Elsevier

Science of The Total Environment

Volume 572, 1 December 2016, Pages 986-994
Science of The Total Environment

Deterministic modeling of the impact of underground structures on urban groundwater temperature

https://doi.org/10.1016/j.scitotenv.2016.07.229Get rights and content

Highlights

  • Individual impact of underground structures on groundwater temperature were assessed.

  • A Thermal Affected Zone is shown to occur approximately 100 m around the structure.

  • The cumulative impact on ground water temperature was assessed in Lyon (France).

  • The area impacted represents 10 times the total surface area of structures.

  • The total annual heat flow from deep structures represents 4.5 GW · h.

Abstract

Underground structures have a major influence on groundwater temperature and have a major contribution on the anthropogenic heat fluxes into urban aquifers. Groundwater temperature is crucial for resource management as it can provide operational sustainability indicators for groundwater quality and geothermal energy. Here, a three dimensional heat transport modeling approach was conducted to quantify the thermally affected zone (TAZ, i.e. increase in temperature of more than + 0.5 °C) caused by two common underground structures: (1) an impervious structure and (2) a draining structure. These design techniques consist in (1) ballasting the underground structure in order to resist hydrostatic pressure, or (2) draining the groundwater under the structure in order to remove the hydrostatic pressure. The volume of the TAZ caused by these underground structures was shown to range from 14 to 20 times the volume of the underground structure. Additionally, the cumulative impact of underground structures was assessed under average thermal conditions at the scale of the greater Lyon area (France). The heat island effect caused by underground structures was highlighted in the business center of the city. Increase in temperature of more than + 4.5 °C were locally put in evidence. The annual heat flow from underground structures to the urban aquifer was computed deterministically and represents 4.5 GW · h. Considering these impacts, the TAZ of deep underground structures should be taken into account in the geothermal potential mapping. Finally, the amount of heat energy provided should be used as an indicator of heating potential in these areas.

Introduction

Half of the world's population now lives in cities. This phenomenon of urbanization is such that this proportion will reach 70% before 2050 (Un-Habitat, 2008). Land constraints lead to the vertical development of urban areas, with the construction of ever-deeper structures (Bobylev, 2009) (e.g., subways, building foundations, underground carparks). In parallel, the urban subsoil is now recognized as a space rich in resources: available water, geomaterials and geothermal energy (Li et al., 2013b, a), which play a vital role in ensuring sustainable territorial development (Goel et al., 2012), but for which regulations remain wanting (Foster and Garduño, 2013). This results in a lack of coordination and planning in the exploitation of this space, illustrated by conflicts over use (Bobylev, 2009).

In particular, the resilience of groundwater resources has become a major issue. On the one hand, 40% of the water distributed in the water supply networks of Europe comes from urban aquifers (Eiswirth et al., 2004), while on the other hand, geothermal energy is now considered as a strategic urban resource (Lund et al., 2011), (Herbert et al., 2013) since the European Council made a commitment to reduce greenhouse gas emissions by 20% by 2020 (European Commission, 2009). In parallel, underground structures involving impervious elements or pumping and re-injection devices, can impact groundwater flow (Attard et al., 2016c). Impervious structures can act as an obstacle to the flow (Epting et al., 2008), (Pujades et al., 2012). Draining structures can result in a fragmentation of urban flow systems (Attard et al., 2016b). In addition, underground structures can impact groundwater quality (Chae et al., 2008), (Attard et al., 2016a) and temperature (Hu et al., 2008), (Epting and Huggenberger, 2013), (Ferguson and Woodbury, 2004).

Regarding groundwater temperature, the heat island effect on groundwater due to urbanization has been clearly observed in many cities around the world (e.g. Zhu, K., et al., 2010, Taniguchi, M., et al., 2009, Menberg, K., et al., 2013a). In particular, Menberg et al. (2013b and Benz et al. (2015) used an analytical heat flux model and a GIS approach to demonstrate that underground structures makes up a significant share of the total anthropogenic heat flux into urban aquifers. In addition to that, Ampofo et al. (2004) used a mathematical model written with an engineering equation solver to investigate the heat load of an underground railway. The authors showed that heat absorbed by the earth surrounding a subway can reach 30% of the total heat generated by the structure. Finally, Epting and Huggenberger (2013) used a deterministic modeling approach to assess the thermal potential natural state and the present state of the groundwater body of Basel (Switzerland). The heat-transport model showed a major influence of deep underground structures on groundwater temperature. On the one hand, the total anthropogenic heat flux of a city into groundwater provides a potentially sustainable geothermal resource (Benz et al., 2015). However, according to (Hähnlein et al., 2013) the shallow geothermal system is only sustainable if the generated energy is mainly renewable energy. Consequently, the total anthropogenic heat flux should be quantified (Benz et al., 2015) and extracted in areas where groundwater temperatures are high (Allen, A., et al., 2003, Revesz, A., et al., 2016). On the other hand, groundwater cooling systems can be disturbed where temperatures are increased by anthropogenic heat flux Epting et al. (2013).

