidden large-scale batteries that constitute a source of shallow geothermal energy. Based on our measurements, data surveys and estimated physical ground properties, it is possible to estimate the theoretical geothermal potential of the urban groundwater bodies beneath the studied cities. For instance, by decreasing the elevated temperature of the shallow aquifer in Cologne, Germany, by only 2 K, the obtained energy could supply the space-heating demand of the entire city for at least 2.5 years. In the city of Karlsruhe, it is estimated that about 30% of annual heating demand could be sustainably supplied by tapping the anthropogenic heat loss in the urban aquifer. These results reveal the attractive potential of heated urban ground as energy reservoir and storage, which is in place at many places worldwide but so far not integrated in any city energy plans.

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Numerical Analysis of Seasonal Heat Storage Systems of Alternative Geothermal Energy Pile Foundations

Cited by 6 publications

References 10 publications

Influences on the thermal efficiency of energy piles

Influences on the thermal efficiency of energy piles

A new approach to estimating temperature fields around a group of vertical ground heat exchangers in two-dimensional analyses

Increased temperature in Urban ground as source of sustainable energy

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