Understanding the thermally affected zone (TAZ) of both urban underground structures and groundwater heat pump systems (GWHPS) is important as it could facilitate the management of urban underground development and geothermal exploitation. Since the TAZ of GWHPS has been described thoroughly in previous works (Lo Russo et al., 2012), (Lo Russo et al., 2014), (Sciacovelli et al., 2014), the aim of this paper is to quantify the TAZ of two common underground structures on urban groundwater temperature: (1) impervious deep foundations, and (2) a structure with a drainage and re-injection system. In addition, the cumulative impact of these structures was assessed at the scale of the city of Lyon (France). The consequences on the geothermal potential of urban aquifers are discussed regarding the TAZ and the heat flow generated by underground structures.

Section snippets

Study site

The area of the city of Lyon (France) (GPS coordinates: 45.75 N/4.85 E) was chosen to study the impact of underground structures on groundwater temperature. This city has a great potential for urban underground development in the light of the criteria proposed in (Li et al., 2013b) (i.e. subsurface geotechnical quality, groundwater quality, geothermal energy, geomaterial quality, urban population, population density and GDP per capita). In practice, this potential is reflected by the economic

Individual impacts of impervious and draining structures

First, the impacts of two design techniques, (1) an impervious structure and (2) a draining structure, on groundwater temperature were simulated in a generic 1 km2 bi-layered aquifer with hydraulic and material properties similar to that of the Lyon urban aquifer. This generic case was assumed to reproduce an urban aquifer recharged by precipitations and network losses, and discharging into a river downstream. As described in (Youngs, 1990) in form of analytical results, this configuration leads

Individual impacts of the impervious and draining structures - scenarios 1 and 2

Before running the transient 20-year simulation, the initial situations of scenarios 1 and 2 were simulated in steady state. In both cases, the temperature ranges from 15 °C at the upper surface of the aquifer (i.e. Z = 0 m), to 18 °C at the lower surface of the aquifer (i.e. Z =  150 m). In the following, the results dealing with temperature disturbances were presented relatively to these initial situations.

The horizontal and vertical distribution of temperature disturbances in scenarios 1 and 2 were

Summary and conclusions

The first aim of this paper was to assess the TAZ of two common underground structures design techniques on urban groundwater under unconfined conditions. The second aim was to assess the cumulative TAZ of deep underground structures at the scale of an urban area. A deterministic 3D modeling approach was used and three simulations were run under average thermal conditions: (1) the impervious structure scenario, (2) the draining structure scenario, and (3) the cumulative impact scenario at the

Acknowledgements

The authors thank the Ministère de l'Écologie, du Développement Durable et de l'Énergie (the French Ministry of Ecology, Sustainable Development and Energy) for its financial support.

References (48)

  • HerbertA. et al.

    Thermal modelling of large scale exploitation of ground source energy in urban aquifers as a resource management tool

    Appl. Energy

    (2013)
  • HuZ.-H. et al.

    Numerical analysis of factors affecting the range of heat transfer in earth surrounding three subways

    J. China Univ. Min. Technol.

    (2008)
  • KimK.-H. et al.

    An experimental study on thermal conductivity of concrete

    Cem. Concr. Res.

    (2003)
  • LiH. et al.

    An integrated planning concept for the emerging underground urbanism: deep city method part 2 case study for resource supply and project valuation

    Tunn. Undergr. Space Technol.

    (2013)
  • LiH.-Q. et al.

    An integrated planning concept for the emerging underground urbanism: deep city method part 1 concept, process and application

    Tunn. Undergr. Space Technol.

    (2013)
  • Lo RussoS. et al.

    Groundwater heat pump (GWHP) system modeling and thermal affected zone (TAZ) prediction reliability: influence of temporal variations in flow discharge and injection temperature

    Geothermics

    (2014)
  • Lo RussoS. et al.

    Development of the thermally affected zone (TAZ) around a groundwater heat pump (GWHP) system: a sensitivity analysis

    Geothermics

    (2012)
  • LundJ.W. et al.

    Direct utilization of geothermal energy 2010 worldwide review

    Geothermics

    (2011)
  • MenbergK. et al.

    Subsurface urban heat islands in German cities

    Sci. Total Environ.

    (2013)
  • PouloupatisP. et al.

    Measurements of ground temperatures in Cyprus for ground thermal applications

    Renew. Energy

    (2011)
  • PujadesE. et al.

    Barrier effect of underground structures on aquifers

    Eng. Geol.

    (2012)
  • ReveszA. et al.

    Ground source heat pumps and their interactions with underground railway tunnels in an urban environment: a review

    Appl. Therm. Eng.

    (2016)
  • SciacovelliA. et al.

    Multi-scale modeling of the environmental impact and energy performance of open-loop groundwater heat pumps in urban areas

    Appl. Therm. Eng.

    (2014)
  • TaniguchiM. et al.

    Anthropogenic effects on the subsurface thermal and groundwater environments in Osaka, Japan and Bangkok, Thailand

    Sci. Total Environ.

    (2009)
  • Cited by (0)

    View full text